1Hematology and Oncology Division, National Cancer Center Hospital East, Kashiwa; 2Hematology Division and Clinical Laboratory Division, National Cancer Center Hospital, Tokyo; 3Department of Hematology and Chemotherapy and Department of Pathology, Aichi Cancer Center Hospital, Nagoya; 4First Department of Internal Medicine, Nagoya University School of Medicine, Nagoya; 5Department of Internal Medicine, Sapporo Hokuyu Hospital, Sapporo; 6Division of Hematology, National Kyushu Cancer Center, Fukuoka; 7Third Department of Internal Medicine, Kyoto Prefectural University of Medicine, Kyoto; 8Division of Hematology, Tochigi Cancer Center Hospital, Utsunomiya; 9Third Department of Internal Medicine, Hamamatsu University School of Medicine, Hamamatsu; 10Department of Pathology, Institute of Medical Science, University of Tokyo, Tokyo; 11Biostatistics Sciences, School of Health Science and Nursing Biostatistics, University of Tokyo, Tokyo, Japan
Received 3 September 2001; revised 5 December 2001; accepted 9 January 2002.
Abstract
Background
The aim of the study was to determine factors affecting the toxicity and efficacy of rituximab monotherapy in relapsed patients with indolent B-cell lymphoma and mantle cell lymphoma (MCL).
Patients and methods
A total of 90 patients were enrolled and treated with rituximab infusions at 375 mg/m2 once weekly for 4 weeks. Central pathology review revealed that histologically, 81 patients had indolent B-cell lymphoma or MCL: 59 with follicular lymphoma, 17 with MCL, four with marginal zone lymphoma and one with lymphoplasmacytoid lymphoma. Of these, four were ineligible due to violation of other eligibility criteria. Pre-treatment variables affecting toxicities were analyzed for all 90 patients, and those affecting response and progression-free survival (PFS) were analyzed for 77 eligible patients with confirmed indolent B-cell lymphoma or MCL. The relationship between serum rituximab levels and efficacy was also analyzed for 66 eligible patients.
Results
Hematological toxicities (grade 3) occurred more frequently in females (P <0.05), and thrombocytopenia and leukopenia were more frequent in patients with high lactate dehydrogenase (LDH) levels (P <0.05). Non-hematological toxicities (grade
2) were more frequent in patients with extranodal disease or bone marrow involvement. The overall response rate (ORR) in patients receiving one prior chemotherapy regimen was higher than those receiving two or more regimens (P <0.05). The median PFS was shorter in MCL patients, in those with extranodal disease, or in those receiving two or more prior chemotherapy regimens (P <0.01). The PFS intervals of patients with higher serum rituximab levels (
70 µg/ml) immediately before the third infusion were longer than in other patients (P <0.01).
Conclusions
Several prognostic factors and serum rituximab levels are useful for predicting the toxicity and efficacy of rituximab monotherapy.
Key words: indolent B-cell lymphoma, mantle cell lymphoma, prognostic factor, rituximab, serum level
Introduction
The majority of patients with indolent B-cell lymphoma, especially those with follicular lymphoma, present with advanced-stage diseases and cannot be cured with presently available treatment modalities, including high-dose chemoradiotherapy with autologous stem cell transplantation [1, 2]. Although indolent B-cell lymphoma responds well to chemotherapies, repeated relapse is common, and a transformation to an aggressive histology is frequently observed [1]. There is no evidence of a plateau in the survival rate curve of patients with advanced-stage disease, and 10-year survival has been reported to be only 35% [3]. Most patients will ultimately die of lymphoma progression or the complications of treatment. Mantle cell lymphoma (MCL) is another entity of incurable B-cell lymphoma [4, 5]. Most patients with MCL also present with advanced-stage disease and its prognosis has been reported to be less favorable [4, 6, 7]. Therefore, new treatment modalities with different mechanisms of action and with lower toxicity profiles are required for such patients. Among the various new treatment modalities against indolent B-cell lymphoma and MCL, monoclonal antibody (mAb) therapy has been considered one of the most promising treatment strategies [810].
The CD20 antigen is an ideal target for mAb therapy. Its expression is restricted to B-cell lineage and is observed in almost all B-cell lymphomas. It does not modulate in response to antibody binding and is not shed from the cell surface. It has been reported that ligation of CD20 by mAb inhibited malignant B-cell proliferation and induced apoptosis [11].
Rituximab (IDEC-C2B8) is a chimeric IgG1 mAb with a mouse variable region and human constant regions that recognizes the CD20 antigen on B-lymphocytes [12]. Several mechanisms have been proposed for the anti-tumor activities of rituximab, including complement-dependent cytotoxicity (CDC), extended half-life, blockade of signaling pathways and activation of apoptosis [1118]. A recent investigation by Clynes et al. [19] demonstrated that antibody-dependent cell-mediated cytotoxicity (ADCC) through Fc receptors contributed substantially to the cytotoxic action of mAbs.
Considering the high response rates and acceptable toxicity profiles of rituximab in relapsed indolent B-cell lymphoma patients in previous trials in the USA, we began to investigate the potential use of this chimeric mAb for treating Japanese patients with B-cell lymphoma. After we confirmed that the dose of four, once weekly 375 mg/m2 infusions of rituximab was safe and effective in Japanese patients with relapsed B-cell lymphoma in the preceding feasibility and pharmacokinetic study [17], we conducted a multicenter phase II study of rituximab in relapsed patients with indolent B-cell lymphoma or MCL. A recent European, single agent, phase II study of rituximab reported correlations between response and some histopathological categories; rituximab has moderate activity against MCL and lymphoplasmacytoid lymphoma, but only limited activity against small lymphocytic lymphoma (SLL) [20]. However, more information is needed to clarify the therapeutic efficacy of rituximab monotherapy for each histopathological category. In the USA pivotal trial, pre-treatment variables affecting response were analyzed; however, those affecting toxicity, time to progression (TTP) or progression-free survival (PFS) were not analyzed [16]. We, therefore, analyzed pre-treatment variables affecting toxicity, overall response rate (ORR) and PFS in patients with indolent B-cell lymphoma or MCL who were treated with rituximab in the present Japanese phase II study. We also analyzed the association of serum rituximab levels and therapeutic efficacy.
Patients and methods
Study design and end points
This study was a multicenter phase II trial. Patients were recruited into one of two groups: group I comprised patients with indolent B-cell lymphoma, and group II contained MCL patients. The primary end point was an ORR in eligible patients. The expected ORRs (P1) for both groups were set at 40% based on the results of the preceding phase II and pivotal studies in the USA [15, 16], while the threshold response rate (P0) was set at 20% for group I and 15% for group II. The number of patients required for the study was 42 for group I ( = 0.05 and 1 ß = 0.9) and 16 for group II (
= 0.05 and 1 ß = 0.8) when calculated in accordance with Flemings two-stage testing procedure [21]. Assuming, however, that up to 30% of patients might be ineligible mainly due to an inaccurate histopathological diagnosis at the participating institutions revealed by the central pathology review, we planned to enroll 60 and 20 patients for groups I and II, respectively. All patients were followed-up either until disease progression or for at least 6 months after the completion of rituximab administration. PFS was evaluated for all eligible patients, including non-responders, and TTP was evaluated for responders only. Biopsy specimens from all patients in the study were reclassified by a central pathology review committee according to the Revised EuropeanAmerican Lymphoma (REAL) classification [22].
Patient eligibility criteria
Patients were enrolled between July 1997 and March 1999 from 17 institutions in Japan (see Appendix for a list of participating investigators and institutions). Study subjects included patients with indolent B-cell lymphoma or MCL who had relapsed or were refractory to conventional chemotherapy. The pathology of a lymphoma was to be consistent with a type 16 peripheral B-cell neoplasm, according to REAL classification [22], which corresponds to a type AE of the Working Formulation [23], MCL or marginal zone lymphoma (MZL) [4, 22, 24]. The expression of CD20 antigen on lymphoma cells was confirmed by either immunohistochemical analysis or flow cytometry using B1 [25] or L26 [26] anti-CD20 mAb. Eligible patients had to have at least one measurable lesion of 2 cm diameter. The last chemotherapy session had to have been completed at least 2 weeks prior to entry into the study and had to have had no influence on organ functions. Patients were to be between 15 and 75 years of age, with an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of
2 at the time of entry [27]. All patients were supposed to survive for >2 months. Patients had to have no other malignancies, serious illness or infection, and had to have adequate organ function [aspartate aminotransferase (AST) and alanine aminotransferase (ALT) <4 x the upper limit of normal (ULN); total bilirubin <2 x ULN; serum creatinine <1.5 x ULN; and PaO2
65 mmHg]. The absolute neutrophil count was to be
1200/µl and the platelet count
75 000/µl.
Patients with any of the following criteria were excluded from the trial: (i) a history of treatment with a murine, chimeric or humanized mAb, unless it was demonstrated that they were negative for human anti-chimeric antibody (HACA); (ii) >5000/µl lymphoma cells in peripheral blood (PB); (iii) symptomatic central nervous system involvement; (iv) seropositive for hepatitis B virus surface antigen, hepatitis C virus antibody or human immunodeficiency virus antibody; (v) pregnancy or potential pregnancy. Patients who had received hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) in the 1 week before registration were also excluded. All patients were required to stay in the hospital for at least 2 days after the first infusion of rituximab.
Each patient signed an informed consent form at the time of entry. This study was approved by the institutional review board of each institution.
Central pathology review
Thin-layer preparations on slides of lymphoma tissues obtained at the initial diagnosis and/or at relapse were collected. These specimens were stained with hematoxylineosin. In addition, immunohistochemical analyses were conducted using an anti-CD20 mAb (L26) [26], an anti-CD3 polyclonal antibody, and an anti-cyclin D1 mAb [28, 29]. The anti-cyclin D1 mAb (5D4 antibody) was kindly provided by Dr M. Seto (Aichi Cancer Center, Nagoya, Japan). Hematoxylineosin and immunohistochemically stained preparations were microscopically examined by a central pathology review committee composed of the following three hematopathologists: Drs Y. Matsuno (National Cancer Center Hospital, Japan), S. Nakamura (Aichi Cancer Center Hospital, Japan) and S. Mori (Institute of Medical Science, University of Tokyo, Japan). The diagnosis by the central pathology review committee was regarded as the final one in cases where there was a discrepancy between the diagnosis of an institution and that of the committee.
Rituximab administration and pre-medications
Rituximab (manufactured by Genentech, San Francisco, CA, USA) was supplied by Zenyaku Kogyo (Tokyo, Japan) as a liquid preparation containing 10 mg/ml of rituximab in a 10-ml vial, and was stored at 28°C until use. Patients were pre-medicated with antihistamine (d-chlorpheniramine maleate 2 mg) and antipyretic (ibuprofen 200 mg) 30 min before each infusion of rituximab. The diluted drugs in normal saline (final concentration of 1 mg/ml) were given by venous access line through a 0.2 µm polyethylene filter. The dosage and schedule of rituximab in this study was 375 mg/m2 once weekly for 4 weeks. The infusion speed was increased from 25 to 100 mg/h, and then maintained at 200 mg/h unless non-hematological toxicities of grade 2 or greater (except for fever) were observed, as described previously [17]. Standard supportive care was provided except for corticosteroids, which may affect the evaluation of tumor response by rituximab. The use of other anticancer agents and radiotherapies was prohibited during the study period. In some patients, the three subsequent weekly infusions were given on an outpatient basis provided that there were no infusion-related toxicities exceeding grade 1 during the first infusion. Rituximab infusion was to be discontinued if grade 3 or 4 non-hematological toxicities, other than fever, occurred during infusion.
Monitoring of patients
In the 2 weeks before entry into the study, patients underwent pre-treatment tumor assessment at all sites where a tumor could be evaluated or measured using routine X-ray films or computed tomography (CT) scans. Gallium-67 (67Ga) scintigraphy and/or endoscopic examinations were performed if necessary. In cases of patients with leukemic transformation, tumor cell counts in the PB or bone marrow (BM) were performed by either microscopy or flow cytometry. Clinical observations and routine laboratory examinations were performed 2 days after the first infusion, and were repeated weekly during rituximab administration and approximately every month thereafter. Counting of B-lymphocytes (CD19- and CD20-positive cells) and T-lymphocytes (CD3-positive cells) in PB and determining serum immunoglobulins and complement C3 levels were also performed regularly.
Adverse events and adverse drug reactions
Any detrimental change in a patients condition was considered to be an adverse event (AE), regardless of whether there was a relationship with rituximab administration. All AEs that were associated with rituximab administration or for which the relationship to rituximab was unknown were regarded as adverse drug reactions (ADRs). The ADRs were graded according to the toxicity criteria of the Japan Clinical Oncology Group (JCOG) [30], which is an expanded version of the Common Toxicity Criteria of the National Cancer Institute (version 1.0).
Measurement of human anti-chimeric antibody (HACA) and serum rituximab levels
The presence of HACA was monitored immediately before the first and the third rituximab infusions, as well as 3 and 6 months after rituximab administration, using an enzyme-linked immunosorbent assay (ELISA) as previously described [14, 15, 17]. Serum rituximab levels were assayed immediately before the third infusion using sera collected for HACA assay by ELISA, as previously described [14, 15, 17].
Response, progression-free survival and time to progression
Tumor response was assessed according to the same criteria as those adopted in the USA pivotal trial of rituximab [16, 31]. In brief, a complete response (CR) was defined as the normalization (<1 cm on CT scan) of all lymph node sizes and the disappearance of all known diseases, including the clearance of lymphoma cells from BM, lasting for at least 28 days. Partial response (PR) was defined as a >50% decrease in the sum of the products of the greatest perpendicular diameters (SPD) of all measurable lesions, lasting for at least 28 days. Stable disease (SD) was defined as either a decrease of <50% or an increase of <50% in the SPD of any previously identified lymph nodes in the measurable lesions. Progressive disease (PD) was defined as either a >50% increase from the nadir in the SPD of the measurable lesions of PRs or non-responders, or the appearance of a new lesion. PFS was defined for all eligible patients, including non-responders, as the interval from the day of the first rituximab infusion to the day on which progression or death due to any cause was observed. TTP was defined for all responders as the interval from the day of the first rituximab infusion to the day on which progression was observed.
Statistical methods
The following factors affecting non-hematological (grade 2 or greater) and hematological (grade 3 or greater) toxicities were analyzed for all 90 patients who were treated with rituximab: age (60 years versus <60 years), sex (male versus female), PS (0 versus 1 or 2), Ann Arbor clinical stage (II or III versus IV), B-symptom (absent versus present), pathology (indolent B-cell lymphoma versus MCL), serum LDH (normal versus elevated), extranodal disease (absent versus present), bone marrow involvement (absent versus present) and number of prior chemotherapy regimens (less than three versus three or more regimens). Analyses of ORRs and PFSs for groups I and II were conducted prospectively on the basis of protocol; patients with centrally diagnosed MCL were excluded at analysis for group I, and those with centrally diagnosed indolent B-cell lymphoma were excluded at analysis for group II. On the other hand, the analyses of pre-treatment variables affecting the ORR and PFS were performed retrospectively for 77 patients with centrally confirmed indolent B-cell lymphoma or MCL, so far as they met all other eligibility criteria. The following variables were analyzed: age (
60 years versus <60 years), sex (male versus female), PS (0 versus 1 or 2), pathology (indolent B-cell lymphoma versus MCL), B-symptom (absent versus present), serum LDH (normal versus high), extranodal disease (absent versus present), largest tumor diameter (<5 cm versus
5 cm), number of prior chemotherapy regimens (one regimen versus 2 or more regimens) and response to the last chemotherapy regimen (responder versus non-responder). For the analysis of pre-treatment variables affecting ORR and the incidence of toxicities, univariate analysis was performed, from which crude odds ratios were then derived. Multivariate analysis was then conducted by logistic regression model [stepwise procedure with entry and stay probability (P) levels of <0.25 and <0.15, respectively], from which the adjusted odds ratios were derived [32]. The PFS and TTP were estimated using the method of Kaplan and Meier [33]. Univariate analysis of pre-treatment factors affecting PFS was performed by log-rank test [34]. Multivariate analysis was then performed by Coxs proportional hazard regression model (stepwise procedure with entry and stay P levels <0.25 and <0.15, respectively), from which the risk ratios were derived. The relationship between serum rituximab levels and pre-treatment variables was analyzed by Students t-test. All statistical analyses were performed using SAS software (version 6.12; SAS Institute Inc., Cary, NC, USA).
Results
Patients characteristics
A total of 90 patients (69 in group I and 21 in group II) were enrolled in the study. The pre-treatment characteristics of patients are summarized in Table 1. Four patients were judged ineligible by the extramural review committee because they were positive for hepatitis B virus surface antigen or hepatitis C virus antibody, were infected with methicillin-resistant Staphylococcus aureus (MRSA) or had >5000 lymphoma cells/µl of PB. Twelve patients (seven in group I and five in group II) were ineligible for the prospective study based on pathology, as described in the following section. The characteristics were similar between the enrolled patients and the eligible patients. There were eight patients with stage II disease (all in group I), but the remaining 82 were either with stage III or IV disease. Three patients in group I showed pulmonary involvement compared with none in group II. Instead, six enrolled patients in group II showed gastrointestinal tract involvement, while none in group I did. BM was involved in 19 enrolled patients (28%) in group I and in 11 (52%) in group II. All patients had been previously treated with at least one chemotherapy regimen. Three patients in group II had been treated with high-dose chemotherapy and autologous stem cell transplantation.
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Non-hematological toxicities
The numbers of patients who developed grade 2 or greater non-hematological toxicities are shown in Table 3. The most commonly observed non-hematological toxicities, most of which did not exceed grade 2, were infusion-related symptoms such as fever, chills/rigor, vomiting, rash, pruritus, perspiration, asthenia, headache, pain, urticaria and dyspnea. These symptoms generally occurred during the first infusion. They were effectively managed with prophylactic or supportive antihistamines and antipyretics, and resolved within 24 h. Infusion-related ADRs decreased with subsequent infusions. Four patients developed grade 3 non-hematological toxicities. The first patient, who developed a grade 3 skin rash 2 weeks after the last infusion, was hospitalized but recovered following supportive therapy including prednisolone. The second patient, who developed a grade 3 herpes zoster infection 6 months after rituximab administration, was also hospitalized and treated with acyclovir and anti-varicella-zoster virus immunoglobulins; the patient recovered 1 week later. The third patient, who had stage IVB MCL, developed grade 3 pain at a splenic lesion concomitantly with grade 3 hypertension during the first infusion. Rituximab infusion was discontinued and the patient was treated with hydrocortisone; he recovered 3 h after discontinuation of the infusion. The fourth patient, who experienced grade 3 rigors and systemic perspiration during the first infusion, was withdrawn from the study as he refused to receive further infusions. His symptoms were resolved by supportive therapy with hydrocortisone. Elevation of hepatic enzymes was observed in 13 patients (grade 1 elevation in 11 patients and grade 2 in two). One patient suffered from renal dysfunction (grade 2) associated with tumor lysis syndrome. Transient hypocalcemia was noted in one patient, grade 2 hyperglycemia in three, and grade 3 hypoglycemia in one. All non-hematological toxicities were reversible.
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Infection
Seven episodes of infection were noted within 6 months after rituximab administration. Five were grade 1 infections, including one case each of respiratory infection, herpes simplex, Candida pharyngitis, influenza, and infection around the nails. As mentioned above, grade 3 herpes zoster infection was noted in one patient. None of these infections caused serious outcomes.
Early death
One patient died within 30 days after the last rituximab infusion due to lymphoma progression. The 58-year-old patient with relapsed stage IV MCL had been heavily pre-treated. He developed tumor lysis syndrome after the initial rituximab infusion and the number of lymphoma cells in the PB decreased. However, he then developed lymphomatous pleuritis after the third rituximab infusion and died 4 weeks later. The fourth infusion of rituximab was not performed.
Factors affecting toxicity
The pre-treatment variables that affected the development of grade 2 or greater non-hematological toxicities and grade 3 or greater hematological toxicities were examined for all 90 patients by univariate analysis (Table 4). With respect to the grade 2 or greater non-hematological toxicities, fever occurred more frequently in patients with high LDH levels than in those with normal levels [11/25 cases (44%) versus 10/65 cases (15%); P = 0.006]. Chills/rigor occurred more frequently in patients with extranodal disease such as hepatomegaly, splenomegaly, PB and/or BM involvement, pleural effusion, ascites and skin infiltration than those without it [11/49 (22%) versus 2/41 (5%); P = 0.03]. Non-hematological toxicities were more frequent in patients with BM involvement [18/30 (60%) versus 21/60 (35%); P = 0.03] and with extranodal disease [26/49 (53%) versus 13/41 (32%); P = 0.04]. The incidence of grade 3 or 4 hematological toxicity was higher in females than males [15/40 (38%) versus 8/50 (16%); P = 0.02]. Being female was significantly associated with the development of grade 3 or 4 neutropenia [14/40 (35%) versus 4/50 (8%); P = 0.003] and leukopenia [10/40 (25%) versus 4/50 (8%); P = 0.03]. High LDH was also associated with grade 3 or 4 leukopenia [8/25 (32%) versus 6/65 (9%); P = 0.01], but not with neutropenia. Multivariate analysis demonstrated that sex and BM involvement were independently associated with grade 3 or greater hematological toxicities (P = 0.005 and 0.008, respectively; data not shown in Table 4).
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Serum immunoglobulins and complements
There was little change in serum immunoglobulin levels (IgG, IgA and IgM) as long as they were monitored for 12 months (data not shown). There was also no consistent change in the levels of complement C3 (data not shown).
Monitoring of HACA development
Among all patients who had received at least one full dose (375 mg/m2) of rituximab infusion, four patients developed HACA at 3 months (n = 1), 6 months (n = 2) and 12 months (n = 1), respectively. In three patients, HACA levels were below the quantifiable limit (3.9 ng/ml), while in one, HACA levels were 398 ± 53 ng/ml.
ORR, PFS and TTP for groups I and II
Sixty-one eligible patients in group I and 13 eligible patients in group II were evaluated prospectively on a protocol-compatible (PC) basis, whereas 69 patients in group I and 21 patients in group II were evaluated on an ITT basis. As shown in Table 5, the ORRs for patients in group I were 61% [37/61; 95% confidence interval (CI) 47% to 73%] and 59% (41/69; 95% CI 47% to 71%) on a PC and an ITT basis, respectively; the ORRs for patients in group II were 46% (6/13; 95% CI 19% to 75%) and 33% (7/21; 95% CI 15% to 57%), respectively. The median PFSs for patients in group I and II, respectively, were 245 days (95% CI 189 to 337 days) and 111 days (95% CI 50 to 146 days) by PC analysis, and 231 days (95%CI 185 to 329 days) and 68 days (95% CI 35 to 112 days) by ITT analysis. The median TTP intervals for eligible responders in groups I (n = 37) and II (n = 6) were 337 days (95% CI 245 to 376 days) and 144.5 days (95% CI 111 to 230 days), respectively.
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Serum rituximab levels and correlation with factors affecting PFS
Among the 77 patients whose tumor pathologies were centrally confirmed to be indolent B-cell lymphoma or MCL, serum rituximab levels were determined for 66 patients immediately before the third infusion. As shown in Table 7, the mean serum levels of 36 patients with extranodal disease were significantly lower than those of 30 patients without extranodal disease (P = 0.004). There were no significant differences in the serum rituximab levels between responders and non-responders; the mean serum levels ± SD immediately before the third rituximab infusion were 71.5 ± 33.5 µg/ml and 62.6 ± 36.6 µg/ml in 40 responders and 26 non-responders, respectively (data not shown in Table 7). On the other hand, PFS was correlated with serum rituximab levels. As shown in Figure 2, there was a significant difference in PFS between the patients showing higher serum rituximab levels (70 µg/ml; i.e. the value near to either the mean, 68.0 µg/ml, and the median, 71.5 µg/ml) and those showing lower serum rituximab levels (log-rank test, P <0.05).
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We reported here the findings of a multicenter phase II study conducted in Japan to evaluate the efficacy and safety of four, once weekly administrations of rituximab for relapsed indolent B-cell lymphoma and MCL. The dosage and schedule of rituximab administration in this study were based on the results of our preceding phase I study [17], and were similar to those recommended by Maloney et al. [14]. Overall, toxicities were generally mild, and rituximab treatment on an outpatient basis was feasible, as was reported in other studies [15, 16, 20, 38]. Non-hematological toxicities, however, such as vomiting, rash/urticaria, pruritus, perspiration and headache, were more frequently observed in the present study than in other studies. The difference in infusion-related toxicity profiles may be partially derived from a difference in pre-medication drugs. We used d-chlorpheniramine maleate as an antihistamine and ibuprofen as an antipyretic, whereas diphenhydramine and acetaminophen were used in most other studies. On the other hand, peripheral edema, bronchospasm and pain such as myalgia and arthralgia were less frequent in the present study. This may be due to the difference in patients histopathology, e.g. no patient was confirmed to have SLL in this study, and 17 patients (19%) with MCL were included (Table 2), whereas 30 patients (18%) with SLL were enrolled in the USA pivotal study, and MCL was not included [16].
In the present study, factors affecting toxicity were analyzed for all 90 patients on an ITT basis. By univariate analysis, overall non-hematological toxicities (grade 2 or greater) were observed more frequently in patients with extranodal disease, and especially with BM involvement. Fever occurred more frequently in patients with elevated LDH, while chills/rigor and vomiting (data not shown in Table 4) were more frequent in patients with extranodal disease. These findings suggest that patients with elevated LDH or extranodal disease should be monitored more closely during rituximab infusion. The incidence of grade 3 or greater hematological toxicities was much higher (26%) than our pre-study expectation, which may be ascribed to the entry criteria utilized in the present study. For example, the lower limit of the absolute neutrophil count at entry was 1200 cells/µl in the present study, while it is generally set at 1500 cells/µl. In addition, the protocol of the present study did not specify a lower limit of leukocyte count as an entry criterion. The present analysis revealed that grade 3 or greater hematological toxicities that derive mainly from leukopenia and neutropenia were observed more frequently in females than in males by univariate and multivariate analyses. This difference may mainly be ascribed to the differences in baseline counts of leukocytes and neutrophils in females and males. In females, the mean numbers (± SD) of leukocytes and neutrophils at baseline (3700 ± 1200 cells/µl and 2300 ± 1000 cells/µl, respectively) were lower than those found in males (5400 ± 2300 cells/µl and 3000 ± 1000 cells/µl, respectively). Although only three patients developed grade 3 or greater thrombocytopenia, the development was associated with high LDH (P = 0.02) and worsened PS (P = 0.02), as determined by Fishers exact probability test (data not shown in Table 4). By univariate analysis, leukopenia was more frequent in patients with elevated LDH. Accordingly, patients with elevated LDH or worsened PS should be monitored more frequently than other patients for the development of hematological toxicities.
Most patients with elevated LDH, extranodal disease and/or worsened PS before rituximab treatment had also high tumor burden in the present study. The frequent appearance of higher-grade toxicities observed in these patients may be associated with the release of cytokines such as tumor necrosis factor-alpha (TNF-), interleukin-6 (IL-6), interleukin-8 (IL-8) and interferon gamma (IFN-
) due to the tumor destruction by rituximab. Winkler et al. reported that there were elevations of TNF-
and IL-6 in the serum of patients with chronic lymphocytic leukemia (CLL) and with a high number of circulating tumor cells (>50.0 x 109/l) after receiving the first rituximab infusion [39]. Byrd et al. reported that IL-8 and IFN-
were also increased in addition to the increase of TNF-
and IL-6 in patients with CLL and SLL, who experienced significant infusion-related toxicities [40].
According to prospective PC analysis, the ORRs obtained in the present study in relapsed indolent B-cell lymphoma and MCL were 61 and 46%, respectively. These response rates are comparable to those obtained in other studies [15, 16, 20]. In the preceding USA pivotal study, the ORR for follicular subtype was as high as 60% [16], which is close to the ORR for indolent B-cell lymphoma in the present study. According to the European phase II study, the ORR of previously untreated or treated MCL patients was 3738% [20], which is similar to the ORR of MCL patients in the present study. In this study, the median values for PFS and TTP in group I (indolent B-cell lymphoma) were 8.2 months (range 0.6 to 19.8 months) and 11.2 months (range 2.3 to
19.8 months), respectively. The median TTP of group I in the present study was long, as was reported in the USA and UK studies in low-grade or follicular lymphomas [15, 38], while it was slightly shorter than the 13.0 months found in the USA pivotal study [16].
Several prognostic factors for patients with advanced indolent lymphoma have been proposed [4151]. Advanced clinical stage, tumor mass, two or more extranodal sites, BM involvement, anemia, peripheral lymph node involvement, bcl-2 gene rearrangement, low serum albumin level, abnormal liver function, hepatosplenomegaly, high ß2-microglobulin level, high LDH level, B-symptom, sex, age and/or PS have been reported to be prognostic factors for response or survival in untreated indolent lymphoma [36, 37, 4151]. In the present study, prognostic factors affecting efficacy were retrospectively analyzed for 77 patients with centrally confirmed indolent B-cell lymphoma or MCL. We found that the number of prior chemotherapy regimens (one versus two or more) represented a factor that affected ORR by univariate and multivariate analyses. This result was consistent with that of a UK study conducted for patients with follicular lymphoma; in that study the ORR of patients who had received only one prior regimen was reported to be 80% (12/15 cases; 95% CI 51% to 96%), which was higher than that of patients who had received two (36% of cases; 95% CI 12% to 65%) and three or more prior regimens (37% of cases; 95% CI 22% to 54%) [38].
Univariate analysis of pre-treatment variables affecting PFS in the present study showed that the median PFS of relapsed indolent B-cell lymphoma and MCL patients was unfavorably affected by the following five factors: PS (1), pathology (MCL), B-symptom, extranodal disease, and resistance to the last chemotherapy. Multivariate analysis revealed that pathology (MCL), extranodal disease and the number of prior chemotherapy regimens (two or more regimens) were independently significant factors. The median PFS (254 days) of indolent B-cell lymphoma patients (n = 63) was significantly longer than that (107 days) of MCL patients (n = 14). These findings suggest that the efficacy of rituximab is superior in treating indolent B-cell lymphoma as compared with MCL. These findings are consistent with those reported previously [20, 52], and suggest that histopathological diagnosis according to the REAL classification is useful for predicting the efficacy of rituximab monotherapy. McLaughlin et al. analyzed the findings of the USA pivotal study and reported that IPI (high or highintermediate risk) was an unfavorable factor significantly correlated with TTP; we, however, could not find a significant difference in PFS by IPI in the present study, probably because the number of patients with high or highintermediate risk was only seven. Although we have not shown this in Figure 1, when analyzed by generalized Wilcoxons test, there was significant difference in PFS between groups of low risk and lowintermediate risk (P = 0.03), suggesting that a large sized patient study would elucidate the correlation of IPI to PFS.
Berinstein et al. suggested that the residual rituximab levels in blood after a significant period of systemic drug exposure might be an important factor for ORR [53]. With respect to the influence of histopathology on the serum levels of rituximab, they reported that serum rituximab levels in patients with SLL were significantly lower than those of patients with other histopathological subtypes. In the present study, we analyzed the serum rituximab levels of patients with indolent B-cell lymphoma and those with MCL. As shown in Table 7, the mean serum rituximab levels ± SD of 55 patients with indolent B-cell lymphoma was 71.1 ± 34.9 µg/ml, which was higher than that (52.3 ± 34.9 µg/ml) of 11 patients with MCL; the difference, however, was not significant (P = 0.10). There was no significant difference between the mean serum rituximab levels in 39 patients who had received two or more prior chemotherapy regimens (56.6 ± 35.9 µg/ml) and that of 27 patients receiving one regimen (71.4 ± 33.6 µg/ml), while number of prior chemotherapy regimens was an independent factor affecting PFS. While Berinstein et al. postulated that serum rituximab levels would be affected by tumor burden, by number of cells expressing CD20 antigen, by intensity of CD20 expression on the B-lymphoma cell surface, by the number of extranodal sites and by tumor sizes, the present study could reveal that the presence of extranodal disease only correlated with serum rituximab levels.
We demonstrated a significant correlation between PFS and serum rituximab levels immediately before the third infusion, but did not find the correlation between ORR and serum rituximab levels. Coiffier et al. demonstrated that there was no difference between the efficacy of the two arms, i.e. 375 mg/m2 followed by seven, once weekly 500 mg/m2 infusions versus eight, once weekly 375 mg/m2 infusions, while the histology of the study patients was aggressive B-cell lymphoma [54]. On the other hand, Piro et al. reported that by dosing eight times, the median TTP of responders increased to 19.4 months from 13.0 months with four doses, while ORR increased slightly (60% for eight doses versus 50% for four doses) [55]. These findings suggest that extended dosing or repeated treatment might be a reasonable option to improve the therapeutic efficacy of rituximab further.
In the population examined in the present study, the mean serum rituximab levels appeared to be lower than those reported previously [14, 56] although the assays were conducted using the same methods [14, 17]. Whether the lower serum rituximab levels in the present study indicate different pharmacokinetic profiles (i.e. drug clearance, etc.) in Japanese patients remains undetermined. As discussed earlier, the TTP of responders in the present study was somewhat shorter than that of responders in the USA study. The shorter TTP in the present study might be associated with the lower serum levels of rituximab.
Although it has been reported that the incidence of follicular lymphoma in some parts of Asia is lower than that in western countries [57, 58], several recent clinicopathological or epidemiological studies suggest that follicular lymphoma appears to have increased in recent years in Japan [50, 5860]. In addition, a retrospective morphologic study of malignant lymphoma among Japanese immigrants living in Hawaii revealed that the incidence of follicular lymphoma was between those of native-born Americans and Japanese living in Japan [61]. The recent changes in the Japanese lifestyle towards a western one may result in a further increase in follicular lymphoma in Japan in the near future. It is suggested that the introduction of rituximab would result in significant progress in the treatment of B-cell lymphoma patients in Japan.
In conclusions, rituximab is a highly effective agent in relapsed indolent B-cell lymphoma and MCL, and has acceptable toxicities. Rituximab is more effective in the treatment of relapsed indolent B-cell lymphoma than of MCL and in patients without extranodal disease or with a history of having received only one prior chemotherapy regimen. Several prognostic factors and serum rituximab levels are useful in predicting the toxicity and efficacy of rituximab monotherapy.
Acknowledgements
This study was supported by Zenyaku Kogyo Co. Ltd (Tokyo, Japan). We thank all the investigators, including the physicians, nurses and laboratory technicians in the participating institutions of this multicenter trial for their excellent collaboration. We are grateful to Drs K. Oshimi (Juntendo University School of Medicine, Tokyo), K. Toyama (Tokyo Medical College, Tokyo) and S. Shirakawa (Yurinkai Kyoritsu Hospital, Osaka) for their critical review of the clinical data as members of the independent monitoring committee. We also acknowledge Y. Arita, Y. Ikematsu, K. Endo, T. Uesugi, M. Tachikawa, H. Iimura, K. Inatomi, M. Soejima and T. Kayo (Zenyaku Kogyo Co. Ltd) for their help with data collection, statistical analysis and pharmacological analysis.
Appendix
Participating institutions and investigators of the IDEC-C2B8 Study Group in Japan include the following: Sapporo National Hospital (K. Aikawa), Sapporo Hokuyu Hospital (M. Kasai, Y. Kiyama), Tochigi Cancer Center (Y. Kano, M. Akutsu), International Medical Center of Japan (T. Miwa, N. Takesako), National Cancer Center Hospital East (T. Ohtsu, T. Igarashi, Y. Sasaki), National Cancer Center Hospital (K. Tobinai, Y. Kobayashi), Tokai University School of Medicine (T. Hotta, A. Masumoto), Hamamatsu University School of Medicine (K. Ohnishi, K. Naitoh), Aichi Cancer Center Hospital (Y. Morishima, M. Ogura, Y. Kagami), Nagoya University School of Medicine (T. Kinoshita, T. Murate, H. Nagai), Nagoya National Hospital (K. Tsushita), Mie University School of Medicine (M. Masuya, S. Kageyama), Kyoto Prefectural University of Medicine (M. Taniwaki), Kyoto University School of Medicine (H. Ohno), Center for Cardiovascular Diseases and Cancer, Osaka (A. Hiraoka, T. Karasuno), National Kyushu Cancer Center (N. Uike, Y. Yufu) and Nagasaki University School of Medicine (T. Maeda).
Footnotes
+ Correspondence to: Dr K. Tobinai, Hematology Division, National Cancer Center Hospital, 5-1-1, Tsukiji, Chuo-ku, Tokyo 104-0045, Japan. Fax: +81-3-3542-3815; E-mail: ktobinai@ncc.go.jp
References
1. Horning SJ. Natural history of and therapy for the indolent non-Hodgkins lymphomas. Semin Oncol 1993; 20 (Suppl 5): 7588.[ISI][Medline]
2. Bierman PJ, Vose JM, Anderson JR et al. High-dose therapy with autologous hematopoietic rescue for follicular low-grade non-Hodgkins lymphoma. J Clin Oncol 1997; 15: 445450.[Abstract]
3. Dana BW, Dahlberg S, Nathwani BN et al. Long-term follow-up of patients with low-grade malignant lymphomas treated with doxorubicin-based chemotherapy or chemoimmunotherapy. J Clin Oncol 1993; 11: 644651.[Abstract]
4. Banks P, Chan J, Cleary M et al. Mantle cell lymphoma: A proposal for unification of morphologic, immunologic and molecular data. Am J Surg Pathol 1992; 16: 637640.[ISI][Medline]
5.
Weisenburger DD, Armitage JO. Mantle cell lymphoma: An entity comes of age. Blood 1996; 87: 44834494.
6.
Non-Hodgkins Lymphoma Classification Project: a clinical evaluation of the International Lymphoma Study Group Classification of non-Hodgkins lymphoma. Blood 1997; 89: 39093918.
7.
Yatabe Y, Suzuki R, Tobinai K et al. Significance of cyclin D1 overexpression for the diagnosis of mantle cell lymphoma: a clinicopathologic comparison of cyclin D1-positive MCL and cyclin D1-negative MCL-like B-cell lymphoma. Blood 2000; 95: 22532261.
8.
Davis TA, Maloney DG, Czerwinski DK et al. Anti-idiotype antibodies can induce long-term complete remissions in non-Hodgkins lymphoma without eradicating the malignant clone. Blood 1998; 92: 11841190.
9. Kaminski MS, Zasadny KR, Francis IR et al. Iodine-131: anti-B1 radioimmunotherapy for B-cell lymphoma. J Clin Oncol 1996; 14: 19741981.[Abstract]
10. Knox SJ, Goris ML, Trisler K et al. Yttrium-90-labeled anti-CD20 monoclonal antibody therapy of recurrent B-cell lymphoma. Clinical Cancer Res 1996; 2: 457470.[Abstract]
11.
Shan D, Ledbetter JA, Press OW. Apoptosis of malignant B cells by ligation of CD20 with monoclonal antibodies. Blood 1998; 91: 16441652.
12.
Reff ME, Carner K, Chambers KS et al. Depletion of B cells in vivo by a chimeric mouse human monoclonal antibody to CD20. Blood 1994; 83: 435445.
13.
Maloney DG, Liles TM, Czerwinski DK et al. Phase I clinical trial using escalating single-dose infusion of chimeric anti-CD20 monoclonal antibody (IDEC-C2B8) in patients with recurrent B-cell lymphoma. Blood 1994; 84: 24572466.
14. Maloney DG, Grillo-Lopez AJ, Bodkin DJ et al. IDEC-C2B8: results of a phase I multiple-dose trial in patients with relapsed non-Hodgkins lymphoma. J Clin Oncol 1997; 15: 32663274.[Abstract]
15.
Maloney DG, Grillo-Lopez AJ, White CA et al. IDEC-C2B8 (Rituximab) anti-CD20 monoclonal antibody therapy in patients with relapsed low-grade non-Hodgkins lymphoma. Blood 1997; 90: 21882195.
16. McLaughlin P, Grillo-Lopez AJ, Link BK et al. Rituximab chimeric anti-CD20 monoclonal antibody therapy for relapsed indolent lymphoma: Half of patients respond to a four-dose treatment program. J Clin Oncol 1998; 16: 28252833.[Abstract]
17. Tobinai K, Kobayashi Y, Narabayashi M et al. Feasibility and pharmacokinetic study of a chimeric anti-CD20 monoclonal antibody (IDEC-C2B8, rituximab) in relapsed B-cell lymphoma. Ann Oncol 1998; 9: 527534.[Abstract]
18. Taji H, Kagami Y, Okada Y et al. Growth inhibition of CD20-positive B lymphoma cell lines by IDEC-C2B8 anti-CD20 monoclonal antibody. Jpn J Cancer Res 1998; 89: 748756.[ISI][Medline]
19. Clynes RA, Towers TL, Presta LG et al. Inhibitory Fc receptors modulate in vivo cytotoxicity against tumor targets. Nature Med 2000; 6: 443446.[ISI][Medline]
20.
Foran JM, Rohatiner AZS, Cunningham D et al. European phase II study of rituximab (chimeric anti-CD20 monoclonal antibody) for patients with newly diagnosed mantle-cell lymphoma and previously treated mantle-cell lymphoma, immunocytoma, and small B-cell lymphocytic lymphoma. J Clin Oncol 2000; 18: 317324.
21. Fleming TR. One sample multiple testing procedure for phase II clinical trials. Biometrics 1982; 38: 143151.[ISI][Medline]
22.
Harris NL, Jaffe ES, Stein H et al. A revised EuropeanAmerican classification of lymphoid neoplasms: a proposal from the International Lymphoma Study Group. Blood 1994; 84: 13611392.
23. Non-Hodgkins Lymphoma Pathologic Classification Project. National Cancer Institute sponsored study of classifications of non-Hodgkins lymphomas: summary and description of a Working Formulation for clinical usage. Cancer 1982; 49: 21122135.[ISI][Medline]
24.
Fisher RI, Dahlberg S, Nathwani BN et al. A clinical analysis of two indolent lymphoma entities: mantle cell lymphoma and marginal zone lymphoma. A Southwest Oncology Group study. Blood 1995; 85: 10751082.
25.
Stashenko P, Nadler LM, Hardy R et al. Characterization of a human B lymphocyte-specific antigen. J Immunol 1980; 125: 16781685.
26. Mason DY, Comans-Bitter W, Cordell JL et al. Antibody L26 recognizes an intracellular epitope on the B-cell-associated CD20 antigen. Am J Pathol 1990; 136: 12151222.[Abstract]
27. Oken MM, Creech RH, Tormey DC et al. Toxicity and response criteria of Eastern Cooperative Oncology Group. Am J Clin Oncol 1982; 5: 649655.[ISI][Medline]
28. Banno S, Yoshikawa K, Nakamura S et al. Monoclonal antibody against PRAD1/cyclin D1 stains nuclei of tumor cells with translocation or amplification at BCL-1 locus. Jpn J Cancer Res 1994; 85: 918926.[ISI][Medline]
29. Nakamura S, Seto M, Banno S et al. Immunohistochemical analysis on the cyclin D1 protein in hematopoietic neoplasms with special reference to mantle cell lymphoma. Jpn J Cancer Res 1994; 85: 12701279.[ISI][Medline]
30. Tobinai K, Kohno A, Shimada Y et al. Toxicity grading criteria of the Japan Clinical Oncology Group (JCOG). Jpn J Clin Oncol 1993; 23: 250257.[ISI][Medline]
31. Grillo-Lopez AJ, Cheson BD, Horning SJ et al. Response criteria for NHL: importance of normal lymphnode size and correlation with response rates. Ann Oncol 2000; 11: 399408.[Abstract]
32. Cox DR. Regression models and life tables. J R Stat Soc [B] 1972; 34: 187220.[ISI]
33. Kaplan EL, Meier P. Nonparametric estimation from incomplete observations. J Am Stat Assoc 1958; 53: 457481.[ISI]
34. Mantel L. Evaluation of survival data and two new rank order statistics arising in its consideration. Cancer Chemother Rep 1966; 50: 163170.[Medline]
35.
The International Non-Hodgkins Lymphoma Prognostic Factors Project: a predictive model for aggressive non-Hodgkins lymphoma. N Engl J Med 1993; 329: 987994.
36. Lopez-Guillermo A, Montserrat E, Bosch F et al. Applicability of the International Index for aggressive lymphomas to patients with low-grade lymphoma. J Clin Oncol 1994; 12: 13431348.[Abstract]
37.
Hermans J, Krol ADG, van Groningen K et al. International Prognostic Index for aggressive non-Hodgkins lymphoma is valid for all malignancy grades. Blood 1995; 86: 14601463.
38. Foran JM, Gupta RK, Cunningham D et al. A UK muticenter phase II study of rituximab (chimeric anti-CD20 monoclonal antibody) in patients with follicular lymphoma with PCR monitoring of molecular response. Br J Haematol 2000; 109: 8188.[ISI][Medline]
39.
Winkler U, Jensen M, Manzke O et al. Cytokine-release syndrome in patients with B-cell chronic lymphocytic leukemia and high lymphocyte counts after treatment with an anti-CD20 monoclonal antibody (rituximab, IDEC-C2B8). Blood 1999; 94: 22172224.
40.
Byrd JC, Waselenko JK, Maneatis TJ et al. Rituximab therapy in hematologic malignancy patients with circulating blood tumor cells: association with increased infusion-related side effects and rapid blood tumor clearance. J Clin Oncol 1999; 17: 791795.
41. Romaguera JE, McLaughlin P, North L et al. Multivariate analysis of prognostic factors in stage IV follicular low-grade lymphoma: a risk model. J Clin Oncol 1991; 9: 762769.[Abstract]
42. Bastion Y, Berger F, Bryon PA et al. Follicular lymphomas: assessment of prognostic factors in 127 patients followed for 10 years. Ann Oncol 1991; 2 (Suppl 2): 123129.[Abstract]
43. Soubeyran P, Eghbali H, Bonichon F et al. Low-grade follicular lymphomas: analysis of prognosis in a series of 281 patients. Eur J Cancer 1991; 27: 16061613.[ISI][Medline]
44. Gallagher CJ, Gregory WM, Jones AE et al. Follicular lymphoma: Prognostic factors for response and survival. J Clin Oncol 1986; 4: 14701480.[Abstract]
45. Bremnes RM, Vik A, Helbekkmo N. Low-grade non-Hodgkins lymphoma in northern Norway: treatment, outcome and prognostic factors. Anticancer Res 1998; 18: 19211930.[ISI][Medline]
46. Wendum D, Sebban C, Gaulard P et al. Follicular large-cell lymphoma treated with intensive chemotherapy: an analysis of 89 cases included in the LNH87 trial and comparison with the outcome of diffuse large B-cell lymphoma. J Clin Oncol 1997; 15: 16541663.[Abstract]
47.
Lopez-Guillermo A, Cabanillas F, McDonnell TI et al. Correlation of bcl-2 rearrangement with clinical characteristics and outcome in indolent follicular lymphoma. Blood 1999; 93: 30813087.
48. Davidge-Pitts M, Dansey R, Bezwoda WR. Prolonged survival in follicular non-Hodgkins lymphoma is predicted by achievement of complete remission with initial treatment: results of a long-term study with multivariate analysis of prognostic factors. Leuk Lymphoma 1996; 24: 131140.
49. Bastion Y, Sebban C, Berger F et al. Incidence, predictive factors and outcome of lymphoma transformation in follicular lymphoma patients. J Clin Oncol 1997; 15: 15871594.[Abstract]
50. Katsumata N, Matsuno Y, Nakayama H et al. Prognostic factors and a predictive model of follicular lymphoma: a 25-year study at a single institution in Japan. Jpn J Clin Oncol 1996; 26: 445454.[Abstract]
51. Foussard C, Desablens B, Sensebe L et al. Is the International Prognostic Index for aggressive lymphomas useful for low-grade lymphoma patients? Applicability to stage IIIIV patients. Ann Oncol 1997; 8 (Suppl 1): 4952.[Abstract]
52. Nguyen DT, Amess JA, Doughty H et al. IDEC-C2B8 anti-CD20 (rituximab) immunotherapy in patients with low-grade non-Hodgkins lymphoma and lymphoproliferative disorders: Evaluation of response on 48 patients. Eur J Hematol 1999; 62: 7682.[ISI][Medline]
53. Berinstein NL, Grillo-Lopez AJ, White CA et al. Association of serum rituximab (IDEC-C2B8) concentration and anti-tumor response in the treatment of recurrent low-grade or follicular non-Hodgkins lymphoma. Ann Oncol 1998; 9: 9951001.[Abstract]
54.
Coiffier B, Haioun C, Ketterer N et al. Rituximab (anti-CD20 monoclonal antibody) for the treatment of patients with relapsing or refractory aggressive lymphoma: a multicenter phase II study. Blood 1998; 92: 19271932.
55. Piro LD, White CA, Grillo-Lopez AJ et al. Extended rituximab (anti-CD20 monoclonal antibody) therapy for relapsed or refractory low-grade or follicular non-Hodgkins lymphoma. Ann Oncol 1999; 10: 655661.[Abstract]
56. Iacona I, Lazzarino M, Avanzini MA et al. Rituximab (IDEC-C2B8): validation of a sensitive enzyme-linked immunoassay applied to a clinical pharmacokinetic. Ther Drug Monit 2000; 22: 295301.[ISI][Medline]
57. Kadin ME, Berard CW, Nanba K et al. Lymphoproliferative diseases in Japan and western countries: Proceedings of the United StateJapan seminar, September 6 and 7, 1982, in Seattle, Washington. Hum Pathol 1983; 14: 745772.[ISI][Medline]
58. Ohsawa M, Aozasa K, Tsujimura T et al. Non-Hodgkins lymphoma of follicular center cell type in Osaka, Japan. Eur J Cancer Clin Oncol 1989; 25: 18751878.[ISI][Medline]
59. Ohshima K, Suzumiya J, Sato K et al. B-cell lymphoma of 708 cases in Japan: incidence rates and clinical prognosis according to the REAL classification. Cancer Lett 1999; 135: 7381.[ISI][Medline]
60. Izumo T, Maseki N, Mori S et al. Practical utility of the revised EuropeanAmerican classification of lymphoid neoplasms for Japanese non-Hodgkins lymphomas. Jpn J Cancer Res 2000; 91: 351360.[ISI][Medline]
61. Yanagihara ET, Blaisdel RK, Hayashi T et al. Malignant lymphoma in HawaiiJapanese: a retrospective morphologic survey. Hematol Oncol 1989; 7; 219232.[ISI][Medline]