Delayed Surgery after Neoadjuvant Short-course Radiation for Rectal Cancer Improves Pathologic Outcomes without Impacting Survival: A National Cancer Database Analysis.

Purpose: Interval to surgery following short course radiotherapy (SCRT) for rectal cancer is not standardized. This study investigated pathologic outcomes and survival with varying intervals to surgery.

Methods: Using the National Cancer Database, adults who received SCRT from 2005 to 2020 were grouped by additional neoadjuvant chemotherapy. Outcomes were analyzed for early (within 1 week) and delayed (over 4 weeks) intervals.

Results: Of 1154 patients, 671 received neoadjuvant SCRT and chemotherapy (Group 1: median interval 29 days, 50% delayed) and 483 received SCRT only (Group 2: median interval 9 days, 27% delayed). In Group 1, delay was associated with tumor downstaging (OR 1.61; 95% CI, 1.03-2.51; p = 0.036), decreased lymphovascular invasion (OR 0.53; 95% CI, 0.33-0.85; p = 0.009), and complete pathologic response (OR 2.86; 95% CI, 1.06-7.76; p = 0.039). Delay was associated with decreased tumor deposits in Group 1 (OR 0.46; 95% CI, 0.30-0.71; p < 0.001) and Group 2 (OR 0.37; 95% CI 0.21-0.65; p = 0.001). Survival was not affected.

Conclusion: Delaying surgery following neoadjuvant SCRT results in favorable pathologic outcomes without impacting overall survival, regardless of neoadjuvant chemotherapy.