(B-168) Real-world treatment patterns and clinical outcomes in patients with metastatic castration-resistant prostate cancer (mCRPC) who received a third line treatment

Background: Prostate cancer is the most common cancer among US men. Antiandrogen therapy remains the standard systemic treatment for hormone sensitive prostate cancer, but many patients progress to metastatic castration-resistant prostate cancer (mCRPC). Novel hormonal therapies have improved outcomes for mCRPC patients, yet no standard of care exists after disease progresses on these therapies.

Objectives: Describe real-world (RW) treatment patterns and clinical outcomes in mCRPC patients who received a third line of therapy.

Methods: Patients diagnosed with mCRPC who received at least 3 systemic therapies from the electronic health record-derived de-identified US -based Flatiron Health database (data cutoff May 01, 2023) were included. The index date was the treatment initiation date of each of line of therapy (LOT). Top therapeutic classes and regimens in each LOT were obtained. RW overall survival (rwOS), RW time to discontinuation (rwTTD), RW time-to-next treatment (rwTTNT) and corresponding 95% confidence intervals (CI) were obtained using the Kaplan-Meier estimator.

Results: The dataset included 3,612 patients who initiated 3L with a median age of 71 years, of which 30% did not receive subsequent treatment due to death. Most patients received novel hormonal therapy in 1L (72%) and/or 2L (63%). For 3L, most patients received novel hormonal therapy (41%) or chemotherapy (40%), with the most common regimens including docetaxel (24%), enzalutamide (14%), or abiraterone (12%). The median (95%CI) months of rwOS, rwTTNT, and rwTTD from 3L were 13.5 (13.0, 14.1), 5.9 (5.7, 6.1), and 3.4 (3.4, 3.5), respectively. Among those who received 4L or 5L treatments, a variety of therapies were used, and the most commonly used were docetaxel and cabazitaxel. The median (95%CI) months of rwOS, rwTTNT, and rwTTD were 11.1 (10.5, 11.8) , 5.1 (4.9, 5.4), 2.8 (2.7, 2.9) from 4L; and 10.3 (9.4, 11.1), 5.2 (5.0, 5.6), 2.8 (2.4, 3.0) from 5L.

Conclusions: Among patients with mCRPC who received 3L therapy, novel hormonal therapy and chemotherapy were commonly used in earlier lines and a broad range of subsequent treatments, including docetaxel and cabazitaxel , were used afterward. The short median rwOS, rwTTNT, and rwTTD across later lines highlights a significant unmet need for new therapies to improve clinical outcomes for patients with mCRPC in later lines.