Prognostic value of pretherapy platelet elevation in oropharyngeal cancer patients treated with chemoradiation

The purpose of this study is to evaluate potential associations between increased platelets and oncologic outcomes in oropharyngeal cancer patients receiving concurrent chemoradiation. A total of 433 oropharyngeal cancer patients (OPC) treated with intensity-modulated radiation therapy (IMRT) with concurrent chemotherapy between 2002 and 2012 were included under an approved IRB protocol. Complete blood count (CBC) data were extracted. Platelet and hemoglobin from the last phlebotomy (PLT_pre-chemoRT, Hgb_pre-chemoRT) before start of treatment were identified. Patients were risk-stratified using Dahlstrom-Sturgis criteria and were tested for association with survival and disease-control outcomes. Locoregional control (LRC), freedom from distant metastasis (FDM) and overall survival (OS) were decreased (p < 0.03, p < 0.04 and p < 0.0001, respectively) for patients with PLT_pre-chemoRT value of ≥350 × 10⁹/L. Actuarial 5-year locoregional control (LRC) and FDM were 83 and 85% for non-thrombocythemic patients while patient with high platelets had 5-year LRC and FDM of 73 and 74%, respectively. Likewise, 5-year OS was better for patients with normal platelet counts by comparison (76 vs. 57%; p < 0.0001). Comparison of univariate parametric models demonstrated that PLT_pre-chemoRT was better among tested models. Multivariate assessment demonstrated improved performance of models which included pretherapy platelet indices. On Bayesian information criteria analysis, the optimal prognostic model was then used to develop nomograms predicting 3-, 5- and 10-year OS. In conclusion, pretreatment platelet elevation is a promising predictor of prognosis, and further work should be done to elucidate the utility of antiplatelets in modifying risk in OPC patients. What's new? In an effort to identify novel prognostic indicators of treatment response, the authors examined pre-therapy platelet counts in patients with oropharyngeal cancer undergoing chemotherapy. Elevated platelet counts were associated with significantly less five-year overall survival as well as reduced locoregional control and freedom from metastasis as compared to patients with normal platelet counts. These results point to elevated platelet counts as a novel pre-therapy risk-stratifying parameter and underscore the need for studies of the molecular role of platelets in oropharyngeal cancer.