Radiation Treatment for Cancer of the Anal Margin

Objective:To identify best treatment practices by examining outcomes of anal margin cancer patients treated with radiotherapy. Methods:Relevant literature was compared with 38 patients at our institution treated 1979 to 2019 with curative radiotherapy. Median age was 51. Four patients had T1, 22 had T2, and 12 had T3 disease based on the American Joint Committee on Cancer (AJCC) staging at time of diagnosis. Nodal staging distribution was: N0=33; N1=2; N2=2; N3=1. Median radiation dose was 56 Gy/30 fractions. Five received nodal radiation for node positivity, 29 received elective nodal radiation, and 29 had perineal boost. Twenty-seven received concurrent chemotherapy. Results:Three patients experienced isolated local recurrence, 2 had isolated inguinal node recurrences, and 2 developed distant metastases, 1 of whom also had local and regional recurrence. Ten-year disease-free survival (DFS), cause-specific survival, and overall survival were 87%, 92%, and 68%, respectively. One patient did not complete radiation, and 4 had unexpected treatment breaks. Two received salvage abdominoperineal resections. At last follow-up, 17 were alive with no evidence of disease, 2 were alive with anal margin cancer present, 3 had died with anal margin cancer present at 11, 18, and 21 months from radiation therapy, and 16 had died from intercurrent disease. Median follow-up was 6.6 years (range 0.9 to 29.0 y). Age >= 51 was associated with worse locoregional control (P=0.018) and DFS (P=0.0233), males had worse DFS (P=0.0311), and HIV-positive patients had worse overall survival (P=0.006). Conclusions:Radiation provides high locoregional control of anal margin cancer with good long-term outcomes.