Endocrine therapy reduces the risk of recurrent breast cancer, but nonadherence is high. Researchers from Utrecht University, Leiden University Medical University, Diaconessenhuis Hospital, and the Netherlands Institute for Health Services Research, all in the Netherlands, felt there was more to nonadherence than most surveys were reporting. So they developed the Tailored Medicine Inventory, which allowed respondents to skip irrelevant items and expand on areas that are usually more limited, such as practical problems they encounter with the treatment.
The 241 survey respondents answered questions about their perceptions of the efficacy of endocrine therapy, worries about adverse effects (AEs), and practical problems that impact adherence, such as packaging, refills, and understanding information. The researchers also assessed perceived self-efficacy, using the Medication Use and Understanding Self-Efficacy scale. They used 2 scales to assess nonadherence: the Medication Adherence Rating Scale-5 and because that scale seemed to underrepresent unintentional nonadherence, they included the Morisky Medication Adherence Scale, with additional questions about forgetting to take the endocrine tablets and persistence.
A substantial number of women were not convinced of the efficacy of endocrine therapy (30%). Some did not believe it was necessary (14%) or doubted its capacity to prevent cancer recurrence (32%). Nineteen percent of the women said they didn’t know how endocrine therapy works, and 20% said that they lacked information about it and didn’t know to what extent it reduced the chance of recurrence.
One hundred sixteen of the women surveyed (48%) experienced ≥ 1 practical problems, most often in the categories of information, intake of tablets, and packaging. All categories except “limitations in daily life” posed “substantial bother” to the women, the researchers say. Practical problems more than doubled the chance of unintentional nonadherence.
Self-reported unintentional nonadherence was high (85%), and intentional nonadherence or premature discontinuation was even higher (90%-92%). However, the researchers found no association between perceptions of the efficacy of endocrine therapy and nonadherence. Older women and those who were being treated for recurrent breast cancer were less likely to be unintentionally nonadherent. Perceived self-efficacy was associated with lower levels of both unintentional and intentional nonadherence.
The likelihood of intentional nonadherence rose by 20% for every additional AE experienced. Common AEs were a source of worry; particularly the best-known ones, such as hot flushes, reduced libido, cramps, joint ache, and joint stiffness. But the respondents often mentioned other AEs than those most often described in the literature. Memory and concentration problems, the researchers say, are consistent with AEs documented in the neuropsychologic side study of the Tamoxifen Exemestane Adjuvant Multinational trial. This finding, the researchers say, underscores the importance of not restricting assessment in clinical practice to only familiar AEs.
The researchers concluded with the acknowledgment that endocrine nonadherence is a complex and multifaceted issue in which women’s varied experiences are all factors. In short, one size does not fit all. Thus, they suggest—absent a unifying causal model—that a “promising approach” is to investigate a wide array of women’s experiences and perceptions. Targeting specific concerns and helping women boost self-efficacy could help drive up adherence.
Wouters H, Stiggelbout AM, Bouvy ML, et al. Clin Breast Cancer. 2014;14(6):460-467e2.