Abstract PS1-04-09: Complexities of Weight Change in Breast Cancer Survivors: A Report from the Black Women’s Health Study

Abstract Background: Weight changes during treatment and survivorship impact health outcomes in breast cancer survivors. These treatment-related changes include both substantial weight gain and loss. Many patients gain 5-15 lbs during treatment due to reduced physical activity, chemotherapy, hormonal therapy, and corticosteroids. Conversely, some experience weight loss related to treatment side effects or cancer cachexia.Our prior work suggests that women undergoing chemotherapy may shift their weight to a higher weight category during active treatment. Up to 70% of Black breast cancer patients have reported weight gain during survivorship. Weight gain increases cardiovascular risk, which is concerning given the elevated cardiac risk Black BCS face from therapies like doxorubicin and radiation. Heart disease is a leading cause of death among BCS and is most common in Black women. Emerging data also suggest that post-diagnosis weight gain may increase recurrence and lower survival, particularly in hormone receptor-positive cancers—types in which Black women experience the highest recurrence rates. Up to 50-70% of Black breast cancer survivors (BCS) experience weight changes during treatment and survivorship.Weight fluctuations may worsen insulin resistance and increase diabetes risk, which could affect cancer outcomes. Aromatase inhibitors can intensify these metabolic effects. Previous studies on weight change during treatment often lacked sufficient power to focus on Black women specifically, excluded cancer-related endpoints, or had limited data on lifestyle factors. This study aims to fill these gaps using detailed pre-diagnosis data and long-term follow-up of weight, lifestyle, and psychosocial factors in Black BCS. Methods: We examined 1,665 incident breast cancer cases (1995-2015) from the Black Women’s Health Study (BWHS), a nationwide prospective cohort of 59,000 Black women. Mortality and cancer details were obtained through medical record review. Post-treatment weight change was defined as the percentage difference between weight reported near diagnosis and at the 2-year follow-up. A change exceeding 10% from diagnosis weight was considered clinically significant. Survival analysis (Kaplan-Meier, Cox proportional hazards) was used to evaluate the relationship between weight change and all-cause mortality, controlling for age at diagnosis, education, stage, ER status, comorbidities, menopausal status, physical activity, and BMI. Women with metastatic disease at diagnosis were excluded. Results: Among 1,248 eligible women, 82% had no significant weight change (±10%) by 2 years post-diagnosis. Ten percent had significant weight gain (≥10%) and 8% experienced significant loss. There were 248 deaths during follow-up. Risk of death was higher among women with 10% weight change. Significant weight loss was associated with higher mortality (adjusted hazard ratio HR: 1.65; p = 0.02), but weight gain was not (HR: 1.24; p = 0.26). However, among women receiving both chemotherapy and hormone therapy, weight gain was linked to higher mortality (HR: 3.44; p = 0.02). Conclusion: Nearly half of Black breast cancer survivors experience weight changes that start during treatment and continue afterward. Monitoring weight fluctuations is crucial in survivorship care to improve health and cancer outcomes. Weight loss may indicate more advanced disease, while weight gain could increase cardiometabolic risks. Including dietary data in future research might help better understand modifiable factors behind these patterns. The link between higher weight gain and increased mortality among women undergoing both chemotherapy and hormonal therapy highlights the need for comprehensive interventions for this group. Citation Format: V. B. Sheppard, D. Chiranjeev, M. C. Edmonds, A. M. Kumar, L. L. Adams-Campbell. Complexities of Weight Change in Breast Cancer Survivors: A Report from the Black Women’s Health Study 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 PS1-04-09.