Predictive factors of complete response to neoadjuvant chemoradiotherapy in patients with rectal cancer

Purpose. Pathological complete response (pCR) after neoadjuvant chemoradiotherapy is a favourable prognosticator in rectal cancer patients. We investigated whether the biologic features of the primary tumor affect pCR. Materials and Methods. Forty-six patients treated with capecitabine-oxaliplatin with pelvic conformal radiotherapy were considered. Forty-three patients underwent surgery, and the pathologic response was scored according to the Tumor Regression Grade (TRG) scale. EGFR, VEGF, PARP1, XRCC1, TS and Ki67 expression was evaluated by immunohistochemistry on rectal biopsies obtained before chemoradiotherapy, and scored as percentage of positive cells. Cut-offs were selected based on ROC analysis. The correlation between the biological factors and the TRG coded as TRG1 (pCR) vs TRG ≥ 2 (no pCR) was assessed by the 2 test and logistic regression analysis. Results. Low EGFR (p=0.007), high TS (p=0.002), and high Ki67 (p=0.05) were strongly associated to pCR. At univariate analysis, TRG significantly affected DFS (p=0.03). Conclusions. pCR was significantly associated with high TS, high Ki-67 and low EGFR expression. Patients with pCR have significant lower incidence of relapse.