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Background: Sarcopenia, or severe skeletal muscle loss, is associated ith poor cancer outcomes including increased toxicity and reduced survival. This study investigates body composition indices including muscle quantity and quality in patients ith metastatic breast cancer MBC receiving first line taxane-based chemotherapy and compares these indices to treatment toxicity and related outcomes. Methods: Skeletal muscle area SMA and density ere measured at the level of the third lumbar vertebrae using computerized tomography CT images taken for the evaluation of disease burden. Sarcopenia as defined as Skeletal Muscle Index SMI = SMA height^2 lt 41 Martin et al, JCO, 2013 . Skeletal Muscle Integrated Density SMID , a novel marker of body composition as created by multiplying SMI x Mean Muscle Density. Fishers exact and t-tests ere used to compare groups, hazard ratios HR ere estimated for time to event outcomes. Results: MBC patients N = 46 ho had CT scans ithin 45 days of starting chemotherapy. Mean age as 56 range 34-80 . 59 percent ere sarcopenic; median SMID as 1208 range: 372-2499 . Grade 3-4 toxicity CTCAE version 4.0 as reported in 56 percent of sarcopenic vs 21 percent of non-sarcopenic patients p= 0.03 . Toxicity-related hospitalizations ere significantly higher in sarcopenic patients 33 percent vs 5 percent, p= 0.031 . Any adverse event grade 3-4 chemotherapy-related toxicities, hospitalizations, dose reductions, and dose delays as significantly higher in sarcopenic patients 74 percent vs 37 percent, p= 0.016 . Lo SMID as significantly associated ith hospitalization p= 0.03 and approached significance ith G3-4 toxicity p= 0.06 and any adverse event p= 0.08 . For each 100 unit increase in SMID, a patients risk of treatment failure progression or toxicity decreased by 8 percent p= 0.035, HR = 0.92, 95 percent CI 0.85-0.99 and risk of death decreased by 7 percent p= 0.055, HR = 0.93, 95 percent CI 0.87-1.00 . Conclusions: Skeletal muscle indices, including a novel measure SMID, are associated ith toxicity outcomes and survival. Further studies are needed to explore ho routinely obtained CT scans can be used to individualize dosing and other elements of the oncologic treatment plan.,J Clin Oncol 34, 2016 suppl; abstr 1021 00:00.0,Breast CancerTriple-NegativeCytotoxicsLocal Therapy
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