Changes in regulatory T-cells in responding and non-responding patients with indolent B-cell or mantle cell lymphomas during treatment with lenalidomide, dexamethasone, and rituximab.

8085 Background: Lenalidomide may enhance anti-tumor immune responses by inhibiting regulatory T-cells (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, dexamethasone, and rituximab in patients (pts) with indolent B-cell or mantle cell lymphomas refractory to rituximab, defined as failure to respond to or progression within 6 months of rituximab monotherapy, prior rituximab-chemotherapy, or rituximab maintenance. The regimen consists of two 28-day treatment cycles of lenalidomide 10 mg daily and dexamethasone 8 mg once weekly (Part 1). During cycle 3, all pts receive rituximab 375 mg/m2 weekly for 4 doses (Part 2). Lenalidomide-dexamethasone therapy is continued during and after rituximab until disease progression. Peripheral blood is collected for assessment of immune parameters by flow cytometry at enrollmen...