Optimizing expectations about endocrine treatment for breast cancer: Results of the randomized controlled psy-breast trial

Background: Medication side effects are strongly determined by non-pharmacological, nocebo mechanisms, particularly patients' expectations. Optimizing expectations could minimize side effect burden. This study evaluated whether brief psychological expectation management training (EXPECT) optimizes medication-related expectations in women starting adjuvant endocrine therapy (AET) for breast cancer. Method: In a multisite randomized controlled design, 197 women were randomized to EXPECT, supportive therapy (SUPPORT), or treatment as usual (TAU). The three-session cognitivebehavioral EXPECT employs psychoeducation, guided imagery, and side effect management training. Outcomes were necessity-concern beliefs about AET, expected side effects, expected coping ability, treatment control expectations, and adherence intention. Results: Both interventions were well accepted and feasible. Patients' necessity-concern beliefs were optimized in EXPECT compared to both TAU and SUPPORT, d = .41, p < .001; d = .40, p < .001. Expected coping ability and treatment control expectations were optimized compared to TAU, d = .35, p = .02; d = .42, p < 001, but not to SUPPORT. Adherence intention was optimized compared to SUPPORT, d = .29, p = .02, but not to TAU. Expected side effects did not change significantly. Conclusion: Expectation management effectively and partly specifically (compared to SUPPORT) modified medication-related expectations in women starting AET. Given the influence of expectations on long-term treatment outcome, psychological interventions like EXPECT might provide potential pathways to reduce side effect burden and improve quality of life during medication intake.