Rituximab in Treating Patients With Newly Diagnosed Stage II, Stage III, or Stage IV Follicular Non-Hodgkin's Lymphoma

DISEASE CHARACTERISTICS: * Histologically confirmed follicular non-Hodgkin's lymphoma * Diagnosed within the past 3 months * Grade 1, 2, or 3a disease * Stage II-IV disease * No evidence of histological transformation * Bidimensionally measurable disease by clinical examination or radiography * Asymptomatic disease without B symptoms or severe pruritus * Low tumor burden, defined by all of the following criteria: * Lactic dehydrogenase normal * Largest nodal or extranodal mass \< 7 cm * No more than 3 nodal sites with a diameter \> 3 cm * No clinically detectable significant serous effusion by chest x-ray * Clinically non-evident small effusion on CT scan is not considered significant * Spleen enlargement ≤ 16 cm by CT scan * Circulating tumor cells \< 5,000/mm\^3 * No organ compression (i.e., ureteric obstruction) PATIENT CHARACTERISTICS: Age * 18 and over Performance status * ECOG 0-1 Life expectancy * Not specified Hematopoietic * Absolute neutrophil count \> 1,500/mm\^3 * Platelet count \> 100,000/mm\^3 * Hemoglobin \> 10 g/dL Hepatic * AST and ALT normal * Alkaline phosphatase normal * Bilirubin normal Renal * Creatinine \< 2 times upper limit of normal (unless due to lymphoma) Other * Not pregnant or nursing * Fertile patients must use effective contraception during and for 12 months after completion of rituximab * No known HIV positivity * No other malignancy within the past 2 years except curatively treated basal cell or squamo…