53BP1 expression and immunoscore are associated with the efficacy of neoadjuvant chemoradiotherapy for rectal cancer

Purpose Considering the effects of P53 binding protein 1 (53BP1) expression and T lymphocyte infiltration density on tumor radiosensitivity, we investigated the relation of 53BP1 expression and immunoscore based on T lymphocyte infiltration density with the efficacy of neoadjuvant chemoradiotherapy (CRT) for rectal cancer. Methods Fifty-five patients with rectal cancer receiving neoadjuvant CRT followed by surgery were enrolled. The 53BP1 expression level and the density of CD3(+), CD8(+), and CD45RO(+) T lymphocytes in the tumor tissues were examined by immunohistochemistry, and the relation of these findings to the rates of tumor regression, disease-free survival (DFS), and overall survival (OS) was analyzed. Results The levels of 53BP1 and the CD3/CD8 immunoscore were closely correlated with the response to CRT (p < 0.05), with an area under the receiver operating characteristic curve for CRT efficacy prediction of 0.626 and 0.717, respectively. Further survival analysis revealed that high 53BP1 expression effectively prolonged 2-year DFS compared with low 53BP1 expression (87.5% [95%CI 77.3-97.7] vs. 53.3% [95%CI 28.1-78.6]; p < 0.05), while the effect of immunoscore on survival was restricted by the expression status of 53BP1. Cox multivariate analysis confirmed 53BP1 as an independent prognostic factor in DFS. Conclusion The pretreatment levels of 53BP1 and the immunoscore based on CD3(+)/CD8(+) T cell infiltration density in tumor tissues are effective predictors for the CRT response, and 53BP1 has a more pronounced impact on prognosis.