# Adherence to Antidiabetic Medication and Cardiovascular Outcomes in Cancer Patients: A Nationwide Population-Based Cohort Study

## TL;DR

Many cancer patients with diabetes don't take their medications as prescribed, leading to higher risks of death, heart disease, and healthcare costs.

## Contribution

This study is the first to show the link between antidiabetic medication adherence and cardiovascular outcomes in cancer patients using a nationwide cohort.

## Key findings

- Poor medication adherence was found in 59.7% of cancer patients with diabetes.
- Nonadherent patients had significantly higher risks of overall and cardiovascular mortality.
- Good adherence was associated with lower healthcare costs and fewer cardiovascular events.

## Abstract

Cancer survivors are increasing, and diabetes is a common comorbidity among them. This study aimed to assess how well cancer patients with diabetes adhere to their antidiabetic medications and the potential impact of poor adherence on health outcomes. We found that a substantial proportion—three out of five patients—did not take their antidiabetic medications as prescribed. Poor medication adherence was linked to higher risks of death, cardiovascular disease, and increased healthcare costs. These findings highlight the urgent need for better strategies to support antidiabetic medication adherence in cancer patients to improve health outcomes and reduce healthcare burdens.

Background/Objectives: Cancer survivors increasingly face cardiovascular disease (CVD), with diabetes as a major risk factor. This study investigates the relationship between adherence to antidiabetic medications and cardiovascular (CV) outcomes in cancer patients. Methods: Using data from the Korean National Health Insurance Service—National Sample Cohort, we assessed the clinical outcomes of adult cancer patients prescribed antidiabetic medications. The study population was categorized based on medication adherence, as determined by the medication possession ratio (MPR): good (MPR ≥ 0.8), moderate (0.5 ≤ MPR < 0.8), and poor (MPR < 0.5) adherence. The primary outcomes included overall and CV mortality, with secondary outcomes encompassing hospitalization for major CVDs and healthcare costs. Results: Among the 7928 cancer patients with diabetes, 59.7% were nonadherent (22.1% with moderate and 37.6% with poor adherence). Over a median follow-up of 5.7 years, 1462 deaths and 2897 CV events were confirmed. Multivariable adjusted analyses showed a 1.70-fold and 2.11-fold higher risk of overall mortality for the moderate and poor adherence groups, respectively, compared to the good adherence group. For CV mortality, moderate adherence was associated with a 1.51-fold higher risk, and poor adherence with a 2.10-fold higher risk. The risk for new-onset CV events increased by 1.32-fold in the moderate adherence group and 1.44-fold in the poor adherence group. The good adherence group also showed significantly lower total healthcare costs compared to the nonadherence group. Conclusions: The present study underscores the importance of adherence to antidiabetic medications in cancer patients, revealing significant associations with decreased mortality, CV events, and healthcare costs.