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High medication nonadherence rate, elevated CVD risk after breast cancer diagnosis

Roshini Claire Anthony
27 Dec 2018

Women diagnosed with nonmetastatic breast cancer who were adherent to cardiovascular disease (CVD) medications pre-diagnosis had a high risk of becoming nonadherent post-cancer treatment, with nonadherence increasing their risk of CV events, according to a poster presented at the recent San Antonio Breast Cancer Symposium (SABCS 2018).

Researchers used data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare database to identify 23,080 women with nonmetastatic (stage 1–3) breast cancer diagnosed between 2008 and 2013, of whom 67 percent (n=15,576) were adherent to one or more CVD medications prior to diagnosis. Adherence to medications (80 percent medication possession ratio) was assessed 1 year prior and 1–2 years after breast cancer diagnosis.

A total of 2,732 women (17.5 percent) were nonadherent to at least one CVD medication after breast cancer treatment.

Among those who were adherent to CVD medications before diagnosis, 19.2 percent were nonadherent to antihypertensives, 26.2 percent nonadherent to lipid-lowering medications, and 30.7 percent nonadherent to diabetes medications after 1 year of treatment for breast cancer. [SABCS 2018, abstract PD6-10]

Factors that affected the risk of nonadherence to antihypertensives were older age (hazard ratio [HR], 1.15; p=0.04 for age 80 vs 65–69 years), increasing comorbidities (HR, 1.34; p<0.0001 for Charlson score 1 vs 0), more advanced disease (HR, 1.18; p=0.0005 for stage 2–3 vs 1), and hormone receptor-negative status (HR, 1.15; p=0.04 vs hormone receptor-positive status).

Factors that increased the risk of nonadherence to lipid-lowering medications were increasing comorbidities (HR, 1.26; p<0.0001), more advanced disease (HR, 1.11; p=0.05), and hormone receptor-negative status (HR, 1.18; p=0.03), while only more advanced disease (HR, 1.19; p=0.007) and hormone receptor-negative status (HR, 1.23; p=0.02) increased nonadherence to diabetes medications.

Medication nonadherence after cancer treatment increased the risk of CVD events in women who had been adherent pre-treatment with elevated risks of hypertension (HR, 1.33; p<0.0001), hyperlipidaemia (HR, 1.21; p=0.009), and diabetes (HR, 1.31; p=0.003).

The cumulative 5-year incidence rate of CVD was also higher among patients who were nonadherent compared with those who were adherent to their CVD medications (34.20 percent vs 26.68 percent for antihypertensives, 30.56 percent vs 25.69 percent for lipid-lowering medications, and 33.07 percent vs 26.15 percent for diabetes medications; p<0.01 for all comparisons).

“Studies [have] shown that patients diagnosed with early-stage breast cancer are more likely to die from CVD than breast cancer,” said the researchers.

“[This study showed that] a large proportion of women who were previously adherent to their medications to prevent CVD events prior to their breast cancer diagnosis were nonadherent following treatment [with] nonadherence to CVD medications associated with an increased risk of a subsequent cardiac event,” they said.

“Improving outcomes and reducing morbidity following a breast cancer diagnosis also requires focused attention on non-breast cancer conditions. As breast cancer survival improves, physicians should pay particular attention to addressing CVD risk factors and medication adherence,” they suggested. 

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