Outcomes of a Canadian real-world cohort of metastatic castration-sensitive prostate cancer patients stratified by early PSA nadir

Introduction Real-world data can complement trial analyses and validate biomarkers in metastatic castration sensitive prostate cancer (mCSPC) population.Methods A prospective, multi-center cohort study recruited mCSPC patients across Canada between 2018 to 2021. Baseline characteristics, treatment patterns, and clinical outcomes were reported.Results Two hundred and four mCSPC patients were enrolled, 87.3% with de-novo diagnoses, 63.2% with high-volume disease. Median PSA was 81 ng/ml (interquartile range [IQR] 19.3 – 339), median age 70 years, and 88.7% ECOG performance status of 0-1. 84.8% (n=173) received treatment intensification, mainly with ARPi (androgen receptor pathway inhibitors) (73%). A higher proportion of patients intensified with ARPi agents (56%) reached PSA nadir ≤0.2 ng/ml between 6-9 months of treatment initiation (PSA6-9mos≤0.2) compared to other treatments. Overall survival (OS) and time to castration-resistant prostate cancer (ttCRPC) were significantly better for PSA6-9mos≤0.2 compared with PSA6-9mos>0.2 [HR 10.68 (2.34-48.82) and 5.06 (1.81-14.14) respectively]. In multivariable analysis, PSA6-9mos>0.2 was significantly associated with poor 2-year survival [HR 29.32 (5.08-169.24)].Conclusions This multi-center prospective real-world mCSPC cohort confirms the prognostic significance of PSA nadir at 6-9 months in stratifying patient outcomes. mCSPC patients not achieving PSA nadir by 6-9 months could be considered for further treatment intensification.