Real World Patterns of PSA Response and Survival with Abiraterone and Enzalutamide in Metastatic Castrate Resistant Prostate Cancer (mCRPC)

Background: We investigated our institution’s mCRPC enzalutamide or abiraterone patients examining PSA responses and impact of sequencing of these drugs. Methods: All enzalutamide / abiraterone mCRPC patients (2011-2018) were included. Rates of PSA >50% response (PSA50) were compared. Time to treatment failure (TTF) and overall survival (OS) was analysed as per lines of previous therapy and timing of chemotherapy. Results: 363 patients included (Enza n=236, Abi n=127), with 15.6 months median follow-up. PSA50 was greater in enzalutamide group (58% vs 31% p<0.0005) but TTF was similar for both groups (median Abi 4.2m vs Enza 6m, p=0.965). There was no significant median OS difference between the groups (Enza 13.8m vs Abi 12.5m p=0.065). Number of lines of prior therapy (p=0.735) or timing of chemotherapy before or after Abi/Enza (p=0.21) had no significant OS impact. Conclusion: Enzalutamide showed higher PSA50 response than abiraterone. Previous lines of therapy or sequencing of chemotherapy with abiraterone / enzalutamide showed no significant survival differences indicating no detriment in either treatment sequence.