Antibiotic Therapy in Treating Patients With Low Grade Gastric Lymphoma

DISEASE CHARACTERISTICS: Histologically proven, previously untreated, low grade gastric lymphoma Clinical stage I and II1 No bulky disease No high grade component (grade 5 and 4, if monoclonality proven, allowed) Documented presence/absence of H. pylori infection Measurable and/or evaluable disease PATIENT CHARACTERISTICS: Age: 18 and over Performance status: WHO 0-2 Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: Not pregnant or lactating Fertile patients must use effective contraception No prior or concurrent malignancies unless: At least 1 year remission Low risk or recurrence No prior gastric malignancy No nonmalignant disease causing poor medical risk No allergy to omeprazole PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Not specified Endocrine therapy: Not specified Radiotherapy: No prior radiotherapy to the abdomen Surgery: No prior gastric surgery except simple closure of perforated ulcer with or without wedge excision of the ulcer Other: No prior therapy for gastric lymphoma At least 30 days since experimental therapy No other concurrent experimental therapy At least 30 days since antibiotics with activity against H. pylori