4.1. Patient Selection and Study Design

The Surgical Department of the University Hospital Mannheim of Heidelberg University is a certified centre for esophageal surgery. A detailed clinico-pathologic database is prospectively maintained for all patients with esophageal cancer since January 2018 including data on short-term postoperative outcome. In this analysis we included patients having been operated between January 2018 and July 2019 in the Surgical Department of the University Hospital Mannheim of Heidelberg University. The local ethical committee “Ethikkomission II, University of Heidelberg” gave approval for the analysis (ethic code 2020-803R) and all patients gave written informed consent.

There were 52 patients who underwent surgery for treatment of esophageal cancer in whom CT scans were sufficient to determine the skeletal muscle index. Of the 52 patients, 48 underwent neoadjuvant chemotherapy before surgery (FLOT regimen).

The skeletal muscle index was measured using computer tomographic images at the time of diagnosis as well as before surgery.

Out of the 52 patients 13 did not have two usable computer tomographies either because they did not undergo neoadjuvant treatment or because imaging was not done in-hospital and was not sufficient for measurement of the SMI.

The skeletal muscle index (SMI) was calculated as the cross-sectional area of the total skeletal muscle volume (cm²) at L3.

At the level of the third lumbar vertebra (L3) we measured the area (cm²) of the left and right psoas major muscles, the side abdominal muscles, rectus abdominis muscles, erector spinae muscles, and quadratus lumborum muscles using “syngo.share view diagnostic” (Siemens Healthineers, Erlangen, Germany). Two adjacent axial images within the same series were selected, and total muscle cross-sectional area (cm²) at L3 was determined and averaged for each patient (1).

Low SMI was defined as <52.4 cm²/m² for male patients and as <38.5 cm²/m² for female patients according to current literature [44].