1178 Post-diagnosis aspirin use and overall survival in patients with melanoma

Abstract

Melanoma is the fifth most common cancer in the US in 2017 and advanced melanoma is still a deadly disease. We recently showed that platelets promote melanoma growth by suppressing T cell anti-tumor immunity in mouse models. Moreover, tumor-derived prostaglandins and platelets aid in melanoma immune evasion and metastasis in preclinical studies. Therefore, aspirin could have a protective role in melanoma. This is a retrospective cohort study of 1,522 Caucasian patients at an academic center, diagnosed with melanoma between 2000 and 2014 and followed up through 2016. Aspirin use was associated with longer overall survival in univariate analysis and after controlling for age, sex, stage, and treatment modalities (HR 0.58, 95% CI [0.45-0.75]). The association persisted after adjusting for cardiovascular comorbidities/risk factors. While aspirin use was not associated with survival in patients with in situ and stage I melanoma, it was associated with longer survival in stages II (HR 0.45, 95% CI [0.24-0.82]) and III (HR 0.57, 95% CI [0.34-0.96]). A similar trend was observed in a smaller number of stage IV patients (n=112), without reaching statistical significance (HR 0.55, 95% CI [0.27-1.13]). In turn, patients using aspirin before diagnosis were less likely to be diagnosed in stages III (13.1% versus 20.4%) and IV (2.4% versus 8.6%) disease. Moreover, higher platelet count at diagnosis was a poor prognostic indicator: patients in the highest tertile experienced shorter overall survival (HR 1.66, 95% CI [1.13-2.43]). Lastly, in a mouse model of thrombocytopenia, low platelet counts resulted in protection from melanoma dissemination to the lungs. Therefore, aspirin could provide survival advantage in advanced melanoma and clinical trials are warranted.