Changes in chronic medication adherence, costs, and health care use after a cancer diagnosis among low-income patients and the role of patient-centered medical homes

Background: Approximately 40% of patients with cancer also have another chronic medical condition. Patient-centered medical homes (PCMHs) have improved outcomes among patients with multiple chronic comorbidities. The authors first evaluated the impact of a cancer diagnosis on chronic medication adherence among patients with Medicaid coverage and, second, whether PCMHs influenced outcomes among patients with cancer. Methods: Using linked 2004 to 2010 North Carolina cancer registry and claims data, the authors included Medicaid enrollees who were diagnosed with breast, colorectal, or lung cancer who had hyperlipidemia, hypertension, and/or diabetes mellitus. Using difference-in-difference methods, the authors examined adherence to chronic disease medications as measured by the change in the percentage of days covered over time among patients with and without cancer. The authors then further evaluated whether PCMH enrollment modified the observed differences between those patients with and without cancer using a differences-in-differences-in-differences approach. The authors examined changes in health care expenditures and use as secondary outcomes. Results: Patients newly diagnosed with cancer who had hyperlipidemia experienced a 7-percentage point to 11-percentage point decrease in the percentage of days covered compared with patients without cancer. Patients with cancer also experienced significant increases in medical expenditures and hospitalizations compared with noncancer controls. Changes in medication adherence over time between patients with and without cancer were not determined to be statistically significantly different by PCMH status. Some PCMH patients with cancer experienced smaller increases in expenditures (diabetes) and emergency department use (hyperlipidemia) but larger increases in their inpatient hospitalization rates (hypertension) compared with non-PCMH patients with cancer relative to patients without cancer. Conclusions: PCMHs were not found to be associated with improvements in chronic disease medication adherence, but were associated with lower costs and emergency department visits among some low-income patients with cancer.