Where Should Enzalutamide Be in The Metastatic Castration Resistant Prostate Cancer (mCRPC): A Multi-center Study

Objectives: Enzalutamide(ENZ) is an effective hormonal treatment modality in mCRPC. It can be used before or after docetaxel(DTX) in this setting. Herein, we aimed to show the efficacy of ENZ before or after DTX use and the factors predicting the efficacy. Methods: We retrospectively collected the data of 320 patients from 12 centers who were treated with ENZ in mCRPC. The initial stage, age, line of treatment, serum prostate-specific antigen (PSA) levels before ENZ treatment and at nadir, site of metastasis, gleason score were evaluated. Results: Median age of 320 patients were 69. At a median follow-up of 56 months, 271/320 (84.7%) disease progression and 230/320(71.9%) death had been observed. Median PFS was 11(8.9-13)) and median OS was 25(22.1-27.8) months in all patients group. Median PFS was 10(7.4-12.5) months, 11(8-13.9) months in pre-DTX and post-DTX groups respectively. Median OS was higher in the post-DTX group than the pre-DTX group (28(25.7-30.2) vs 19(15.0-22.9-46.6) (p:0.000). Gleason score ≥ 8 (HR 0.59, 95%CI 0.46-0.77, p=0.00), presence of non-visceral metastasis (HR 0.72, 95%CI 0.53-0.97, p=0.031), initial PSA value<43(median) (HR 0.70, 95%CI 0.54-0.91, p=0.009), PSA at nadir <2 (HR 0.61, 95%CI 0.44-0.85, p=0.004), >50% decline in PSA (HR 0.27, 95%CI 0.19-0.36, p=0.000) significantly predicted ENZ response regarding rPFS. Conclusion: ENZ has shown equal efficacy before and after DTX treatment in mCRPC regarding rPFS. But OS rate was significantly better in the pre-DTX group. Therefore, we recommend starting with DTX in patients who can tolerate chemotherapy in mCRPC setting.