The influence of extending the interval from neoadjuvant chemoradiotherapy to surgery on tumor downstaging and pathological response in rectal adenocarcinoma

Background: Delaying surgery following neoadjuvant concurrent chemoradiotherapy (CCRT) may permit continuing tumor cell death and regression over time. This exploratory pilot study examines the influence of extending the time interval from completion of CCRT to surgery on achieving a pathological complete response (pCR) across a rectal cancer cohort. Methods: This pilot analysis reviewed data from 64 patients with Stage II–III rectal cancer who completed neoadjuvant protocols were reviewed. Patients were stratified based on the real-world resting interval between CCRT completion and total mesorectal excision (TME) into Shorter Interval group (<8 weeks, n = 10) and an Extended Interval group (≥ 8 weeks, n = 54). Univariate logistic regression analyzed the impact of resting intervals, alongside clinical stage, tumor grade, and histology on pCR and overall response rates (ORR). Primary outcome included analyzing if a prolonged interval between the completion of CCRT and radical surgery yields superior tumor regression without escalating surgical morbidity, Secondary outcomes included factors influencing pCR. Results: Surgery executed ≥8weeks weeks post-CCRT demonstrated a prevailing, non-significant trend toward significantly higher odds of achieving a pCR compared to shorter intervals (OR = 3.250, 95% CI: 0.369–28.650, P=0.289).