Background: Mantle cell lymphoma (MCL) is an unfavorable subtype of B-cell non-Hodgkin lymphoma characterized by median progression-free survival (PFS) and median overall survival (OS) of only 1.5 and 3–4 years respectively. Although high-dose therapy and an autotransplant may prolong OS, it does not result in a long-term disease free survival. Therefore, there is a need for novel therapeutic approaches for this entity.

Methods: We conducted a single-arm phase II study in subjects with newly-diagnosed MCL to assess efficacy and safety of a novel intensive regimen R-MACLO-IVAM-T, a modification of a protocol designed by Magrath et al (

). The study size of 22 patients was based on precision of a two-sided 95% confidence interval for the 18-month progression free survival rate. Eligible subjects had a confirmed diagnosis of MCL using WHO criteria, age 18–75 years, ECOG PS ≤ 2, adequate organ function and no history of HIV or prior cancer. Lymphoma extent at presentation was assessed by standard staging procedures as well as esophagogastroduodenoscopy and colonoscopy. Prior to initiating thalidomide maintenance, subjects were enrolled in the STEPS® program. Cycle 1 consisted of R-MACLO: rituximab 375 mg/m2 IV on day 1, doxorubicin 45 mg/m2 IV on day 1, cyclophosphamide 800 mg/m2 IV on day 1 and 200 mg/m2/day on days 2–5, vincristine 1.5 mg/m2 on days 1 and 8 capped to 2mg, methotrexate 1.2 g/m2 IV on day 10 over 1 hour followed by 5.52 g/m2 IV over 23 hours followed by leucovorin 36 hours later. G-CSF was begun on day 13. When the ANC was >1.5×109/L, cycle 2 with R-IVAM was begun: rituximab 375 mg/m2 IV day 1, cytarabine 2 g/m2 IV every 12 hours on days 1 and 2, etoposide, 60 mg/m2 on days 1–5 and ifosfamide 1.5 g/m2 on days 1–5 with mesna. Fourteen days after ANC recovery from cycle 2, cycles 3 and 4 were given in identical fashion to 1 and 2. Four weeks after ANC recovery from cycle 4, subjects were re-staged and responses were assessed by standard criteria. Subjects achieving CR at the end of therapy received thalidomide 200 mg/day until MCL relapse or intolerable toxicity.

Results: Accrual started in 4/2004 and ended in 3/2008 when the planned 22 subjects were enrolled. All subjects were evaluable for toxicity and 21 were evaluable for response. Median age was 56.5 years (range 39–73). All subjects had at least stage 3 disease with bone marrow involvement in 19 and gastrointestinal involvement in 10. Distribution according to IPI: 0–1 factor, 3; 2 factors, 8; 3 factors, 8; and 4 factors, 3. Twenty subjects had diffuse variant and 2 had blastic variant. Nineteen subjects completed all 4 cycles of therapy; treatment was stopped in 2 subjects after 2 and 3 cycles respectively, and one subject died during the first cycle. Of the 21 subjects completing 2 cycles of therapy, 20 achieved CR and one PR. Two subjects relapsed at 9 and 33 months respectively, while 19 remain relapse free after median follow-up of 25 months (range 5–51). With a total follow-up of 545 months, the estimated relapse rate is 4.4 per 100 patients per year. There were two deaths: 1 from sepsis on cycle 1 day 8 and the other in CR at 38 months from non-small cell lung cancer diagnosed 19 months after MCL. Common severe toxicities were grade 3–4 neutropenia, thrombocytopenia and anemia in 33%, 19% and 17% of R-MACLO cycles and in 50%, 88% and 68% of R-IVAM cycles respectively. There were 14 bacteremias in 82 cycles, 12 of which were after R-IVAM therapy. Six episodes of reversible grade 1–2 renal toxicity occurred after methotrexate. The thalidomide maintenance dose was reduced in 6 subjects due to grade 3–4 neutropenia and reduced or stopped in 8 subjects because of grade 3–4 peripheral neuropathy. Patients remain under follow-up for relapse and survival.

Conclusions: R-MACLO-IVAM-T results in a high overall response rate of 100% (95% CR and 5% PR) and a low relapse rate. At a median follow-up of 25 months, median PFS and OS were not reached. The 2-year actuarial PFS of 94% compares favorably with previously reported 2-year actuarial PFS of 40% and 67% for CHOP-like regimens without and with upfront bone marrow transplantation (

). The contribution of thalidomide maintenance to this outcome requires additional study. A multicenter clinical trial is suggested.

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