Purpose: To report the results of primary radiotherapy for treatment of anal canal carcinoma from the University of Florida series and review issues related to treatment of this disease.
Methods and materials: Forty-nine patients were treated with primary radiation therapy (RT) for cure. Patients had a minimum 2-year follow-up (median, 9.8 years). After 1990, patients with lesions of at least 3 cm also received chemotherapy with fluorouracil (1000 mg/m(2)) plus cisplatin (100 mg/m(2)) or mitomycin (10-15 mg/m(2)) if medically fit (n = 26). RT was delivered with a 4-field box technique to deliver 45 Gy in 25 fractions. The inguinal nodes were treated daily using electrons to supplement the dose in that region to a total dose of 45 Gy if clinically negative or about 60 Gy if involved. There were no planned breaks. A 10- to 15-Gy boost was delivered using interstitial iridium 192 implant (n = 32), en face (60)Co field (n = 5), or external-beam photon fields (n = 11).
Results: Local control rates at 5 years were 100% for T1N0, 92% for T2N0 or N1, 75% for T3N0, 67% for T4N0, 88% for T4N(pos) or T(any)N2-3, and 85% overall. With surgical salvage, ultimate local control rates were 100%, 100%, 81%, 100%, and 88%, respectively, with 92% overall. Cause-specific survival rates at 5 years were 100% for Stage I, 88% for Stage II, 100% for Stage IIIA, and 70% for Stage IIIB. Absolute survival rates at 5 years were 62%, 68%, 100%, and 70%. Sphincter preservation rates were 83%, 79%, 75%, and 100% by stage and 81% overall. There was an improvement in local control with the addition of chemotherapy in more advanced disease, but it was not significant. There was an increase in acute toxicity with the addition of chemotherapy (12% > or = Grade 4) but not long-term toxicity. Late toxicity requiring colostomy occurred in 6% of patients and consisted of soft tissue necrosis.
Conclusions: The majority of patients with anal canal carcinoma can be treated with curative intent using a sphincter-sparing approach of radiation with or without chemotherapy even with advanced disease. With the addition of chemotherapy to radiation, there is an increased risk of acute toxicity and about 1-2% incidence of toxic death. Smaller tumors (T1 and early T2) probably do not require the addition of chemotherapy.