Adherence to Oral Treatments in Older Patients with Advanced Prostate Cancer, the ADHERE Study: A Prospective Trial of the Meet-URO Network

Adherence to prescribed oral anticancer treatments is underestimated and difficult to measure in oncology and can affect treatment efficacy, safety, and costs, especially in frail and older patients. This article evaluates adherence to abiraterone and enzalutamide in an observational cohort study of older patients with metastatic castration-resistant prostate cancer. Background Novel androgen receptor signaling inhibitors for prostate cancer (PC) impose the burden of self-administration on older patients overwhelmed by the requirement of many other concomitant medications. Patients and Methods This study evaluated the proportion of non-adherence in a 12-month follow-up period and the first 3 months to abiraterone (ABI) or enzalutamide (ENZ). In a prospective multicenter observational cohort study, patients with metastatic castration-resistant PC (mCRPC) aged >= 70 years receiving ABI or ENZ pre- or post-docetaxel were enrolled. Treatment monitoring included pill counting, a self-assessment questionnaire, and clinical diaries at each clinical visit. Non-adherence rates were based on proportions of missed/prescribed pills ratios by pill counting. Results Overall, 234 patients were recruited with median age of 78 years (range, 73-82); 86 (37%) were treated with ABI, and 148 (63%) with ENZ. The median follow-up for adherence was seven monthly cycles (IQR: 4-12). The two cohorts were well balanced for baseline characteristics. The percentage of non-adherence by pill counting was slightly higher for ABI than ENZ (5.2% vs. 4.2%, P < .001). By self-reporting, patients on ENZ tended to report more frequently than those with ABI forgetfulness as the reason for missing events (42% vs. 17%, P < .001). A lower Geriatric G8 score correlated with non-adherence (P = .004). Overall survival (OS) was 48.8 months. Patients on ABI had radiographic progression-free survival (rPFS) of 28.4 [24.2-32.5], while for ENZ patients, we reported a median rPFS of 23.1 [18.2-28.1] months. Conclusion Physicians tend to treat older mCRPC patients with ENZ. Non-adherence rate is relatively low overall but can be higher with ABI than with ENZ and correlates with the Geriatric G8 score. Forgetfulness is a potential barrier for ENZ.

Automated summary

This article evaluates adherence to abiraterone and enzalutamide in older patients with metastatic castration-resistant prostate cancer. The study finds that non-adherence rate is slightly higher with abiraterone than with enzalutamide, and it correlates with the geriatric G8 score. Forgetfulness may be a potential barrier for enzalutamide.