Is There a Relationship between Shared Decision Making and Breast Cancer Patients' Trust in Their Medical Oncologists?

Background. Adjuvant systemic treatment for early stage breast cancer significantly reduces the risk of mortality but is associated with side effects, reducing patients' quality of life. Decisions about adjuvant treatment are preference sensitive and are thus ideally suited to a shared decision making (SDM) approach. Whether and how SDM affects patients' trust in their oncologist is currently unknown. We investigated the association between patients' trust in their oncologist and 1) observed level of SDM in the consultation, 2) congruence between patients' preferred and perceived level of participation, and 3) patient and oncologist characteristics. Methods. Decision consultations (n = 101) between breast cancer patients and their medical oncologist were audio-recorded and transcribed verbatim. Patients' trust in their oncologist was measured using the Trust in Oncologist Scale (TiOS). The observed level of SDM was scored using the 12-item Observing Patient Involvement In Decision Making scale (OPTION-12), preferred level of participation with the Control Preferences Scale, and perceived level of participation with an open question in telephonic interviews. Results. The average TiOS score was high overall (mean [SD] = 4.1 [.56]; range, 2.6-5.0). Low levels of SDM were observed (mean [SD] = 16 [11.6]; range, 2-56). Neither observed nor perceived level of participation in SDM was associated with trust. Patients' preferred and perceived role in decision making was incongruent in almost 50% of treatment decisions. Congruence was not related to trust. A larger tumor size (β = 4.5, P = 0.03) and the use of a risk prediction model during the consultation (β = 4.1, P = 0.04) were associated with stronger trust. Conclusion. Patients reported strong trust in their oncologist. While low levels of SDM were observed, SDM was not associated with trust. These findings suggest it may not be necessary to worry about negative consequences for trust of using SDM or risk prediction models in oncological consultations. Considering the increased emphasis on implementing SDM, it is important to further explore how SDM affects trust in clinical practice.