Aspirin improves outcome in high risk prostate cancer patients treated with radiation therapy

Purpose: High-risk prostate cancer (PC) has poor outcomes due to therapeutic resistance to conventional treatments, which include prostatectomy, radiation, and hormone therapy. Previous studies suggest that anticoagulant (AC) use may improve treatment outcomes in PC patients. We hypothesized that AC therapy confers a freedom from biochemical failure (FFBF) and overall survival (OS) benefit when administered with radiotherapy in patients with high-risk PC. Materials and Methods: Analysis was performed on 74 high-risk PC patients who were treated with radiotherapy from 2005 to 2008 at UT Southwestern. Of these patients, 43 were on AC including aspirin (95.6%), clopidogrel (17.8%), warfarin (20%), and multiple ACs (31.1%). Associations between AC use and FFBF, OS, distant metastasis, and toxicity were analyzed. Results: Median follow-up was 56.6 mo for all patients. For patients taking any AC compared with no AC, there was improved FFBF at 5 years of 80% vs. 62% (P = 0.003), and for aspirin the FFBF was 84% vs. 65% (P = 0.008). Aspirin use was also associated with reduced rates of distant metastases at 5 years (12.2% vs. 26.7%, P = 0.039). On subset analysis of patients with Gleason score (GS) 9-10 histology, aspirin resulted in improved 5-year OS (88% vs. 37%, P = 0.032), which remained significant on multivariable analysis (P < 0.05). Conclusions: AC use was associated with a FFBF benefit in high-risk PC which translated into an OS benefit in the highest risk PC patients with GS 9-10, who are most likely to experience mortality from PC. This hypothesis-generating result suggests AC use may represent an opportunity to augment current therapy.