Supplementary Material for: Risk factors for lower adherence to epidermal growth factor receptor tyrosine kinase inhibitors for non-small cell lung cancer: A nationwide retrospective cohort study in Japan

Introduction: The prognosis of patients with epidermal growth factor receptor mutation-positive non-small cell lung cancer (EGFR-m-NSCLC) has improved with the introduction of oral EGFR- tyrosine kinase inhibitor (TKI). Lower adherence to oral anticancer medications is reportedly associated with a poor prognosis. It is important to understand the causes of lower adherence to oral anticancer medications. We aimed to assess the potential risk factors associated with low adherence to EGFR-TKIs in a real-world clinical setting using administrative claims data in Japan.
Methods: We identified 10,809 outpatients routinely prescribed EGFR-TKIs between December 2015 and January 2023. Adherence to EGFR-TKIs was assessed based on the medication possession ratio (MPR) during the 12-month follow-up period from the date of first outpatient EGFR-TKI prescription. Multivariable linear regression analysis was performed to identify the potential risk factors associated with lower adherence.
Results: The mean (standard deviation) MPR was 94.1% (14.0). Lower adherence was associated with increasing age (per 10-year increase), female sex, dysphagia, and a higher number of concomitant oral medications (per doubling of the count).
Conclusion: Adherence to EGFR-TKIs was generally high, but the findings support tailored adherence strategies, especially for older patients and for those with a higher number of concomitant oral medications, including medication review to reduce pill burden and proactive support for swallowing difficulties.