Longitudinal changes in skeletal muscle and adipose tissue during surgical treatment of oesophagogastric cancer: a prospective study.

Background Low muscle mass, myosteatosis, and excess adiposity are associated with adverse outcomes after oesophagogastric (OG) cancer surgery. There is limited prospective data to evaluate body composition throughout treatment. We aimed to measure longitudinal changes in skeletal muscle and adipose tissue and describe variations according to baseline BMI. Methods This prospective longitudinal study included patients having OG cancer surgery at Alfred Health, Melbourne, Australia. CT images and bioimpedance spectroscopy (BIS) were used to assess body composition at multiple time points up to 12 months postoperatively. Low skeletal muscle, myosteatosis and visceral obesity were defined using published thresholds. BMI groups were defined as ≥ 30kg/m ² (obese) and < 30kg/m ² (non-obese). Results There were 50 patients. During neoadjuvant treatment, CT-muscle declined (152.7 vs 142.4cm ² , p<0.001) and adipose tissue was stable. Postoperatively, total adipose tissue reduced (357.7 vs 224.4cm ² , p<0.001), but muscle did not (142.4 vs 133.6cm ² , p=0.064). Low CT-muscle prevalence increased during neoadjuvant treatment (diagnosis 33%, restaging 49%, p=0.02) but not at 12 months (54%, p=0.21). Visceral obesity was common and stable between diagnosis and restaging (58% vs 54%, p=1.00) with a marked reduction at 12 months (19%, p<0.001). BIS-muscle declined rapidly early after surgery and did not recover. The proportion of muscle and adipose tissue loss between BMI groups was comparable. Conclusion Weight loss during OG cancer treatment is significant. Skeletal muscle loss occurs during neoadjuvant treatment, while adipose tissue loss is predominant postoperatively. Anticipated changes in body composition should be considered throughout treatment, focusing on early muscle loss.