Cancer Diagnosis Among Patients With Diabetes Reduced Adherence to Evidence-Based Medications

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“A cancer diagnosis among patients with diabetes reduced adherence with evidence-based medications, particularly if patients’ life expectancy was short,” according to a study among Medicare beneficiaries reported in the Journal of Oncology Practice. “These findings emphasize the vulnerability of individuals faced with a new cancer diagnosis and the difficulty in maintaining ongoing therapy for comorbid conditions, which may have potentially important consequences for longer-term survivorship,” concluded Bruce C. Stuart, PhD, of the University of Maryland School of Pharmacy, Baltimore, and colleagues.

The study compared 4,348 patients with newly diagnosed cancer between January and December 2007 with 28,507 cancer-free controls “assigned a pseudo­diagnosis date,” the researchers explained, so that the distribution of index months was the same for the patients with cancer and the controls. All patients were selected from a 5% random sample of Medicare beneficiaries with diabetes enrolled in Medicare Part D in 2007 and 2008.

The patients with cancer were older, had higher rates of comorbid conditions, and were less likely to receive Medicare Part D low-income subsidies.

Key Findings

Adherence was determined by tracking for 6 months before and 6 months after the diagnosis (or pseudodiagnosis) date the proportion of days covered with oral hypoglycemic agents, renin-angiotensin-aldosterone system inhibitors, and statins. Overall, the patients with cancer had “relatively larger declines in medication adherence” of between 3% and 5% (P < .001) than did the controls, the researchers reported. Patients with cancer who had sharper declines of between 8% and 11% (P < .001) had a short life expectancy, defined by the investigators as death occurring 7 to 12 months after the index date.

For longer-term survivors, the researchers noted, “the declines in proportion of days covered values were relatively small but still appear larger for patients with cancer than for controls.”

The largest declines in adherence to evidence-based medications recommended in diabetes treatment guidelines “were observed for patients who died in the 6 months after our observation period, suggesting that poor cancer prognosis was at least partly responsible. The declines in treatment associated with a cancer diagnosis persisted even when limited to persons with longer-term survival, suggesting that not all of the decline can be attributed to short life expectancy,” the investigators observed.

“We did not find a differential effect on diabetes medication adherence associated with Part D low-income subsidy enrollment, suggesting that new financial burdens associated with cancer treatment were not associated with the observed declines in adherence to these drug classes after a cancer diagnosis,” the researchers reported. “Many of the medications recommended for individuals with diabetes during this period were generic, and copayments for generic drugs, which were already low, decreased further during the study period. Recent evidence indicates that the financial burden associated with adherence to typical diabetes drug regimens is not large.” ■

Stuart BC, Davidoff AJ, Erten MZ: J Oncol Pract. June 23, 2015 (early release online).