Abdominal tumors, primarily consisting of gastrointestinal malignancies such as gastric cancer, colorectal cancer, pancreatic cancer, and liver cancer, are often associated with varying degrees of malnutrition and muscle wasting (1–3). These conditions are typically characterized by high mortality rates, primarily due to the subtle onset of symptoms, with many patients being diagnosed at advanced stages (4–7). Given that the majority of these cancers are diagnosed at later stages, treatment options are limited, and surgical resection remains the primary therapeutic approach (8, 9). Therefore, improving postoperative outcomes for these patients is crucial to enhancing their overall health and well-being.

Cancer patients often present with complex conditions and multiple comorbidities, with numerous factors influencing their prognosis (10). Identifying more controllable, simple factors that can improve postoperative outcomes is essential. Since the 1990s, numerous studies have highlighted the widespread issue of poor nutritional status among cancer patients, which has been associated with unfavorable postoperative outcomes (11–13). The growth of abdominal tumors and symptoms such as anorexia can impair gastrointestinal function, leading to malnutrition (14). Surgical interventions further increase metabolic demands, exacerbating pre-existing nutritional deficiencies (15). Research indicates that malnutrition not only compromises immune function but may also result in slower postoperative recovery, increased complication rates, and prolonged hospitalization (16, 17). Therefore, early assessment and intervention of the preoperative nutritional status may have a positive impact on the postoperative prognosis of patients undergoing abdominal cancer surgery.

Previous studies have demonstrated that preoperative malnutrition is associated with adverse postoperative outcomes in cancer patients (18). However, many of these studies rely on subjective questionnaires to assess nutritional status (19–21), which may introduce biases such as communication difficulties, recall errors, social desirability biases, and comprehension issues, potentially affecting the accuracy of the results. This underscores the need for more objective tools to assess the risk of malnutrition.

In response to this need, several objective nutritional assessment tools have been proposed, offering a more accurate and reliable means of evaluating nutritional status. These tools include the Prognostic Nutritional Index (PNI) (22), the Controlling Nutritional Status (CONUT) score (23), and the Geriatric Nutritional Risk Index (GNRI) (24). PNI, which includes serum albumin levels and lymphocyte count, has been widely used to assess immune-nutritional status and predict postoperative outcomes in gastrointestinal cancers (22). The CONUT score, a system for evaluating nutritional status, incorporates serum albumin levels, total lymphocyte count, and total cholesterol levels, and has become an important prognostic tool for patients undergoing abdominal tumor resections, including pancreatic cancer, liver cancer, and other abdominal cancers (23). The GNRI, calculated using serum albumin levels and the ratio of ideal to actual body weight, has also been identified as a key predictor of overall survival in patients undergoing abdominal tumor resections (25).

In the context of modern oncologic surgery, the emergence of the Enhanced Recovery After Surgery (ERAS) program further supports the integration of nutritional assessment into preoperative evaluation. These multidisciplinary pathways, which emphasize early mobilization, pain control, and nutritional support, have been shown to improve postoperative outcomes and shorten hospital stays (26). Despite the substantial evidence linking poor nutritional status with increased postoperative complications and reduced survival rates, the current literature remains fragmented, with variations in assessment methods and outcome measures.

To address the gap in this field, our systematic review and meta-analysis aim to evaluate the prognostic role of preoperative nutritional status on overall survival (OS) in patients undergoing abdominal tumor surgery, based on objective nutritional assessment tools. This study seeks to support clinical risk stratification and intervention strategies, provide a theoretical foundation for future research, and ultimately optimize the management of patients undergoing abdominal tumor surgery, thereby improving their long-term outcomes.

This systematic review and meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement (27). The study is registered with PROSPERO under registration number CRD420251008979.

Our systematic review and meta-analysis indicate that preoperative nutritional status is a critical prognostic factor for OS following abdominal tumor surgery. Several studies involving colorectal cancer, gastric cancer, pancreatic cancer, and hepatocellular carcinoma have shown that poor nutritional status, characterized by low serum albumin levels, decreased PNI, reduced GNRI, elevated CONUT, reduced skeletal muscle mass, and adverse inflammation-nutrition composite scores, is associated with lower long-term survival rates and increased postoperative complications (30–35). These findings underscore the necessity of incorporating routine and standardized nutritional assessments into the preoperative evaluation of patients with abdominal tumors. Over the past few decades, advances in surgical techniques and perioperative care have further emphasized the need to reassess the relationship between nutrition and clinical outcomes. In the era of ERAS, optimizing patients’ preoperative physiological status has gained increasing importance. ERAS protocols advocate for early mobilization, minimally invasive surgical techniques, and targeted perioperative nutritional support as key strategies to reduce postoperative complications and improve recovery times (36–38). Recent studies have demonstrated that adequate nutritional intervention can mitigate the harmful impact of preoperative malnutrition on OS (39), highlighting the potential positive effects of improving preoperative nutritional status on patient prognosis.

Additionally, with the promotion of precision medicine and the implementation of individualized treatment models, there is a growing demand for comprehensive assessments of patients’ overall condition, including their nutritional and functional status. Clarifying the prognostic role of preoperative nutritional status in abdominal tumor surgery not only provides risk stratification and decision-making support for surgeons but also plays a pivotal role in multidisciplinary clinical pathways. This is particularly relevant for elderly patients and high-risk groups, where optimizing preoperative nutritional status can greatly enhance postoperative recovery, improve overall survival, and quality of life. Such improvements can profoundly impact the development of modern surgical treatment models, transitioning toward an integrated approach of “prevention-intervention-recovery” (40).

Malnutrition often leads to increased postoperative complication rates, prolonged hospital stays, and heightened mortality risk (40). In addition to these adverse outcomes, malnourished patients are more prone to infections, exhibit poorer responses to cancer treatments, and experience impaired overall prognosis (30, 41). Previous studies have indicated that nutrition plays a critical role in immune response, with malnutrition leading to immune deficiencies (42). Furthermore, malnutrition is a major cause of zinc deficiency, which impairs cell-mediated immune function and is associated with host cell-mediated immune damage (43). Beyond impairing host immunity, poor nutritional status can alter drug metabolism, reduce tolerance to adjuvant therapies, and diminish patients’ overall functional reserves (44). In summary, maintaining optimal preoperative nutritional status is crucial for the recovery of patients undergoing tumor surgery.

While there are existing studies investigating the prognostic impact of individual preoperative nutritional assessments such as PNI, GNRI, or CONUT scores on tumor surgery outcomes, there is still a lack of integrative evaluations on the combined application of these scoring systems, particularly in terms of their applicability and effectiveness across different tumor types. Therefore, we conducted this meta-analysis by integrating studies that included these three nutritional scoring systems and abdominal tumors. This approach enhances the evidential value of the conclusions. To the best of our knowledge, our study is the first meta-analysis to combine multiple simple, objective nutritional scores with various types of abdominal tumors.

Ultimately, this study included a total of 32 studies and 10,352 patients who underwent abdominal cancer surgery. Our findings indicate that preoperative malnutrition negatively impacts the OS of patients. To assess the heterogeneity between the included studies and the influence of different study characteristics on the prognostic value of preoperative nutritional status scoring, we performed subgroup and meta-regression analyses based on the preoperative nutritional status assessment methods, the country of origin of the study, sample size, study design, follow-up duration, data analysis methods, and tumor type. We found that, regardless of these factors, preoperative malnutrition was consistently associated with significantly poorer OS. Sensitivity analyses further confirmed the robustness of our results. This suggests that preoperative nutritional status may serve as an important prognostic indicator for patients undergoing abdominal tumor surgery.

The PNI is calculated using serum albumin levels and peripheral blood lymphocyte count to assess the immune-nutritional status and a low PNI indicates poor prognosis (22); The CONUT score is calculated based on serum albumin levels, total lymphocyte count, and total cholesterol levels, with higher scores indicating worse nutritional statu (23). The GNRI is calculated using serum albumin concentration and the ratio of actual body weight to ideal body weight, and it is also used to evaluate nutritional risk, with lower values indicating higher risk of adverse events (24). All three indices are key tools for evaluating patients’ nutritional status and prognosis. These measures, based on specific laboratory markers, offer higher reliability compared to many subjective scales or imaging markers. These measures, based on specific laboratory markers, offer higher reliability compared to many subjective scales or imaging markers. They are also simpler and more practical for clinical use. The objective nature of these indices, when applied widely in clinical research and practice, can assist physicians in developing more targeted treatment strategies, thus improving overall health outcomes and quality of life for patients. Effective utilization of these scoring systems allows medical teams to better identify high-risk patients, enabling timely intervention to reduce complications and improve survival rates.

Of course, there are certain limitations to our study. For instance, subgroup analyses based on study design (single-center vs. multi-center studies) revealed some heterogeneity, highlighting the need for further investigation to address this potential source of variability in future studies. Additionally, careful and rigorous consideration of research designs related to preoperative nutritional status and prognosis is required. Another limitation is the variability in the definition of “abdominal tumors.” Although our systematic review attempted to encompass a broad range of abdominal tumors, the majority of studies focused on gastric, liver, pancreatic, and colorectal cancers, with relatively few studies on gallbladder and bile duct cancers, as well as renal cancer. This limitation emphasizes the need for future research to include a broader spectrum of abdominal tumors and to analyze outcomes based on tumor type, which may reveal more subtle prognostic differences.

One important factor to consider is the potential cultural or geographical bias inherent in the studies included in our analysis. The majority of the included studies originated from Japan and China, and these regions may have distinct healthcare systems, nutritional practices, and patient demographics compared to Western populations. These geographical differences could influence the generalizability of our findings, as nutritional status assessments, treatment protocols, and patient care approaches may differ across regions. In particular, the prevalence of certain abdominal cancers, as well as the approach to preoperative nutritional interventions, may vary significantly between Eastern and Western countries (45).

While the current meta-analysis provides valuable insights into the impact of preoperative nutritional status on postoperative outcomes in abdominal cancer surgery, it is essential to consider how these findings can be applied to Western populations or global practices. In Western countries, the prevalence of abdominal cancers such as colorectal and liver cancer may differ, and the typical patient demographic may also exhibit different nutritional challenges, such as varying rates of obesity or malnutrition (46, 47). Moreover, the healthcare infrastructure and access to preoperative nutritional interventions may differ, potentially influencing the effectiveness of these interventions.

Future studies in Western or other diverse populations are needed to confirm whether the results from this analysis are consistent across different geographic and cultural settings. It will be important to examine how nutritional assessment tools like PNI, CONUT, and GNRI are applied in Western healthcare systems, as well as to explore the role of different treatment regimens, tumor types, and preoperative interventions in these settings. Such studies could provide a more global perspective on the role of nutrition in cancer surgery and help standardize clinical practices worldwide.

By addressing these cultural and geographical variations, future research will be better equipped to tailor preoperative nutritional strategies for diverse patient populations and enhance the global applicability of these findings.

In addition, heterogeneity in defining malnutrition using various nutritional assessment tools such as PNI, CONUT, and GNRI cutoffs may have influenced the pooled estimates. Future studies should aim to standardize these thresholds to minimize this variability. Although the overall heterogeneity in our study was moderate to low, the CONUT subgroup exhibited substantial heterogeneity (I² = 76.3%). This finding may be attributed to the differences in the standardization of the CONUT score across studies (48). The CONUT score, as a tool for assessing nutritional status, may have been applied differently in various studies, influenced by patient characteristics, tumor types, and treatment protocols. For example, different studies may have used varying CONUT score thresholds or assessment methods, which could be affected by factors such as tumor staging and treatment regimens (49). Certain tumor types, such as gastric, liver, and pancreatic cancers, may show a higher sensitivity to the CONUT score, while other cancers may present different results (50). These factors likely explain the observed heterogeneity in the CONUT subgroup. Future studies should aim to standardize the use of the CONUT score, particularly in multi-center studies involving diverse tumor types and treatment approaches, to reduce such heterogeneity.

Moreover, while study design differences account for some of the heterogeneity, other potential confounders remain unexplained, including tumor stage, neoadjuvant therapies, the complexity of the surgical procedures, and the missing data related to these factors. These factors are likely to contribute to residual heterogeneity and should be carefully considered in future research.

Despite these limitations, our study holds significant clinical value. Integrating nutritional status assessment into preoperative evaluations can help identify patients at risk of reduced survival. This understanding provides a window for preoperative nutritional interventions, which can optimize patient outcomes through tailored dietary counseling, oral nutritional supplementation, and even prehabilitation programs such as resistance training to improve muscle mass. These interventions may be especially important for elderly or frail populations, who typically have limited physiological reserves.

Looking ahead, future research should focus on several key areas. First, large-scale, prospective trials are needed to examine the impact of targeted nutritional interventions on short- and long-term outcomes in abdominal cancer surgery. Standardized nutritional assessment methods (such as PNI, CONUT, and GNRI scores) should be used in studies to facilitate data aggregation and improve the reliability of meta-analytic estimates. Second, future studies should explore the combined effects of nutritional and inflammatory biomarkers, as their interaction appears to play a critical role in tumor progression and postoperative recovery (51).

Moreover, research should explore the integration of nutritional optimization into multimodal prehabilitation programs, which may include physical training, psychosocial support, and medical optimization. Such comprehensive programs can not only improve nutritional status but also enhance patients’ overall psychological resilience, leading to better surgical outcomes (52). Finally, integrating genomic and metabolomic research with nutritional assessment could identify new biomarkers, further refining our understanding of the relationship between host nutritional status and cancer outcomes (53). These interdisciplinary approaches may pave the way for personalized nutritional therapies in oncologic surgery.

In conclusion, our meta-analysis confirms that preoperative nutritional status is one of the key determinants of OS in patients undergoing abdominal cancer surgery. The significant association between poor nutritional indicators and adverse postoperative outcomes underscores the necessity for comprehensive preoperative assessments and the potential for nutritional interventions to improve long-term survival. Despite some heterogeneity and research limitations, a large body of evidence from various cancer types and clinical settings supports the inclusion of nutritional assessments in routine surgical planning and the development of targeted preoperative optimization strategies. Future research, particularly prospective multi-center studies, should standardize assessment tools and develop evidence-based nutritional intervention protocols that can be seamlessly integrated into clinical practice. Ultimately, addressing preoperative nutritional deficiencies may significantly improve surgical outcomes and increase the OS rate of patients with abdominal malignancies.