Nonadherence to Tamoxifen in Breast Cancer Survivors: A 12 Month Longitudinal Analysis

Objective: Previous research has shown that up to 50% of breast cancer survivors prescribed tamoxifen do not take it as recommended, which is associated with increased risk of recurrence and mortality. Little research has attempted to identify modifiable psychosocial factors associated with tamoxifen nonadherence. This study aimed to examine how tamoxifen adherence rates change over a year and to identify modifiable predictors of nonadherence. Method: Three hundred and forty-five breast cancer survivors who were in their first year of tamoxifen prescription were sent questionnaires at 4 points over a 12-month period. Questionnaires assessed demographic and clinical factors, side effects, beliefs about the illness and medication, social support, distress and tamoxifen adherence. Adherence was assessed using the Medication Adherence Rating Scale. Latent Growth Modeling was used to identify predictors of tamoxifen nonadherence. Results: Reported rates of nonadherence increased over time (37-48%). Several demographic, clinical, and psychosocial variables were associated with nonadherence. Women who were nonadherent were more likely to be from a minority ethnic group, to have more negative medication beliefs and to have lower confidence in their ability to take tamoxifen. Conclusions: These demographic and clinical variables can be used to identify women at higher risk of nonadherence. The modifiable psychosocial variables can be used as the basis for psychological interventions to improve adherence in this population. Interventions should focus on both intentional and unintentional nonadherence.