Rapid and Deep Prostate-Specific Antigen Decline is a Prognostic Marker in Metastatic Hormone-Sensitive Prostate Cancer: A Real-World Multi-Intuitional Analysis

Background: Prostate-specific antigen (PSA) kinetics has been investigated as a prognostic marker in post hoc analyses of clinical trials. This study validated the prognostic value of rapid and deep PSA decline in metastatic hormone-sensitive prostate cancer (mHSPC) using real-world data. Methods: In total, 1296 patients with mHSPC were retrospectively reviewed. We assessed the prognostic value of a PSA decline to <= 0.2 ng/mL after 12 weeks of treatment and investigated several potential risk factors for a poor PSA response. Results: Of 1296 patients, 714 (cohort 1: 55.1%) were treated with conventional hormonal therapy, while 582 (cohort 2: 44.9%) received androgen signaling inhibitors. There were significant differences in progression-free survival and overall survival between patients with PSA decline to <= 0.2 ng/mL by 12 weeks of treatment and others (p < 0.001 for each). In addition, patients with an initial PSA >= 200 ng/mL, Clinical T4 and Grade Group 5 were less likely to achieve PSA decline to <= 0.2 ng/mL by 12 weeks of treatment, with odds ratios of 0.31 (p < 0.001), 0.67 (p = 0.039) and 0.70 (p = 0.043), respectively. Conclusion: Our findings suggested that PSA decline to <= 0.2 ng/mL by 12 weeks of treatment may be a useful prognostic biomarker for mHSPC in the real-world setting. The prognostic value of this should be further investigated in a prospective cohort, and identification of an optimal cutoff value is necessary for its application in clinical trial design or clinical practice.