Statistical analysis was performed with SPSS Statistics for Windows 20.0 (Chicago, IL, USA). ATM expression was compared with clinicohistopathological data using Pearson’s χ2 test, and the association of MRE11 expression with clinicohistopathological variables was assessed by Fisher's exact test. ATM and MRE11 expression levels were compared and combined by binary logistic regression as described previously . Survival analyses were performed in the overall cohort and separately in patients who received preoperative radiotherapy. Univariate and multivariate analyses were performed using Kaplan Meir curves and Cox’s proportional hazards survival modeling for the combined two-marker expression levels from cancer core and periphery samples. Covariates were sex, age, TNM stage, grade, vascular invasion, perineural invasion, treatment with chemotherapy and radiotherapy, and TRG. Univariate analysis by the Mann–Whitney U test was also used to assess associations between the single and combined two-marker expression levels in rectal tumor tissue with TRG, which was further characterized with receiver operating characteristic—area under curve (ROC-AUC) analysis. P<0.05 was considered statistically significant.