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NARFIB: A Novel Prognostic Score Based on the Neutrophil-to-Albumin Ratio and Fibrinogen Can Predict the Prognosis of Gastrointestinal Stromal Tumors

Objective The neutrophil-to-albumin ratio (NAR) and fibrinogen are significantly related to tumor progression. The present study evaluated the prognostic impact of the NAR plus fibrinogen concentration in gastrointestinal stromal tumor (GIST) cases. Methods The baseline characteristics, postoperative NAR, and fibrinogen concentrations were retrospectively analyzed for 229 Chinese patients who underwent radical gastrectomy for GIST. Receiver operating characteristic (ROC) curves were applied to estimate the optimal critical points for NAR and fibrinogen. Cox regression analysis was applied to determine significant prognostic variables. Results Multivariate analyses revealed that poor recurrence-free survival was associated with elevated values for fibrinogen (hazard ratio [HR]: 5.015, 95% confidence interval [CI]: 1.993–12.619, P=0.001) and NAR (HR: 4.669, 95% CI: 1.776–12.273, P = 0.002). Combining fibrinogen and the NAR into the NARFIB score provided an area under the ROC curve of 0.833, which was greater than the areas for NAR (0.708) or fibrinogen (0.778). When the NAR and fibrinogen were replaced by the NARFIB score in the multivariate analysis, the independent prognosticators were tumor site (HR: 2.927, 95% CI: 1.417–6.045, P=0.004), mitotic index (HR: 2.661, 95% CI: 1.110–6.380, P=0.028), and the NARFIB score (HR: 14.116, 95% CI: 3.243–61.443, P<0.001). The NARFIB score retained its prognostic significance in various subgroup analyses and was significantly related to gender, surgical approach, tumor size, mitosis, tumor site, risk classification, and recurrence. Conclusion These results suggest that the NARFIB score may help guide prognostication and risk stratification for GIST, which might benefit from targeted therapy.


Introduction
In the digestive tract, the most common mesenchymal tumors are gastrointestinal stromal tumors (GISTs), which have an annual incidence rate of 10-15 cases/ 1,000,000 population. The GIST tumor types vary from benign tumors to fatal sarcomas, and the optimal treatment for GIST is curative resection. 1 The prognosis of GIST has improved after the introduction of imatinib as targeted therapy, although relapse after radical resection remains common, especially among high-risk patients, and <50% are free from recurrence at 5 years after surgery. 2 Moreover, the median survival time is <2 years after relapse. 1,2 The modified National Institutes of Health (mNIH) category is the most common risk classification for GIST, which aims to predict and stratify the risk of GIST relapse according to mitotic count, tumor location, tumor size, and rupture. 3 However, these parameters require pathological evaluation of tumor specimens and it would be useful to have non-invasive and effective methods for screening and prognostication among moderateand high-risk cases of GIST, which might benefit from targeted therapy.
Various studies have indicated that tumorigenesis and tumor progression are related to systemic inflammation, malnutrition, immune status, and hypercoagulability. [4][5][6] For example, the progression of various tumors is related to the neutrophil-to-albumin (NAR) ratio and fibrinogen concentration. Furthermore, the NAR is an independent prognosticator of pathological complete remission post-chemotherapy for rectal cancer, as well as a predictor of survival among patients receiving palliative treatment for pancreatic cancer. 7,8 Fibrinogen concentrations also have prognostic value for hepatocellular carcinoma, 9 colorectal cancer, 10 and GIST. 11 Therefore, we speculated that a score that combined the NAR and fibrinogen concentration (the NARFIB score) might be useful for prognostication in cases of GIST, and we retrospectively tested this hypothesis among cases who had received curative surgery for GIST.

Patients and Methods Patients
We retrospectively identified 229 cases that had received curative surgery for pathologically confirmed GIST at our center between November 2003 and August 2018, and evaluated their clinicopathological data. The inclusion criteria were (1) patients with complete clinicopathological data and follow-up records, (2) age of ≥18 years, and (3) patients with no neoadjuvant therapy before surgery. The exclusion criteria were (1) a history of anticoagulation or albumin transfusions within 3 months before the surgery, (2) patients with active inflammation, (3) patients with malignant tumors, (4) patients with hematological diseases or connective tissue diseases, and (5) patients with R1-R2 resection. The Beijing Hospital Medical Ethics Committee approved the study.

Data Collection
The clinicopathological facts included age, gender, body mass index (BMI), surgical approach, operative time, tumor site, tumor rupture, tumor size, mitosis, mNIH category, neutrophil count, hemoglobin concentration, albumin concentration, fibrinogen concentration, adjuvant imatinib treatment. The data regarding neutrophil count, hemoglobin concentration, albumin concentration, and fibrinogen concentration were all collected <7 days before the operation. The NAR was calculated as the neutrophil count (10 9 /L) divided by the albumin level (g/L).

Follow-Up
The patients underwent follow-up evaluations every 6 months for 3 years post-operation, and then once a year after 3 years. The most recent follow-up was performed on September 20, 2019. The follow-up evaluations consisted of magnetic resonance imaging or computed tomography of the chest, pelvis, and abdomen, as well as endoscopy and bone marrow scans if necessary. Relapse-free survival (RFS) refers to the time from operation to tumor recurrence.

Calculating the NARFIB Score
The receiver operating characteristic (ROC) curves revealed optimal critical points of 0.086 for the NAR and 3.57 g/L for fibrinogen concentration, based on the areas under the curves (AUCs) and 95% confidence intervals (CIs). Combining NAR and FIB, we categorized patients into three "NARFIB" groups: NARFIB0 = NAR<0.086 and fibrinogen <3.57 g/L, NARFIB1 = either NAR≥0.13 or fibrinogen ≥3.57 g/L, NARCA2 = NAR≥0.13 and fibrinogen≥3.57 g/L.

Statistical Analysis
SPSS software 22.0 was applied for all statistical analyses. The ROC curves were applied to evaluate the prognostic role of NAR, fibrinogen concentration, and the NARFIB score, with optimal critical points determined using the estimated Youden index (sensitivity + specificity-1). The chi-squared test or Fisher's exact test was applied to assess the relationships between clinicopathological variables and the NARFIB score. The Kaplan-Meier method was conducted to generate survival curves and the Log rank test was applied to compare. The prognostic value of various clinicopathological variables was evaluated by Cox regression analysis. P < 0.05 was considered statistically significant.

ROC Analysis
According to the ROC curves (Figure 1) Figure 2  Optimal critical points for the neutrophil-to-albumin ratio, fibrinogen, and the NARFIB score were determined using receiver operating characteristic curves. Abbreviations: FIB, fibrinogen; NEUT/ALB, neutrophil/albumin; NARFIB, score combining the neutrophil-to-albumin ratio and fibrinogen.   (Figure 3).

Discussion
The present study first indicates that the NAR can help predict the prognosis of GIST, and that the novel NARFIB score (combining the NAR and fibrinogen concentration) provided even better prognostic value than the individual factors. Based on our results, the NARFIB score had better ability to predict RFS in this setting, relative to the NAR or fibrinogen concentration alone, and was useful for risk stratification. That information might be helpful to identify cases that might benefit from personalized treatment, such as using targeted therapy. Moreover, the subgroup analyses revealed that the NARFIB score can predict RFS among cases with very low/low/medium risk classifications and even patients with a high-risk classification. The most commonly used clinical risk classification system for GIST is the mNIH system, although it requires pathological evaluation of surgical specimens. Furthermore, the outcomes can vary substantially among patients with the same risk classification and treatment regimen, 3,12 which highlights the need for an accurate and non-invasive prognostic index. Fibrinogen is an indispensable coagulation factor that can predict the prognosis of certain tumors. As an example, Lu et al 11 found that elevated fibrinogen concentrations were an independent predictor of RFS among GIST patients, and 3.7 g/L was the optimal critical point. The present study revealed a similar relationship, although the optimal critical point defined as 3.57 g/L, which suggests that large-scale multicenter studies are needed to clarify the most effective fibrinogen critical point. In this context, fibrinogen helps regulate tumor cells' proliferation and migration, as well as angiogenesis, which is thought to be related to fibrinogen up-regulating pro-inflammatory cytokines and leading to a pro-tumor microenvironment. 13,14 As an extracellular matrix protein, fibrinogen can also induce the epithelial-tomesenchymal transition to promote tumor cell migration and invasion, which involves modulating the expressions of E-cadherin and vimentin. 15,16 Fibrinogen also acts as a molecular bridge to facilitate adhesion between endothelial cells, platelets, and tumor cells, which contributes to metastasis. 17 Moreover, an animal model of fibrinogen deficiency revealed that a microenvironment without fibrinogen can inhibit the migration of tumor cells. 18 We are only aware of two studies that have investigated the relationship between NAR and tumors. Tawfik et al 7 found that the NAR was an independent prognosticator of a complete pathological response post neoadjuvant chemotherapy for rectal cancer, while Tingle et al 8 reported that the NAR was related to survival among patients receiving palliative treatment for pancreatic cancer. These results may be related to the fact that neutrophils are essential for tumor-related inflammation, which drives the generation of reactive oxygen species as well as release of proteases to promote tumorigenesis. 19,20 Neutrophils can also promote angiogenesis by releasing prokineticin 2 and vascular endothelial growth factor. 21 Moreover, neutrophils can weaken the immune system by inhibiting natural killer cells, which promotes tumor cell proliferation and extravasation. 22,23 Albumin is a parameter that is commonly applied to evaluate nutritional status, as hypoalbuminemia is related to malnutrition and weakened immunity. 24,25 Hypoalbuminemia is also a prognostic factor for various tumors, which may be related to a systemic inflammatory response that induces the release of tumor-related cytokines and promotes tumorigenesis. [26][27][28] Serum albumin can also increase the number of G0/G1 cells by suppressing Rb protein phosphorylation, which inhibits tumor cell proliferation. 28 There is inconsistent information regarding the prognostic role of hemoglobin concentrations in GIST. Stotz et al 29 have reported that hemoglobin is an independent prognosticator for GIST patients, while Yang et al 30 reported that hemoglobin was not. We performed Cox regression analysis and observed that hemoglobin concentrations were not significantly related to the prognosis of GIST patients (p=0.14). It is possible that these inter-study differences are related to different critical points and patient samples, which indicates that the prognostic importance of hemoglobin in GIST patients needs further verification.
This study has several limitations. First, the small retrospective single-center design may be a source of bias. Second, partial intermediate-or high-risk cases did not undergo adjuvant therapy or to complete adjuvant therapy because of adverse drug reactions or high drug costs. Thus, it is possible that we introduced selection bias by omitting some cases with intermediate-or high-risk disease.

Conclusion
The present study revealed that the NARFIB score, which combines the NAR and fibrinogen concentration, was an accurate, non-invasive, and low-cost prognostic indicator for GIST patients who were undergoing radical surgery.
This scoring system may complement the current risk classification system and guide personalized treatment and postoperative follow-up.

Ethics Approval and Consent to Participate
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Moreover, for investigations containing human test subjects, patients' informed consent has been obtained from the participants involved before study commencement.

Funding
There is no funding to report.