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 cancer cells and either kill them or deliver cancer-killing substances to them without harming normal cells. Radiation therapy uses high-energy x-rays to damage cancer cells. Combining chemotherapy with monoclonal antibody therapy and radiation therapy may kill more cancer cells.

PURPOSE: Phase II trial to study the effectiveness of combination chemotherapy plus rituximab and radiation therapy in treating patients who have stage I or stage II non-Hodgkin's lymphoma.

OBJECTIVES: I. Assess two year progression free survival after treatment with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) plus rituximab followed by radiotherapy in patients with stage I, IE, or non-bulky stage II or IIE high risk localized intermediate or high grade non-Hodgkin's lymphoma. II. Determine the toxicity of this treatment in these patients.

OUTLINE: Patients receive rituximab IV on days 1 and 8 of the first course, then on day 1 of courses 2 and 3. Patients receive cyclophosphamide IV over 1-2 hours, doxorubicin IV, and vincristine IV on day 10 of the first course, then on day 3 of courses 2 and 3. Patients receive oral prednisone on days 10-14 of the first course, then on days 3-7 of courses 2 and 3. Treatment repeats every 21 days for 3 courses in the absence of disease progression or unacceptable toxicity. Chemotherapy is followed by radiotherapy administered 5 days a week for 4-5 weeks. Patients are followed every 6 months for two years, and then annually thereafter.

PROJECTED ACCRUAL: A total of 60 patients will be accrued for this study.

DISEASE CHARACTERISTICS: Histologically confirmed stage I, IE, or non-bulky II or IIE non-Hodgkin's lymphoma of one of the following subtypes: Diffuse large B-cell Mantle cell High grade B-cell, Burkitt's or Burkitt like Anaplastic large cell (B-cell phenotype only) Lymphoma must express CD20 All disease must be encompassable in a single radiation port (including any resected disease) Must have at least 1 of the following adverse prognostic features: Non-bulky stage II or non-bulky stage IIE disease Over 60 years of age Zubrod performance status of 2 Elevated serum LDH A new classification scheme for adult non-Hodgkin's lymphoma has been adopted by PDQ. The terminology of "indolent" or "aggressive" lymphoma will replace the former terminology of "low", "intermediate", or "high" grade lymphoma. However, this protocol uses the former terminology.

PATIENT CHARACTERISTICS: Age: Over 18 Performance status: Zubrod 0-2 Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: No medical contraindications to CHOP chemotherapy or rituximab No prior malignancy within past 5 years except adequately treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix No AIDS or HIV Not pregnant or nursing Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY: Biologic therapy: No prior monoclonal antibody therapy Chemotherapy: No prior chemotherapy for lymphoma Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy for lymphoma Surgery: Not specified