Impact of Sex-Specific Preoperative Fat Mass Assessment on Long-Term Prognosis after Gastrectomy for Gastric Cancer

SIMPLE SUMMARY: Gastric cancer has a different characteristic than other cancers in that it causes postoperative body weight loss associated with gastric volume loss. It has been reported that the greater the rate of body weight loss after gastrectomy, the poorer the long-term prognosis. Therefore, a higher preoperative fat content may be a nutritional advantage. However, it is controversial whether a higher fat mass is associated with a better prognosis. In obesity, men tend to have visceral fat and women tend to have subcutaneous fat. In order to clarify the prognostic impact of obesity, it is necessary to investigate the prognostic relevance of fat distribution by sex. This study revealed that a low visceral fat mass in men and a low subcutaneous fat mass in women were independent poor prognostic factors after radical gastrectomy for advanced gastric cancer. ABSTRACT: We investigated the impact of the difference in fat distribution between men and women on long-term prognosis after gastrectomy in patients with advanced gastric cancer. Patients with advanced gastric cancer deeper than p-T2 who underwent gastrectomy between April 2008 and June 2018 were included. Visceral fat mass index (VFI) and subcutaneous fat mass index (SFI) were calculated by dividing the cross-sectional area at the umbilical level by the height squared. The medians of VFI and SFI by sex were defined as cut-off values, below which values were defined as low VFI and low SFI. Of the 485 patients, 323 (66.6%) were men and 162 (33.4%) were women. Men with a low VFI had a significantly worse overall survival (OS) (p = 0.004) and women with a low SFI had a significantly worse OS (p = 0.007). Patients with a low VFI and low SFI had the worst prognosis. Multivariate analysis showed that a low VFI was an independent poor prognostic factor in men, while a low SFI was an independent poor prognostic factor in women. In conclusion, a low visceral fat mass in men and a low subcutaneous fat mass in women were independent poor prognostic factors after radical gastrectomy for advanced gastric cancer.