The pre‐treatment and post‐treatment CT images were retrieved for analysis. Body weight and height were obtained from medical records within 2 weeks of the initial and follow‐up CT scans. In our institution, routine abdominal and pelvic CT images were obtained for women after intravenous administration of iohexol 300 (Omnipaque 300, GE Healthcare) or iopromide 300 (Ultravist 300, Bayer HealthCare) in a single uniphasic bolus dose of 80–100 mL via a power injector at 2 mL/s. The portal‐venous phase was obtained with a fixed delay of 70 s after the administration of the contrast material, and a pitch between 1.0 and 1.5 before the contrast medium was excreted into the bladder. The following CT image parameters included the following information: contrast‐enhanced, 5 mm slice thickness, 120 kVp, and approximately 290 mA.
Two consecutive transverse CT images extending from L3 to the iliac crest were analysed by using the Varian Eclipse software (Varian Medical Systems Inc., Palo Alto, CA, USA).31, 37 Predetermined Hounsfield unit (HU) thresholds were −29 to +150 HU for skeletal muscle, −50 to −150 HU for visceral adipose tissue, and −30 to −190 HU for subcutaneous and intermuscular adipose tissues.31, 32 The cross‐sectional areas (cm2) of the skeletal muscle (including the psoas, paraspinal, transversus abdominis, rectus abdominis, and internal and external oblique muscles) and adipose tissues were calculated. The mean radiation attenuation of the entire cross‐sectional area of the skeletal muscle was the SMD. The total adipose tissue (TAT) area was calculated as the sum of the areas of the subcutaneous, intermuscular, and visceral adipose tissues. The mean tissue areas were calculated by using two consecutive images. One researcher, blinded to the patient information, measured the body composition parameters. The intraobserver coefficients of variation were 0.8%, 0.8%, and 1.0% for the skeletal muscle area, SMD, and TAT area, respectively, in a sample of 60 patients randomly selected from this cohort. The cross‐sectional areas of the skeletal muscle and TAT were normalized based on the patients' height to determine the skeletal muscle index (SMI) and total adipose tissue index (TATI; cm2/m2).
As body composition varies greatly between regions, ethnicities, and cancer types,38, 39, 40, 41 we defined our own cut‐off values for defining sarcopenia, myosteatosis, and low TATI on the basis of previous studies with similar population sizes 7, 8, 9, 15. Cut‐off values were set at the lowest tertile for SMI and SMD and at the highest tertile for TATI. The post‐treatment body composition change was the difference between the pre‐treatment and post‐treatment CT images. In this study, the median duration to complete PDS and adjuvant chemotherapy was 127 days [interquartile range (IQR): 120–140 days]. The median duration between pre‐treatment and post‐treatment CT scans was 182 days (IQR: 161–225 days). To account for variations in the scan interval duration, body composition changes were calculated as the change per 180 days for providing a standardized unit for comparisons between patients. Per the current definition of cachexia,2 patients with a reduction in the weight, SMI, SMD, or TATI of ≥5% were classified as having ‘loss’;6 patients with a reduction in the weight, SMI, SMD, or TATI of <5% or gain in the weight, SMI, SMD, or TATI were classified as having ‘maintained’.