Myosteatosis is associated with poor physical fitness in patients undergoing hepatopancreatobiliary surgery

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Background: Body composition assessment, measured using single computed tomography (CT) slide at L3 level, and aerobic physical fitness, objectively measured using cardiopulmonary exercise testing (CPET), are each independently used for perioperative risk assessment. Both sarcopenia (i.e. low skeletal muscle mass), myosteatosis (i.e. low skeletal muscle radiation attenuation) and impaired objectively measured aerobic fitness (reduced oxygen uptake) have been associated with poor post-operative outcomes and survival in various cancer types. However, the association between CT body composition and physical fitness has not been explored. In this study, we assessed the association of CT body composition with selected CPET variables in patients undergoing hepatobiliary and pancreas surgery. Methods: A pragmatic prospective cohort of 123 patients undergoing hepatobiliary and pancreas surgery were recruited. All patients underwent preoperative CPET. Preoperative CT-scans were analysed using a single CT-slice at L3 level. Multivariate linear regression was used to test the association between CPET variables and body composition. Main outcomes were oxygen uptake at anaerobic threshold (VO2 at AT), oxygen uptake at peak exercise (VO2 peak), skeletal muscle mass and skeletal muscle radiation attenuation (SM-RA). Results: One-hundred-and-thirteen patients were included. Of the CT-body composition variables, SM-RA had the strongest correlation with VO2 peak (r=0.57, p<0.001) and VO2 at AT (r=0.45, p<0.001) while skeletal muscle mass was only weakly associated with VO2 peak (r=0.24, p<0.010). In multivariate analysis, only SM-RA was associated with VO2 Peak (B=0.25, 95%-CI 0.15-0.34, p<0.001, R2=0.42) and VO2 at AT (B=0.13, 95%-CI 0.06-0.18, p<0.001, R2=0.26). Conclusion: There is a positive association between preoperative CT SM-RA and preoperative physical fitness (VO2 at AT and at Peak). This study demonstrates that myosteatosis, and not sarcopenia, is associated with reduced aerobic physical fitness. Combining both myosteatosis and physical fitness variables may provide additive risk stratification accuracy and guide interventions during the perioperative period.