Treatment patterns and outcomes in older adults with castration-resistant prostate cancer: Analysis of an Australian real-world cohort

Introduction: Prostate cancer (PC) is the second commonest malignancy and fifth leading cause of cancer death in men worldwide. Older men are more likely to develop PC but are underrepresented in pivotal clinical trials, leading to challenges in treatment selection in the real-world setting. We aimed to examine treatment patterns and outcomes in older Australians with metastatic castration-resistant prostate cancer (mCRPC). Materials and Methods: We identified 753 men with mCRPC within the electronic CRPC Australian Database (ePAD). Clinical data were analysed retrospectively to assess outcomes including time to treatment failure (TTF), overall survival (OS), PSA doubling time (PSADT), PSA(50) response rate, and pre-defined adverse events of special interest (AESIs). Descriptive statistics were used to report baseline characteristics, stratified by age groups (<75y, 75-85y and >85y). Groups were compared using Kruskal-Wallis and Chi-square analyses. Time-to-event analyses were performed using Kaplan-Meier methods and compared through log-rank tests. Cox proportional hazards univariate and multivariate analyses were performed to evaluate the influence of variables on OS. Results: Fifty-seven percent of men were aged <75y, 31% 75-85y, and 12% >85y. Patients >= 75y more frequently received only one line of systemic therapy (40% of <75y vs 66% 75-85y vs 68% >85y; P < 0.01). With increasing age, patients were more likely to receive androgen receptor signalling inhibitors (ARSIs) as initial therapy (42% of <75y vs 70% of 75-85y vs 84% of >85y; p < 0.01). PSA(50) response rates or TTF did not significantly differ between age groups for chemotherapy or ARSIs. Patients >85y receiving enzalutamide had poorer OS but this was not an independent prognostic variable on multivariate analysis (hazard ratio [HR] 0.93(0.09-9.35); p = 0.95). PSADT >3 months was an independent positive prognostic factor for patients receiving any systemic therapy. Older patients who received docetaxel were more likely to experience AESIs (18% in <75y vs 37% 75-85y vs 33% >85y, p = 0.038) and to stop treatment as a result (21% in <75y vs 39% in 75-85y; p = 0.011). Discussion: In our mCRPC cohort, older men received fewer lines of systemic therapy and were more likely to cease docetaxel due to adverse events. However, treatment outcomes were similar in most subgroups, highlighting the importance of individualised assessment regardless of age.