Elevated platelet count is a negative predictive and prognostic marker in locally advanced rectal cancer undergoing neoadjuvant chemoradiation: a retrospective multi-institutional study on 965 patients.

Background: In patients with locally advanced rectal cancer treated by neoadjuvant chemoradiation, pathological complete response in the surgical specimen is associated with favourable long-term oncologic outcome. Based on this observation, nonoperative management is being explored in the subset of patients with clinical complete response. Whereas, patients with poor response have a high risk of local and distant recurrence, and appear to receive no benefit from standard neoadjuvant chemoradiation. Therefore, in order to develop alternative treatment strategies for non responding patients, predictive and prognostic factors are highly needed. Accumulating clinical observations indicate that elevated platelet count is associated with poor outcome in different type of tumors. In this study we investigated the predictive and prognostic impact of elevated platelet count on pathological response and long-term oncologic outcome in patients with locally advanced rectal cancer undergoing neoadjuvant chemoradiation.

Methods: A total of 965 patients were selected from prospectively maintained databases of seven Centers within the SICO Colorectal Cancer Network. Patients were divided into two groups based on a pre-neoadjuvant chemoradiation platelet count cut-off value of 300 × 10/L identified by receiver operating characteristic curve considering complete pathological response as the outcome.

Results: Complete pathological response rate was lower in patients with elevated platelet count (12.8% vs. 22.1%, p = 0.001). Mean follow-up was 50.1 months. Comparing patients with elevated platelet count with patients with not elevated platelet count, 5-year overall survival was 69.5% vs.76.5% (p = 0.016), and 5-year disease free survival was 63.0% vs. 68.9% (p = 0.019). Local recurrence rate was higher in patients with elevated platelet count (11.1% vs. 5.3%, p = 0.001), as higher was the occurrence of distant metastasis (23.9% vs. 16.4%, p = 0.007). At multivariate analysis of potential prognostic factors EPC was independently associated with worse overall survival (HR 1.40, 95% CI 1.06-1.86), and disease free survival (HR 1.37, 95% CI 1.07-1.76).

Conclusions: In locally advanced rectal cancer elevated platelet count before neoadjuvant chemoradiation is a negative predictive and prognostic factor which might help to identify subsets of patients with more aggressive tumors to be proposed for alternative therapeutic strategies.