e13026 Background: Obesity has been associated with negative outcomes in early breast cancer. Addition of everolimus (Eve) to endocrine therapy improves progression-free survival (PFS) in patients with hormone-receptor (HR) positive, HER2-negative metastatic breast cancer (MBC). Eve targets the mTOR signaling pathway which regulates cell growth/metabolism and has been implicated in obesity and diabetes. Changes in weight and body mass composition and its correlation with PFS have not been described in patients with MBC treated with Eve. We aim to compare total adipose tissue (TAT), subcutaneous adipose tissue (SAT), and visceral adipose tissue (VAT) before and after treatment with Eve in patients with HR+/HER2- MBC. Methods: Patients with metastatic HR+/HER2- MBC treated with Eve and endocrine therapy (Eve/ET) between 2012 and 2018 were identified. Each Eve/ET case was matched to a patient who received endocrine therapy alone (ET) by age at diagnosis (+/- 5 yrs), body mass index [BMI] (+/-5 kg/m2) and visceral metastatic disease. VAT, SAT, TAT, and skeletal muscle index (SMI) were measured by computerized tomography at L3 level using TOMOVISION software prior to treatment initiation (T0) and after 3-6 months of treatment (T3). TAT was defined as SAT + VAT and sarcopenia as SMI < 40. Paired t-test and Wilcoxon paired-test were used to compare body composition parameters at T3 vs T0 in Eve/ET and ET groups. Results: 78 patients (Eve/ET: 41 and ET: 37) with a median age of 65.5 yrs were included. Of these, 16 (21.3%) were Non-Hispanic White, 31 (41.3%) were Non-Hispanic Black and 27 (36%) were Hispanics. Visceral metastases were seen in 57 (73.1%) cases. Mean weight, BMI, VAT and SAT at T0 were 70.8 kg, 27.4 kg/m2, 170.1 cm2 and 196.1 cm2, respectively and did not differ between Eve/ET and ET groups at baseline. At T3, there was a reduction in TAT (348.4 to 289.2 cm2, p < 0.01) and SAT (181.7 to 142.7 cm2, p < 0.01) in the Eve/HT group; while there were no significant changes in TAT (373.1 to 363.9 cm2, p = 0.39) or SAT (212 to 221.8 cm2, p = 0.33) in the ET group. No changes in visceral fat %, VAT/SAT ratio and sarcopenia between T0 and T3 in either treatment group were seen. In patients treated with Eve/ET, there were no differences in PFS between low TAT-loss (TAT loss < 40 cm2) and high TAT-loss (TAT loss > 40 cm2) (3.6 vs 4.8 months, p = 0.97). Conclusions: Eve induces TAT loss in patients with HR+/HER2- MBC, specifically driven by decrease in SAT. The pathophysiology of this association is still to be discerned. Further studies are required to evaluate TAT or SAT as a predictive/prognostic biomarker in patients receiving Eve.
Physical Activity, Weight, and Outcomes in Patients Receiving Chemotherapy for Metastatic Breast Cancer (C40502/Alliance)
