ASCO GU 2018: Treatment Duration And Utilization Patterns In Metastatic Castration-resistant Prostate Cancer Patients Receiving Enzalutamide or Abiraterone Acetate

San Francisco, CA ( Enzalutamide (ENZA) and abiraterone acetate (ABI) are approved hormonal therapies for men with metastatic castration-resistant prostate cancer (mCRPC). The authors presented a study assessing the real-world treatment duration and utilization patterns in patients receiving ENZA or ABI.

Adult mCRPC patients initiating ENZA or ABI before or after cytotoxic chemotherapy were identified from the Truven MarketScan® claims database (2012–2015). The index date was the first initiation of ENZA or ABI. Treatment discontinuation was defined as a prescription gap of ≥45 days. Treatment switching was defined as starting a new mCRPC-related therapy within 30 days before to 45 days after the discontinuation date. Analyses were separately conducted for chemo-naïve and chemo-experienced patients.

The study included 3230 chemo-naive (ENZA 920; ABI 2310) and 692 chemo-experienced patients (ENZA 262; ABI 430).
Among chemo-naive patients:
ENZA cohort had older patients (mean age 74.5 vs 73.5; p = 0.013), with a higher proportion of comorbidities, when compared to the ABI cohort. Treatment duration was longer for the ENZA cohort than for the ABI cohort (log-rank p = 0.008; median = ENZA 10.7 vs ABI 8.8 months). Within 1 year of initiation, 55.7% of ENZA and 60.8% of ABI cohort discontinued treatment and 22.5% and 34.7%, respectively, switched to other mCRPC therapies. Results were consistent among subgroups with specific comorbidities.
Among chemo experienced patients:
The treatment duration was shorter than for chemo-naive patients; the difference between ENZA vs ABI was not statistically significant (log-rank p = 0.255; median = ENZA 7.5 vs ABI 7.1 months).

Despite a more complex profile at baseline, chemo-naive mCRPC patients in the ENZA cohort had a longer treatment duration and lower proportion of switching to other prostate-cancer-directed therapies, when compared to the ABI cohort. In contrast, the difference of treatment duration between the two cohorts was not statistically significant for chemo-experienced patients.

Presented by: Vahan Kassabian

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA