OBJECTIVETo discuss the mechanism of rectal cancer apoptosis induced by preoperative chemoradiotherapy and evaluate its effect by detection of apoptosis related proteins in locally advanced colorectal cancer patients who had received preoperative chemoradiation.

METHODSTo detect Bcl-XL and Bax expression in rectal cancer before and after chemoradiotherapy by EnVision method, combined with patients clinical and pathological index, statistically analysis and evaluation their relationship and clinical significance.

RESULTSPatients with or without tumor shrinkage after preoperative chemoradiotherapy was 13 cases and 21 cases. While the positive rate of Bcl-XL in rectal cancer before and after chemoradiotherapy were 58.8% (20/34) and 52.9% (18/34), respectively. There were significant difference between Bcl-XL change before and after chemoradiation with tumor size, tumor cells shrinkage and operation pattern. The positive rate of Bax in rectal cancer before and after chemoradiotherapy were 32.4% (11/34) and 44.1% (15/34), respectively. There were no significant difference between Bax change before and after chemoradiotherapy with tumor cells shrinkage. There were statistically significant difference between Bax ratio (χ(2) = 9.607, P = 0.048) before and after chemoradiation while there were no significant difference between Bcl-XL/Bax ratio before and after chemoradiation with tumor shrinkage. According to layered analysis with preoperative therapy, there were statistically significant difference (χ(2) = 13.964, P = 0.007) between Bcl-XL change with operation pattern while the same of significant difference between Bax change with tumor infiltration and tumor shrinkage (χ(2) = 10.806 and 10.455, both P < 0.05).

CONCLUSIONSPreoperative chemoradiation can influence rectal cancer cell's apoptosis and treatment effect by changing Bcl-XL and Bax expression. Bcl-XL downregulation and Bax upregulation have shown important function in colorectal cancer cell apoptosis which induced by preoperative chemoradiation, it can also improve the effection of chemoradiation in rectal cancer.