SAN ANTONIO – Hypertension, dyslipidemia, and type 2 diabetes are common among breast cancer survivors – and so is nonadherence to medications prescribed for these major comorbid conditions.
That was the central finding from COMBO (Commonly Used Medications and Breast Cancer Outcomes), a retrospective cohort study of 4,216 breast cancer survivors belonging to Group Health Cooperative, Gregory S. Calip, Pharm.D., reported at the San Antonio Breast Cancer Symposium.
“This is the first study to investigate breast cancer characteristics and treatments in relation to nonadherence to chronic medications for hypertension, diabetes, and dyslipidemia,” said Dr. Calip of the University of Illinois, Chicago. “Our results suggest that some breast cancer treatments may be associated with nonadherence to antihypertensive agents and oral diabetes medications, but not statins. These findings highlight possible opportunities to improve comorbid condition care in the growing population of breast cancer survivors.”
The irony is that while experiencing breast cancer understandably renders survivors deeply concerned about the prospect of cancer-related death, by not taking their medications for these common comorbid conditions these women increase their overall mortality risk, and particularly their risk of death due to cardiovascular disease and stroke.
The women in the COMBO study had been diagnosed with stage I or II breast cancer during 1990-2008 and did not experience recurrence or a second primary breast cancer during their second year after breast cancer diagnosis. Their medication adherence during that second year was measured via automated health plan pharmacy dispensing records. Patients were classified as nonadherent if their medication possession ratio, or MPR, was less than 0.8.
Antihypertensive agents were prescribed for 1,929 of the subjects, statins for 1,072, and oral diabetes drugs for 449.
During days 366-730 post breast cancer diagnosis, 37% of the women were nonadherent to antihypertensive medications, 39% to prescribed statins, and 75% to their oral diabetes medications.
Common forms of breast cancer therapy were independently associated with increased likelihood of nonadherence in multivariate logistic regression analysis. For example, chemotherapy was associated with a 67% increased likelihood of nonadherence to diabetes medications during year 2 after breast cancer diagnosis. Patients who received radiation therapy or hormonal therapy were, respectively, 21% and 25% more likely to be nonadherent to antihypertensive therapy.
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