Development and Validation of Prognostic Model for Metastatic Castration-Resistant Prostate Cancer Patients Treated With First-Line Abiraterone or Enzalutamide

Introduction: Over the years, several prognostic models were developed in patients receiving chemotherapy for metastatic castration resistant prostate cancer (mCRPC), while data on androgen-receptor signaling inhibitors (ARSI) in a real-world setting are limited. Patients and methods: We compared a consecutive series of 565 mCRPC patients receiving first-line ARSI at 4 high-volume Italian Centers (development set) to an external series of 180 patients receiving the same treatment at another Italian high-volume Center (training set), between 2011 and 2022. Sixteen clinical and baseline laboratory variables were selected to develop a prognostic model. Patients were categorized into risk groups according to the number of independent factors positively associated with overall survival (OS). Results: In the development cohort, after a median follow-up of 21.1 months, the median OS was 30.4 months (95% CI 27.5-33.4). At the multivariate analysis, 7 variables [age, prostate specific antigen (PSA) doubling time, baseline levels of hemoglobin, PSA, time to castration resistance, ECOG PS and bone metastases number) were included into the final model. The median OS was 13.4, 25.7 and 46.4 months in poor (0-2 factors), intermediate (3-4 factors) and good (≥ 5 factors) prognosis group, respectively. The application of the model to the validation set confirmed its ability to prognosticate for OS. The model c-indexes were 0.68 (95% CI 0.64-0.72) and 0.75 (95% CI 0.68-0.81) in the development and validation cohort, respectively. Conclusions: Our model, based on clinical and laboratory variables readily assessable in clinical practice, might prognosticate the OS of mCRPC patients receiving first-line ARSI.