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Originally published as JCO Early Release 10.1200/JCO.2005.04.164 on December 14 2004 © 2005 American Society of Clinical Oncology. Effect of Single-Agent Rituximab Given at the Standard Schedule or As Prolonged Treatment in Patients With Mantle Cell Lymphoma: A Study of the Swiss Group for Clinical Cancer Research (SAKK)From the Oncology Institute of Southern Switzerland, Bellinzona; Swiss Institute of Applied Cancer Research Coordinating Centre, Bern; Institute of Medical Oncology, Inselspital, University of Bern; Swiss Reference Centre for Lymphoma Pathology; Kantonsspital, Aarau; Kantonsspital St Gallen, St Gallen; Kantonsspital Luzern, Luzern; Universitätsspital Zürich, CHUV, Lausanne, Switzerland Address reprint requests to Michele Ghielmini, MD, Oncology Institute of Southern Switzerland, Ospedale San Giovanni, 6500 Bellinzona, Switzerland; e-mail: mghielmini{at}ticino.com
PURPOSE: To evaluate the effect of single-agent rituximab given at the standard or a prolonged schedule in patients with newly diagnosed, or refractory or relapsed mantle cell lymphoma (MCL). PATIENTS AND METHODS: After induction treatment with the standard schedule (375 mg/m2 weekly x 4), patients who were responding or who had stable disease at week 12 from the start of treatment were randomly assigned to no further treatment (arm A) or prolonged rituximab administration (375 mg/m2) every 8 weeks for four times (arm B). RESULTS: The trial enrolled 104 patients. After induction, clinical response was 27% with 2% complete responses. Among patients with detectable t(11;14)-positive cells in blood and bone marrow at baseline, four of 20, and one of 14, respectively, became polymerase chain-reactionnegative after induction. Anemia was the only adverse predictor of response in the multivariate analysis. After a median follow-up of 29 months, response rate and duration of response were not significantly different between the two schedules in 61 randomly assigned patients. Median event-free survival (EFS) was 6 months in arm A versus 12 months in arm B; the difference was not significant (P = .1). Prolonged treatment seemed to improve EFS in the subgroup of pretreated patients (5 months in arm A v 11 months in arm B; P = .04). Thirteen percent of patients in arm A and 9% in arm B presented with grade 3 to 4 hematologic toxicity. CONCLUSION: Single-agent rituximab is active in MCL, but the addition of four single doses at 8-week intervals does not seem to significantly improve response rate, duration of response, or EFS after treatment with the standard schedule.
Mantle cell lymphoma (MCL) has a low-grade histologic presentation but an aggressive clinical course. It is both rapidly progressing and incurable, with a median survival of only 3 years.1 Patients usually respond to first-line therapy with conventional agents, but the remission duration is short, and further lines of therapy are less effective. High-dose chemotherapy with autologous stem-cell transplantation can prolong remission, but is only feasible in younger and otherwise healthy patients. Several drugs are active in this disease, but none can alter its natural history.2 Therefore, the search for new active drugs in MCL remains important. Rituximab, a human/mouse chimeric monoclonal antibody with specificity for the CD20 B-cellsurface antigen, is active as a single-agent treatment for non-Hodgkin's lymphoma. Response rates (RRs) of 45% to 70% have been observed in several types of indolent lymphoma,3,4 while in more aggressive non-Hodgkin's lymphoma, RRs are approximately 30%.5 When added to chemotherapy, rituximab has been shown to significantly improve survival compared with chemotherapy alone.6 The majority of clinical experience with rituximab in MCL has been collected in patients receiving the standard schedule (375 mg/m2 weekly x 4). In a study of 34 previously untreated and 40 previously treated patients, the RRs were 38% and 37%, respectively, with 16% and 14% complete response (CR). The time to progression was 7 months, and the response duration was 1 year.7 Other smaller studies reported similar results.5,8 Because pharmacokinetics data suggested that persistence of rituximab in patients' blood is associated with a higher RR,9 we speculated that a longer exposure to rituximab might augment its biologic effect. Two parallel trials (one in follicular lymphoma and one in MCL) were designed to test this hypothesis. We compared the standard rituximab schedule with a prolonged rituximab schedule in which the standard treatment was followed by a single 375-mg/m2 infusion every 2 months at four intervals, in order to maintain a biologically active serum concentration for approximately 1 year. The 2-month interval was chosen based on preliminary pharmacokinetics data.9 This article reports the results of the trial in MCL.
Trial Design Patients were enrolled from January 1998 to January 2002 in 23 institutions. The trial was approved by the local ethics committee of each participating institution and was conducted in accordance with the Declaration of Helsinki and currently applicable amendments. All patients gave written informed consent. Patients were initially treated with rituximab 375 mg/m2 per week for 4 weeks ("induction" phase). Patients with stable disease (SD), or in partial response (PR) or CR at week 12 (from treatment start) were randomly assigned in a 1:1 ratio to no further treatment (arm A, "standard treatment") or to treatment with a single infusion of rituximab 375 mg/m2 at week 12, and again at months 5, 7, and 9 (arm B, "prolonged treatment"). The randomization was stratified, using the minimization method,10 according to status of disease at trial entry (first presentation v refractory or relapsed), response to induction treatment (SD v response), and center. Patients were centrally randomized by fax via the Swiss Group for Clinical Cancer Research (SAKK) Trials Office in Bern, Switzerland. On disease progression or relapse, further treatment was at the treating physician's discretion. Event-free survival (EFS) time was the primary end point and was calculated as the time from first induction infusion to progression, relapse, second tumor, or death from any cause. Remission duration was defined in the same way, but was restricted to responding patients. For the randomized phase of the trial, a group sequential design with two interim analyses and one final analysis using EFS as the primary end point was adopted.
Patients
Trial Assessments
Statistical Methods
The comparisons between treatment arms or groups defined by other factors (ie, previously treated v chemotherapy-naïve, or responders v nonresponders) were carried out by Wilcoxon rank sum test for continuous variables and by The simultaneous impact of some potential predictive variables on clinical response and EFS was analyzed by multiple logistic regression and multiple Cox regression, respectively, employing a stepwise model selection procedure. All tests were two-sided. No adjustment for multiple comparisons was performed. CIs for RR, OR, HR, and median EFS time are provided where appropriate. For randomly assigned patients, all between-arm comparisons were carried out according to the intention-to-treat principle.
Patient Characteristics The characteristics of the 104 patients enrolled are summarized in Table 1. Fifteen patients were retrospectively judged ineligible: 14 because the pathology review could not confirm the mantle cell histology and one because the disease was not measurable according to protocol criteria. One patient was not assessable because he died before the trial treatment could be initiated.
Of the 88 eligible and assessable patients, 27 were not randomly assigned to the second phase of the study: 24 because of disease progression and three because of major toxicity during the induction phase. The clinical and pathological characteristics of the 61 randomly assigned patients (27 in arm A and 34 in arm B) were similar in the two arms (Table 1) and had, as expected, more favorable characteristics at randomization than at baselinethe levels of hemoglobin, platelets, and lactate dehydrogenase were nearer to normal, and the incidence of bulky disease and BM infiltration was lower. The proportion of patients having responded to previous treatments was similar in the two arms (44% v 47%, respectively), while the response to induction treatment (37% v 47%, respectively) tended to be higher in arm B.
Description of Treatment Prolonged treatment phase. The majority of patients in the prolonged treatment arm received the treatment according to the protocol. Fifteen patients had an interruption of the treatment before the fourth administration: two because of toxicity, 11 because of disease progression or relapse, and two because of refusal. The timing of the infusions followed the protocol for the majority of patients, but with a rather wide range: the planned week-20 infusion was administered at median week 20 (range, 15 to 26 weeks), week-28 infusion at median week 28 (range, 25 to 36 weeks), week-36 infusion at median week 36 (range, 30 to 47 weeks), and week-52 infusion at week 51 (range, 47 to 63 weeks).
Objective Response Prolonged treatment/observation phase. The response assessments at 3, 7, 12, 18, and 24 months, and the overall best response for randomly assigned patients are summarized in Figure 1. In arm A, the proportion of patients with response decreased steadily from 33% (95% CI, 17% to 54%) at week 12, to 26% (95% CI, 11% to 46%) at month 12 and 15% (95% CI, 4% to 34%) at 24 months. In arm B, the proportion of patients remained initially stable, with 39% (95% CI, 23% to 58%) at week 12 and 36% (95% CI, 20% to 55%) at month 12, declining then to 9% (95% CI, 2% to 24%) at 24 months from the start of treatment. The proportion of patients in CR remained low in both arms: overall, 11% of patients in arm A and 12% in arm B experienced a CR at some time during the study. The number of patients improving their response in the first 2 years (from PR to CR, from SD to CR, or from SD to PR) was low in both armsthree cases in arm A and six cases in arm B. The difference in RR between arms was not statistically significant at any time point. Among patients with BM involvement at baseline and with BM re-evaluation after random assignment, six of seven in arm A and seven of 11 in arm B became negative. Among responders at week 12 (n = 22), the proportion of CR and PR at month 12 was surprisingly higher in arm A compared with arm B (67% v 54%, respectively), but the difference was not significant (P = .67).
In the selected population of randomized patients (ie, eligible, assessable, and not progressing under induction treatment with rituximab), the overall best response was 41% (95% CI, 22% to 61%) for arm A and 55% (95% CI, 36% to 72%) for arm B (P = .31). The overall best response for chemotherapy-naive patients (n = 27) was 39% (95% CI, 14% to 68%) for arm A and 50% (95% CI, 23% to 77%) for arm B (P = .70). The median time to response was 9 weeks in both arms, and the median remission duration among week-12 responders was 15 months in both arms.
EFS
Toxicity During the induction phase, the majority of toxicities were mild infusion-related symptoms during the first infusion. Additionally, 13% and 11% of patients had grade 3 and 4 toxicity, respectively, including two episodes (one patient) of pneumonia, three episodes (two patients) of pain, three cases (two patients) of dyspnea, three reports (one patient) of thrombocytopenia, one major cardiac event, one allergic reaction, and one case of nausea. Cardiac ejection fraction was reassessed in 40 patients at week 12 and remained stable (from 63% [range, 50% to 78%] at baseline to 64% [range, 44% to 79%]). Seventeen cases of serious adverse events were documented during induction treatment. Two patients died of causes other than progressionone of a probable myocardial infarction and one of Pneumocystis carinii pneumonia. After random assignment, nonhematological grade 3 or 4 toxicity included two cases of pain, one diarrhea episode, and one case of cholecystitis in arm A; and one patient experienced three episodes of pneumonia, one case of hepatitis, and one renal failure case in arm B. Grade 3 or 4 hematological toxicity was observed in 13% of patients in arm A and 9% in arm B. Among 19 patients with cardiac function reassessed after random assignment (seven in arm A and 12 in arm B), the median ejection fraction was 62% (range, 60% to 66%) in arm A and 59% (range, 40% to 75%) in arm B. The number of serious adverse events after random assignment (including follow-up period) was six in arm A (including two second tumors) and eight in arm B (including one second tumor, one septic shock, and one cardiac death). The lymphocytes subset analysis (performed excluding patients with baseline WBC > 10 x 109/L who were suspected of having leukemic disease) showed a very early and important reduction of circulating B cells, while T-helper, T-suppressor, and natural killer cells remained approximately stable during the induction phase. The evolution of B lymphocytes for randomly assigned patients throughout the first 12 months of follow-up is shown in Figure 4. Median B-cell levels returned to levels similar to baseline values after 9 months in arm A, while in arm B, the B-cell recovery had still not taken place after 12 months. The difference at 9 months was significant (median, 90.5 x 106/L v 13.9 x 106/L; P = .03).
This trial confirms that rituximab is an agent with activity in MCL, with a RR in the range of 30% and a median response duration of 6 to 12 months. A longer median EFS was obtained with the prolonged schedule, but the difference between the two EFS curves of the standard and the prolonged treatment arms was not statistically significant. Rituximab was generally well tolerated, and B-cell depletion, which was of longer duration in the prolonged treatment arm, did not translate into a higher incidence of infections. In phase II trials, a minimum RR of 30% is required for a drug to be considered a potentially active new anticancer agent. Although rituximab reaches this threshold, the relatively short duration of response (compared with what was seen in other types of lymphomas), and the fact that this RR is surprisingly not higher in chemotherapy-naïve patients relegates the antibody in the group of modestly active drugs for this disease. It is therefore not astonishing that the effect of a prolonged administration is similarly modest. Compared with the only other sufficiently sized study of single-agent rituximab in MCL,7 our trial has the following advantages: larger sample size, histologic diagnosis reviewed centrally according to strict criteria, and evaluation of the evolution of lymphocyte subsets and molecular remission (at least in a subset of patients). Unfortunately, although this latter analysis was performed in the majority of patients at trial entry, it was repeated in only a minority at restaging, reducing the reliability of the molecular response results. Compared with the other series, we observed a slightly lower RR (possibly due to our more stringent response criteria), a similar response duration, and concordant prognostic factors.7 The parallel trial, which was conducted with exactly the same design by our group in patients with follicular lymphoma, showed that (in rituximab responders only) the prolonged schedule significantly doubles the median EFS (from 12 to 23 months, P = .02), and we concluded that single-agent rituximab, particularly if given with a prolonged schedule, is a valid treatment option for follicular lymphoma.12 The same conclusion cannot be made for MCL. In this disease, single-agent rituximab is less active at either schedule; therefore, the drug should instead be incorporated into combination schemes with chemotherapy. Several phase II trials and preliminary data from randomized studies confirm this assumption.15,16 Because rituximab can induce molecular remissions, its use in combination with chemotherapy as an in vivo purging agent for peripheral stem collection is theoretically sound; this application in MCL has already shown promising results.17 The use of rituximab maintenance therapy following autologous stem-cell transplantation also seems to improve outcomes in patients with advanced MCL.18 It is not surprising that MCL responds less well to single-agent rituximab than indolent lymphomas (the same is true for chemotherapy), but it is surprising that the agent shows a similar effect in chemotherapy-naïve and pretreated patients: in oncology practice, RR and duration are usually higher in newly diagnosed patients. Even though the same observation was made by Foran et al,7 in our trial, the number of previous regimens in pretreated patients is a prognostic factor, raising the suspicion that the amount of previous treatment is indeed important. The similar outcomes in chemotherapy-naïve and pretreated patients observed in our trial could be explained by the small group sizes (38 and 66 patients, respectively) and/or an unfavorable selection of chemotherapy-naïve patients proposed for rituximab monotherapy as a first-line treatment.
The following authors or their immediate family members have indicated a financial interest. No conflict exists for drugs or devices used in a study if they are not being evaluated as part of the investigation. Owns stock (not including shares held through a public mutual fund): Gabriella Pichert, Roche. Acted as a consultant within the last 2 years: Michele Ghielmini, Roche; Sergio Cogliatti, Roche; Thomas Cerny, Roche. Received more than $2,000 a year from a company for either of the last 2 years: Michele Ghielmini, Roche; Sergio Cogliatti, Roche; Thomas Cerny, Roche.
We thank Patricia Katz and Corinne Friedly for central data management, Dina Delle Pezze for the fluorescence-activated cell sorting analysis of lymphocyte subsets, and Michela Gisi for assistance in molecular biology analysis.
Supported in part by research funding from Roche Pharma Schweiz AG to the Swiss Group for Clinical Cancer Research (SAKK). Presented orally (in summary) at the 2003 Annual Meeting of the European Haematology Association (EHA), Lyon, France, June 2003. Authors' disclosures of potential conflicts of interest are found at the end of this article.
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Copyright © 2005 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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