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Annually, almost 1 million instances of gastric cancer are diagnosed globally1. Despite a consistent decrease in incidence, gastric cancer continues to be one of the most prevalent and lethal neoplasms, accounting for 783,000 cases (8.2% of all cancer fatalities) in 20182. Surgery is the principal treatment for gastric cancer, with a 5-year survival rate of about 25.7% in cases of locally advanced disease in Europe and the United States3. Despite advancements in surgical techniques and perioperative care in recent years, a majority of gastric cancer patients experience significant malnutrition due to the characteristics of gastric cancer, surgical trauma, perioperative dietary management, and inadequate caloric intake, which adversely affect their nutritional status and body composition4. Furthermore, malnutrition is exacerbated by intensified catabolism resulting from immune response dysregulation and metabolic disturbances, leading to anorexia, elevated energy consumption, and weight loss5. These factors constitute the foundation of what is termed disease-related malnutrition6. In this context, laboratory and clinical instruments have been established to evaluate the nutritional status of cancer patients6. The evaluation of nutritional status includes data on body weight, body mass index, body composition metrics, e.g., fat-free mass or fat mass, and biochemical indicators, e.g., albumin and prealbumin levels6. Various nutritional status markers, including the prognosis nutritional index, body mass index, serum albumin, and preoperative body weight reduction, have been evaluated as prognostic indicators in gastric cancer7,8. Indeed, deteriorations in nutritional status can result in an amplified occurrence of complications, diminished progression-free survival, and reduced overall survival7. These findings underscore the imperative to identify malnutrition and provide appropriate nutritional support to enhance nutritional status, hence optimizing the quality of life and survival of gastric cancer patients. The effects of various nutritional treatments on nutritional status across different contexts remain contentious.
To study such contentious effects, we need to use a standardized methodology. Traditional narrative reviews lack the systematic rigor to synthesize this heterogeneous evidence, while individual trial data alone cannot provide definitive conclusions about comparative effectiveness. This protocol employs a meta-analysis approach, which offers distinct advantages over these alternatives by providing a structured and reproducible methodology for evidence synthesis. Meta-analysis minimizes bias through comprehensive search strategies and explicit inclusion criteria. It also enables quantitative pooling of results to increase statistical power and precision9. The chosen approach is particularly valuable in nutritional oncology research, where interventions vary considerably in composition, timing, and administration routes.
Specifically, this protocol addresses gaps in existing methodologies by providing explicit guidance for categorizing different nutritional interventions, standardizing outcome measurement timepoints, offering transparent criteria for model selection based on heterogeneity, and incorporating comprehensive sensitivity analyses. The protocol is applicable to studies examining any nutritional intervention in gastric cancer patients, with outcomes including anthropometric measures (body weight), biochemical markers (albumin, prealbumin, transferrin), and functional assessments. However, conclusions may not generalize to other cancer types or nutritional interventions not specifically addressed, and applicability may be limited for studies with substantial methodological heterogeneity or incomplete outcome reporting. The aim of the study was to systematically evaluate and compare the effects of different nutritional therapies, including oral nutritional supplementation, early enteral nutrition, parenteral nutrition, and enteral immunonutrition, on the nutritional status of gastric cancer patients, as measured by changes in body weight, albumin, prealbumin, and transferrin levels.