Association of very deep prostate-specific antigen (PSA) decline with longer radiologic-progression-free survival (rPFS) in patients with metastatic castration-sensitive prostate cancer.

e17074 Background: Previous studies have shown rare PSA and rapid reduction in PSA to be associated with survival in patients with metastatic castration-sensitive prostate cancer (mCSPC) treated with ADT, docetaxel, abiraterone, or enzalutamide. The ability to accurately rate nadir PSA level may help inform treatment intensification or de-escalation decisions. PSA nadir level was determined as 0.2 ng/mL for mCSPC in previously reported. However, the deeper the reduction in PSA level, the better the survival outcomes in prostate cancer may be. In the current study, we evaluated the association between a very deep PSA decline and rPFS in patients treated with mCSPC. Methods: Patients with mCSPC treated with ADT, Abiraterone acetate, Enzalutamide, or Docetaxel in the first line setting were included in the study. Serum PSA values were recorded at baseline, 1st, 3rd, and 6th months (mo ). Based on the lowest reached PSA level, patients were divided into four subgroups (PSA 4 ng/mL). Median follow-up and rPFS were estimated using the Kaplan-Meier method. Results: Data from 151 patients were analyzed. 11 patients were excluded due to insufficient data, and 7 patients were not included due to inadequate follow-up. The median age was 68 (38–91) years, and the majority of patients (51.1%) had Eastern Cooperative Oncology Group performance status (ECOG PS) scores of 1≥. Of the patients, 54.1% had high-volume disease, and 65.4% had synchronous metastasis. Additionally, 82% of the patients had bone metastasis, 15% had lung metastasis, and 7% had liver metastasis. When patients were stratified into 4 subgroups based on their lowest PSA levels, the distribution was as follows: PSA4 ng/mL, 15.8% (n=21). The median follow-up time was 32.3 (3–86) mo. The median rPFS for all populations was calculated as 18.1 mo 15.1–20.9 mo, 95% CI. In the PSA4 ng/mL group, 8 mo 1.4-14.6 mo, 95% CI. The statistical analysis revealed a significant relationship between very deep PSA levels and rPFS p<0.01. 5-year rPFS were %78, %16, %8 and %0 for each group, respectively(p<0.01). Conclusions: Very deep prostate-specific antigen decline is associated with longer rPFS in patients with mCSPC. Very deep prostate-specific antigen decline is a more potent surrogate marker for longer rPFS and it can be used new primary endpoint for clinical trials.