Combination Chemotherapy Plus Filgrastim With or Without Rituximab in Treating Older Patients With Non-Hodgkin's Lymphoma

RATIONALE: Drugs used in chemotherapy use different ways to stop cancer cells from dividing so they stop growing or die. Monoclonal antibodies such as rituximab can locate tumor cells and either kill them or deliver tumor-killing substances to them without harming normal cells. Combining monoclonal antibody therapy with chemotherapy may kill more tumor cells. It is not yet known if combination chemotherapy plus filgrastim is more effective with or without rituximab in treating non-Hodgkin's lymphoma. PURPOSE: Randomized phase III trial to determine the effectiveness of combination chemotherapy plus filgrastim with or without rituximab in treating older patients who have non-Hodgkin's lymphoma.