A Retrospective Observational Analysis of Overall Survival with Sipuleucel-T in Medicare Beneficiaries Treated for Advanced Prostate Cancer

Introduction Since sipuleucel-T approval in 2010, the treatment landscape for metastatic castration-resistant prostate cancer (mCRPC) now includes the androgen-receptor signaling pathway inhibitors (ASPIs) abiraterone acetate or enzalutamide. In 2013 and 2014, these oral agents were approved for use in men with metastatic prostate cancer who had minimal to no symptoms. We compared overall survival (OS) in men who received their first mCRPC treatment using the Medicare Fee-for-Service 100% administrative claims research dataset with patient-level linkage to the National Death Index. Methods This retrospective cohort analysis (January 2013 to December 2017) included men who were chemo-naive at treatment start in 2014 and who had continuous Medicare Parts A, B, and D eligibility during the 3-year observation period. We compared: first-line sipuleucel-T vs. first-line ASPIs and any-line sipuleucel-T vs. any-line ASPIs (without sipuleucel-T). We used a multivariable regression model to help control for potentially confounding factors while assessing survival outcomes. Results The model included 6044 eligible men (average age 75-78 years) with similar disease severity; > 80% were white. Median OS, presented as sipuleucel-T vs. ASPI, was 35.2 vs. 20.7 months (n, 906 vs. 5092; any-line cohort) and 34.9 vs. 21.0 months (n, 647 vs. 4810; first-line cohort). Model outcomes indicated sipuleucel-T was associated with significantly prolonged OS compared with ASPIs: adjusted hazard ratio, 0.59 (95% CI 0.527-0.651) and 0.56 (0.494-0.627) for the any-line and first-line cohorts, respectively. Conclusion This analysis suggests use of sipuleucel-T at any time was associated with improved OS compared with ASPI use alone. Of note, these analyses are intended as descriptive rather than definitive as this dataset contains limited data on key clinical factors. While selection bias is a risk in secondary claims data, this research provides important insight into real-world treatment outcomes.