Abstract Background: Adjuvant chemotherapy for early-stage breast cancer is associated with numerous side effects, including nausea, fatigue, and neuropathy, which may lead to early discontinuation. Psychosocial variables may influence how patients experience and tolerate these side effects. Personality traits such as optimism and neuroticism at diagnosis may impact psychosocial outcomes and recurrence in long-term survivors. Optimism has been linked to better coping, reduced anxiety, and greater resilience, whereas neuroticism correlates with distress and poor coping. No prior studies have directly examined the relationship between optimism, coping, and chemotherapy side effects. This study aimed to evaluate whether psychosocial factors are associated with chemotherapy-related side effects. Methods: We conducted a prospective study of women with stage I-III breast cancer receiving standard neoadjuvant or adjuvant chemotherapy. At baseline (prior to treatment), participants completed four psychosocial questionnaires: the Revised Life Orientation Test (LOT-R), NEO-Five Factor Inventory Neuroticism Scale (NEO-N), Connor-Davidson Resilience Scale 10 (CD-RISC 10), and Brief COPE (B-COPE). Patients also completed the PRO-CTCAE v1 and PROMIS surveys at baseline, during chemotherapy, end of treatment, and one year post-therapy. The primary endpoint was to determine correlations between optimism, coping, and resilience with treatment-related toxicity (PRO-CTCAE). The secondary endpoint was to examine associations between psychosocial factors and physical, mental, and social domains of health-related quality of life (HRQOL). Spearman correlations assessed relationships between psychosocial and symptom scores. Linear mixed-effects models evaluated longitudinal associations, with time point and psychosocial variables as fixed effects and participant as a random intercept. Analyses were conducted in R (v4.4.0). Results:A total of 107 patients were enrolled (median age: 51 range 42-58). The cohort was diverse: 18.7% Hispanic, 37.3% White, 24.3% Black, 10.3% Asian, and 9.3% other. Symptom scores increased significantly by the end of chemotherapy compared to baseline (Estimate = 0.49, p 0.01). Higher optimism was modestly associated with lower symptom burden (Estimate = -0.03, p = 0.05). Resilience was not significantly associated with symptom scores. Greater use of coping strategies was linked to higher symptom burden (Estimate = 0.02, p 0.01), possibly reflecting increased efforts to manage symptoms. No specific coping strategy was significantly associated with symptom scores. Symptom burden increased during and shortly after chemotherapy but declined one year later. In the mixed-effects model, none of the psychosocial scores (optimism, coping, or resilience) remained significantly associated with symptom burden over time. Conclusions: Patients with higher optimism experienced fewer chemotherapy-related side effects, suggesting that optimism may serve as a potential psychological marker for reduced treatment burden. Greater coping effort was observed in those reporting higher symptom scores, possibly indicating a reactive coping response. These findings may inform future development of behavioral interventions aimed at reducing chemotherapy-related side effects in breast cancer patients. Citation Format: K. M. Cronin, J. Fasano, C. Shapiro, G. Montgomery, s. julie, a. tiersten, a. bhardwaj, h. irie, p. klein, a. goel, t. sheng, t. shao. The impact of optimism and coping on the experience of side effects of adjuvant chemotherapy in women with early-stage breast cancer abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-02-23.
Cronin et al. (Tue,) studied this question.