Factors Associated with Suboptimal Adherence to Tyrosine Kinase Inhibitors in Patients with Renal Cell Carcinoma—A Retrospective Cohort Study

Background: Adherence to tyrosine kinase inhibitors (TKIs), the first-line treatment for renal cell carcinoma (RCC), is critical to ensure intended treatment outcomes. However, 75% of patients with RCC have persistency gaps (>7 days) within the first 90 days after initiating TKIs. This study explored factors affecting TKI adherence in RCC patients to inform future interventions. Methods: A retrospective cohort study was conducted at a specialist oncology hospital in Northwest England from October 2020 to October 2022 on patients with RCC treated with TKIs. TKI prescriptions and persistence gaps (>7 days) were identified from electronic dispensing records. Factors associated with persistence gaps were retrieved by reviewing patients’ clinical records. We used descriptive statistics to summarise the results and Kaplan–Meier analysis to assess the probability and the time to the first gap, stratified by adverse drug effect (ADE)-related and non-ADE-related gaps. Results: Among 165 included patients, 611 persistence gaps were identified. ADEs accounted for 59% (n = 464) of 787 recorded factors, with diarrhoea being the most frequent ADE (9.5%). Patients holding leftover TKIs were the primary (15.1%) non-ADE factor for persistency gaps. At least one gap was observed with 82% of patients (n = 135); 19% had ≥5 ADE-related gaps, and 25% had ≥5 non-ADE-related gaps. ADE-related gaps typically occurred within the first three months (50%), while non-ADE-related gaps were not time-dependent. Conclusions: ADEs, including diarrhoea and pain-related reactions, were the most frequently reported issues affecting TKI persistency in patients with RCC. These ADEs are likely to impact patients’ quality of life and adherence. Future qualitative research is warranted to explore patients’ care needs and additional factors such as health literacy and self-efficacy.