Establishment of a logistic regression model for the predicting of radio-sensitivity of preoperative radiotherapy in rectal cancer

Objective To investigate the correlation between the biomarkers related to radio-sensitivity and preoperative radiotherapy in rectal cancer patients, and to establish a logistic regression model to predict the effect of the preoperative radiotherapy through detecting the expression levels of the molecular markers. Methods 33 patients with rectal cancer who received preoperative radiotherapy from January 2010 to January 2015 were retrospectively analyzed. Patients' information was also collected including the serum level of carcino-embryonic antigen(CEA), the immune-histochemical expression levels of vascular endothelial growth factor (VEGF), epidermal growth factor receptor (EGFR), thymidylate synthase (TS) and Ki-67, and image data (CT or magnetic resonance imaging) before radiotherapy, preoperative clinical staging and the postoperative pathologic staging. According to the postoperative pathological remission, the treatment effects of preoperative radiotherapy included effective (CR+PR) and ineffective (PD+SD) were evaluated. The relationship between these molecular markers and the curative effect of preoperative radiotherapy was analyzed by logistic regression analysis using SPSS v17.0 software, and a logistic curative effect prediction model was established. Results As a result of single factor and multiple factors logistic binary regression analysis, CEA, VEGF and Ki-67 were recognized as the interested factors for the radio-sensitivity predicting in patients with rectal cancer who received preoperative radiotherapy. A molecular markers predictive model for radio-sensitivity in preoperative radiotherapy in rectal cancer is as follow: log P=1.700-0.276×CEA-0.238×VEGF-0.135×EGFR+1.377×TS+0.080×Ki-67. Serum CEA level and the expression of VEGF might associate with radio-resistant, and the expression of Ki-67 might associate with better reaction to preoperative radiotherapy. Conclusion The levels of serum CEA, VEGF and Ki-67 may be the predictors of radio-sensitivity in rectal cancer patients who received preoperative radiotherapy. Key words: Rectal neoplasms; Radiotherapy; Tumor markers, biological; Radiation tolerance