Real-world comparison of cost and adherence between patients receiving low-dose versus standard-dose abiraterone acetate (AA) in a safety-net hospital.

54 Background: While the standard dose of AA (1,000 mg) is taken on an empty stomach, low-dose AA (250 mg with a low-fat meal) is also an option, with both listed as standard of care in national guidelines for the treatment of prostate cancer (PCa). We sought to evaluate the cost and adherence of low-dose AA (LDAA) versus standard-dose AA (SDAA) in a diverse population treated at the University of Illinois Chicago (UIC), a Chicago safety-net hospital. Methods: PCa patients treated at UIC who filled at least oneprescription for AA between April 2017 and September 2024 were identified retrospectively. Key data such as age, race, ethnicity, insurance status, disease stage, monthly copays, medication fill history, dates of disease progression or death, and adverse events were obtained. Chi square analysis was used to compare cost, adherence, progression-free survival (PFS), and adverse events between the two groups. Adherence was calculated as the number of 30-day fills divided by the number of months the patient was prescribed AA, expressed as a percentage. Results: We identified 138 patients who filled a prescription for AA during the study timeframe (Table). 72.5% were Black, 55.1% had Medicare as their primary insurance, and 35.5% had Medicaid as their primary insurance. 26.8% had localized disease upon starting AA while 73.2% had metastatic disease (Table 1). Patients receiving LDAA were less likely to have a monthly copay of $100 or greater at any point compared to those receiving SDAA (7.3% vs. 19.6%, p=0.04). The percentage of patients with less than 80% adherence was 4.9% for those receiving LDAA compared to 10.7% of those receiving SDAA, however this difference did not meet statistical significance (p=0.20). Adverse events were similar in both cohorts, with 13.4% of those receiving LDAA having discontinued the medication due to toxicities compared to 10.7% of those receiving SDAA (p=0.64). Median PFS was 23 months in the standard-dose group but was not reached in the low-dose group due to data immaturity. Conclusions: Patients receiving LDAA experienced lower financial burden than those receiving SDAA, as quantified by copays of $100 or greater. There was not a statistically significant difference between the two groups in adherence or rate of adverse events requiring discontinuation. Data on the impact of dose and clinical outcomes are ongoing and maturing. LDAA (n=82, median age 65) SDAA (n=56, median age 68) Total (n=138, median age 66) Medicare 42 (51.2%) 34 (60.7%) 76 (55.1%) Medicaid 32 (39.0%) 17 (30.4%) 49 (35.5%) Private or other insurance 8 (9.8%) 5 (8.9%) 13 (9.4%) Black, non-Hispanic 59 (72.0%) 41 (73.2%) 100 (72.5%) White, non-Hispanic 7 (8.5%) 8 (14.3%) 15 (10.9%) Hispanic of any race 14 (17.1%) 7 (12.5%) 21 (15.2%) Other race 2 (2.4%) 0 (0%) 2 (1.4%) Localized disease 27 (32.9%) 10 (17.9%) 37 (26.8%) Metastatic disease 55 (67.1%) 46 (82.1%) 101 (73.2%)