Probiotic Therapy in Preventing Gastrointestinal Complications in Patients Undergoing Chemotherapy and Pelvic Radiation Therapy

DISEASE CHARACTERISTICS: * Current diagnosis of cancer that supports the use of continuous definitive or adjuvant external-beam radiotherapy (RT) to the pelvis to a minimum dose of 4,500 cGy with the following parameters: * The pelvis must be encompassed by the planned RT fields * The superior border may not lie inferior to the most inferior aspect of the sacroiliac joints * Portions of the rectum may have special blocking, depending upon disease site * The total prescription dose must lie between 4,500-5,350 cGy (inclusive) * A boost to primary tumor or tumor bed may be planned * Planned treatment is to be given 4-5 times per week on a one- treatment-per-day basis * The daily prescribed dose must lie between 170-210 cGy (inclusive) per day * No planned split-course RT * No proton RT * Will receive concurrent administration of chemotherapy (fluorouracil, capecitabine, cisplatin, oxaliplatin, carboplatin, and/or mitomycin C) during pelvic RT * No current or prior metastases beyond regional lymph nodes PATIENT CHARACTERISTICS: * ECOG performance status (PS) of 0, 1, or 2 * Life expectancy ≥ 6 months * Able to complete questionnaire(s) by themselves or with assistance * Not pregnant or nursing * Negative pregnancy test done ≤ 7 days prior to registration, for women of childbearing potential only * Fertile patients must use effective contraception * Hemoglobin \> 10.0 g/dL * White blood cells (WBC) \> 3,500/mm³ * Absolute neutrophil count (ANC) \> 1,500/mm³ * Platelet count \> 100,000/mm³ * Willing to abstain from ingestion of yogurt products and/or any product containing probiotics during study drug treatment * No known allergy to a probiotic preparation * No history of inflammatory bowel disease * No ≥ grade 3 diarrhea, ≥ grade 3 rectal bleeding, abdominal cramping, or incontinence of stool ≤ 7 days prior to registration * No medical condition that may interfere with ability to receive protocol treatment * No history of gastrointestinal or genitourinary obstruction or porphyria * No history of irritable bowel syndrome (IBS) PRIOR CONCURRENT THERAPY: * See Disease Characteristics * No prior abdominal-perineal resection, Hartmann procedure, or other surgical procedure leaving the patient without a functioning rectum * No planned use of leucovorin * No prior pelvic RT * No use of probiotics ≤ 2 weeks prior to registration * No use of antibiotics ≤ 3 days prior to registration * No planned continuous antibiotic treatment during RT