e13026 Background: BC measurement can distinguish adipose tissue distribution, as well as the quantity and quality of muscle. Dysregulation in the mammalian target of rapamycin (mTOR) signaling pathway is associated with obesity and its related diseases. Everolimus (Eve), an mTOR inhibitor, is used in combination with endocrine therapy (ET) in hormone positive, HER2 negative (HR+/HER2-) MBC. However, there is limited data on the effect of Eve on BC. We aim to assess the effect of Eve on BC in patients (pts) with HR+/HER2- MBC. Methods: Pts with HR+/HER2- MBC who received Eve and ET between 2012 and 2019 at our institution were identified. We collected information about breast cancer diagnosis and treatment, weight (wt), body mass index (BMI), and computed tomography (CT). BC measurements; including skeletal muscle area (SMA), skeletal muscle density (SMD), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and muscle adiposity (MA); were analyzed at the L3 region on CT scans using Tomovision’s SliceOmatic Version 5.0. Total adipose tissue (TAT) was defined as SAT+VAT+MA. To isolate the effect of Eve on BC we also identified a cohort of pts who received ET only. We compared change in wt, BMI, and BC before and after 3 and 6 months of therapy. Wilcoxon signed rank test was used to compare BC parameters. Results: Our study included 42 pts who received Eve plus ET; 43% were Hispanic and 33% were Black. The median number of prior ET and chemotherapy lines were 1 and 0, respectively. The cohort who received ET alone included 63 patients. Median age was 68 years (interquartile range [IQR] 56-74) for the Eve and ET group and 67 years (IQR 55-74) for the ET only group (p = 0.74). Median baseline BMI was 25.8 kg/m2 (IQR 23.1-28.2) for the Eve and ET group and 28.5kg/m2 (IQR 24.2-30.8) for ET only (p = 0.08). Visceral disease was present in 24 (57%) pts on Eve and ET and 41 (65%) pts on ET only (p = 0.54). At month 3 of treatment with Eve and ET, there was a significant decrease in wt (-2.75kg, IQR -4.53-0.40, p < 0.005), BMI (-1.15kg/m2, IQR -1.71-0.14, p < 0.01), SAT (-21.93cm2, IQR -50.13-5.08, p < 0.01), and TAT (-22.34cm2, IQR -69.89-11.98, p = 0.02), which remained statistically significant at month 6 (wt: -5.70kg, IQR –7.75-1.83, p < 0.01; BMI: -2.3kg/m2, IQR -2.83-0.72, p < 0.01; SAT: -43.00cm2, IQR -73.81-10.69, p < 0.01; TAT: -32.56cm2, IQR –92.18-9.61, p = 0.03). These findings were not seen in pts who received ET only at 3 months (wt: 0.00kg, IQR –2.65-2.38, p = 0.99; BMI: 0.00kg/m2, IQR –1.07-0.91, p = 0.94; SAT: -1.82cm2, IQR -26.10-25.15, p = 0.59; TAT: 0.71cm2, IQR -44.39-27.43, p = 0.35), with similar results at 6 months. There were no statistically significant changes in VAT, SMA, SMD, or MA in both groups at 3 or 6 months. Conclusions: Everolimus is associated with decrease in SAT, with no significant change in VAT, SMA, or SMD. Further investigation is required to determine if these changes are associated with disease outcomes or everolimus toxicities.
e13033 Background: CDKIs with endocrine therapy (ET) is first-line treatment in HR+/HER2- MBC. Mouse models have shown that CDKIs prevent pRB phosphorylation in the mediobasal hypothalamus, a pathway hyper-activated in diet-induced obesity; and CDKIs lead to fat mass decrease without significant effect on lean mass. We aimed to assess the impact of CDKIs on weight (wt) and BC in pts with HR+/HER2- MBC. Methods: We identified pts with HR+/HER2- MBC who received CDKIs and ET from 2015-2018. To isolate the effect of CDKIs on BC, we identified another cohort of pts who only received ET. Body mass index (BMI), wt, and computed tomography (CT) records were reviewed. BC was analyzed at L3 on CT scans using Tomovision’s SliceOmatic v5.0 and included skeletal muscle area (SMA), skeletal muscle density (SMD), subcutaneous adipose tissue (SAT), visceral adipose tissue (VAT), and muscle adiposity (MA). Total adipose tissue (TAT) was defined as SAT+VAT+MA. BC changes at 3 and 6 months of therapy were evaluated using paired t-tests. Results: There were 107 pts who received CDKI plus ET - 43% were Black, and 41% were Hispanic. CDKIs used were palbociclib (85%), abemaciclib (9%), and ribociclib (6%). ETs used were letrozole (47%), fulvestrant (39%), anastrozole (12%), and exemestane (2%). Median number of prior chemo and ET lines was 0 (range 0-5). 63 pts received ET alone. There was no difference in age (63 vs. 65 years, p = 0.26), BMI (28.80 vs. 28.12kg/m2, p = 0.48), and visceral disease (69% vs. 65%, p = 0.64) between CDKI plus ET and ET alone group. At month 3 of CDKI plus ET, there was a significant decrease in wt (-0.30kg, Interquartile range [IQR] -2.55-0.95, p = 0.02), BMI (-0.12kg/m2, IQR -1.06-0.46, p = 0.02), SAT (-8.05cm2, IQR -32.58-14.74, p = 0.01), and TAT (-8.51cm2, IQR -50.42-17.84, p < 0.01), with similar results at month 6. These findings were not seen in pts on ET only at 3 months (wt: 0.00kg, IQR -2.65-2.38, p = 0.98; BMI: 0.00kg/m2, IQR -1.07-0.91, p = 0.93; SAT: -2.97cm2, IQR -26.10-25.15, p = 0.60; TAT: -0.58cm2, IQR -44.39-27.43, p = 0.18), or at 6 months. There were no significant changes in VAT, SMA, SMD, or MA in both groups at 3 or 6 months. In the CDKI plus ET group, baseline wt (74.64 vs. 72.72kg, p = 0.60), BMI (29.21 vs. 27.88kg/m2, p = 0.31), and SAT (280.29 vs. 252.75cm2, p = 0.31) were not significantly different for those who did or did not develop grade 3/4 toxicities. We obtained similar results when stratifying toxicities into hematological- and GI-related events. Conclusions: CDKIs are associated with decrease in BMI and SAT with no significant effect on VAT, SMA, or SMD. Given the known effect of obesity on breast cancer prognosis, CDKIs may have an additional effect on breast cancer prognosis by modulating body fat. Further studies are required to determine if decrease in SAT is associated with breast cancer outcomes or toxicities in pts on CDKIs.
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