Optimal Timing of Surgical Resection After Radiation in Locally Advanced Rectal Adenocarcinoma: An Analysis of the National Cancer Database

Background. In the treatment of rectal cancer, a longer radiation-surgery interval from the end of neoadjuvant radiation therapy to surgery has been associated with higher rates of complete pathologic response (pCR), but the optimal interval with respect to survival has not been established. Data from the National Cancer Database (NCDB) was used to evaluate the impact of radiation-surgery interval on oncologic outcomes. Methods. The NCDB was searched for patients diagnosed with nonmetastatic rectal cancer who underwent preoperative radiation followed by radical surgical resection. A Cox proportional hazards model was constructed to examine the influence of radiation-surgery interval while controlling for potential confounding factors. Sensitivity analysis was used to confirm the results of the model. Results. A cohort of 6397 patients meeting all inclusion and exclusion criteria from 2004-2006 was identified, and the pCR rate for this cohort was 6.9 %. Of those who experienced a pCR, 76.2 % had done so by 60 days. Intervals greater than 60 days were associated with higher rates of positive surgical margins (6.7 vs. 4.8 %, p = 0.009) and lower rates of sphincter-preserving surgery (64.9 vs. 68.9 %, p = 0.007). An interval greater than 60 days was associated with significantly shorter survival (hazard ratio (HR), 1.314; 95 % CI 1.191-1.449; p < 0.001). Conclusions. Radiation-surgery interval beyond 60 days is associated with increased rate of positive surgical margins, decreased rate of sphincter-preserving surgery, and decreased survival. Delay of surgery for rectal cancer beyond 60 days after the completion of neoadjuvant therapy should be done with caution.