The relationship between muscle protein content and CT-derived muscle radio-density in patients with upper GI cancer.

Introduction: Cancer cachexia is a multifactorial syndrome characterized by skeletal muscle loss. Cross-sectional analysis of CT scans is a recognized research method for assessing skeletal muscle volume. However, little is known about the relationship between CT-derived estimates of muscle radio-density (SMD) and muscle protein content. We assessed the relationship between CT-derived body composition variables and the protein content of muscle biopsies from cancer patients.

Methods: Rectus abdominis biopsies from cancer patients (n = 32) were analysed for protein content and correlated with phenotypic data gathered using CT body composition software.

Results: Skeletal muscle protein content varied widely between patients (median μg/mg wet weight = 89.3, range 70-141). There was a weak positive correlation between muscle protein content and SMD (r = 0.406, p = 0.021), and a weak positive correlation between protein content and percentage weight change (r = 0.416, p = 0.018).

Conclusion: The protein content of skeletal muscle varies widely in cancer patients and cannot be accurately predicted by CT-derived muscle radio-density.