There are conflicting data regarding the relationship between pathologic complete response (pCR) and post-operative complications following rectal cancer resection. The objective of this study was to compare the rates of morbidity among pCR patients and non-pCR patients and to identify factors that predict pCR morbidity in a large national database.

This is a retrospective study using American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) targeted proctectomy data (2016–18). Patients with neoadjuvant chemoradiation therapy followed by proctectomy were included, and divided into pCR and non-pCR groups according to final stage. The groups were compared with Student’s t-test, Chi-squared or Fisher’s exact test. Multivariate logistic regression models were constructed to estimate the association between pCR status and post-operative morbidity while adjusting for key covariates.

244 pCR and 1656 non-pCR patients were included. pCR patients had higher body mass index (28.1 ± 6.2 vs. 29.1 ± 5.9 kg/m²; p = 0.01) and lower pre-operative stage (T stage, p = 0.03; N stage, p < 0.001). The groups were equivalent with respect to surgical approach, type of surgery, and operative time (p > 0.05). Post-operative complications in pCR patients were less frequent than in non-pCR patients (23.0% vs. 29.3%; p = 0.04). This association was robust to adjustment for confounders in logistic regression, as patients with pCR had decreased odds of post-operative morbidity (OR 0.66, CI [0.43, 0.96], p = 0.04).

pCR is associated with fewer post-operative complications compared to non-pCR, suggesting that pCR is not a marker of severe pelvic fibrosis. This difference may be due to underlying tumor biology, and associated increased technical challenges resecting larger, non-responsive tumors.