Background: We investigated weight change in postmenopausal Stage I-III breast cancer (BC) survivors on adjuvant endocrine treatment (ET) -- tamoxifen or aromatase inhibitors (AI) [anastrozole, exemestane, letrozole]. Clinical focus on > 2kg (4.7lbs) weight change within first 2 years of ET. Methods: Retrospective chart review. Weight measures taken during routine clinic visits. Fisher’s exact tests and ANOVA were used to compare patient characteristics between weight change groups. Results: Sample N = 212; 75% Caucasian, mean age 66 (8.4). Stage I: 51%, Stage 2: 38%, Stage III: 11%. Body Mass Index (BMI) at diagnosis 29.6 (6.4). 42% chemotherapy, 64% radiation. ET: 10% tamoxifen only, 45% anastrozole only, 16% letrozole only, 2% exemestane only, 15% more than one AI; 12% both tamoxifen and AI. Comorbidities: 0-1 32%, 2-3 48%, > 4 20%. Weight gain > 2kg was associated with higher BC stage (p = 0.01) and chemotherapy (p = 0.006). Both > 2kg weight loss and > 2kg weight gain were associated with higher baseline BMI (p = 0.005) and greater number of baseline comorbidities (p = 0.02). No significant association between weight change and race, radiation, or ET type. (Table 1) Conclusions: In our sample, 27% had clinically significant weight loss and 37% weight gain within first 2 years of ET. We found no significant differences in weight change by type of ET. The first 2 years of ET present an opportunity to educate BC survivors about the importance of weight management for overall wellness, prognosis and survival.

*p ≤ 0.05 **p ≤ 0.01