Weight stability masks changes in body composition in colorectal cancer: a retrospective cohort study.

BACKGROUND There is an emerging viewpoint that change in body weight is not sufficiently sensitive to promptly identify clinically meaningful change in body composition, such as skeletal muscle depletion. OBJECTIVES We aimed to determine whether body weight stability is associated with skeletal muscle depletion and whether skeletal muscle depletion is prognostic of death independently of change in body weight. METHODS This retrospective cohort included 1921 patients with stage I-III colorectal cancer. Computed tomography (CT)-based skeletal muscle characteristics and body weight were measured at diagnosis and after a mean 15.0-mo follow-up. Body weight stability was defined as weight change less than ±5% during follow-up. Sarcopenia and myosteatosis were defined using established thresholds for patients with cancer. Multivariable-adjusted logistic and flexible parametric proportional hazards survival models were used to quantify statistical associations. RESULTS At follow-up, 1026 (53.3%) patients were weight stable. Among patients with weight stability, incident sarcopenia and myosteatosis occurred in 8.5% (95% CI: 6.3%, 10.6%) and 13.5% (95% CI: 11.1%, 15.9%), respectively. Men were more likely to be weight stable than were women (56.7% compared with 49.9%; P = 0.04). Weight-stable men were less likely to develop incident sarcopenia (5.4% compared with 15.4%; P = 0.003) and myosteatosis (9.3% compared with 20.8%; P = 0.001) than weight-stable women. Among all patients, the development of incident sarcopenia (HR: 1.40; 95% CI: 1.02, 1.91) and of myosteatosis (HR: 1.41; 95% CI: 1.05, 1.90) were associated with a higher risk of death, independently of change in body weight. Patient sex did not modify the relation between skeletal muscle depletion and death. CONCLUSIONS Body weight stability masks clinically meaningful skeletal muscle depletion. Body composition quantified using clinically acquired CT images may provide a vital sign to identify patients at increased risk of death. These data may inform the design of future cachexia trials.