Low-Dose Abiraterone in Metastatic Castration-Resistant Prostate Cancer

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.

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.

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).

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