Real-world treatment patterns in patients diagnosed with metastatic castration-resistant prostate cancer in the US, 2018-2023.

74 Background: The treatment landscape in patients with metastatic castration-resistant prostate cancer (mCRPC) has evolved in recent years. This real-world study evaluates treatment patterns among a large contemporary cohort of patients with mCRPC in the US. Methods: This retrospective cohort study included patients with a confirmed mCRPC diagnosis from 1/1/2018 to 12/31/2023 in the US nationwide Flatiron Health electronic health record-derived deidentified database. Treatment patterns were evaluated by disease setting (metastatic hormone-sensitive prostate cancer [mHSPC], nonmetastatic castration-resistant prostate cancer [nmCRPC], mCRPC) and by use of androgen receptor pathway inhibitors (ARPI; abiraterone, enzalutamide, apalutamide, darolutamide) before mCRPC diagnosis. Patients were considered ARPI-experienced if they received at least 1 line of therapy (LOT) containing an ARPI before progressing to mCRPC. Patients were considered ARPI-naive otherwise. Results: Of 6301 patients with mCRPC (mean age, 75 years), 4915 (78%) received ≥1 LOT in the mCRPC setting. Among those with ≥1 LOT, 48% received second-line (2L) therapy. The most common first-line (1L) and 2L therapies in mCRPC were ARPI (1L, 75%; 2L, 55%) and chemotherapy (1L,16%; 2L, 33%). Most patients (4491, 71%) were ARPI-naive before mCRPC diagnosis. Among the 1810 (29%) patients who were ARPI-experienced before their mCRPC diagnosis, the median treatment duration with ARPI was 23 months. Use of ARPI in the mHSPC setting increased from 11% to 39% in patients diagnosed with mCRPC in 2018 and 2022, respectively. Similarly, in the nmCRPC setting, this figure rose from 20% to 39%. Consecutive use of ARPI in the mCRPC setting, with variations based on the year of mCRPC diagnosis, was observed in 54% to 65% of ARPI-naive patients and 31% to 48% of ARPI-experienced patients who received 1L ARPI and any 2L therapy. Use of chemotherapy increased from 13% to 19% in 1L and 29% to 40% in 2L in the mCRPC setting but decreased from 11% to 7% in mHSPC setting. Conclusions: In this community practice-based study, ARPI was the most common 1L and 2L therapy, followed by chemotherapy, in patients diagnosed with mCRPC from 2018 to 2023. Although ARPI use before mCRPC diagnosis has increased, more than two-thirds of patients overall remain ARPI-naive at mCRPC diagnosis. Despite not being recommended by guidelines, consecutive use of ARPI in the mCRPC setting was common in patients regardless of ARPI use before mCRPC diagnosis.