Reduction of elective lymph node volume in radiotherapy of early anal squamous cell cancer : a comparative study between two Swedish university hospitals

Background: Anal squamous cell cancer (ASCC) in early stages (T1–2N0M0) is treated with chemoradiotherapy with a 3-year overall survival (OS) exceeding 90%. In Swedish guidelines, it has been optional to include the external iliac and presacral lymph node (LN) stations in radiotherapy (RT) treatment fields in early ASCC. Two Swedish hospitals treating ASCC (SU: Sahlgrenska University Hospital; UU: Uppsala University Hospital) have chosen different approaches since 2010. Material and methods: This study included consecutive patients with early ASCC (T1–2N0M0) treated between 2010 and 2017 at both sites (SU n = 70; UU n = 46). Data were retrieved from medical records and RT charts. Results: At SU, the external iliac and presacral LN stations were included in elective LN irradiation in 96.8% (n = 60) and 95.2% (n = 59) patients compared to 2.4% (n = 1) and 29.3% (n = 12) at UU. The mean elective LN volume was 2,313 cc (interquartile range [IQR] 1,951–2,627) in the SU cohort compared to 1,317 cc (IQR 1,192–1,528) in the UU cohort, p < 0.0001. No case of regional LN recurrence was seen in either cohort. Disease specific survival (DSS) at 5 years was 95.7% (confidence interval [CI] 90.1–100.0) in the SU cohort and 97.8% (CI 93.2–100.0) in the UU cohort (p 0.55). OS at 5 years was 84.5% (CI 76.1–93.0) in the SU cohort and 82.6% (CI 69.6–89.1) in the UU cohort (p 0.8). Interpretation: We found no differences in regional recurrence, DSS or OS between the cohorts treated with different elective LN volumes. In this population-based study, reduction of RT volume in early ASCC did not lead to inferior outcome