Adverse Drug Reactions and Predictors of Medication Adherence in Patients with Prostate Cancer.

Background: Adherence to therapy with prostate cancer medicines is critical for delaying the progression of disease and enhancing health outcomes.

Objectives: To determine patients' medication adherence, the predictors of adherence, and the frequency and types of adverse drug reactions (ADRs) in persons with prostate cancer.

Methods: A serial entry-point cross-sectional study of patients with prostate cancer was conducted in 3 cancer hospitals in Nigeria over a 12-month period (January 7, 2022, to January 3, 2023). Data on medication adherence were self-reported by patients, and data on ADRs were obtained from hospital records. Descriptive and inferential statistical analyses were performed, and p less than 0.05 was considered statistically significant.

Results: Of the 133 study participants, most 112 (84.2%) reported high medication adherence. The cost of drugs was the most frequently reported potential barrier to adherence (n = 63, 47.4%). Adherence was significantly dependent on family history of cancer (df = 3, F = 4.557, p = 0.005) and health-related quality of life (HRQOL) (ß = 0.275, T = 2.170, p = 0.032) but not illness perception (ß = 0.046, T = 0.360, p = 0.72). Adverse events were observed in 36 participants (27.1%) and were deemed to be "possible ADRs" (n = 19, 53%) or "probable ADRs" (n = 17, 47%); all were nonpreventable and expected (100%), and most (n = 31, 86%) were within the level 1 category of severity. Loss of erection and low libido was the most frequently reported ADR (n = 14, 39%).

Conclusions: In this study, medication adherence was high, with cost being a potential barrier to adherence. Family history of cancer and HRQOL significantly predicted medication adherence. The medications were well tolerated, and observed ADRs had minor severity. Policies targeting the reduction of cost-related factors for prostate cancer medications are essential.