Avrutin, Egor2021-02-122022-02-132021-02-122021-01-27http://hdl.handle.net/10012/16805Skeletal muscle health is an important predictor of survival, treatment toxicity, and physical function in cancer patients and survivors. While accelerated rates of muscle wasting are often observed in patients with advanced cancer, the links between lower than optimal muscle mass and adverse outcomes have been reported across diverse cancer types and stages. With improvements in detection strategies and treatment, the 5-year survival rate in breast cancer patients is relatively favorable. With detrimental body composition changes that occur during treatment and extend into survivorship, mitigating derangements in muscle health may help improve quality of life, mobility and metabolic outcomes. For this purpose, it is important to not only understand the alterations in muscle characteristics that occur throughout the breast cancer trajectory, but also potential links between muscle features such as size, composition and architecture with respect to muscle strength and function. Computed Tomography (CT) and Dual-energy X-ray Absorptiometry (DXA) are two tools commonly used to study muscle mass or muscle size. DXA assesses lean mass at the whole body or regional level and offers an opportunity to evaluate functionally relevant muscle groups. The first research study of this thesis examined DXA-based body composition profiles of breast cancer patients with lower that normal muscle mass, along with common strategies proposed to help adjust for differences in body size, in relation to muscle strength. The focus of studies 2 and 3 is on use of ultrasound-based imaging methods for evaluating skeletal muscle size, composition and architecture features in breast cancer patients and in a healthy, young adult reference cohort. Ultrasound is a portable, relatively inexpensive and accessible modality that may evaluate muscle size, composition and architecture, this modality has not been used for body composition analysis in cancer patients to date. Overall, finding of the studies in this thesis highlight several areas that warrant further method development both for DXA-based lean tissue mass and ultrasound-based muscle features, in order to help the assessment of muscle size, composition, architecture and strength in breast cancer patients in- and post-treatment.enbody composition analysismuscle massmuscle strengthbreast cancerultrasound imagingmuscle compositionadiposityDoctoral Thesis