Abstract PS1-01-30: Protein Intake, Exercise, and Chemotherapy-Related Fatigue in Women with Breast Cancer

Abstract Background: For individuals with breast cancer undergoing chemotherapy, a nutritious, protein-rich diet may reduce side effects and improve outcomes. While emerging evidence supports the role of protein in managing cancer-related fatigue, few studies have focused on non-metastatic breast cancer or considered physical activity. This study examined the relationship between protein intake, physical activity, and fatigue in women with Stage I-III breast cancer receiving chemotherapy. Methods: This is a secondary analysis of the Genetics, Molecular Mechanisms, and Symptom Science (GEMMS) study, a longitudinal cohort of women undergoing curative-intent chemotherapy with follow up for 5 years. Protein and total caloric intake were assessed at baseline using the Automated Self-Administered Dietary Assessment (ASA24). Suboptimal protein intake was defined as 55 indicating clinically significant fatigue. Linear and logistic regression models evaluated associations between protein intake, exercise, and fatigue post-chemotherapy completion while adjusting for age, stage of cancer, chemotherapy intensity, and baseline fatigue. Results: A total of 95 women, median age 53 years [IQR 42-63] were included. Of these, 39% (n = 37) had suboptimal protein intake, with median protein intake of 0.88g/kg [IQR 0.60-1.12]. The characteristics of women with optimal and suboptimal protein intake are compared in Table 1. At chemotherapy competition, 41% (n = 39) reported clinically significant fatigue. This was numerically higher among women with suboptimal protein intake (43.2% compared to 39.7%) but did not reach statistical significance. In multivariable models, neither protein intake nor exercise were associated with fatigue. Baseline fatigue was the only consistent predictor: for each 1-unit increase in baseline fatigue T-score, the odds of post-treatment fatigue increased by 10% (aOR 1.10; 95% CI 1.03-1.17; p = 0.003). Conclusion: Protein intake and exercise were not significantly associated with fatigue during chemotherapy; however, baseline fatigue was a strong predictor of post-treatment fatigue. Future studies may benefit from exploring the micronutrient composition of dietary intake to discover other contributing factors to chemotherapy fatigue. Citation Format: I. V. Critchfield-Jain, M. A. Fiala, Y. Park, E. Salerno, L. Peterson. Protein Intake, Exercise, and Chemotherapy-Related Fatigue in Women with 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 PS1-01-30.