Associations between self-efficacy and symptom burden in young women with breast cancer initiating endocrine therapy (ET) on SWOG S2010.

521 Background: Self-efficacy (SE) is the belief in one's ability to succeed in specific situations or accomplish a task, influencing motivation, behavior, and resilience. Both symptom (sx) burden at the time of ET initiation and lower SE for sx management are associated with ET nonadherence. The SWOG S2010 clinical trial enrolled premenopausal women starting adjuvant ovarian function suppression (OFS) plus ET for breast cancer. We examined associations between sx burden and self-efficacy at the time of ET initiation. Methods: All participants completed the FACT GP5 question evaluating bother from side effects of treatment, individual symptom PROMIS measures, and the PROMIS SE for managing sx and for managing medication (meds)/treatment (tx). GP5 is measured on a 5 point scale ranging from “Not at all” to “Very much.” T scores were calculated for PROMIS measures (Table), with a mean score of 50 and higher scores reflecting more of the item being assessed. We evaluated associations between baseline sx and SE using logistic regression. Results: Of 528 participants with data, mean age was 44.1 years (SD 5.8), 23.5% were Hispanic, 5.5% Black, 6.4% Asian, and 77.7% White. The majority (69.9%) had received chemotherapy. On the FACT GP5 (n=503), only 31.6% reported no treatment side effect burden. Patients reporting a higher side effect burden from tx immediately prior to ET initiation had lower SE for sx (odds ratio (OR) 0.93 (95% CI 0.91-0.96, p<.0001)) and lower SE for meds & tx (OR 0.97 (95% CI 0.95-1.00, p=.04). Increased baseline sx and worse physical function were also statistically significantly associated with worse SE for managing both sx and meds & tx (Table). For example, patients with greater than average fatigue had lower SE for sx (OR 0.32 (95% CI 0.23-0.46, p<.001)). Conclusions: Symptom burden at the time of ET initiation is high for premenopausal women starting OFS plus ET, which may partially explain high rates of early ET discontinuation in this patient population. Lower SE was strongly associated with worse individual symptoms. Interventions to improve SE for sx and med management starting at or before ET initiation may improve ET adherence, which could thereby improve disease outcomes and quality of life for young women with breast cancer. Funding: NIH/NCI/NCORP grant UG1CA189974. Clinical trial information: NCT05568472 . Associations between self-efficacy and symptoms. PROMIS Self Efficacy Sx PROMIS Self Efficacy Meds & Tx PROMIS domain <50 ≥50 OR (CI) P value (Chi square) <50 ≥50 OR (CI) P value (Chi square) Fatigue <50 97 144 0.32 (0.23,0.46) <.001 82 158 0.52 (0.36,0.74) <.001 ≥50 194 93 143 143 Anxiety/Fear <50 56 105 0.30 (0.20,0.44) <.001 42 118 0.36 (0.24,0.54) <.001 ≥50 235 132 183 183 Sleep disturbance <50 85 120 0.40 (0.28,0.58) <.001 69 135 0.54 (0.38,0.78) .001