Body weight changes and associated predictors in a prospective cohort of young breast cancer survivors

Background: Weight gain after a breast cancer diagnosis is common and is associated with inferior outcomes. Young survivors may be especially susceptible to weight changes given the impact of treatment on menopausal status. Methods: The authors identified women who were diagnosed with stage 0 to III breast cancer at age 40 years or younger between 2006 and 2016 from a multicenter prospective cohort. Self-reported weight was collected at diagnosis and at 1 year and 3 years postdiagnosis. Tumor and treatment data were obtained from medical records and patient surveys. Multinomial logistic regression was used to identify the factors associated with weight gain (≥5%) or weight loss (≥5%) versus stable weight at 1 year and 3 years postdiagnosis. Results: The cohort included 956 women with a median age of 37 years at diagnosis. Mean weight significantly increased over time from 66.54 ± 14.85 kg at baseline to 67.33 ± 15.53 and 67.77 ± 14.65 kg at 1 year and 3 years, respectively (p ≤.001 for both comparisons). The proportion of women experiencing ≥5% weight gain increased from 24.8% at 1 year to 33.9% at 3 years. At 1 year, less self-perceived financial comfort, Black race, and stage III disease were significantly associated with weight gain; at 3 years, only less self-perceived financial comfort remained significant. Baseline overweight or obesity was significantly associated with weight loss at both time points. Chemotherapy, endocrine therapy, and treatment-related menopause were not associated with weight change. Conclusions: One third of young breast cancer survivors experienced clinically significant weight gain 3 years after diagnosis; however, treatment-related associations were not observed. Age-appropriate lifestyle interventions, including the reduction of financial barriers, are needed to prevent weight gain in this high-risk population.