Analyses of predictive factors for pathological complete remission in neoadjuvant therapy for locally advanced rectal cancer

Purpose: To analyze relevant factors for pathological complete remission (pCR) after neoadjuvant therapy for locally advanced rectal cancer. Methods: The clinical data of 531 patients with the American Joint Committee on Cancer (AJCC) stage II or III rectal cancer from January 2014 to December 2017 were retrospectively analyzed Among these patients, 100 (18.83%) patients achieved pCR. Univariate and multivariate logistic regression analyses were applied to analyze the predictive factors for pCR after neoadjuvant therapy. Results: According to univariate analysis, carcinoembryonic antigen (CEA) before chemo-radiotherapy (CRT) (p=0.021), tumor (T) stage before CRT (p=0.002), interval between the end of CRT and surgery (p <0.001) and maximum depth of tumor invasion before CRT (p=0.039) influenced significantly pCR. Multivariate analysis manifested that the CEA level before CRT [p=0.037, odds ratio (OR) =0.435] and the interval between the end of CRT and surgery (p=0.004, OR=2.864) were significant predictive factors for pCR. Stratified analysis showed that low-level CEA before CRT (p=0.029) affected pCR only in non-smoking group. Conclusions: pCR can be observed in some patients with locally advanced rectal cancer after neoadjuvant therapy. Low-level CEA before CRT and long interval between CRT and surgery are predictive factors for pCR of preoperative neoadjuvant therapy for locally advanced rectal cancer, but low-level CEA is effective in predicting pCR in non-smokers only.