Importance of hematological and inflammatory markers in the localization of gastric cancer.

INTRODUCTION
Cancer remains among the leading global causes of morbidity and mortality, with gastric cancer and other malignancies posing distinct diagnostic and therapeutic challenges[1-4]. Gastric cancer is a major contributor to cancer cases and related fatalities and is commonly diagnosed at an advanced stage[5]. Despite advancements in treatment, early detection is still difficult, which contributes to the poor prognosis. The clinical presentation varies depending on the location of the gastric cancer[6]. Proximal gastric cancer (PGC) and distal gastric cancer (DGC) are the two forms of gastric cancer that have been identified based on the cancer site[7]. Previous studies have shown that PGC differs from DGC in terms of clinicopathological characteristics[8-10]. According to the National Cancer Database from China, DGC is associated with older patients, more advanced tumor stage, and a higher prevalence of poorly differentiated tumors compared to PGC[11].
Some peripheral blood-based tests are used as indicators of systemic inflammation and are frequently linked to tumor development and metastasis[12]. The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) are among the most well studied markers, and they are prognostic factors in various malignancies[13,14]. Of note, NLR and PLR have advantages over other inflammatory markers, including their established utility, accessibility, and cost-effectiveness. These markers are derived from routine complete blood count tests, making them readily available in clinical practice without additional costs or specialized assays. Unlike some novel markers that may require advanced laboratory techniques, NLR and PLR offer practical advantages for widespread implementation, particularly in resource-limited settings. Furthermore, in the literature, these parameters have been used not only for prognosis but also for the diagnosis and localization of malignancy. For example, Fang et al[15] demonstrated that inflammatory markers possess considerable diagnostic significance for the early identification of gastric cancer, outperforming traditional tumor markers in sensitivity[15]. Alizamir et al[16] established that the preoperative inflammatory parameters are predictive of the severity of breast masses, highlighting their critical roles in both diagnosis and prognosis. In a study from Turkey, the authors investigated the relationship between NLR and the localization of colon cancer[17].
We aimed to elucidate the diagnostic importance of inflammatory and hematological indicators in differentiating between PGCs and DGCs. We also explored the relationship between these markers and clinical attributes of gastric cancer.

MATERIALS AND METHODS

Patient characteristics
A comprehensive screening was conducted on 8900 patients who underwent esophagogastroduodenoscopy at the Ağrı Training and Research Hospital Gastroenterology Endoscopy Unit between May 2022 and December 2023. This retrospective cohort study included 150 patients histopathologically diagnosed with gastric adenocarcinoma. A histopathological diagnosis was established using tissue samples obtained during esophagogastroduodenoscopy. Patients were included if they had histopathologically confirmed gastric adenocarcinoma, comprehensive clinical and laboratory data, and sufficient follow-up information. Patients with prior malignancies, concurrent systemic infections, cirrhosis, or severe cardiovascular diseases were excluded from the study. Additionally, individuals who had recently received antiplatelet agent therapy, were on steroid use at the time of admission, had recurrent gastric cancer, or were diagnosed with hematological malignancies were excluded. The flow chart illustrating the patient inclusion process is summarized in Figure 1.
Patient demographic data, clinical presentations, comorbidities, and laboratory results were retrieved from electronic health record data. Tumor characteristics, including stage, localization, and metastatic status, were determined based on imaging and pathology reports. Tumor localization (proximal or distal) was confirmed via endoscopic imaging, and an official stage classification system was used to stage the patients[18]. Accordingly, gastric cancer patients were categorized into two groups based on the localization of cancer: PGC and DGC[19]. Patients with diffuse gastric cancer involvement at the time of diagnosis were excluded from this study.
Laboratory parameters analyzed included hemoglobin concentration, white blood cell count, neutrophil count, lymphocyte count, platelet count, red cell distribution width, mean platelet volume, C-reactive protein concentration, and albumin concentration. In addition, inflammatory indices such as NLR, PLR, lymphocyte-to-monocyte ratio (LMR), and systemic immune-inflammation index (SII) were analyzed. NLR was calculated by dividing the absolute count of neutrophils by the absolute count of lymphocytes. The PLR was determined by dividing the platelet count by the lymphocyte count. The LMR was established through the division of the lymphocyte count by the monocyte count. The SII was computed with the formula (platelet count × neutrophil count)/lymphocyte count. All values are expressed as absolute counts, and calculations were performed using data from pre-diagnostic blood samples.

Outcome measures
The primary objective was to compare clinical, laboratory, and pathological characteristics between PGC and DGC groups. Assessing the predictive importance of inflammatory markers and their correlation with all-cause mortality were secondary goals.

Statistical analysis
All statistical analyses were conducted utilizing statistical product and service solutions version 24.0 (IBM Corp., Armonk, NY, United States). The normality of the data was evaluated through the Kolmogorov-Smirnov and Shapiro-Wilk tests. Continuous variables are presented as mean ± SD or median (range) and were compared using the Student’s t-test for parametric data or the Mann-Whitney U test for non-parametric data. Categorical variables were reported as frequencies (n) and percentages (%) and were analyzed using Pearson’s χ2 test or Fisher’s exact test, as appropriate. Survival analyses were executed using Kaplan-Meier curves, with group differences assessed via the log-rank test. The Cox proportional hazards regression model was employed to identify independent predictors of all-cause mortality, with results expressed as hazard ratios (HR) and 95% confidence intervals (CI). A P value < 0.05 was considered statistically significant.

RESULTS

Patient characteristics
The research encompassed a cohort of 150 individuals diagnosed with gastric adenocarcinoma, with 84 patients classified as having PGC and 66 patients classified as having DGC. (Figure 1). The cohort’s mean age was determined to be 66.4 ± 10.4 years, with no significant age disparity found between the PGC group (65.3 ± 11.0 years) and the DGC group (67.7 ± 9.5 years). Conversely, the analysis of gender distribution indicated a significant difference, as men represented a larger proportion of the cohort at 63% (P = 0.005).

Clinical presentations and comorbidities
The primary complaints at admission varied. The most frequent complaint at admission was dyspepsia, which was observed in 56% of patients diagnosed with PGC and in 67% of those diagnosed with DGC. Dysphagia solely appeared in the PGC group (P < 0.001). In contrast, anemia was more commonly found in the DGC group, affecting 24% of patients (P = 0.048).
We examined a range of comorbidities including hypertension, diabetes mellitus, cardiovascular disease, atrial fibrillation, chronic renal failure, cerebrovascular disease, and chronic respiratory disease. While the difference did not reach statistical significance (P = 0.284), the occurrence of cardiovascular disease was greater in the PGC group, with a prevalence of 24%, compared to 17% in the DGC group. The rates of diabetes mellitus and hypertension were similar between the groups (P > 0.05). Additionally, the occurrence of other conditions was low and did not reveal any significant differences between the groups.

Tumor characteristics and staging
In terms of tumor staging, most patients in both categories were found to have advanced-stage disease (stages 3 or 4). In particular, 85% of individuals in the PGC group and 77% of those in the DGC group were in these later stages. Despite these considerable values, the stage distribution did not reveal any noticeable differences between the PGC and DGC groups (P = 0.525). Metastasis was noted in 37% of the entire cohort, with similar rates observed in the PGC (40%) and DGC (36%) groups (P = 0.946).

Laboratory findings and inflammatory markers
Laboratory analyses revealed no significant differences in complete blood count and biochemical parameters between the PGC and DGC groups (P > 0.05). White blood cell count, neutrophil and lymphocyte counts, hemoglobin levels, platelet count, and other standard blood parameters were among the important indicators covered in this study. Likewise, the two groups’ levels of biochemical indicators such as albumin, liver enzymes (alanine transferase and aspartate transferase), and C-reactive protein were similar.
Notably, the PLR was significantly higher in the DGC group (191.2 ± 115.2) than in the PGC group (157.3 ± 91.5, P = 0.031). Analysis of other indices indicated no significant differences between the groups (P > 0.05).
Comparison of clinical, laboratory, and pathological features between cardia and non-cardia gastric adenocarcinomas is presented in Table 1.

Age-related differences
In this study, 150 patients were categorized into two age groups. Older patients (≥ 65 years) exhibited a greater occurrence of comorbidities, such as hypertension and cardiovascular disorders, while no notable differences were found in tumor staging or metastasis rates between the two groups. Younger patients showed higher levels of hemoglobin and albumin, whereas other laboratory results and inflammatory markers were consistent across both age groups. Mortality rates did not show any significant variation when comparing different age groups (Table 2).

Cox regression analysis for all-cause mortality
Univariate Cox regression analysis identified tumor stage (HR = 2.020, 95%CI: 1.137-3.590, P = 0.017) and NLR (HR = 1.194, 95%CI: 1.086-1.313, P < 0.001) as significant predictors of all-cause mortality. Multivariate analysis confirmed stage (HR = 1.905, 95%CI: 1.039-3.492, P = 0.037) and NLR (HR = 1.205, 95%CI: 1.091-1.332, P < 0.001) as independent predictors (Table 3).

DISCUSSION
This investigation sought to determine the relevance of inflammatory markers in establishing the localization of gastric adenocarcinoma, while also comparing the clinical attributes of gastric cancer. The results indicated that dysphagia was more prevalent in the PGC group, whereas anemia was more prevalent in the DGC group. Moreover, there was a significant increase in PLR in patients with DGC. The link between tumor location and gastric cancer prognosis is unclear. Studies suggest that PGC is associated with larger tumors and advanced stages, whereas DGC tends to manifest in older individuals and is often associated with advanced stages of the disease and poorly differentiated tumors[11,20]. This study showed that PGCs and DGCs have different clinical and inflammatory features, which can help improve their diagnosis and treatment.
Our results implied that PGC and DGC have different clinical manifestations. The physical proximity of the tumor to the esophagogastric junction, which can result in mechanical blockage, is probably why dysphagia was more common in the PGC group. Anemia, on the other hand, was more frequently seen in the DGC group, most likely as a result of ongoing blood loss linked to ulcerative lesions frequently seen in distal tumors. In a study designed in the United States, dysphagia was found to be a more common complaint in PGCs at time of diagnosis, and bleeding was observed with a similar frequency in proximal and non-PGCs[21]. Bleeding is a common symptom in ulcerative gastric cancer[22]. This study suggests that bleeding may be a universal symptom that does not depend on location. Recognizing these variations is essential for improving early detection and optimizing tumor-specific, patient-centered treatment strategies. Ultimately, this will enhance clinical results and better manage patients with gastric cancer.
The present investigation did not reveal statistically significant variations in tumor stage or metastatic rates between the two groups; however, previous studies have reported conflicting findings[20,23,24]. This discrepancy may be explained by variations in study sample numbers, demographics, staging, and diagnostic techniques. It also highlights the potential influence of regional and demographic factors on tumor biology and clinical presentation.
Regarding the anatomical distribution of gastric cancer, DGCs exhibited a notably elevated PLR. However, no notable differences were detected for the other parameters. Similarly, in a study conducted in China, the authors found that elevated PLR was significantly more common in tumors located in the lower esophagus than in those located in the middle esophagus. This study did not reveal any statistically significant difference in NLR levels between tumors located in the middle and lower esophagus[25]. The PLR has been acknowledged as a prognostic indicator in gastric cancer, extending beyond its role as a diagnostic marker[15,26]. The relationship between platelets and cancer has been previously investigated. Platelets actively contribute to the growth and spread of tumors through various mechanisms, such as transmigration of tumor cells out of the vasculature, prevention of cell-mediated immunity that eliminates malignant cells, and creation of the tumor[27-31]. The association between higher PLR and DGC observed in this study may be linked to chronic inflammation often associated with DGC, potentially driven by Helicobacter pylori infection or dietary and environmental factors that are more common in distal gastric carcinogenesis[32,33]. This study underscores the diagnostic significance of the PLR in differentiating the localization of gastric cancers. Gaining more profound insight into the mechanisms that govern this relationship could aid in the creation of innovative therapeutic strategies. Conversely, the NLR, LMR, and SII were not significantly different between the PGC and DGC groups. This implies that these markers may not be enough to detect the distinct anatomical differences in gastric cancer.
In this investigation, tumor stage and NLR were recognized as significant independent predictors of all-cause mortality, as demonstrated by the results of both univariate and multivariate Cox regression analyses. According to previous studies, poor prognosis and distant metastases are linked to an elevated NLR in gastric cancer[34,35]. Although NLR was not a guide in distinguishing PGC from DGC in our study, it was associated with poor prognosis, supporting other studies.
As emphasized in prior studies, the quality of nucleic acids extracted from biological samples is a critical determinant of the reliability of genomic and transcriptomic analyses[36]. In the context of inflammatory marker analysis, the preservation methods employed for tumor samples play a pivotal role in maintaining molecular integrity[37-40]. Suboptimal preservation conditions can lead to RNA degradation, altered expression profiles, and potential biases in the quantification of inflammatory markers. Consequently, standardizing preservation protocols and evaluating their impact on specific biomarkers, particularly those linked to inflammation in tumor microenvironments, are essential steps to enhance the reproducibility and validity of genomic studies in oncology.
PLR and NLR are simple and cost-effective biomarkers widely used to evaluate systemic inflammation. In conditions such as gastric cancer, where inflammation plays a crucial role, these markers have shown significant potential for prognostication and treatment monitoring[15,41]. Elevated PLR and NLR levels have been associated with poor outcomes and advanced disease stages. However, further studies are required to establish standardized cutoff values and validate their predictive utility across diverse populations before integration into routine clinical practice[41,42]. Nevertheless, integrating these markers into standard oncology workflows requires robust evidence from large, prospective studies that address potential confounding variables, such as concurrent infections or comorbidities. Moreover, the establishment of personalized cutoff thresholds that account for factors like age, tumor biology, and treatment modalities could further refine the predictive accuracy of PLR and NLR. Ultimately, combining these inflammatory markers with emerging molecular and genetic analyses may provide a more comprehensive approach to risk stratification and therapeutic monitoring in gastric cancer.
This study also had several limitations. First, our study is a single-center and retrospective study. Second, we could not evaluate the tumor subgroups in this study. Third, the exclusion of patients with systemic diseases and prior malignancies limits the generalizability of the findings, and may affect the applicability of the results. Future studies should validate these findings in larger prospective cohorts and explore molecular and genomic data to enhance the diagnostic accuracy.

CONCLUSION
In conclusion, PGC has different clinical presentations and laboratory behaviors than DGC. Dysphagia is more common in PGC, whereas bleeding is frequently observed in DGC. The PLR is significantly higher in patients with DGC. Elevated PLR may offer valuable insights into the role of systemic inflammation in gastric cancer location. Therefore, the PLR can be included in clinical evaluation and effective treatment regimens.

ACKNOWLEDGEMENTS
We would like to express our gratitude to all of the patients who participated in this study for their patience and encouragement.