Predicting time to castration resistance with androgen-receptor signaling inhibitors in hormone-sensitive prostate cancer: data from ULTRA-Japan Consortium

Background: Androgen-receptor signaling inhibitors (ARSIs) become the new standard of care for metastatic hormone-sensitive prostate cancer (mHSPC). It is unknown whether time to castration resistance (TTCR), when using the first-line ARSIs, offers predictive value in mHSPC. We sought to assess the clinical outcomes for mHSPC patients treated with first-line ARSIs focusing on the TTCR. Methods: Data from the ULTRA-Japan study cohort from five academic institutes (496 mHSPC patients) were retrospectively analyzed. Results: The median overall survival (OS) in the total cohort was 80 months with a median follow-up of 18 months. Of 496 patients, 332 (67%), 82 (16.5%), and 82 (16.5%) were treated with first-line abiraterone acetate + prednisone, enzalutamide, and apalutamide, respectively. During the follow-up, a total of 155 (31%) were diagnosed with mCRPC with a median TTCR of 10 months. In those 155 patients, TTCR > 12 months is an independent predictor of longer OS from the first-line ARSIs. Cox regression analysis of the TTCR from initiating first-line ARSI in 496 mHSPC patients revealed three variables as independent predictors of shorter TTCR, including Gleason’s score (GS) ≥ 9, the extent of disease (EOD) ≥ 2, and the presence of liver metastasis. Conclusion: Our results indicate that mHSPC patients with those three features are likely to have primary resistance to first-line ARSIs (doublet therapy), thus requiring consideration of other options, such as the recent triplet approach.