The association between PSA pattern changes and progression in patients with metastatic hormone-sensitive prostate cancer (mHSPC) treated with abiraterone and prednisone (AA/P).

Abstract

18 Background: Despite treatment with AA/P, many patients with mHSPC will develop castrate resistant disease (CRPC). Early recognition of progression is difficult. Changes in PSA patterns in patients with mHSPC treated with AA/P may help identify evolution to mCRPC. Methods: All patients with mHSPC who initiated ADT and AA/P from June 2017 to February 2019 at the Cleveland Clinic were eligible. Patterns of PSA change were evaluated using a longitudinal mixed model at time 0, 3, 6, 9, and 12 months (mo) from AA/P initiation. Time to PSA<0.03 and CRPC were estimated using Kaplan-Meier method. Progression was defined as a PSA rise at two consecutive time points. Results: Of the 143 patients who initiated AA/P, 134 men (median Gleason score 8, baseline PSA 15.0 ng/mL) with follow up were included. 52% had de novo mHSPC, 47.8% had prior therapy (21% surgery, 20% radiation, 7% both), and 16% had visceral disease. PSA levels dropped 98.2% in the first 3 mo (p<0.001), slowed from 3-9 mo (p<0.05) and plateaued after 9 mo. The % PSA reduction from time 0 to the other time points was small. The median time to PSA<0.03 was 11 mo. Of those who progressed to CRPC, the reduction within the first 3 mo was more significant than in those who did not (Table). Measurable PSA was higher in patients who progressed to CRPC at all-time points and plateaued by 6 mo. 12-mo CRPC-free after AA/P was 86.7% (95% CI: 79.2, 94.1). Patients with ≥ 98% 3-mo PSA reduction had better CRPC-free survival than patients with <98% reduction (12-mo CRPC-free: 94.4% vs 78.4%), p<0.001. Conclusions: The degree of PSA decline within 3 mo of AA/P may be used as treatment efficacy measurement. Tracking PSA pattern changes may alert clinicians for potential progression, consider frequent PSA and imaging, as well as initiate sequential therapy.[Table: see text]