Capecitabine, Oxaliplatin, and Radiation Therapy in Treating Patients With Stage II or Stage III Anal Cancer

OBJECTIVES: Primary * Determine time to treatment failure in patients with stage II-IIIB squamous cell carcinoma of the anal canal treated with capecitabine, oxaliplatin, and radiotherapy (i.e. Capecitabine (Xeloda)/Oxaliplatin (Eloxatin) With Concomitant Radiotherapy (XRT) shortened to XELOX/XRT). * Determine the toxic effects of this regimen in these patients. Secondary * Determine the complete response rate in patients treated with this regimen. * Determine 2-year local regional control in patients treated with this regimen. * Determine 2-year colostomy-free survival in patients treated with this regimen. * Determine 2-year median overall survival in patients treated with this regimen. * Determine 2-year progression-free survival in patients treated with this regimen. OUTLINE: Patients receive oral capecitabine\* twice daily on days 1-2, 6-10, 20-24, 27-31, and 41-42, and undergo radiotherapy\* once daily on days 1-3, 6-10, 13-17, 20-24, 27-31, 34-38, and 41-42. Patients also receive oxaliplatin intravenous (IV) over 2 hours on days 1, 8, 22, and 29. Treatment continues in the absence of disease progression or unacceptable toxicity. NOTE: \*Patients with T3-4 lesions also receive oral capecitabine twice daily and undergo radiotherapy once daily on days 43 and 44. Patients are followed at 4-6 and 12 weeks and then periodically thereafter. PROJECTED ACCRUAL: A total of 71 patients will be accrued for this study.