Purpose: Obesity and weight gain after breast cancer (BC) diagnosis can affect cancer outcomes. This study explores the question of weight change during the first 2 years of endocrine treatment (ET) to identify the independent effects of BC diagnosis and treatment on post-diagnosis weight trajectories in early-stage postmenopausal BC survivors. Methods: The study design is a retrospective chart review. Chi square tests and ANOVA were used to compare patients who gained >2 kg, lost >2 kg, or had stable weight. Log-binomial regression models were used to evaluate associations between patient characteristics and weight trajectories. Results: The final sample is N = 300, with mean age at BC diagnosis of 65 years and 76% white. After 2 years of ET, 39% of study participants had gained >2 kg, 27% had lost >2 kg, and 34% had stable weight. Relative risks (RR) for weight gain were as follows: age at diagnosis = 0.98 (0.96, 0.99), being married = 1.48 (1.04, 2.12), weight change between BC diagnosis and start of ET = 0.98 (0.97, 0.99), Stage II = 1.42 (1.01, 2.01) or Stage III = 1.99 (1.41, 2.82), PR negative = 0.70 (0.51, 0.96), HER2 positive = 1.51 (1.07, 2.13), mastectomy = 1.49 (1.12, 1.98), axillary node dissection = 1.67 (1.27, 2.20), adjuvant chemotherapy = 1.49 (1.02, 2.19), and neoadjuvant chemotherapy = 2.29 (1.67, 3.14). Type of ET (tamoxifen or aromatase inhibitor) was not significant. Conclusions: In our sample of postmenopausal early-stage BC survivors, a majority had stable or lost weight during the first 2 years of ET. Higher disease complexity and associated treatment posed higher RR for weight gain
