The prechemoradiotherapy/nadir ratio of white blood-cell count to predict tumor response and survival in locally advanced rectal cancer.

Abstract

783 Background: Predicting treatment response of preoperative chemoradiotherapy (CRT) in patients with rectal cancer is important for physicians to guide a patient to the relevant treatment. We evaluate the change of white blood cell (WBC) count before and during CRT if it is associated with susceptibility to the CRT and affects tumor response. Methods: Medical records of 641 patients with rectal cancer who received preoperative CRT followed by curative surgery were retrospectively reviewed. Complete blood cell counts were measured weekly before and during the radiation therapy. We assessed the pre-CRT/nadir ratio of WBC count for the treatment response to CRT and recurrence-free survival. Results: The enrolled patients were divided into two groups of high WBC ratio (HWR) and low WBC ratio (LWR) with the cutoff value of 0.49, which was found by receiver operating characteristic curve (Sensitivity, 0.38 and 1-Specificity, 0.22; p=0.007). In 641 patients, 490 (76.4%) were HWR group and 151 (23.6%) were LWR group. Complete pathologic response rates were 12.2% in HWR group and 23.8% in LWR group, respectively (p=0.001). Downstaging rates of each group were 37.8% and 48.3%, respectively (p=0.02). In the logistic regression analysis, CEA level over 5ng/ml (Adjusted OR 0.566, 95% CI 0.351-0.912; p=0.019) and HWR (Adjusted OR 0.412, 95% CI 0.256-0.663; p=0.001) were significant adverse factors of the pathologic complete response. The 5-year recurrence-free survival rate was significantly higher in LWR group than in HWR group (67.6% and 83.3%; p=0.001). Conclusions: Low WBC ratio predicts a good tumor response to the preoperative CRT, and is significantly associated with an improved recurrence-free survival in rectal cancer.