Nadir/pre-chemoradiotherapy ratio of white blood-cell count can predict tumor response and recurrence-free survival in locally advanced rectal cancer: a multi-institutional analysis.

Purpose: The objective of this study was to evaluate whether change of white blood-cell (WBC) count before and during chemoradiotherapy (CRT) might be associated with susceptibility to radiation and tumor response.

Methods: Medical records of 641 patients with rectal cancer who received preoperative CRT followed by curative surgery were retrospectively reviewed in five tertiary centers. Complete blood cell with differential count was measured weekly during the period of CRT. We assessed nadir/pre-CRT ratio of WBC count as a predictor for tumor response to CRT and a prognostic factor for recurrence-free survival.

Results: Enrolled patients were divided into low WBC ratio (LWR) and high WBC ratio (HWR) arms with cut-off value of 0.49 calculated by receiver operating characteristic curve. Of 641 patients, 490 (76.4%) and 151 (23.6%) were categorized into HWR (> 0.49) arm and LWR (≤ 0.49) arms, respectively. Complete pathologic response rate after CRT was significantly higher in LWR arm than that in HWR arm (23.8% vs. 12.2%, p = 0.001). In logistic regression analysis, carcinoembryonic antigen (CEA) level over 5 ng/ml [adjusted odds ratio (OR) 0.566, 95% confidence interval (CI) 0.351-0.912; p = 0.019) and HWR (adjusted OR 0.412, 95% CI 0.256-0.663; p = 0.001) were significantly negative factors of pathologic complete response. The 5-year recurrence-free survival rate was significantly higher in the LWR group than that in the HWR group (83.3% vs. 67.6%, p = 0.001).

Conclusion: Low nadir/pre-chemoradiotherapy ratio during preoperative CRT can predict good tumor response. It is significantly associated with improved recurrence-free survival in rectal cancer.