Maarten van Egmond

75 The association of muscle strength with muscle mass 4 DISCUSSION In this study we investigated the relation between muscle mass and muscle strength in patients with esophageal cancer awaiting esophagectomy, before neoadjuvant chemoradiation. The study results show a significantly high association between muscle mass on CT-scan and muscle strength, expressed as right and left HGS, MIP, MEP and 30CST. To our knowledge, this is the first study that showed an independent association between aspects of muscle strength and muscle mass in patients with esophageal cancer awaiting surgery, corrected for clinical characteristics. Patients with esophageal cancer are likely to develop a loss of muscle mass and weight, eventually leading to loss of muscle function and subsequently decreased functional performance and poor long-term outcome. 4 Previous studies have mainly reported on functional outcome measures related to sarcopenia. Cruz- Jentoft et al. 9 provided an overview of measurable variables and their cut-off points for sarcopenia. For example, muscle strength estimated by HGS lower than 30 kilograms for men and 20 kilograms for women was considered as an indirect measure for sarcopenia. The direct relation with muscle mass was, however, lacking. Only dual x-ray absorptiometry (DXA), computed tomography (CT), and magnetic resonance imaging (MRI) are able to measure muscle mass directly. Despite its accuracy, these technologies are very expensive or they inflict high radiation exposure. 16,17 Therefore, we need methods to easily and rapidly assess muscle mass in a clinical setting with minimal patient burden to identify patients with decreased muscle mass. This selected population then may benefit from a tailored physiotherapeutic and nutritional treatment regimen to prevent them from functional decline. 9,35 These treatment programs should contain progressive resistance exercise training leading to an increased muscle protein mass, maximal voluntary muscle strength and muscle fiber hypertrophy. 36 In our opinion, the main strength of this study is that physiotherapists could use the results to predict muscle mass based on muscle strength and its functional consequences in preoperative patients with esophageal cancer. 10,15 This study has some limitations. Although the association between muscle strength and muscle mass is obvious, we cannot use the results to predict sarcopenia. First of all, despite the reported prevalence of sarcopenia in preoperative patients with esophageal cancer, only 2 male patients (2%) in our cohort were sarcopenic. 4,14,17