Neoadjuvant Radiation Therapy and Capecitabine in Treating Patients With Stage III or Stage IV Colorectal Adenocarcinoma

DISEASE CHARACTERISTICS: Histologically or cytologically confirmed colorectal adenocarcinoma Clinical stage T3, T4, N+ Measurable disease Awaiting surgery and likely to benefit from neoadjuvant radiotherapy PATIENT CHARACTERISTICS: Age 18 to 80 Performance status ECOG 0-2 OR Karnofsky 60-100% Life expectancy Not specified Hematopoietic Absolute neutrophil count at least 2,000/mm^3 Platelet count at least 100,000/mm^3 Hemoglobin at least 10 g/dL Hepatic Bilirubin no greater than 1.5 times upper limit of normal (ULN) AST and ALT no greater than 2.5 times ULN No hepatic condition that would interfere with study medication Renal Creatinine clearance at least 80 mL/min No renal condition that would interfere with study medication Cardiovascular No serious cardiac failure with the past year No myocardial infarction within the past year No cardiac insufficiency No angina No uncontrolled arrhythmia No uncontrolled hypertension Gastrointestinal No superior intestinal tract malfunction No malabsorption syndrome Other Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception No concurrent serious infection No other serious illness No other malignancy within the past 5 years except curatively treated basal cell skin cancer or carcinoma in situ of the cervix No metabolic condition that would interfere with study medication No dementia or altered mental status No psychiatric illness that would preclude study participation PRIOR CONCURRENT THERAPY: Biologic therapy Not specified Chemotherapy No prior chemotherapy for colorectal cancer Endocrine therapy Not specified Radiotherapy No prior radiotherapy for colorectal cancer Surgery Not specified Other More than 30 days since prior participation in another clinical study