What is the optimal treatment for T1N0 anal squamous cell carcinoma? Analysis of current practices in the prospective French FFCD ANABASE cohort.

Abstract Introduction for localized T1N0 squamous cell carcinoma of the anus (SCCA) standard radiotherapy (RT) may result in overtreatment and alternative strategies are debated. Methods T1N0M0 SCCA treated between 2015 and 2020 by local excision (LE) or RT were analyzed from the French prospective FFCD ANABASE cohort. Treatment strategies, recurrence-free and colostomy-free survivals (RFS, CFS) and prognostic factors were reported. Results among 1135 SCCA patients, 99 T1N0M0 were treated by LE(n = 17,17.2%), or RT (n = 82,82.8%) including RT alone (n = 65,79.2%) or chemo-RT (n = 17, 20.7%). Median follow-up was 27.2 months [0.03–54.44]. Median tumor size were 11.4 mm [0.9–20] and 15.3 mm [2–20] in the LE and RT groups respectively. Mean RT tumor dose was 59.4 Gy [18–69.4 Gy]. One patient in LE group and 9 in RT group had a pelvic recurrence, either local (60%), nodal (10%) or both (30%). RFS and CFS at 24 months were 92.2%[95%CI,83.4–96.4] and 94.6%[95%CI,86.1–98.0], at 36 months 88.1%[95%CI,77.1–94.2] and 88.5%[95%CI,77.0–94.5], in LE and RT group respectively, without any significative difference (HR = 0.57;[95%CI,0.07–4.45];p = 0.60). By univariate analysis, male gender was the only prognostic factor(HR = 5.57;95%CI, 1.76–17.63; p = 0.004). Conclusion this cohort confirms the heterogeneity of T1N0M0 SCCA management, questioning the place of RT alone, reduced dose or RT volume, and the safety of LE.