Time interval between neoadjuvant radiation therapy and surgery and overall survival of rectal cancer patients

<b>Aim:</b> To investigate the association of time interval between neoadjuvant RT and surgery (RS-interval) with pathological complete response (pCR) and overall survival (OS) of rectal cancer patients. <b>Methods:</b> We used the National Cancer Database and reported Odds ratios (OR) and Hazard ratios. <b>Results:</b> Patients with an RS-interval of 5–24 weeks were more likely to achieve pCR compared with ≤4 weeks. RS-interval of 13–24 weeks was associated with a reduced OS compared with ≤4 weeks only in patients who did not achieve pCR. <b>Conclusion:</b> RS-interval of 5–8, 9–12, 13–16, 17–20, or 21–24 weeks was associated with a higher likelihood of achieving pCR compared with ≤4 weeks. In patients without pCR, delaying surgery &gt;12 weeks was associated with reduced OS. The optimal time between the completion of neoadjuvant radiation therapy (RT) and surgery in patients diagnosed with locally advanced rectal cancer is controversial and there is no study that has investigated this association by the pathological completed response (pCR) status. Patients who received surgery between 5 and 8 weeks, 9 and 12 weeks, 13 and 16 weeks, 17 and 20 weeks, or 21 and 24 weeks after the completion of RT were more likely to achieve pCR compared with ≤4 weeks. Patients who achieved pCR had comparable overall survival (OS) regardless of when the surgery took place within 24 weeks after RT completion. Among patients who did not achieve pCR, OS was only similar if surgery was received between 5 and 8 or 9 and 12 weeks after RT compared with ≤4 weeks. Among patients who did not achieve pCR, Surgery between 13 and 16, 71 and 20 or 21 and 24 weeks after RT was associated with worse OS compared with ≤4 weeks.