Sarcopenia: the ‘hidden’ marker of surgical outcome

Sarcopenia is common, particularly in cancer patients. Over the decades, the definition has evolved from a clinical term described by Rosenberg as ‘age-related decrease in muscle mass’, to a more complex definition that has objective measurement methods based on patient’s physical findings and structural imaging. Moreover, the definition of sarcopenia over the years had previously overlapped with other conditions like aging and frailty, making it more difficult for clinicians to identify and understand the disease, let alone treat. Importantly, the latest consensus by the European Working Group on Sarcopenia (EWGSOP2) uses low muscle strength as the primary parameter of sarcopenia. It can occur in normal weight or overweight patients, distinguishing it from weight loss or cachexia. It has been reported that the prevalence of sarcopenia is 10% in the general population, but the mean incidence increases to 34.7% (range from 2.1 to 83.3%) in gastrointestinal cancer patients. The clinical importance with sarcopenia is the association with poor shortand long-term outcomes. For example, a large meta-analysis on gastrointestinal cancer has shown the preoperative incidence of sarcopenia increased risk of overall mortality (HR 1.602), diseasefree mortality (HR = 1.461), total complications (RR = 1.188) and major complications (RR = 1.228). Finally, sarcopenia significantly increases personal, social, and healthcare costs through impaired activity, lower quality of life, higher hospitalization and supported care requirements. Taking all these into consideration, sarcopenia is a good clinical marker for poorer outcomes and should be routinely measured. Most importantly, there has been reported data on preventing, delaying, treating and even reversing sarcopenia with early and effective interventions. These include enhanced physical therapy and weight training which maintain strength and increase skeletal muscle mass. The American Cancer Society recommends aerobic exercise and resistance training to improve the overall outcomes following surgery. Dietary supplementation with specific amino acids and pharmacotherapy can also help improve outcomes by reversing the detrimental effects of sarcopenia. However, a larger prospective study is required to validate these findings. Our survey of colorectal surgeons found that whilst 80% of respondents can define sarcopenia, only a minority screen for sarcopenia and a smaller percentage use this as part of their practice. There are knowledge gaps regarding the significance and management of sarcopenia. Only half of surgeons stated that sarcopenia is predictive of short-term outcomes, while under a third believe it is predictive of oncological outcomes. Even so, most consider it as part of their role to recognize sarcopenia and ensure appropriate management is initiated. Currently, barriers to perform these duties include a lack of access to evidence-based protocols, services and perioperative programs to support identification and management in hospitals. There is a need to further define and simplify sarcopenia measurements so that it is cost-effective, easy to use and enable greater research consistency. Equipment and cost limitations can be overcome by employing the reliable technique of measuring Skeletal Muscle Index (SMI) with third lumbar level CT cross sections. Adding on deep learning automated CT segmentation would enable opportunistic sarcopenia detection and monitoring. Trials on reversing sarcopenia are necessary to improve our understanding and increase management options. It is time hospitals invest in facilities to improve patient’s physical wellbeing before surgery. The future model of care is one where sarcopenia can be diagnosed early in all patients so that personalized multimodal therapy in the form of exercise, nutritional intervention, and upcoming drugs can reverse it. This in turn may improve surgical outcomes and decrease the financial healthcare burden.