To our knowledge, this is the first study to investigate the impact of visceral obesity and GLIM-defined malnutrition in patients with rectal cancer on short-term and long-term outcomes. This study demonstrated that patients with both visceral obesity and GLIM-defined malnutrition were more likely to suffer postoperative complications and poorer OS.
GLIM, the universal malnutrition criteria, was used in this study. The prevalence of GLIM-defined malnutrition was 25.0% in the present study. GLIM consisted of three phenotypic criteria and two etiologic criteria. In the present study, cancer diagnosis was used as the etiologic criteria. GLIM-defined malnutrition was diagnosed when at least one phenotypic criterion was met. Non-volitional weight loss as a phenotypic criterion was the most traditional indicator of malnutrition and was present in almost any malnutrition screening tools [21]. Skeletal muscle mass had attracted much attention in recent years. Many articles demonstrated the correlation between muscle mass and survival [19, 22]. When alternative phenotypic criteria were met, malnutrition may also be diagnosed despite high BMI values when other phenotypic criteria were met. Thus, the GLIM criteria offer a major conceptual advance in diagnosing malnutrition even in cases of high BMI and adiposity. Different combinations of phenotypic and etiologic criteria allowed for a wide range of applicability of GLIM [21]. Previous articles pointed out that GLIM-defined malnutrition was a predictor of OS [23, 24]. Therefore, we used GLIM to evaluate the nutritional status.
While BMI was a convenient way to measure body weight, it failed to distinguish between body composition, body fat distribution, fluid accumulation, and absolute weight gain, among other factors [8, 25]. Therefore, visceral obesity was used in this study and the prevalence of visceral obesity was 50.8%. Many trials had demonstrated that visceral obesity was associated with longer operative times, higher blood loss during surgery, longer postoperative hospital stays and higher postoperative complication rate after elective colorectal surgery [10, 11]. Furthermore, visceral obesity showed no influence on OS but was significantly associated with disease-free survival in patients with resectable colorectal cancer [12]. However, it had not been verified in this article, which may be caused by our separation of the MO group from total visceral obesity group.
It was no surprise that TNM stage and tumor differentiation correlated with survival. In this study, CCI was a significant predictor of postoperative complication, but showed no influence on OS. Furthermore, ASA index was a significant predictor of OS, but showed no influence on postoperative complication. It showed that preoperative comorbidity or not were related to postoperative complications, while preoperative comorbidity that limited activity was related to OS. Patients with low BMI had an effect on postoperative complications in the univariate analysis but did not appear in the multivariate analysis. The possible reason for this was that low BMI was one of the indicators for the diagnosis of malnutrition and was excluded as a confounding factor in the multivariate analysis. It had been reported that the association between BMI and colorectal cancer survival is U-shaped or J-shaped [26]. In our study, high BMI was a protective factor in the survival univariate analysis and was excluded in the multivariate analysis. In this study, MN group was a protective factor for OS in the univariate analysis and was excluded in the multivariate analysis. It may be caused by the fact that we cut out the MO group from the malnutrition group.
With the growth of urbanization and industrialization in Asia, food of low nutritional value was easily available and affordable, while sedentary lifestyles were promoted, contributing to the double burden of obesity and malnutrition [13]. Our study showed that visceral obesity and malnutrition were well evaluated by CT and GLIM. How to intervene in it is also a challenge. Previous studies have pointed out that preventing malnutrition should be a part of the obesity medical care plan, which included a lifestyle change, making the right food choices and avoiding unhealthy foods [27]. Fortified foods, such as specific vitamin supplements, should also be included to prevent shortages. It was not widely accepted that multi-model pre-habilitation should include exercise therapy, nutritional supplementation, and hematologic optimization before surgery [28]. Further research was needed to explain the factors shaping MO in patients, as well as appropriate treatment strategies.
This study has some limitations that should be considered. Firstly, despite our attempts to minimize confounding factors, the retrospective nature of our analysis posed a risk of selection bias. Secondly, we are supposed to keep in mind whether our cut-points are appropriate to define low SMI and visceral obesity. Several studies have established definitions for low SMI and visceral obesity according to different criteria [11, 29, 30]. Due to the lack of a uniform threshold for CT measured low SMI and visceral obesity, we applied cutoff values for SMI based on our previous study [19] and cutoff values for visceral obesity based on Japanese research [20]. There still remained the need for definitive criteria of CT measured low SMI and visceral obesity for Asian. Finally, this was a single-center study among Chinese patients with rectal cancer, which may not be applicable to other ethnic populations and regions. In the future, a multicenter prospective study in different populations is required to validate our findings.