Social support at diagnosis and noninitiation, discontinuation, and nonadherence to adjuvant hormonal therapy in the Pathways Study.

7 Background: Exceedingly little research has examined associations between social support and adherence to adjuvant hormonal therapy (AHT) in breast cancer patients. We evaluated associations of social support and noninitiation and discontinuation of, and nonadherence to, AHT in a large, Northern California cohort. Methods: This study included 3,382 women from the Pathways Study who were diagnosed with stages I-III hormone receptor positive breast cancer from 2006-2013 and responded to the Medical Outcomes Study social support survey approximately two months following diagnosis. We used logistic regression to evaluate associations between social support and noninitiation ( < 2 consecutive prescription fills within the first year after diagnosis). Among those who initiated treatment, we used proportional hazards regression to evaluate associations of social support, discontinuation ( > 90 day gap), and nonadherence ( < 80% medical possession ratio) to treatment. Results: Of those who initiated treatment (79%), approximately one fourth either discontinued AHT or were nonadherent. In multivariable-adjusted analyses, adjusted for sociodemographic characteristics, disease severity, other treatment, and presence of comorbidity, women with low (OR = 1.31, 95% CI: 1.06-1.62) and moderate (OR = 1.18, 95% CI: 0.96-1.46) levels of social support were more likely not to initiate AHT treatment, compared to those with high support. Emotional/informational support, tangible support, and positive interaction were each significantly related to noninitiation; affection was not. Of those who initiated treatment, women with low (HR = 1.30, 95% CI: 1.07-1.58) or moderate (HR = 1.19, 95% CI: 0.98-1.44) levels of support were more likely to discontinue treatment. Furthermore, women with low (HR = 1.37, 95% CI: 1.11-1.88) or moderate (HR = 1.24, 95% CI: 1.01-1.52) support had higher nonadherence to treatment. Conclusions: Hormone receptor positive breast cancer patients with low levels of social support had higher noninitiation and discontinuation of, and nonadherence to, AHT. Information on social support may help clinicians determine who is at greater risk of AHT nonadherence.