4CPS-207 Evaluation of prostatic specific antigen depletion with abiraterone as a pronostative factor for survival in metastatic castration-sensitive prostate cancer

Background and Importance In the literature, there is an indicator of response to treatment with enzalutamide and apalutamide, defined as PSA90, for patients with metastatic castration-sensitive prostate cancer (mCSPC). However, no early response marker to abiraterone treatment in the setting of synchronous mCSPC has been described. Aim and Objectives The aim was to analyse the deep prostatic specific antigen (PSA) response in patients with mCSPC treated with abiraterone. Material and Methods Retrospective analysis of patients with metastatic mCSPC treated with abiraterone according to the LATITUDE clinical trial criteria (2 of 3 criteria: bone metastases ≥3, Gleason score ≥8 or presence of visceral metastases), in our centre from September 2017 to January 2023. Data collected for each patient were: age, PSA at baseline (PSA0), percentage of PSA decline after 14±7 days since the start of abiraterone treatment (%PSA), Gleason score at baseline (GS), type of metastases, event (defined as progression or death) and progression-free survival (PFS). Receiver operating characteristic (ROC) curve was used to evaluate the optimal PSA cut-off point to identify a greater possibility of response. Event-time distributions were estimated using Kaplan-Meier methodology. Log-rank tests were used to test for differences in event-time distributions. All p-values are 2-sided and CIs are at the 95% level, with significance pre-defined to be at the 0.05 level. Results Data from 41 patients were analysed, of which there was no biochemical response in five of them. Table 1 shows the median and standard deviation of the variables analysed. Fifty percent of patients had a GS=9. The percentage of patients with bone, visceral and lymph node metastases was 50%, 33% and 17%, respectively. A cut-off of 30% for PSA decline was established. Median PFS was 10.1 months (95%CI: 5.3–14.8) in patients with PSA decline Conclusion and Relevance This real-life study shows that an early decline in PSA value ≥30% after initiating abiraterone treatment may be an indicator of improved treatment response in patients with mCSPC. Larger studies are needed to confirm this hypothesis. References and/or Acknowledgements Conflict of Interest No conflict of interest.