Effects of the delay of surgery in localized rectal cancer.

63 Background: The treatment landscape for localized rectal cancer has evolved significantly in recent years, with long-course neoadjuvant chemoradiation (CRT) and total neoadjuvant therapy (TNT) emerging as the primary options. However, the optimal timing of surgery remains an important clinical question, particularly in resource-limited settings where surgical delays can occur. Data from previous studies have shown conflicting results. This retrospective study aimed to assess the impact of delaying surgery beyond the longer interval used in previous studies, focusing on its effects on Pathologic Complete Response (pCR), DFS, and OS. Methods: We conducted a retrospective cohort study using electronic medical records from three centers in Brazil between the years 2013-2024. The study included 236 patients with localized rectal cancer treated with neoadjuvant CRT and/or chemotherapy. Patients were divided into two pre-specified groups based on the interval between the end of neoadjuvant therapy and surgery: ≤11 weeks and >11 weeks. The primary endpoint was DFS. Secondary endpoints were pCR rates, and OS. Descriptive statistics were used for population analysis, while the Kaplan-Meier method estimated DFS and OS, with comparisons made using the log-rank test. A Cox proportional-hazards model was used to estimate hazard ratios and 95% confidence intervals. Results: The median age of the study population was 62 years, with males comprising 56.4% of the sample. The majority of the sample consisted of stage III patients, making up 72.2%, followed by stage II patients at 25.8%, and stage I patients at 1.9%. Most patients (77.8%) had surgery more than 11 weeks after completing neoadjuvant therapy, with a median time to surgery of 16 weeks. The pCR rates did not significantly differ between the two groups (29% for ≤11 weeks vs. 21.5% for >11 weeks; p = 0.271). After a median follow-up of 30 months, the median DFS was not reached, and there was no significant difference between the groups (HR: 0.86; 95% CI: 0.48-1.5; p = 0.63). Similarly, the median OS was not reached, and no difference was observed between the groups (HR: 0.85; 95% CI: 0.47-1.54; p = 0.88). Conclusions: Delaying surgery beyond 11 weeks did not result in greater tumor downstaging in patients with localized rectal cancer. Furthermore, DFS and OS were not significantly impacted by extended intervals between neoadjuvant therapy and surgery.