Lenalidomide With or Without Rituximab After Standard Chemotherapy in Treating Patients With Diffuse Large B-Cell Non-Hodgkin Lymphoma

RATIONALE: Lenalidomide may stop the growth of cancer cells by blocking blood flow to the cancer. It may also stimulate the immune system in different ways and stop cancer cells from growing. Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some block the ability of cancer cells to grow and spread. Others find cancer cells and help kill them or carry cancer-killing substances to them. It is not yet known whether lenalidomide is more effective with or without rituximab in treating diffuse large B-cell non-Hodgkin lymphoma. PURPOSE: This randomized phase II trial is studying lenalidomide to see how well it works when given with or without rituximab after standard chemotherapy in treating patients with diffuse large B-cell non-Hodgkin lymphoma.