Background: Cancer cachexia is characterized by skeletal muscle loss. A feature of muscle wasting, reduction in the mean muscle attenuation from computed tomography images is believed to reflect pathological infiltration of fat into muscle. It is a reported prognostic indicator in cancer patients.
Objectives: To develop an explanatory multivariate model of muscle attenuation of cancer patients incorporating age, sex, disease characteristics, body composition. Time to death ≤92 days was included in the model as the demarcation of end-stage disease.
Design: Multivariate general linear model regression analysis of total mean muscle attenuation and change in muscle attenuation.
Setting: Regional cancer center (Alberta, Canada).
Participants: Patients with gastrointestinal and respiratory tract cancers (mean age 64±11 years, 44% female).
Measurements: Total adipose tissue and skeletal muscle cross sectional area, and mean muscle attenuation at the 3rd lumbar vertebra were assessed from baseline computed tomography (n=1719), and a subset with repeated measures (n=246 patients with a total of 871 images).
Results: At baseline, muscle attenuation associated with total skeletal muscle (β 0.09; 95% CI 0.07 to 0.11; p<0.001) and adipose tissue (β -0.032; 95% CI -0.035 to -0.029; p<0.001) cross sectional areas, age (β -0.28; 95% CI -0.32 to -0.24; p<0.001), time to death ≤92 days (β -1.9; 95% CI -3.1 to -0.7; p=0.003) and male sex (β -2.3; 95% CI -3.5 to -1.1; p<0.001). Change in muscle attenuation over time associated with total adipose tissue cross sectional area (β -0.008; 95% CI -0.012 to -0.004; p<0.001) and time to death ≤92 days (β -1.6; 95% CI -3.0 to -0.2; p=0.03).
Conclusions: The radiation attenuation of skeletal muscle is lowest in individuals who are older, less muscular, have a higher fat mass and are within 92 days of death. Men had lower muscle attenuation than women when controlled for other variables.