Radiation therapy for epidermoid carcinoma of the anal canal, clinical and treatment factors associated with outcome

Abstract

Background and purpose: In recent years, treatment with combined chemotherapy and radiation has become the standard of care for epidermoid carcinoma of the anus. However, optimal radiotherapy techniques and doses are not well established.Materials and methods: During the period 1975–1997, 106 patients with epidermoid carcinoma of the anal canal underwent radiation therapy. Treatment policies evolved from radiation therapy alone or with surgery, to combined chemotherapy and radiation followed by surgery, to combined chemotherapy and radiation.Results: Overall 74% of patients were NED (no evidence of disease) at last follow-up. The most important clinical correlate with ultimate freedom from disease (includes the contribution of salvage surgery) was extent of disease. The 5-year ultimate freedom from disease was 87±5% for T1/T2N0, 78±10% for T3N0 (15% salvaged by surgery), and 43±10% for either T4N0 or any N+ lesions (P<0.001, Tarone–Ware). There was no difference between planned vs. expectant surgery (5-year ultimate NED: 67±11% planned surgery vs. 73±5% expectant surgery). The most important correlate with late toxicity was a history of major pelvic surgery (surgical vs. non-surgical group: P=0.013, Fisher's exact test, two-tailed summation). Thirty-three additional malignancies have been seen in 26 patients. The most common additional malignancies were gynecologic (nine cases), head and neck (six cases), and lung cancer (five cases).Conclusions: For T1/T2N0 disease, moderate doses of radiation combined with chemotherapy provided adequate treatment. T4N0 and N+ lesions are the most appropriate candidates for investigational protocols evaluating dose intensification. T3N0 tumors may also be appropriate for investigation; however, dose intensification may ultimately prove counterproductive if the cure rate is not improved and salvage surgery is rendered more difficult. The volume of irradiated small bowel should be minimized for patients who have a past history of major pelvic surgery or who (because of locally advanced tumors) may need salvage surgery in the future. Because of the occurrence of additional malignancy, patients with anal cancer should receive general oncologic screening in long-term follow-up.