To investigate the relationship between TRG and tissue levels of ATM, MRE11, and the two-protein combined panel, univariate analysis was carried out using the Mann−Whiney U test (SPSS). A significant association was seen between increasing TRG and TC expression of the MRE11 protein (P = 0.015, Fig 3B) and of the combined two-protein panel (P = 0.011, Fig 3C). The discriminatory power of each protein biomarker and their combination in TC was characterized using a ROC-AUC analysis of good response (TRG 0–2) versus poor response (TRG3) groups. The average ROC-AUC was 0.745 for the combined panel of two proteins, compared with 0.618 for ATM and 0.711 for MRE11 proteins (Fig 3D). These results suggest that the combined two protein biomarkers provide good discrimination between good and poor tumor responses after radiotherapy.