Rectal cancer complete responders after neoadjuvant chemoradiation: when to spare their organs?

The aim of this study is to identify possible clinical predictors of complete response after neoadjuvant treatment (NAT) in locally advanced rectal cancer (LARC) patients. This study included 40 LARC patients (16 males and 24 females) who received NAT followed by total mesorectal excision (TME) in the period between August 2020 and February 2023. Two different NAT protocols were used; long-course chemoradiotherapy (LCRT) or consolidation total neoadjuvant treatment (TNT) according to the decision of the multidisciplinary team (MDT). Reassessment of response is done after completion of radiotherapy by digital rectal examination (DRE), proctoscopy, and pelvic MRI to define complete responders. All these responders received TME and were classified according to their pathology specimens into the pathological complete response group (pCR=22 patients) and nonpathological complete response group (non-pCR=18 patients). Statistical analyses were performed to compare the two groups and identify clinical factors associated with pCR. The significant clinical predictors of pCR in the univariate analysis were patients’ age, preneoadjuvant carcinoembryonic antigen (CEA) level and preneoadjuvant lymphocytic ratio (P=0.030, 0.007, and 0.001, respectively). In multivariate analysis, lymphocytic ratio was the only independent predictor for pCR (P=0.017). Lymphocytic ratio (>26%) has high diagnostic performance for predicting pCR, while age (>50 years) and normal CEA (≤5 ng/ml) have lower diagnostic performance which can be much improved when both are used in combination to predict pCR. Preneoadjuvant lymphocytic ratio and the combined use of age and preneoadjuvant CEA level are significant predictors of pCR, this may help the MDT select rectal cancer patients with complete clinical response (cCR), who are candidates for organ preserving strategies, to spare their rectum and avoid unnecessary radical surgeries.