Differences in regulatory T cells (Tregs) in responding and non-responding patients with indolent B-cell or mantle cell lymphoma during treatment with lenalidomide and rituximab ± dexamethasone.

8060 Background: Lenalidomide may enhance anti-tumor immune responses by inhibiting Tregs and by augmenting NK-cell mediated antibody-dependent cytotoxicity. These immunologic effects may synergize when lenalidomide is combined with rituximab. Methods: We are conducting a single center, open label phase II trial of lenalidomide and rituximab +/- dexamethasone in patients (pts) with indolent B-cell lymphomas or mantle cell lymphoma refractory to rituximab, defined as failure to respond to or progression within 6 months of rituximab-monotherapy, rituximab-containing chemotherapy, or rituximab-maintenance. The regimen consists of two 28-day treatment cycles of lenalidomide 10 mg daily +/- dexamethasone 8 mg once weekly (Part 1). During cycle 3, pts receive 4 weekly doses of rituximab 375 mg/m2 while continuing lenalidomide +/- dexamethasone (Part 2). After cycle 3, lenalidomide +/- dexamethasone is continued until disease progression, as tolerated. Peripheral blood is collected for immune assessment by flow ...