Durable responses with the metronomic rituximab and thalidomide plus prednisone, etoposide, procarbazine, and cyclophosphamide regimen in elderly patients with recurrent mantle cell lymphoma

BACKGROUND: Targeting the tumor microenvironment and angiogenesis is a novel lymphoma therapeutic strategy. The authors report safety, activity, and angiogenic profiling results with the rituximab and thalidomide plus prednisone, etoposide, procarbazine, and cyclophosphamide (RT-PEPC) regimen in patients with recurrent mantle cell lymphoma (MCL). METHODS: RT-PEPC included induction (Months 1-3) of rituximab 4 times weekly, daily thalidomide (50 mg), and PEPC followed by maintenance thalidomide (100 mg), oral PEPC titrated to the neutrophil count, and rituximab every 4 months. Endpoints included safety, efficacy, quality of life (QoL), and translational studies, including tumor angiogenic phenotyping, plasma vascular endothelial growth factor (VEGF), and circulating endothelial cells. RESULTS: Twenty-five patients were enrolled, and 22 were evaluable. The median age was 68 years (range, 52-81 years), 24 patients (96%) had stage III or IV disease, 18 patients (72%) had an International Prognostic Index (IPI) score of 3 to 5, and 20 patients (80%) had high-risk Mantle Cell International Prognostic Index (MIPI) scores. Patients had received a median of 2 previous therapies (range, 1-7 previous therapies), and 15 patients (60%) had progressed on bortezomib. At a median follow-up of 38 months, the overall response rate was 73% (complete response [CR]/unconfirmed CR rate, 32%; partial response [PR] rate, 41%; n=22 patients), and the median progression-free survival was 10 months. Four CRs were ongoing (≥6 months, ≥31 months, ≥48 months, and ≥50 months). Toxicities included grade 1 and 2 fatigue, rash, neuropathy, and cytopenias, including grade 1 and 2 thrombocytopenia (64%) and grade 3 and 4 neutropenia (64%). Two thromboses and 5 episodes of grade 3 or 4 infections occurred. QoL was maintained or improved. Correlative studies demonstrated tumor autocrine angiogenic loop (expression of VEGF A and VEGF receptor 1) and heightened angiogenesis and lymphangiogenesis in stroma. Plasma VEGF levels and circulating endothelial cells trended down with treatment. CONCLUSIONS: RT-PEPC had significant and durable activity in MCL with manageable toxicity and maintained QoL. Novel, low-intensity approaches warrant further evaluation, potentially as initial therapy in elderly patients.