Our current study demonstrates the significance of albumin, prealbumin and platelets in preoperative peripheral blood for LN metastasis in GC. The ROC curve indicated that the utility of albumin, prealbumin and platelets as predictive markers for LN metastasis in GC was comparable to that of traditional GC markers, namely CEA and CA199. The combined application of these indicators improves the efficacy for predicting LN metastasis. Prealbumin was also an independent factor for patient survival in all analyzed blood parameters, as were as D-dimer and GC markers.
Neoadjuvant chemotherapy has shown a survival benefit relative to surgery alone[8], and the possibility of LN metastasis is a key consideration for such treatment. Neoadjuvant chemotherapy is recommended for patients with lymph node metastases in Japan[9]. It has been reported that neoadjuvant chemotherapy can effectively control LN metastasis in GC, thereby reducing tumor N stage and increasing complete resection[10]. Therefore, preoperative assessment of LN status provides a reference for choosing a reasonable treatment plan for patients.
Tumor markers are commonly used to predict prognosis, monitor a positive course, and detect recurrence[11, 12]. As traditional tumor markers, CEA and CA199 may help detect positive lymph nodes[13, 14]. In our current study, we assessed the predictive value of preoperative peripheral blood-derived clinical routine laboratory biomarkers for LN metastasis. Our data showed that the LN metastasis group had significantly elevated CEA and CA199. Multivariate regression analysis showed their clinical significance for predicting LN metastasis. Previous studies reported that CEA, CA199, CA724 and CA242 were all associated with LN metastasis, and their combination could improve diagnostic efficacy[15]. This is consistent with our conclusions, although we only analyzed CEA and CA199 without consideration of CA724 and other GC markers.
In addition to the aforementioned tumor markers, we also found that platelets and nutritional markers (albumin and prealbumin) may independently predict LN involvement. In fact, studies have reported that platelet count may be a reliable biomarker of lymph node metastasis likelihood[16, 17]. Not only that, platelet-derived markers such as platelet-lymphocyte ratio are also useful biomarkers for predicting LN metastasis[18]. Platelets promote cell proliferation, angiogenesis, and epithelial-mesenchymal transition, and protect tumor cells from immune system attack by interacting with tumor cells to form microthrombi[19, 20]. Therefore, the correlation between platelets and LN metastasis is reasonable. Accumulating evidence suggests that tumor-associated inflammation is tumor-promoting[21]. As an inflammatory related marker, the neutrophil-lymphocyte ratio (NLR) has also been reported as a predictor of LN metastasis[22, 23]. In univariate analysis we found an association of neutrophils for LN metastasis, but in multivariate logistic regression we found no predictive value for neutrophils, monocytes and lymphocytes. Although many studies have reported the predictive value of NLR for LN metastasis[24, 25], a report demonstrates that tumor-associated neutrophils infiltrating the tumor microenvironment, rather than circulating NLR, is an independent prognostic factor for LN metastasis of early GC. This suggests that neutrophils are associated with tumor progression. Although it is likely that primarily tumor-infiltrating neutrophils play a key role in this process, circulating neutrophils may reflect the status of tumor progression. In our study, we mainly focused on the role of a single blood marker and therefore did not consider various derived markers of systemic inflammation. Although we did not find an independent predictive role of inflammatory cells and lymphocytes on LN metastasis, platelets showed an advantage. By interacting with inflammatory cells and lymphocytes, platelets are important coordinators of inflammation as well as immune responses[26]. The systemic immune-inflammation index is calculated from neutrophils, lymphocytes and platelets, and it has been demonstrated in the study of LN metastasis[27].
Prealbumin, also known as transthyretin, has a shorter half-life than albumin, only 2 to 3 days, and its levels are mainly affected by liver function and inflammation[28]. Notably, we found that both albumin and prealbumin were independent predictors of LN metastasis. It has been identified that perioperative prealbumin might be useful in predicting postoperative early recurrence of lung cancer and short-term postoperative outcomes after gastrectomy[29, 30]. Although there are few studies on the assessment of LN metastasis by albumin or prealbumin, the combination of prealbumin and inflammatory response index has been implicated in metastasis in GC patients[31]. A study demonstrates the predictive value of platelet-to-albumin ratio for LN metastasis[5]. Given that both platelets and albumin are independent predictors of LN metastasis, our results are consistent with this report. In our study, we did not analyze the clinical significance of the variables calculated from peripheral blood parameters, and it is not difficult to infer that the ratio of platelets to albumin or the ratio of platelets to prealbumin would have a higher predictive value for LN metastasis. In order to more effectively assess the status of LN metastasis, we performed a combined ROC analysis and found that combining CEA, CA199, platelets, albumin, and prealbumin significantly improved the predictive power for LN metastasis compared to combining CEA and CA199 alone. This inspires clinicians that low prealbumin levels before treatment can not only guide nutritional support, but also reflect the status of LN metastasis. The risk of LN metastasis can be further evaluated according to the preoperative blood index in patients with N0 who have not been proved by imaging methods.
GC patients are often accompanied by elevated coagulation markers, such as fibrinogen and D-dimer. In fact, crosstalk between coagulation and inflammation makes them mutually reinforcing and is closely related to tumor progression and prognosis[32]. Studies have shown that preoperative plasma fibrinogen is associated with LN metastasis. Although computed tomography (CT) was more valuable in predicting lymph node metastases, CT could not predict lymph node metastases in 20.6% of patients, and 53.8% of them had plasma fibrinogen above the cutoff value[33]. The predictive value of D-dimer for LN metastasis has also been reported[34]. However, multivariate logistic regression showed that coagulation related markers were not independent risk factors for LN metastasis. Our current study did not compare the predictive power between blood parameters and CT, but the combination of CT and pre-treatment blood parameters can provide evidence for evaluating LN metastasis and then formulating treatment strategies.
Nutrition-related indicators are most used to guide perioperative nutritional support and evaluate the prognosis of tumor patients[35, 36]. Prealbumin is more sensitive to changes in protein-energy status than albumin, therefore more suitable for nutritional monitoring[37]. In terms of survival of patients, albumin and prealbumin are well known as prognostic factors. But few studies compare prognostic superiority of albumin and prealbumin. After our analysis, we found that prealbumin, but not albumin, was an independent risk factor for OS and DFS in GC. Among other preoperative blood parameters, tumor markers (CA199 for OS and CEA for DFS) and D-dimer were independently associated with gastric cancer prognosis, which is consistent with previous studies.
This study has some limitations. First, it is a retrospective study with a small sample size. Second, we only focus on a subset of peripheral blood indicators before treatment, such as inflammatory status through blood cells. However, other indicators of this status, such as C-reactive protein, were not included in the analysis. Similarly, among gastric cancer markers, we only analyzed CEA and CA199. Third, we only considered the individual effects of each index, and did not analyze other markers calculated by these factors, such as NLR, SII, etc. However, we performed a joint ROC analysis by multivariate logistic regression. Fourth, as an effective method for detecting lymph node metastasis, imaging methods have not been compared with those of peripheral blood in their diagnostic performance.