Involved-Field Radiation Therapy in Treating Patients With Previously Untreated Stage I or Stage II Low-Grade Non-Hodgkin's Lymphoma

RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Giving radiation therapy in different ways may kill more tumor cells. It is not yet known which regimen of radiation therapy is more effective for non-Hodgkin's lymphoma. PURPOSE: Randomized phase III trial to compare the effectiveness of radiation therapy to the involved area with or without total-body irradiation in treating patients who have low-grade stage I or stage II non-Hodgkin's lymphoma that has not previously been treated.