The Burden of Exposure and Monitoring of QT-Prolonging Drugs and the Transient Risk of Sudden Cardiac Death among Older Adults with Cancer

Cancer is a leading cause of death in the United States and a major driver of polypharmacy among older adults. Many cancer treatments, particularly QT-prolonging medications, are associated with an increased risk of cardiotoxicity, including sudden cardiac death (SCD). This dissertation utilized SEER-Medicare data to investigate the burden, monitoring, and potential risks of QT-prolonging medications in older adults with cancer through two complementary studies. In Aim 1, we assessed the prevalence and temporal patterns of QT-prolonging medication exposure and electrocardiographic (ECG) monitoring across the cancer care trajectory. We found significant gaps in ECG monitoring, particularly during periods of high QT prolongation risk. These findings highlight critical opportunities to improve cardiac monitoring practices in this vulnerable population. In Aim 2, we evaluated the transient associations between QT-prolonging medication exposure and SCD using two self-controlled study designs. While SCD was a rare event, our results did not demonstrate a significant increase in SCD risk during hazard periods of QT-prolonging medication exposure. These findings underscore the importance of accounting for confounding factors and temporal trends when evaluating medication safety in older adults. Together, these studies provide a comprehensive assessment of QT-prolonging medication use and its implications in older adults with cancer. The findings emphasize the need for targeted interventions, including enhanced ECG monitoring and pharmacist-led medication reviews, to mitigate risks and improve patient outcomes. This dissertation contributes critical evidence to guide future research, inform clinical guidelines, and support equitable cancer care.