Characterization of Body Composition Dynamics Throughout Treatment in Patients with Early-Stage Breast Cancer.

This study characterized computed tomography (CT)-derived body composition and tissue morphology in females with non-metastatic breast cancer (BC), both cross-sectionally (n = 56) and longitudinally (n = 38), with comparative evaluations against healthy controls and cachexia-prone females with lung cancer. Despite relative weight stability, BC patients demonstrated significant declines in skeletal muscle quality and increases in subcutaneous adipose attenuation. Morphologic changes occurred even in the absence of pronounced muscle loss, namely through reductions in lean tissue masked by concurrent increases in intra-compartmental adipose. Longitudinal interactions suggest divergent phenotypes such that non-cachectic patients demonstrated subtle, though measurable, remodeling of stable muscle quantity, whereas wasting of both muscle and adipose quantities and remodeling of externally deposited adipose was characteristic of cachexia. Findings highlight the discordance between weight loss and underlying tissue morphology and suggest that conventional cachexia criteria may under-detect clinically relevant remodeling in early-stage BC. CT-based assessments may improve phenotyping and better inform supportive care strategies across cancer populations.