1Oregon Health and Science University, Portland, OR; 2American Oncology Resources, Houston, TX; 3PRN Research, Dallas, TX; 4Arizona Clinical Research Center, Tucson, AZ; 5Hackensack Medical Center, Hackensack, NJ; 6East Orange VA Medical Center, East Orange, NJ; 7The University of Chicago, Chicago, IL; 8Boulder Valley Oncology, Boulder, CO; 9Georgia Cancer Specialists, Decatur, GA; 10Memorial Sloan Kettering Cancer Center, New York, NY; 11MedImmune Oncology, Inc., Gaithersburg, MD; 12University of Pennsylvania Cancer Center, Philadelphia, PA, USA
Received 12 September 2001; accepted 13 September 2001.
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Abstract |
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Trimetrexate (TMTX) biochemically modulates 5-fluorouracil (5-FU) and leucovorin (LCV). Two phase II trials demonstrated promising activity for TMTX/5-FU/LCV in patients with untreated advanced colorectal cancer (ACC). This trial was designed to demonstrate the safety and efficacy of TMTX/5-FU/LCV as first-line treatment in ACC.
Patients and methods
Eligible patients with ACC were randomized in double-blind fashion to receive placebo or TMTX (110 mg/m2) intravenously (i.v.) followed 24 h later by i.v. LCV 200 mg/m2, and 5-FU 500 mg/m2 plus oral LCV rescue. Both schedules were given weekly for 6 weeks every 8 weeks. Patients were evaluated for progression-free survival (PFS), overall survival (OS), tumor response, quality of life (QoL) and toxicity.
Results
A total of 382 eligible patients were randomized. Significant toxicities were noted more frequently with TMTX/5-FU/LCV. Diarrhea was the most common grade 3 or 4 side-effect (41% and 28% on the TMTX and placebo arms, respectively). QoL scores and response rates did not differ between treatment arms. PFS was 5.3 months and 4.4 months in the TMTX and placebo arms, respectively (P = 0.77; Wilcoxon). OS was 15.8 months and 16.8 months, respectively (P = 0.73; Wilcoxon).
Conclusions
The addition of TMTX to a weekly regimen of 5-FU/LCV worsened grade 3 or 4 diarrhea. The inclusion of TMTX did not yield any significant improvements in response rate, PFS or OS.
Key words: biochemical modulation, colorectal cancer, 5-fluorouracil, leucovorin, randomized trial, trimetrexate
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Introduction |
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Trimetrexate (TMTX) is a synthetic inhibitor of the dihydrofolate reductase [6] which maintains reduced folates which serve as 1-carbon donors in DNA biosynthesis. TMTX also increases intracellular concentrations of 5-phosphoribosyl-1-pyrophosphate by inhibiting purine synthesis, increasing the conversion of 5-FU to its active metabolites. Unlike the classical antifolate methotrexate, TMTX is relatively lipophilic, does not require activation by the enzyme folylpolyglutamyl synthetase, and does not use the reduced folate transport system to enter neoplastic cells, thus avoiding competition for uptake when administered with LCV [79]. Although the combination of MTX, 5-FU and LCV is not more effective in vitro than 5-FU and LCV alone, adding TMTX to 5-FU and LCV clearly enhances cytotoxicity [10].
Two studies of TMTX, 5-FU and LCV in previously untreated patients with ACC demonstrated overall response rates of 50% and 36%, respectively [11, 12]. The triple combination has also been confirmed to have a high response rate in previously untreated ACC patients treated in the community setting [13]. The TMTX/5-FU/LCV regimen may have potential activity in the salvage setting. Conti et al. [14] demonstrated a 20% response rate in heavily pretreated ACC patients using those drugs, although that figure was not confirmed in a dedicated phase II study which has not yet been fully reported [15].
Based on the known biochemical modulation of 5-FU/LCV by TMTX, coupled with significant activity of the three-drug regimen in several phase II trials, we designed a randomized phase III study of TMTX or placebo, with 5-FU/LCV, in patients with previously untreated ACC. We herein report the mature results of 384 patients entered from 35 American institutions between November 1995 and February 1999.
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Patients and methods |
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The primary objective of the study was to detect a difference in median time to progression [calculated as progression-free survival (PFS)] from 7 months on the control arm, to 10 months on the experimental arm. A sample size of 300 (150 patients per arm) was calculated to provide an 80% power of detection at = 0.05 (two-sided) significance level. An interim analysis was initially planned but eventually avoided, to preserve the blinded nature of the study. Secondary objectives on the current study included OS, response rate and comparison of toxicities between arms. Stratification was performed by treatment center, anatomic location (primary colon or rectal tumor), PS (0, 1 or 2), prior irradiation (yes or no), prior adjuvant chemotherapy (yes or no), site of metastases (liver dominant with <30% involvement, or liver dominant
30%, or lung dominant or other dominant), and serum lactate dehydrogenase (LDH) value (<300 U/l or
300 U/l).
Patients were randomized to 5-FU/LCV with or without TMTX/placebo. In the experimental arm, patients received TMTX 110 mg/m2 as a 1-h intravenous (i.v.) infusion, followed 24 ± 2 h later by LCV 200 mg/m2 as a 1-h i.v. infusion and 5-FU 500 mg/m2 as an i.v. bolus, followed by oral (p.o.) LCV 15 mg every 6 h for a total of seven doses, starting 6 h after the i.v. 5-FU. Patients in the control arm received placebo as a 1-h i.v. infusion, followed 24 ± 2 h later by the identical LCV (i.v. and p.o.) and 5-FU as received by patients in the experimental arm. Patients were treated weekly for 6 weeks every 8 weeks, followed by a 2-week rest period, with therapy continuing until tumor progression, untenable toxicity, or patient request for removal from the study. At the onset of any diarrhea, patients were instructed to use an intensive dosing schedule of loperamide: 4 mg after the first liquid stool, then 2 mg every 2 h until 12 h after the last passage of liquid stool. Patients were followed weekly for side-effects, including assessment of a toxicity diary, and they were evaluated every 8 weeks for response (or as prompted by carcinoembryonic antigen rise two-fold over baseline, progressive increase in liver function, or deterioration in PS).
Objective responses were originally defined as: complete response (CR), complete disappearance of all measurable and evaluable disease for at least 4 weeks, with no development of new lesions; partial response (PR), 50% or greater decrease in the sum of the products of the perpendicular diameters of all measured lesions, persisting for at least 4 weeks, without evidence of progression or development of new lesions; stable disease, did not qualify for CR, PR or progression; or progression, any increase of 25% or more in the size of one or more measurable or evaluable lesions or the appearance of a new lesion.
All toxicities encountered during the study were evaluated according to standard USA National Cancer Institute Common Toxicity Criteria. Dose reductions were performed as follows. For hematological toxicity grade 2, 5-FU was reduced by 25%. For hematological and non-hematological toxicity grade 3 or 4, treatment was withheld for a maximum of 2 weeks until recovery to grade 0 or grade 1 and then resumed with 5-FU at 50% of the dose. If at the 50% dose reduction of 5-FU no toxicities greater than grade 2 occurred, 5-FU was increased by 25% increments. If treatment was held for 3 weeks (not including rest weeks), the patient was removed from the study. Patients were asked to complete the functional assessment of cancer therapycolon (FACT-C) quality-of-life (QoL) questionnaire at baseline and at weeks 1 and 5 of each cycle [16]. Information on subsequent antitumor treatment after study discontinuation was collected in the case report forms.
This study was conducted in accordance with the principles of the Declaration of Helsinki, as adopted by the 29th World Medical Assembly, Helsinki, Finland and revised at the 48th World Medical Assembly in Somerset West, Republic of South Africa, 1996. These principles are consistent with those set forth in the International Conference on Harmonization Guidelines on Good Clinical Practice, and the current USA Code of Federal Regulations (21 CFR Parts 56 and 50) regarding the requirements for independent ethics committees and institutional review boards and protection of the rights and welfare of human subjects involved in clinical investigations.
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Results |
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Efficacy
Data on response are summarized in Table 3. The overall unconfirmed response rate was 26% [95% confidence interval (CI) 20% to 32%] for TMTX/5-FU/LCV and 21% (95% CI 15% to 27%) for 5-FU/LCV alone (3% CR on each). Since tumor evaluation was performed on an 8-week cycle, confirmatory evaluation 4 weeks after the first evidence of response was rarely performed. Considering responses that were confirmed by evaluation at least 4 weeks later, the overall response rates were 17% (95% CI 12% to 23%) and 15% (95% CI 10% to 20%), respectively. Differences between arms were not statistically significant. The median duration of response was 6.4 months for TMTX/5-FU/LCV and 5.8 months for 5-FU/LCV (P = 0.45).
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Discussion |
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Neither the European nor the American trial, however, was designed to detect a significant OS difference of small magnitude, leading to an integrated analysis combining data from both studies [18]. Median PFS was 5.4 months for the TMTX-containing arm and 4.4 months for the 5-FU/LCV arm. This difference was not statistically significant (P = 0.07). Median OS was also not statistically different (P = 0.15) at 14.6 months for the experimental arm and 13.0 months for the control arm. The reasons for possible differences between the European and American trials are outlined in the integrated analysis manuscript [18].
The current trial showed no differences in response or survival with the addition of TMTX to standard 5-FU/LCV. The TMTX arm actually did significantly better than similar patients treated in the phase II setting [11, 12], but it should be noted the 5-FU/LCV arm also did markedly better than historical comparitors. In fact, the control arm on the current study had better survival than the comparitor arms on the meta-analysis and Saltz trial [4], and the CPT-11/5-FU/LCV arm on the latter [2, 4]. The reason(s) for this improvement and/or the lack of benefit with TMTX are not clear. Fifty-seven percent of arm II patients did receive CPT-11, a drug proven to prolong survival when given in the salvage setting [19] , but most patients on 5-FU/LCV on the Saltz trial [4] also received that drug (as, of course, did patients on the original triple-therapy arm). Equal numbers of arm I and II patients on the current study were given CPT-11, so a beneficial effect of TMTX was not washed out by less effective salvage on the experimental arm. Patients on arm II did receive significantly more 5-FU, as manifested by achieved dose intensity. Patients on arm I had more toxicity, leading to reductions in TMTX and 5-FU, the latter possibly contributing to the adverse outcome.
The addition of TMTX did slightly worsen toxicities seen with 5-FU/LCV alone, mostly manifested as diarrhea. TMTX did not increase grade 3 or 4 neutropenia, which was rare in both arms. Overall QoL was not affected by the TMTX.
In conclusion, the addition of TMTX to a weekly schedule of 5-FU/LCV did not improve response, PFS or OS. Treatment with TMTX/5-FU/LCV is feasible, but this schedule cannot be recommended for routine use in patients with ACC.
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Acknowledgements |
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Footnotes |
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References |
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