OBJECTIVES : Second generation androgen receptor inhibitors (SGARIs) apalutamide and enzalutamide have been associated with adverse events (AE) such as fatigue, falls, fracture and rash, among others, in non-metastatic castrate resistant prostate cancer (nmCRPC) patients as identified in clinical trials. Objectives of this real-world study were to describe nmCRPC patients and their treatment patterns, and to estimate incidence and management of AEs in patients receiving apalutamide and enzalutamide.

METHODS : This was a retrospective chart review study conducted in 43 nmCRPC-treating sites in the US. In Phase-1, all patients starting an SGARI between February 2018 and December 2018 and any AEs they experienced were recorded. In Phase-2, detailed chart data were collected in a subset of patients with ≥1 AEs to better understand AE severity and management. Descriptive results were summarized.

RESULTS : 699 patients were recorded by 36 medical oncologists and 6 urologist/urologist-oncologists in Phase-1. Among these, 75.1% experienced ≥1 AE and 44.2% experienced ≥1 central nervous system AE (defined as fatigue, asthenia, headache, fracture, falls, seizures, dizziness, cognitive impairment). Most common AEs were fatigue (23.5%), hot flush (13.9%), and arthralgia (13.6%). Phase-2 patient (apalutamide, 125; enzalutamide, 125) demographics were: Caucasian 72%, mean age 71 years; 0-1 ECOG score 86.0%. PSA-doubling time (PSA-DT) <10 months was chosen as reason to initiate treatment in 40% of patients, while 2 consecutive PSA levels that would allow for assessment of PSA-DT were recorded in only 16% of patient-charts. Grade 3-4 and Grade 5 AEs occurred in 14.4% and 0.4% patients, respectively. Actions to manage AEs included treatment of the AE (38.0%), SGARI discontinuation (10.4%), dose reduction (7.6%), and AE-related hospitalization (4.8%).

CONCLUSIONS : Using real-world data, we found that nmCRPPC patients treated with SGARIs have high susceptibility to AEs, with nearly 40% requiring treatment. These results highlight the continued need to improve tolerance of SGARI-based therapies in nmCRPC.