Low-Dose Abiraterone in Metastatic Castration-Resistant Prostate Cancer.

Purpose: Abiraterone acetate (AA) is approved for prostate cancer at a standard dose of 1,000 mg fasting. Because of a significant food effect, a lower dose (250 mg with food-AA low dose [AALD]) shows similar efficacy at 75% lower cost. In Brazil, 80% of patients rely on the public health care system, which does not cover the standard dose. Hospital de Base has been using AALD since March 2021.

Materials and methods: We retrospectively reviewed patients with metastatic castration-resistant prostate cancer (mCRPC) who received AALD at any treatment line, regardless of previous chemotherapy, between March 2021 and May 2023. The primary end point was prostate-specific antigen (PSA) response rate (RR; defined as a decrease of ≥50% in PSA level after 12 weeks of treatment). Secondary end points included time to treatment failure (TTF), overall survival (OS), and PSA RR ≥50% at nadir.

Results: Ninety-six patients were included. Sixty-three patients (65.6%) received AALD in mCRPC first-line. After a median follow-up of 24.4 months, 53 patients (60.2%) achieved the primary end point, and 65 (69.9%) achieved a PSA reduction of ≥50% at nadir. Patients treated with AALD pre-docetaxel in the mCRPC had a higher PSA response at 12 weeks (68.3% v 40%, P = .015) and at nadir (76.1% v 53.8%, P = .036). First-line AALD was associated with better PSA responses. The median TTF was 7.9 months and the median OS was 20.6 months. Achieving a ≥50% PSA response at 12 weeks was associated with improved TTF (13.6 v 4.6 months, hazard ratio [HR] = 0.37, P < .001) and OS (28.9 v 12.2 months, HR = 0.44, P = .004).

Conclusion: AALD showed meaningful efficacy and survival outcomes. We support AALD use, especially where standard dosing is unaffordable.