Prognostic Impact of Initial Prostate Specific Antigen Half‐Life After Abiraterone Acetate in High‐Volume Metastatic Hormone‐Sensitive Prostate Cancer: Who May Need Triplet Therapy?

ABSTRACT Background As no randomized study has compared abiraterone acetate (ABI) doublet and triplet therapy, the optimal target for the add‐on of docetaxel (DTX) to ABI doublet therapy remains unclear. The present study explored patients who may benefit from add‐on DTX using initial prostate‐specific antigen (PSA) reduction after ABI doublet therapy. Methods We retrospectively reviewed 233 patients with CHAATED high‐volume metastatic castration‐sensitive prostate cancer (mCSPC) treated with ABI doublet therapy. Using the initial PSA half‐life calculated by PSA reduction within 6 weeks of treatment (initial PSA T1/2 ), a subgroup of patients with a poor overall survival (OS) was explored. The optimal cutoff value of PSA T1/2 predicting a PSA decline < 90% after 12 weeks of ABI treatment was investigated using a receiver operating characteristic (ROC) analysis. Results A PSA T1/2 of 0.33 months was an ideal cutoff value for predicting a PSA decline < 90% after 12 weeks of ABI treatment. In addition to Grade Group 5 (hazard ratio HR: 3.06, p = 0.002) and an LDH ≥ 250 U/L (HR: 2.30, p = 0.017), an initial PSA T1/2 ≥ 0.33 months (HR: 3.39, p < 0.001) were identified as significant predictors of a poor OS in mCSPC treated with ABI doublet therapy. Only liver metastasis was significantly associated with an initial PSA T1/2 of ≥ 0.33 months. Conclusion We showed that the initial PSA T1/2 of treatment was significantly prognostic in high‐volume mCSPC patients treated with ABI doublet therapy. Our findings suggest that initial PSA reduction may help identify patients who will benefit from the addition of DTX. A prospective study is required to verify our hypotheses.