Oncological outcomes comparing direct vs delayed surgery after neoadjuvant shortcourse radiotherapy in rectal cancer- a national cohort study

Abstract Introduction A trend towards delayed surgery after neoadjuvant radiotherapy for rectal cancer has emerged in Sweden after the publication of Stockholm III trial, as the results concluded lower short-term complications and similar oncological outcomes. The aim of this study was to examine long-term oncological outcomes after short course radiotherapy (5x5 Gy) comparing direct vs delayed surgery for rectal cancer in a real world setting. Method A nationwide registry-based retrospective cohort study was conducted using prospectively collected data from the Swedish Colorectal Cancer Registry (SCRCR). Rectal cancer patients who received neoadjuvant short course radiotherapy between the years 2016-2020 were analyzed for local recurrence, distant metastases and overall survival (OS) after three years. Result A total of 2428 patients were identified with 1253 undergoing direct surgery and 1175 undergoing delayed surgery following radiotherapy. Median age was 70 (62-75) years and 73 (66-79) years in the direct and delayed surgery grouprespectively and 38% were female in both groups.. The HR for local recurrence was 3.6 (1.9-6.7) p<0.01 in the delayed surgery group and the overall 3 year survival rate was 87% vs 78% p<0.01 when comparing direct vs delayed surgery. Discussion Preliminary findings indicate that direct surgery is associated with better 3-year oncolgical outcomes as well OS. The shift towards delayed surgery requires further evaluation.