Combined lenalidomide, low-dose dexamethasone, and rituximab achieves durable responses in rituximab-resistant indolent and mantle cell lymphomas.

BACKGROUND: Lenalidomide is an immunomodulatory drug with effects on the immune system that may enhance antibody-dependent cell-mediated cytotoxicity and reverse tumor-induced immune suppression. Furthermore, single-agent lenalidomide has therapeutic activity in relapsed/refractory B-cell lymphomas. These immunologic effects potentially may enhance the action of rituximab. METHODS: To test the efficacy of lenalidomide combined with rituximab, the authors conducted a phase 2 trial of lenalidomide, low-dose dexamethasone, and rituximab in patients who had rituximab-resistant, relapsed/refractory, indolent B-cell or mantle cell lymphomas. Patients received two 28-day treatment cycles of lenalidomide 10 mg daily and dexamethasone 8 mg once weekly (part I). During cycle 3, 4 weekly doses of rituximab 375 mg/m2 were administered with lenalidomide-dexamethasone (part II). After the part II response assessment, stable or responding patients continued to receive lenalidomide-dexamethasone. RESULTS: Twenty-seven patients with follicular (n=18), mantle cell (n=5), small lymphocytic (n=3), and marginal zone (n=1) lymphomas started therapy; 3 of 27 patients discontinued therapy because of adverse events and were not evaluable for response. For 24 patients, the overall response rate after part I was 29% (4 patients had a complete response [CR] or CR unconfirmed, and 3 patients had a partial response), and the overall response rate after part II was 58% (8 patients had a CR, and 6 patients had a partial response). For 27 patients, at a median follow-up of 12.2 months, the median progression-free survival was 23.7 months. CONCLUSIONS: The combination of lenalidomide, low-dose dexamethasone, and rituximab achieved high response rates with durable responses in patients with rituximab-resistant, indolent B-cell and mantle cell lymphomas. Overall response rate increased from 29% after two 28-day cycles of lenalidomide and low-dose dexamethasone to 58% after the addition of rituximab, suggesting that lenalidomide can overcome resistance to rituximab.