EORTC 10968: a phase I clinical and pharmacokinetic study of polyethylene glycol liposomal doxorubicin (Caelyx®, Doxil®) at a 6-week interval in patients with metastatic breast cancer

A. Hamilton1, L. Biganzoli1, R. Coleman2, L. Mauriac3, P. Hennebert4, A. Awada4, M. Nooij5, L. Beex6, M. Piccart4,+, I. Van Hoorebeeck1, P. Bruning7 and D. de Valeriola4

1IDBBC, Brussels, Belgium; 2Weston Park Hospital, Sheffield, UK; 3Fondation Bergonié, Bordeaux, France; 4Institut Jules Bordet, Brussels, Belgium; 5Academisch Ziekenhuis Leiden, Leiden, The Netherlands; 6Universiteit Ziekenhuis Nijmegen, Nijmegen, The Netherlands; 7Antoni van Leeuwenhoekhuis, Amsterdam, The Netherlands

Received 26 November 2001; accepted 19 December 2001.


    Abstract
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
Background

We performed a phase I study of polyethylene glycol (pegylated, Stealth®) liposomal doxorubicin (Caelyx®, Doxil®) using a prolonged (6-week) dose interval to reduce the incidence of skin toxicity that was dose-limiting at more conventional dose intervals, and which appeared to be schedule dependent.

Patients and methods

Eligible for the study were metastatic breast cancer patients who had received a maximum of one prior therapy for metastatic disease. The defined dose levels were 60, 70, 80 and 90 mg/m2.

Results

Twenty patients were assessed at starting doses of 60 mg/m2 (n = 9) or 70 mg/m2 (n = 11). The dose-limiting toxicity was mucositis. Severe skin toxicity was not observed at the 60 mg/m2 dose level, and occurred in only one patient treated at 70 mg/m2. Significant neutropenia, alopecia, and nausea and vomiting were rare events. No clinical cardiac events occurred, despite a median cumulative doxorubicin dose of 323 mg/m2 (range 5–630 mg/m2). Partial responses were documented in five patients. Pharmacokinetics were assessed in 15 patients, and confirmed the long terminal half-life of the agent (median 77 h) demonstrated in earlier studies.

Conclusions

The recommended dose of Caelyx®/Doxil® using this schedule is 60 mg/m2 every 6 weeks. This is a safe and effective regimen that permits prolonged administration of anthracycline to patients with metastatic breast cancer.

Key words: breast cancer, liposomal doxorubicin, schedule


    Introduction
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
Doxorubicin, a reference agent in breast cancer, is a cytotoxic antibiotic whose mechanisms of action include DNA intercalation and topoisomerase II inhibition [1]. Polyethylene glycol liposomal doxorubicin, also known as pegylated liposomal doxorubicin, or Stealth® liposomal doxorubicin, is registered as Caelyx® in Europe (Schering-Plough, Brussels, Belgium) and as Doxil® in the USA (Alza Pharmaceuticals, Mountain View, CA). Encapsulation of doxorubicin by pegylated liposomes impairs its uptake by the reticuloendothelial system, resulting in significant prolongation of the serum half-life to ~50 h compared with 10 min for the free drug [24]. As a result of this pharmacology, tissue distribution of pegylated liposomal doxorubicin favours accumulation in malignant tissue [5, 6]. Although a direct comparison with free doxorubicin does not yet exist, pegylated liposomal doxorubicin is associated with less myelotoxicity, less nausea and vomiting, less alopecia [7, 8] and less cardiotoxicity [9, 10] than would be expected with free doxorubicin. Pegylated liposomal doxorubicin is associated with skin toxicity, referred to as plantar-palmar erythrodysesthesia or hand-foot syndrome, indistinguishable from that which is classically associated with infusional doxorubicin. The skin toxicity of pegylated liposomal doxorubicin is cumulative, and appears to be dose interval dependent. In breast cancer studies, 54% (7/13) of patients experienced grade 3 or 4 skin toxicity with the 60 mg/m2 every 3 weeks schedule. Severe toxicity remained unacceptably common at 46% (12/26) following dose reduction to 45 mg/m2 every 3 weeks, but fell to 16% (5/32) when the interval of the 45 mg/m2 dose was prolonged to 4-week. Mucositis is the other major toxicity of pegylated liposomal doxorubicin, although no clear schedule dependency is evident; 54% of patients experienced grade 3 or 4 mucositis at 60 mg/m2 every 3 weeks, 19% at 45 mg/m2 every 3 weeks, and 31% at 45 mg/m2 every 4 weeks [7].

The activity of pegylated liposomal doxorubicin as a single agent has been demonstrated in Kaposi’s sarcoma (20 mg/m2 every 3 weeks) [8], in ovarian cancer (40–50 mg/m2 every 3 weeks) [11, 12] and in breast cancer (45 mg/m2 every 4 weeks) [7]. The absolute doses of doxorubicin that can be delivered per cycle in the liposomal formulation are significantly lower than those of the free drug. Despite this, liposomal encapsulation does not appear to impact adversely on the anti-tumour activity of doxorubicin, probably due to the described advantages in pharmacokinetics and tissue distribution. In breast cancer, the potential benefits of liposomal doxorubicin over free doxorubicin are not insignificant. Alopecia is a major psychosocial issue for many women receiving chemotherapy. Patients receiving anthracyclines for metastatic disease often cease therapy while still in response because of a reduction in left ventricular ejection fraction, or concerns relating to cardiac toxicity at cumulative doses >450 mg/m2 [13], and elderly patients are rarely offered anthracyclines at all, again because of concerns regarding cardiac toxicity. Pegylated liposomal doxorubicin rarely causes alopecia, and cumulative doses of >500 mg/m2 have been administered safely [10]. This formulation therefore has the potential to offer effective, ambulatory therapy to women of all ages without hair loss or other significant toxicity, if the schedule-dependent skin toxicity and the mucositis are controlled.

We were not convinced that the optimal schedule for pegylated liposomal doxorubicin had yet been established. Indirect comparison of the toxicity profiles from the published schedules suggested that a longer dose interval might produce less skin toxicity without compromising activity. The selection of the 6-week dose interval, however, was largely pragmatic. It was longer than the 4-week interval that had already been studied, but would combine easily with drugs that required 3-weekly dosing. The potential benefits of the 6-week interval over the 4-week interval included reduced skin and mucosal toxicity, the financial and social benefits of fewer hospital visits, and the possibility of prolonging the duration of effective therapy without cardiac sequelae, particularly in elderly patients and in the metastatic setting. The potential disadvantage was that efficacy might be compromised.


    Patients and methods
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
This was an international multicentre phase I study performed by the Investigational Drug Branch for Breast Cancer (IDBBC) of the European Organization for Research and Treatment of Cancer (EORTC). The study was conducted in concordance with the Declaration of Helsinki and the EU Guidelines on Good Clinical Practice. The protocol was reviewed and approved by the Protocol Review Committee of the EORTC and by the institutional review board of each participating institute. The study was supported by Sequus Pharmaceuticals (now Alza Pharmaceuticals).

Eligibility criteria
Eligibility criteria included patients >=18 years of age with a histological or cytological diagnosis of locally advanced (stage IIIB) or metastatic breast cancer, with measurable disease, defined as bidimensionally measurable lesions with clearly defined margins. This was determined by: (i) chest X-ray with at least one diameter >=1 cm; (ii) CT scan, MRI or other imaging scan with both diameters >=2 cm (at least the distance between cuts of the imaging study); or (iii) palpation with both diameters >=1 cm. Bone lesions and malignant effusions were considered non-measurable. Patients >70 years of age were required to be anthracycline-naïve and to have received a maximum of one prior chemotherapy for metastatic disease. Patients <70 years of age were not permitted to have received anthracyclines for metastatic disease. Those who had received adjuvant anthracyclines were permitted a maximum of 360 mg/m2 of prior doxorubicin (prior epirubicin dose was converted to an approximate prior doxorubicin dose by multiplication by a factor of 0.6), had an anthracycline-free interval of >=12 months and had received a maximum of one prior chemotherapy for metastatic disease. Those who were anthracycline-naïve were required to have received one prior chemotherapy for metastatic disease (patients who were <70 years of age, anthracycline-naïve and had not received prior chemotherapy for metastases were preferentially offered a trial of an anthracycline–taxane combination). In addition, patients had a performance status of 0–2 and adequate organ function [platelets >=100 x 109/l, absolute neutrophil count >=2.0 x 109/l, haemoglobin >=10 g/dl, aspartate aminotransferase/alanine aminotransferase <3x normal, bilirubin <1.5x normal, serum creatinine within normal limits, left ventricular ejection fraction (LVEF) within normal limits]. Patients with any New York Heart Association grade of cardiac disease, or who were requiring medication for cardiac failure were excluded, as were those with non-malignant liver disease or a history of anthracycline hypersensitivity. Also excluded were patients with known brain metastases, uncontrolled infection, impaired mental status, or a history of another cancer other than adequately treated non-melanomatous skin cancer or carcinoma of the cervix in situ, and those who were pregnant or breast feeding. All patients provided written informed consent to participate in the study.

Therapeutic plan and toxicity evaluation
At all dose levels, patients were treated once every 6 weeks. Pegylated liposomal doxorubicin was administered on an out-patient basis as a 1 h intravenous infusion. Patients were permitted to continue therapy until disease progression or unacceptable toxicity, regardless of cumulative anthracycline dose, but six cycles were recommended.

No premedication was specified by the protocol; dexamethasone and 5-HT antagonist were used by some investigators, but these were not routinely administered and many patients received a dopamine antagonist as their only antiemetic therapy. To minimise skin toxicity, patients were instructed to wear loose clothing, to avoid activities that cause increased perfusion of the skin or mild trauma to skin surfaces, and to check skin folds, pressure points, and hands and feet daily for any localised redness or oedema. Initially, instruction in mouth care was left to the individual physician, but the protocol was amended to standardise mouth care when mucositis was observed at the 70 mg/m2 dose level; all patients then received a mouthwash of sodium bicarbonate 1/6 M 500 ml, xylocaine 2% 40 ml and nystatin 4.8 million IU (or institutional equivalent), and were instructed to administer it six times a day throughout each treatment cycle.

Eight evaluable patients were included at each dose level to permit a thorough evaluation of toxicity, an adequate sample for pharmacokinetic evaluation and a limited assessment of anti-tumour activity. If less than four patients developed a dose-limiting toxicity (DLT), the study proceeded to the next dose level. If four or more patients experienced a DLT, the maximum tolerated dose was reached and the previous dose level was defined as the recommended phase II dose (RPTD). The defined dose levels were 60, 70, 80 and 90 mg/m2.

Toxicity was assessed according to the NCIC Common Toxicity Criteria at the end of each cycle. Isotopic LVEF assessments were performed after every second cycle after a cumulative anthracycline dose of 360 mg/m2, and every cycle after 540 mg/m2. Dose-limiting toxicities were defined as any of the following occurring during the first two cycles of therapy: grade 4 neutropenia lasting >7 days or accompanied by fever >=38°C, grade 4 thrombocytopenia, grade 3 or 4 non-haematological toxicity other than alopecia, nausea or vomiting, or grade 2 plantar palmar erythrodysesthesia (PPE) requiring a 2-week dose delay.

Mucosal, skin, neutrophil and platelet toxicities were required to be recovered to grade 0 or 1 before retreatment. Dose reduction by 10 mg/m2 was defined for those patients who had experienced a DLT or who were delayed by >1 week. Those patients who experienced a DLT and were delayed by >1 week were either dose reduced by 20 mg/m2 or withdrawn from study at the investigator’s discretion. Those who could not be retreated after a 2-week delay were withdrawn from study. Patients whose bilirubin was 1.5–2x normal on day 1 of a cycle were dose reduced by 10 mg/m2, and those whose bilirubin was >2x normal were withdrawn from study.

Patients were withdrawn from study if they experienced a relative fall in LVEF of >=10% to an abnormal value (i.e. LVEF fell to <90% of their baseline, and to a value below the normal limit), or a fall of any magnitude to a value >=5% below the normal limit (i.e. LVEF fell to <95% of the normal limit, regardless of the baseline), or congestive cardiac failure. In the absence of toxicity or progression, a total of six cycles over 9 months was planned, but continuation beyond six cycles was permitted.

Response evaluation
All patients were staged within 4 weeks of commencing therapy with chest X-ray or CT scan and liver CT scan (liver ultrasound was accepted only if negative). Bone scan was optional. Therapeutic response was assessed by UICC criteria. Disease evaluation was performed after every second cycle (i.e. every 3 months), and all responses were confirmed at least 4 weeks after the initial observation. All responses were reviewed and confirmed by the assembled study investigators and an independent radiologist. Time to progression was calculated from the first day of treatment to the date when suspicion of disease progression was first documented.

Pharmacokinetic study
Blood for pharmacokinetic analysis was collected in EDTA-containing tubes during the first cycle of therapy. Samples were taken prior to therapy (time 0), at the end of the infusion (+1 h), and at times +2 h, +5 h, +7 h, +25 h, +49 h and weekly thereafter until completion of the cycle. They were stored on ice until centrifugation, within 1 h of collection, at 3000 r.p.m. for 10 min. Plasma was divided into three aliquots and stored at –20°C until transport on dry ice to the analytical laboratory (PHARMout, Sunnyvale, CA, USA). Samples were analysed for total plasma doxorubicin using reverse phase high performance liquid chromatography with fluorescence detection. The linear range of the assay for doxorubicin was established between 0.01 and 4.0 mg/l. Based on the quality control samples (at 0.025, 0.5 and 5.0 mg/l), accuracy was <4%, while between-day precision was <4.73%.

Total plasma doxorubicin concentration–time data were modelled with the ADAPT II program [14] using weighted, iterative, non-linear least squares regression, with weights related to assay error. Models investigated were one-, two- and three-compartment linear models, and a one-compartment model with saturable elimination. Goodness of fit was evaluated using Akaike’s Information Criterion (a smaller number indicated superiority of fit) [15]. For each patient and each model tested, numerical parameter estimation was repeated 10 times with initial estimates chosen randomly and independently, in order to ascertain stability of resulting parameter estimates. Population parameters were obtained using both Bayesian iterative two-stage analysis (IT2S) [16] and non-linear mixed effects methods [17].

Methods used to detect correlations between pharmacokinetic and pharmacodynamic end points included Spearman’s correlation coefficient (correcting for ties) for graded toxicities, Pearson’s correlation coefficients for all toxicities, and the Hill Emax effect model for haematological effects [14, 20].


    Results
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
Patient characteristics
Twenty patients were enrolled in the study. All were female, and their characteristics are described in Table 1. The median age was 67 years, and the oldest patient was 78 years of age. Nineteen patients (95%) had visceral disease. Although only one patient had received chemotherapy in both adjuvant and metastatic settings, 65% had received prior chemotherapy, 45% had received chemotherapy for metastatic disease and 15% had received adjuvant anthracyclines. Two patients were ineligible, as they did not have measurable disease, but they are included in all analyses. Nine patients commenced treatment at 60 mg/m2 (one was not evaluable due to a hypersensitivity reaction in cycle 1), and 11 at 70 mg/m2 (three did not receive standardised mouth care).


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Table 1. Patient characteristics (n = 20)
 
Drug delivery
There was a marked discrepancy in drug delivery between the 60 and 70 mg/m2 dose level cohorts, as described in Table 2. Of the nine patients who commenced at 60 mg/m2, three patients (33%) completed six cycles, all at full dose. Of the 11 who commenced at 70 mg/m2, only one patient (11%) completed six cycles at full dose; another six patients completed six cycles but required dose reduction from cycle two (n = 5) or cycle three (n = 1). A total of seven patients received 60 mg/m2 in cycle six; two patients, both of whom started at 70 mg/m2, completed cycle six at a dose <60 mg/m2. The most common reason for ceasing study therapy was disease progression (11 patients, 55%), however, three of these 11 had completed six cycles at the time of disease progression, and in six patients (30%) the disease remained in response or stable after six cycles (9 months) of therapy. Three patients ceased therapy due to toxicity. As the dose interval was prolonged in this study, the median time on study was 29 weeks (5.5 cycles).


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Table 2. Drug administration (n = 20)
 
One patient experienced a hypersensitivity reaction in the first minutes of her first infusion (60 mg/m2) and received no further therapy. She was therefore not evaluable for other toxicities or for efficacy.

Toxicity
Table 3 describes the observed toxicity by allocated dose level. The dose-limiting toxicity was mucositis, experienced by 9/11 patients at the 70 mg/m2 dose level (eight at grade 3 and one at grade 4). Of those nine, one patient also experienced grade 3 vulvovaginitis, one had grade 3 fatigue and one had grade 3 plantar-palmar erythrodysesthesia. An additional patient had neutropenia for >7 days, but did not experience dose-limiting mucositis. In the initial cohort of eight patients treated at 70 mg/m2, patients who had received rigorous prophylactic mouth washes (n = 5) appeared to have experienced less severe mucositis than those who had not. Three additional patients were therefore treated with strict adherence to the mouth-wash schedule, but two of them experienced dose-limiting mucositis despite these measures.


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Table 3. Worst toxicity per patient (cycles 1–2) by starting dose level (n = 19a)
 
One toxic death occurred at the 70 mg/m2 dose level. This patient was hospitalised on day 16 of her first cycle of therapy with grade 4 mucositis despite prophylactic mouth washes, grade 3 vulvovaginitis and grade 3 neutropenia. On day 18 she became confused and lapsed into a coma without fever or focal neurological signs. She then became hypotensive and died. The family refused post-mortem examination, so the exact cause of death remains uncertain.

In marked contrast, the 60 mg/m2 dose level was well tolerated. Only one patient experienced dose-limiting toxicity (grade 3 cellulitis in cycle 1 and grade 3 mucositis in cycle 2). Of the eight patients whose dose reduced from 70 mg/m2 in the first cycle to <60 mg/m2 in the second cycle, however, two experienced a recurrence of grade 3 mucositis in the second cycle.

Of note, alopecia, nausea and vomiting were rare. Neutropenia was also uncommon. Overall, only 16% of patients experienced grade 4 neutropenia, and only one haematological DLT was documented.

Table 4 describes serious adverse events according to the administered dose. The 60 mg/m2 dose level was generally extremely well tolerated over a full course of six cycles, without evidence of cumulative toxicity.


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Table 4. Grade 3–4 toxicities per cycle (cycles 1–6) by administered dose level (n = 19a)
 
No patient experienced congestive cardiac failure. As the limit of normal LVEF varied widely between the participating institutes, we adjusted all values so that 50% represents the lower limit of the normal value. Three patients (59, 73 and 79 years of age) had asymptomatic falls in their left ventricular ejection fractions of 24, 26 and 17% of baseline values, to final values equivalent to 47, 45 and 45%, respectively, occurring at cumulative anthracycline doses of 345, 360 and 420 mg/m2. Two patients achieved a cumulative anthracycline dose of >=500 mg/m2 while on study, with resting LVEFs of 71% after 595 mg/m2 (baseline 95% at 225 mg/m2) and 58% after 630 mg/m2 (baseline 52% at 270 mg/m2), respectively.

Efficacy
Table 5 describes the anti-tumour efficacy of pegylated liposomal doxorubicin using the 6-week schedule. It is important to note that the schedule of disease assessment in this study (every 2 cycles or 3 months) did not adjust for the long cycle duration. Thus, patients were required to have stable or responding disease for a minimum of 4–6 months to qualify as stable or responding.


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Table 5. Anti-tumour efficacy
 
Five patients were not evaluable for response: two had inadequate target lesions, one was inadequately followed, one died prior to evaluation, and one received less than one cycle of therapy. Five patients had partial responses. Three of these were chemotherapy-naïve, but one had received adjuvant FEC (5-fluorouracil, epirubicin, cyclophosphamide), and the other had received adjuvant CMF (cyclophosphamide, methotrexate, 5-fluorouracil) and docetaxel as first-line therapy for metastatic disease. Target lesions were in liver in four patients, and in pleura in the other. The median duration of response was 36 weeks (range 32–81 weeks), and the median time to progression was 33 weeks (range 2–81 weeks). Sixty-three per cent (12/19) of evaluable patients remained on study and progression-free after 6 months of therapy.

Pharmacokinetics
Individual doxorubicin pharmacokinetic profiles were obtained for 15 patients during the first course of therapy (seven re-ceiving 60 mg/m2, eight receiving 70 mg/m2, for a total of 172 observations).

(i) Individual modelling
The one-compartment model with saturable (Michaelis–Menten) elimination was unstable and did not fit the data well. The Akaike’s Information Criterion value for the three-compartment linear model was smaller than that of the one- and two-compartment linear models for only two patients, but in both cases the three-compartment parameter estimates were extremely unstable in the sense that estimates resulting from different choices of initial parameter values were highly variable. Data for all patients were therefore fitted by either one-compartment (n = 9) or two-compartment linear (n = 6) models.

(ii) Population modelling
The population pharmacokinetic parameters for the one-compartment linear model, estimated by iterative two-stage method, were similar for the two subgroups (60 and 70 mg/m2) (Table 6). Therefore, the data from the two dose levels were pooled in a single population analysis. The use of Bayesian priors in the iterative two-stage method allowed us to perform population two-compartment linear modelling on the whole population (n = 15), despite the unstability of two-compartment model parameters for some individual profiles. Due to numerical difficulties, Nonmem population analysis was performed using the one-compartment linear model.


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Table 6. Mean (CV%) pharmacokinetic parameters estimated by IT2S (one-compartment linear model)
 
Table 7 includes descriptive statistics [mean and coefficient of variation (CV%)] for individual parameters (one- and two-compartment linear models), iterative-two-stage results (two-compartment linear model) and Nonmem results (one-compartment linear model). A small volume of distribution (1.1–1.8 l/m2, comparable to the plasma volume), a terminal half-life of 76–99 h and a mean residence time of ~5 days were estimated.


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Table 7. Mean (CV%) pharmacokinetic parameter estimates in Caelyx®-treated patients
 
No significant correlation (P = 0.05) was found between pharmacokinetic parameters (AUC, clearance, terminal half-life, observed or fitted maximum concentration and mean residence time) and pharmacodynamic end points (LVEF, alopecia, stomatitis, PPE, anaemia, neutropenia and thrombocytopenia).


    Discussion
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
Liposomal encapsulation of doxorubicin dramatically alters both its pharmacodynamics and pharmacokinetics, and the toxicity profile of the encapsulated drug is not only dose- but also schedule-dependent. Prolongation of the cycle interval clearly reduced the incidence of dose-limiting PPE. While the published 3-week schedules are associated with an incidence of grade 3 or 4 skin toxicity of 46–54%, and the 4-week schedule reported an incidence of 16%, only one episode of grade 3 skin toxicity (5.3% of patients, 1.2% of cycles) was observed using this 6-week schedule, and no grade 2–4 skin toxicity was observed at the 60 mg/m2 dose level. Thus, the skin toxicity associated with this drug at a dose intensity of 10 mg/m2/week appears to be a feature of the dose interval rather than the dose per cycle.

In the absence of the schedule-dependent skin toxicity, mucositis emerged as the dose-limiting toxicity. The incidence of mucositis seen with this 6-week schedule (53%) was comparable to that seen with the previously published 60 mg/m2 every 3 weeks schedule (54%). Of the patients who received 45 mg/m2 in that study, 19–31% had dose-limiting mucositis. In our study, only one patient who commenced at 60 mg/m2 every 6 weeks (12.5%) experienced dose-limiting mucositis. A total of five cycles (8.3%) at this dose and schedule were associated with severe mucositis, of which two were in patients who had previously experienced this toxicity at the higher dose level. When Tables 3 and 4 are compared, it is immediately obvious that very few serious adverse events occurred after the first two cycles, indicating that dose reduction from 70 to 60 mg/m2 was generally effective in preventing further severe toxicity.

Other acute toxicities classically associated with anthracycline therapy (nausea, vomiting, alopecia) were observed far less frequently than would be expected with free doxorubicin. Some perspective on the haematological toxicity can be gleaned from comparison with other single-agent anthracycline studies performed by the EORTC. In EORTC 10923 [18], single-agent doxorubicin, at a dose of 75 mg/m2, was administered as first or second line therapy for metastatic breast cancer in anthracycline-naïve patients. In the first cycle of first-line therapy, 53% of patients experienced grade 4 neutropenia, and in the first cycle of second-line therapy the corresponding figure was 44%. Overall, 20% of patients ex-perienced febrile neutropenia while receiving free doxorubicin in that study. In contrast, no patient experienced grade 4 neutropenia in the first cycle of pegylated liposomal doxorubicin in this study; only 16% of patients reported this toxicity at any time during therapy, and febrile neutropenia did not occur, although undocumented haematological toxicity may have contributed to the toxic death.

This study was too small to contribute significantly to the published data regarding the cardiac safety of pegylated liposomal doxorubicin; however, no clinical cardiac events occurred, and two patients safely received cumulative doxorubicin doses of >500 mg/m2.

As only one patient received more than two cycles at 70 mg/m2, the efficacy results reflect almost universal therapy at 60 mg/m2. At first glance, the response rate of 25% is somewhat lower than would normally be expected with an anthracycline, however, this figure should be interpreted in the light of a number of observations. First, the sample size is small, and the confidence intervals are therefore wide. Secondly, this was not a classical anthracycline study population; patients were elderly (median age 67 years) and all but one had visceral disease. Thirdly, a large number (25%) of patients were not evaluable for response, but have been included in the denominator according to the intention-to-treat principle. Finally, we chose to assess response after every second cycle without adjustment for the long dose interval, so that a minimum of 4 months was required for a response to be confirmed. The median time-to-progression is less affected by these factors, and is a very respectable 33 weeks.

Consistent with previous population pharmacokinetic studies of pegylated liposomal doxorubicin in AIDS-related Kaposi’s sarcoma patients [2, 3], the majority of individual plasma doxorubicin concentration–time data and the pooled population data were best described by a two-compartment linear model.

When compared with previous iterative-two-stage pharmacokinetic results in patients with prostate cancer [19] and breast cancer [20], terminal half-life is comparable (76–99 h in the present study versus 70–90 h in [19] and 62–86 h in [20]), while clearance (Cl) and steady-state volume of distribution (Vss) appear to be 45% lower in the present study (Cl {approx} 15 ml/h/m2 here versus 44–45 ml/h in [19] and 32–43 ml/h in [20]; Vss {approx} 1.65–1.8 l/m2 here versus 5 l in [19] and 3.5–4.0 l in [20]). The predicted peak plasma concentrations obtained in this study were consistently 80% higher than in previous publications. Some of these differences may be ascribed to the different populations involved, differences in analytical assays and methodological differences (e.g. variable infusion rates and durations, modelling techniques [20]).

No correlation between pharmacokinetic and pharmacodynamic end points was observed. In particular, possibly due to the very low incidence of PPE, our study was unable to address a previous report [20] correlating half-life with this toxicity.

The recommended dose level of pegylated liposomal doxorubicin using a 6-week schedule is 60 mg/m2, as this dose has been demonstrated to be very well tolerated over multiple cycles in an elderly population. Significant activity has been demonstrated in a population with visceral metastatic breast cancer. This schedule may have pharmacoeconomic advantages over shorter dose intervals, and this should be assessed in future studies.


    Conclusions
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
PPE is a schedule (dose interval)-dependent toxicity of pegylated liposomal doxorubicin, while mucositis appears to be a feature of the dose administered per cycle. The dose-limiting toxicity of the 6-week dose interval schedule is mucositis. The recommended dose of pegylated liposomal doxorubicin (Caelyx®, Doxil®) using a 6-week schedule is 60 mg/m2. At the recommended dose, this anthracycline formulation is extremely well tolerated by young and old patients alike, and can be safely administered for prolonged periods without evidence of cumulative toxicity. Activity has been demonstrated in patients with visceral disease and prior anthracycline and taxane exposure, as well as in elderly patients.


    Acknowledgements
 
The authors thank the J.-C. Heuson Foundation for supporting the clinical research fellowship of Dr A. Hamilton, and Mireille Delval for excellent secretarial assistance.


    Footnotes
 
+ Correspondence to: Dr M. Piccart, Institut Jules Bordet, Department of Medicine, 1 rue Héger Bordet, 1000 Brussels, Belgium. Tel: +32-2-541-32-06; Fax: +32-2-538-08-58; E-mail: martine.piccart@bordet.be Back


    References
 Top
 Abstract
 Introduction
 Patients and methods
 Results
 Discussion
 Conclusions
 References
 
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