Patient knowledge and beliefs about treatment and medical mistrust are mutable factors associated with underuse of effective adjuvant therapies. Physicians may improve cancer care by ensuring that discussions about adjuvant therapy include a clear presentation of the benefits, not just the risks of treatment, and by addressing patient trust in and concerns about the medical system.

6521 Background: We surveyed breast cancer patients in New York City to understand why women did not receive radiotherapy (RT) following lumpectomy, chemotherapy, or hormonal therapy for hormone receptor negative or positive tumors >1 cm, respectively. Methods: 258 New York City women recently surgically treated for a new primary stage I or II breast cancer were surveyed about their experience of care, knowledge and beliefs about breast cancer and its treatment. Adjuvant treatment data were obtained from in and out-patient chart abstraction. Principal components factor analysis was used to create scales of adjuvant treatment beliefs and knowledge, medical mistrust, physician communication about treatment and social support. Scales were scored to 100. Bivariate and multivariate analyses were conducted to determine differences between treated and untreated women; odds ratios were converted to adjusted relative risks. Results: Compared to treated women, untreated women were less likely to know adjuvant therapies increase survival (66 vs 75; p < 0.0001), had greater mistrust (64 vs 53; p = 0.001), and less self efficacy (92 vs 97; p < 0.05); there was no association between physician communication of treatment information and patient knowledge and beliefs about adjuvant treatment (r = 0.8; p = 0.21). Multivariate analysis found that compared to those who were treated, untreated women were more likely to be 70 years or older (OR = 4.46; 95%CI: 1.9–10.7), more likely to have a comorbidity (OR = 3.39;1.5–7.9), more likely to express mistrust in the medical delivery system (OR = 1.03;1.0–1.1), and less likely to believe adjuvant treatments beneficial (OR = 0.91; 0.87–0.96) (model c = 0.84; p =< 0.0001). Conclusions: Patient knowledge and beliefs about treatment and medical mistrust are mutable factors associated with underuse of adjuvant therapies. Despite physicians' discussion of treatment, patients do not have a clear understanding of treatments' benefits and risks. This disconnect between what is said and what is heard may be mediated and addressed by dealing with patients' trust in and concerns about the medical delivery system. No significant financial relationships to disclose.