Identifying Prostate Surface Antigen Patterns of Change in Patients with Metastatic Hormone Sensitive Prostate Cancer Treated with Abiraterone and Prednisone.
BACKGROUND: Despite treatment with abiraterone acetate and prednisone (AA/P), most patients with metastatic hormone sensitive prostate cancer (mHSPC) will develop castration-resistant disease (metastatic castration-resistant prostate cancer [mCRPC]). The early identification of who will progress on AA/P is limited.
OBJECTIVE: This study investigates the role of prostate surface antigen (PSA) kinetics as a predictor of progression in mHSPC patients treated with AA/P.
PATIENTS AND METHODS: All patients with mHSPC who initiated androgen deprivation therapy (ADT) and AA/P from June 2017 to February 2019 at the Cleveland Clinic were eligible. PSA-mCRPC was defined as a PSA rise at two consecutive time points. Patients were followed until first mCRPC or last contact after AA/P. Patterns of PSA change were evaluated using a longitudinal mixed model at time 0, 3, 6, 9, and 12 months from AA/P initiation. The association between PSA profile at 3 months and PSA-mCRPC was examined using survival analysis. Radiographic progression (Rad-mCRPC) was also analyzed.
RESULTS: A total of 130 men with follow-up were included. The median (interquartile range [IQR]) follow-up time was 15.3 (10.5, 22.5) months. Eighty-two percent were Caucasian (median age 68.5 years); participants had a median (IQR) PSA of 16.8 (5.3, 48.0) ng/mL. Half of the patients had de novo disease, and 46.2% had high-risk disease (61% had a Gleason score ≥ 8, 16% had visceral disease, and 54% had three or more bony lesions). The greatest PSA percentage reduction from baseline after AA/P initiation occurred at the first 3 months (median 98.3%). The reduction at 6-12 months from baseline was small (99.7-100%). Patients without PSA-mCRPC had a significantly greater 3-month reduction of PSA values compared to patients who developed PSA-mCRPC (p interaction = 0.0002). 50.8% of patients were able to achieve a non-detectable PSA (median 13.1 months). PSA-mCRPC (n = 20) was observed from 4 to 24 months after AA/P, with the majority of events occurring within the first 12 months. Patients with PSA < 0.3 ng/mL (12-month PSA-mCRPC-free 94.5% vs. 69.4%, p = 0.0004) or a ≥ 98% reduction (94.9% vs. 68.0%, p = 0.0002) at 3 months had better PSA-mCRPC-free survival compared to their counterparts. Absolute reduction at 3 months was not associated with PSA-mCRPC. Similar PSA patterns were seen in those who had Rad-mCRPC compared to no Rad-mCRPC (p interaction < 0.05).
CONCLUSION: The degree of PSA decline at 3 months predicted serologic progression to mCRPC. Those who developed castration-resistant disease had higher PSA and a lower percentage reduction by 3 months. Tracking early PSA pattern changes may alert clinicians to poor treatment effect and potential progression; they should consider frequent PSA measurement and imaging, as well as the initiation of sequential therapy.
Sheng IY, Fallah J, Gupta R, Li H, Allman K, Martin A, Barata P, Ornstein MC, Gilligan TD, Rini BI, Garcia JA. Identifying Prostate Surface Antigen Patterns of Change in Patients with Metastatic Hormone Sensitive Prostate Cancer Treated with Abiraterone and Prednisone. Target Oncol. 2020 Aug;15(4):477-483. doi: 10.1007/s11523-020-00734-w. PMID: 32661959.