Clinical significance of thrombocytosis before preoperative chemoradiotherapy in rectal cancer: predicting pathologic tumor response and oncologic outcome.

BACKGROUND: Thrombocytosis is considered an adverse prognostic factor in various malignancies. However, the clinical significance of thrombocytosis in rectal cancer patients is unknown. We investigated the predictive value of thrombocytosis for pathologic tumor response to preoperative chemoradiotherapy (CRT) and oncologic outcomes in patients with rectal cancer.
METHODS: A total of 314 patients who underwent preoperative CRT and subsequent rectal resection for rectal cancer were retrospectively evaluated at two tertiary institutions. Univariate and multivariate analyses of the clinical parameters were performed to identify markers predictive of a pathologic complete response (pCR). The Kaplan-Meier method was used to estimate 3-year disease-free and overall survival rates.
RESULTS: Sixty-nine patients (22 %) had thrombocytosis before CRT, which significantly correlated with a large tumor size and advanced tumor depth. Thirty-nine patients (12.4 %) achieved a pCR. In the multivariate analyses, a platelet count of <370,000/μl (odds ratio 5.483; 95 % confidence interval, 1.271-23.653; P = 0.023) and a carcinoembryonic antigen (CEA) level of <5 ng/dl (odds ratio, 3.084; 95 % confidence interval, 1.291-7.368; P = 0.011) were identified as independent predictive factors for a pCR. Patients with pretreatment thrombocytosis had lower 3-year disease-free (P = 0.037) and overall survival (P = 0.001) rates than patients with normal pretreatment platelet counts.
CONCLUSIONS: Thrombocytosis is a negative predictive factor for a pCR and has an adverse impact on survival in rectal cancer. The predictive value of this easily available clinical factor should not be underestimated, and better therapeutic strategies for these tumors are required.