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?

[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), a subgroup of patients with a poor overall survival (OS) was explored. The optimal cutoff value of PSA predicting a PSA decline < 90% after 12 weeks of ABI treatment was investigated using a receiver operating characteristic (ROC) analysis.

[RESULTS] A PSA 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 ≥ 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 of ≥ 0.33 months.

[CONCLUSION] We showed that the initial PSA 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.