Abstract 4305: Short-term outcomes of abiraterone in community settings

Introduction: About 32% of men with high-risk prostate cancer have comorbidities, conditions that may be under-represented in randomized clinical trials (RCTs). Because men enrolled on RCTs are often excluded if they have multiple comorbidities, these patients may be at higher risk for serious toxicities from cancer therapies that the results of RCTs may not reflect. This study was undertaken to test the hypothesis that 90-day mortality rates in men undergoing treatment with abiraterone (a novel agent for treating castration-resistant prostate cancer) in the community settings is higher than that observed in the pivotal trial. Methods: SEER-Medicare linked data with Medicare Drug Event File during the period 2006-2012 were used to identify patients who filled prescriptions for abiraterone during the study period and these patients were followed through 12/31/2013 for overall mortality. Ninety-day mortality after abiraterone initiation among patients with Charlson score 0 was compared to that in the pivotal abiraterone trial published in the New England Journal of Medicine 2011. Results: We identified 1,106 patients who took abiraterone during the study period. Among them, 484 (43.8%) were age 75 or older at the time of abiraterone initiation and 61 (5.5%) had comorbidity score 2 or higher. Hospitalization rates among those who had abiraterone were 0.09 per person month during the 6-month window before the initiation of abiraterone and 0.12 per person month within 3 months of drug initiation. The top five diagnoses for hospital admission after drug initiation were general symptoms (ICD-9 780), malignant neoplasm of prostate (ICD-9 185), respiratory abnormality (ICD-9 786), care involving rehabilitation (ICD-9 V57), and urinary tract infection (ICD-9 599). The 90-day all-cause mortality after drug initiation was 14.5% (95% 12.4% - 16.5%) in the entire study cohort, 13.0% (95% CI 10.4% - 15.7%) among those under age 75 and 16.3% (13.0% - 19.6%) among those 75 or older. The 90-day mortality was 15.5% (95% CI 12.2% - 18.8%), 12.8% (95% CI 6.2% - 19.3%), and 18.0% (95% CI 8.3% - 27.8%) among patients with comorbidity score 0, 1, and 2+ respectively. The 90-day mortality among patients with comorbidity 0 in the community settings is substantially higher than those found in the pivotal trial abiraterone arm (risk ratio 2.03; 95% CI 1.48 - 2.78) and control arm (risk ratio 1.43; 1.01 - 2.03). Conclusion: This first US national study shows that 90-day mortality after abiraterone among relatively healthy patients in the community settings is twice that observed in the pivotal trial abiraterone arm. Further studies are needed to improve selection of eligible patients and post-treatment monitoring. Citation Format: Grace L. Lu-Yao, Dirk F. Moore, Yong Lin, Timothy R. Rebbeck, Kitaw Demissie, David Rotter, Kimberly A. McGuigan, Anthony V. D’Amico. Short-term outcomes of abiraterone in community settings. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4305.