Survival benefit of adjuvant radiation therapy after local excision of T1-2 and N0 anal squamous cell carcinoma: A National Cancer Database Analysis.

Abstract

Early stage anal squamous cell carcinoma may be treated with local excision but with considerable risk of recurrence. Adjuvant radiation therapy may be used to reduce recurrence and improve outcomes. This study aimed to assess outcomes of adjuvant radiation therapy after local excision of T1-2 N0 anal squamous cell carcinoma. This study was a retrospective cohort analysis of patients with T1-2, N0, and M0 anal squamous cell carcinoma from the National Cancer Database (2010-2020) who underwent local excision with and without adjuvant radiation therapy. Patients were matched using 2:1 propensity-score matching. The primary outcome was 5-year overall survival. Five thousand sixty-five patients with anal squamous cell carcinoma (61.6% female; median age 60 years; 53% T1 stage and 47% T2 stage) were included; 3,366 patients (66.4%) received adjuvant radiation therapy. After matching for age, sex, race, Charlson score, T stage, tumor size and grade, facility type, and surgical margins, 868 patients were in the adjuvant radiation therapy group and 434 in the local excision group. Adjuvant radiation therapy was associated with improved overall survival (82.8% vs 74.9%; P < .001), which was more pronounced in patients with positive surgical margins (79.9% vs 67.2%; P = .003) than negative margins (84.6% vs 79.7%; P = .037). The survival benefit of adjuvant radiation therapy was specifically noted in patients ≥65 years (74.2% vs 53.9%; P < .001), women (85.8% vs 72.2%; P < .001), T2 (81.2% vs 67.5%; P = .001), and poorly differentiated (82% vs 72.8%; P = .001) tumors. Omitting adjuvant radiation therapy was associated with increased overall mortality (hazard ratio 1.4, 95% confidence interval 1.15-1.71; P < .001). Adjuvant radiation therapy after local excision of T1-2 and N0 anal squamous cell carcinoma was associated with a significant increase in overall survival. Increased survival was mainly noted in female patients ≥65 years with T2 moderately or poorly differentiated anal squamous cell carcinoma.