737. ETHNIC, GENDER AND TUMOR-SPECIFIC ASSESSMENT OF BODY COMPOSITION IS CRITICAL FOR CLINICAL RELEVANCE IN PATIENTS UNDERGOING THERAPY FOR ESOPHAGEAL

Abstract Background Growing evidence has supported a role for body composition in predicting survival in patients undergoing esophagectomy. A contemporary meta-analysis of published data (n=44 studies) conducted for this study confirmed an association between reduced muscle mass at diagnosis and worse overall survival (HR 1.72, 95%CI 1.49-1.97). Variation in methods of assessing and defining parameters of body composition remain however an important barrier to the wider adoption in routine clinical practice. This is particularly pertinent in esophageal cancer due to known sex, biological and geographical difference in tumor subtypes. This study seeks to define baseline variation in body composition parameters and to report their association with 90-day and overall survival in a large international cohort of patients undergoing esophagectomy for cancer. Methods Patients who underwent esophagectomy in fourteen high-volume centers between January 2007 to December 2019 were eligible for inclusion. Survival data were included up until June 2022. Skeletal muscle, visceral and subcutaneous adipose tissues within CT images, acquired at the time of diagnosis, were analyzed in accordance with a standardized protocol. Results 1716 patients were recruited to this study from three global regions: North America (n=386;22.5%), Europe (n=940;54.8%) and Asia (n=390;22.7%). Patients were predominantly male (79.5%) and adenocarcinoma was the most common histological subtype (66.6%). Wide variation of skeletal muscle (17.1-83.5cm2), visceral adiposity (0.2-170.1cm2) and subcutaneous adiposity (0.2-216.8cm2) was observed at presentation. Characteristics significantly associated with levels of muscle and adiposity were global region, sex, age, and histological subtype (P<0.001) (Figure 1). Compared to adenocarcinoma, squamous cell carcinoma was associated with significantly lower levels of muscle and adiposity, a finding that was independent of global region, sex, and age using a multivariable linear regression model (p<.0001). Median follow-up was 71.3 (95%CI 69.1-73.5) months with a median overall survival of 60.9 (95%CI 53.0-68.9) months. Reduced skeletal muscle and an excess of total adiposity at the time of diagnosis was associated with worse 90-day mortality and long-term survival. An interactive online survival prediction tool was developed to provide personalized survival estimates based on relevant predictors including skeletal muscle, total adiposity at diagnosis and other tumor and patient specific variables. Conclusions This is the first and largest study to adopt standardized methods to define international variation in parameters of body composition in esophageal cancer patients. Findings corroborate the potential role of body composition as a method of prognostication in esophageal cancer and presents a on-line tool for convenient integration into clinical practice.