Objective: Both Neutrophil to Lymphocyte (NLR) and C-reactive protein to albumin (CAR) ratio are surrogate markers of host immune system's reaction against systemic inflammation generated by tumor microenvironment. Recent studies have reported the efficacy of host's reaction to systemic inflammation as a prognostic marker in various cancers. However, its association with tumor response to neoadjuvant chemoradiotheraoy treatment in rectal cancer has not been fully elucidated.

Methodology: Pretreatment NLR and CAR along with other clinical and serological markers were evaluated in 54 patients undergoing chemoradiotheray for rectal cancer from February 2019 to February 2020. The predictive significance of these markers were then determined by both univariate and multivariate logistical analysis. Predetermined cutoff values for NLR and CAR and serum CEA levels were used for response prediction

Results: Pretreatment low NLR (<2, p<0.01), pretreatment low CAR (<0.025, p=0.01) and lower CEA levels were significantly associated with both good pathological response and complete pathological response to chemoradiotherapy in univariate analysis. However, in multivariate Cox analysis although both NLR and CAR levels were found to be independent predictors for complete response to neoadjuvant therapy, NLR seemed to be a better predictor in terms of hazard ratio(HR) than the CAR (HR=2.870 versus HR=1.784). Patients with NLR<2 had significantly better response to chemoradiotherapy and NLR was superior to other serum inflammatory markers for predicting response to neoadjuvant therapy.

Conclusion: Pretreatment NLR and CAR were significant predictors of complete pathological response to neoadjuvant chemoradiotherapy in rectal cancer patients. However, NLR is found to be a better discriminator for complete response to neoadjuvant chemoradşotherapy in patients with rectal cancer.