The prognostic value of preoperative plasma fibrinogen in Asian patients with urothelial cancer: a systematic review and meta-analysis

Objective We conducted this meta-analysis to comprehensively explore the prognostic value of the preoperative plasma fibrinogen in Asian patients diagnosed with urothelial cancer (UC). Methods After a systematic search of Web of Science, PubMed, and Embase before May 2024, we included 10 studies in our meta-analysis. The hazard ratios (HRs) with 95% confidence interval (CI) for overall survival (OS), cancer-specific survival (CSS), recurrence-free survival (RFS), and progression free survival (PFS) were estimated using fixed effect model. Results This meta-analysis included a total of 2875 patients. UC patients with an elevated preoperative plasma fibrinogen had worse OS (pooled HR: 2.13, 95% CI: 1.81-2.51; P<0.001), CSS (pooled HR: 2.22, 95% CI: 1.83-2.70; P<0.001), RFS (pooled HR: 1.90, 95% CI: 1.59-2.27; P<0.001), and PFS (pooled HR: 2.12, 95% CI: 1.36-3.29, P=0.001). No significant heterogeneity or publication bias was found. Additionally, statistically significant pooled HRs were also calculated in subgroup analysis when stratified by cancer type, country, and cut-off value. Conclusions The presence of elevated preoperative plasma fibrinogen levels is significantly correlated with unfavorable tumor outcomes in UCs.


Introduction
Urothelial carcinoma (UC) is one of the most common malignancies arising from the entire urinary tract (1), and it mainly includes bladder cancer (BC) and upper tract UC (UTUC).In United States, approximately 168,560 individuals will be diagnosed with UC and 32,590 will die from the disease in 2023 (2).The biological behavior of UC is complicated, making it prone to invasion, recurrence, and metastasis (3).Despite significant improvements in diagnosis and treatment of UC, oncologic outcomes remain poor.The 5-year survival rates for locally advanced UC and metastatic UC were only 34% and 5.4%, respectively (3).Therefore, an effective and applicable biomarker is necessary to accurately predict the prognoses and formulate follow-up strategies based on the stratification of risks for UC patients.
The plasma fibrinogen, serving as a crucial factor in blood coagulation and an indicator of inflammation, plays a pivotal role in maintaining human health (4,5).Numerous studies have revealed that the coagulation/fibrinolytic system is initiated in vivo among cancer patients, and these markers can be employed for predicting tumorigenesis and prognosis (6,7).Recently, an increasing body of evidence suggests that preoperative plasma fibrinogen can be used as a prognostic predictor in patients with UC, including UTUC (8)(9)(10)(11)(12)(13) and BC (14)(15)(16)(17).Song et al. ( 18) conducted a meta-analysis in urological cancers to assess the prognostic value of preoperative plasma fibrinogen.However, their study solely focused on UTUC (no BC, another type of UC) and had limited inclusion of studies.Interestingly, there are well-documented race-based differences in the treatment and outcomes for UC (19).Thus, the present metaanalysis included additional recent studies on UTUC and BC patients to evaluate the prognostic value of preoperative plasma fibrinogen on survival outcomes in UCs among Asian population.

Protocol
Before commencing our study, we registered our systematic review project with the International Prospective Register of Systemic Reviews (PROSPERO; http://www.crd.york.ac.uk/PROSPERO/CRD42024496302).This meta-analysis was conducted in accordance with the Meta-analysis of Observational Studies in Epidemiology (MOOSE) criteria (see Supplementary Files).

Literature search
We systematically searched Web of Science, Embase, and PubMed to obtain all available clinical studies published before May 2024 without any language restrictions.We used the terms (fibrinogen, transitional cell carcinoma, upper urinary tract, urothelial carcinoma, ureter cancer, ureteral cancer, ureter carcinoma, ureteral carcinoma, bladder cancer, bladder carcinoma, and bladder tumor) to search for the related articles in the databases (see Supplementary Files).The literature search was independently conducted by two investigators, Zhengqing Bao and Guizhong Li.

Inclusion and exclusion criteria
The literature search, study selection, and validation were independently performed by two authors (Zhengqing Bao and Guizhong Li), and a third author (Jianwei Wang) was consulted to resolve the disagreements.
Studies were considered eligible if they met all of the following criteria: 1) cohort studies on patients with localized UCs reported the association between the preoperative plasma fibrinogen and oncological outcomes, included overall survival (OS), cancerspecific survival (CSS), recurrence-free survival (RFS), or/and progression free survival (PFS), after surgery.The plasma fibrinogen was tested before a definitive operation or diagnostic procedure (a definitive operation was generally performed shortly thereafter); 2) publications provided sufficient information to extract or calculate hazard ratios (HRs) and their corresponding 95% confidence intervals (CIs); 3) all patients classified into low and high plasma fibrinogen groups; and 4) full-text articles.The following studies were excluded based on any of the following criteria: 1) reviews, abstracts, letters, reviews, case reports, editorials, or basic studies; 2) studies with insufficient information for HRs and 95% CIs; 3) sample size<50; 4) non-Asian population; and 5) duplicate or overlapping studies.

Data extraction and quality assessment
The data extraction was independently performed by two investigators, Zhengqing Bao and Guizhong Li.The extracted data included the first author's name, publication year, country, cancer type, sample size, duration time, age, gender, cutoff value, follow-up duration, HRs (95%CI), and analysis method (univariate/ multivariate).If both univariate and multivariate analyses were performed, we chose the HRs (95%CI) from multivariate analysis.OS, CSS, RFS and PFS were analyzed.The study quality was systematically evaluated according to the Newcastle-Ottawa Scale (NOS) (see Supplementary Files).A 'star system' has been developed in which a study is judged on three broad perspectives: the selection of the study groups; the comparability of the groups; and the ascertainment of either the exposure or outcome of interest for studies respectively.A study can be awarded a maximum of one star for each numbered item within the Selection and Outcome categories.A maximum of two stars can be given for Comparability.Studies with more than 6 stars were considered as high-quality.The quality assessment was independently performed by two investigators (Zhengqing Bao and Guizhong Li), with a third reviewer (Jianwei Wang) consulted to resolve any disagreements.

Statistical analysis
All statistical analyses were conducted using STATA 15.0 (STATA Corporation, College Station, TX, USA).Statistical significance was set as a p-value<0.05.The heterogeneity of included studies was evaluated using Cochran's Q-test and Higgins I 2 statistics (I 2 ).The random effects-model was used for the significant heterogeneity, which was indicated by I 2 >50% or P<0.05.Otherwise, the fixed-effect model was adopted to calculate pooled HRs for no obvious heterogeneity.Subgroup and metaregression analyses were performed to explore the potential factors for heterogeneity.Sensitivity analysis was conducted using a "onestudy removed" model to assess the stability of the overall results.Potential publication bias was assessed by using funnel plots visually, whose results were confirmed by using Begg's and Egger's tests.If significant publication bias was identified, the trim-and-fill method estimated an adjusted effect size.

Characteristics of the included studies
A total of 656 records were identified through a systematic literature search.After excluding 172 duplicates, the titles and abstracts of the remaining 466 records were screened, resulting in the selection of 18 articles for full-text reading.Out of these 18 records, 8 were excluded: two studies included overlapped data with others; two studies did not have OS, CSS, RFS, and PFS as final outcomes; one study had a sample size <50; one study lacked sufficient information to extract or calculate HRs and their CIs; and two studies were based on non-Asian populations.Finally, 10 studies were included in this meta-analysis (Figure 1; Table 1).
The included studies had 2875 cases.6 studies examined the prognostic value of plasma fibrinogen in UTUC (including 2017 patients), and 4 in BC (including 858 patients).As for survival outcomes, 8 studies (including 2539 patients) evaluated the prognostic value of plasma fibrinogen in predicting OS, 5 studies (including 1892 patients) evaluated CSS, 6 studies (including 1703 patients) evaluated RFS, and 2 studies (including 336 patients) evaluated PFS.All included studies achieved a minimum score of 7 on the NOS and were deemed to be of high quality.

Recurrence-free survival
The pooled outcome suggested that high preoperative plasma fibrinogen was significantly associated with short RFS in UCs (fixed effect model, pooled HR: 1.90, 95% CI: 1.59-2.27;P<0.001) with no heterogeneity across studies (I 2 = 0.0%, P=0.640) (Figure 3A; Meta-analysis of the association between the preoperative plasma fibrinogen and OS in urothelial cancers.Forest plot of studies evaluating pooled HR for OS in urothelial cancers (A) Forest plots of subgroup analyses by cancer type (B) for OS.3B; Table 3).In subgroup analyses based on country, high preoperative plasma fibrinogen was associated with poor OS in both Japan (fixed effect model, pooled HR: 1.76, 95% CI: 1.28-2.49,P=0.001), and China (fixed effect model, pooled HR: 1.95, 95% CI: 1.59-2.41,P<0.001).Different cutoff value also showed prognostic value of preoperative plasma fibrinogen for RFS (Table 3).

Sensitivity analysis
The results of sensitivity analysis for OS, CSS, and RFS outcomes demonstrated that the conclusions for OS, CSS, and RFS remained stable because the pooled HRs were not significantly influenced by excluding any individual study (Supplementary Figure 1).

Publication bias
The presence of publication bias in the included investigations was assessed using Begg's test and Egger's linear regression test.In Meta-analysis of the association between the preoperative plasma fibrinogen and RFS in urothelial cancers.Forest plot of studies evaluating pooled HR for RFS in urothelial cancers (A) Forest plots of subgroup analyses by cancer type (B) for RFS.
Begg's test, we found that P-value of 0.536 for OS, 0.806 for CSS, and 0.260 for RFS.In Egger's test, the corresponding P-values were found to be 0.480 for OS (Figure 5A), 0.394 for CSS (Figure 5B), and 0.639 for RFS (Figure 5C).Thus, our meta-analysis did not reveal any significant publication bias.

Discussion
Our meta-analysis incorporated a total of 2875 cases from 10 eligible studies, which were deemed of high quality based on the NOS score system.The results of our study suggest that preoperative plasma fibrinogen levels can serve as a reliable predictor for oncologic outcomes in patients with localized UC.Elevated preoperative plasma fibrinogen levels are associated with unfavorable OS, CSS, RFS, and PFS in patients with UTUC or BC.In subgroup analyses, BC shown a better predictive value for OS, suggesting that preoperative plasma fibrinogen has the best predictive value for OS in BC.UTUC demonstrated a better predictive value for RFS, indicating that preoperative plasma fibrinogen has the best predictive value for RFS in UTUC.Additionally, we found that the preoperative plasma fibrinogen has a better predictive value for OS and RFS among the Chinese population compared to the Japanese population.Therefore, preoperative plasma fibrinogen could serve as a cost-effective and readily accessible prognostic biomarker for urothelial cancers in the Asian population, despite variations in effect sizes.
Although UTUC and BC share some common risk factors, however, they exhibit distinct biological, practical, and clinical characteristics (20), which may account for the difference in prognostic value of preoperative plasma fibrinogen between these two types of UC.The subgroup analysis based on country in our meta-analysis revealed that preoperative plasma fibrinogen exhibited a stronger predictive value within the Chinese population compared to the Japanese population, potentially attributed to limited study availability and inadequate sample sizes.Further studies should be conducted to validate these insignificant results.Sensitivity analyses confirmed the stableness of the pooled outcomes.
Negative associations between preoperative plasma fibrinogen and oncological prognosis have been reported in numerous cancers, not limited to urothelial cancers.These included renal cell carcinoma (21), prostate cancer (22), gastric cancer (23), laryngeal squamous cell carcinoma (24), lung cancer (25), Meta-analysis of the association between the preoperative plasma fibrinogen and CSS/RFS in urothelial cancers.Forest plot of studies evaluating pooled HR for CSS (A) and for PFS (B).
hepatocellular carcinoma (26), and pancreatic cancer (27).However, the underlying mechanisms for the have not been clearly elucidated.Previous in vitro studies have verified that fibrinogen can promote cancer cell proliferation, invasion, epithelial-to-mesenchymal transition (EMT), angiogenesis, and hematogenous dissemination transition (28,29).Thus, fibrinogen could play an important role in tumor progression.The previous studies have demonstrated the ability of fibrinogen to interact with secreted growth factors, such as transforming growth factor-b (TGF-b), fibroblast growth factor-2 (FGF-2), vascular growth factor (VEGF), and platelet-derived growth factor (PDGF) to stimulate tumor cell proliferation and angiogenesis (30)(31)(32).In esophageal squamous cell carcinoma, Zhang et al. (33) have demonstrated that fibrinogen can promote malignant biological tumor behavior involving EMT via the p-AKT/p-mTOR pathway.However, the exact biological mechanism for the relationship between elevated plasma fibrinogen and poor prognosis of UC remains unknow.Further investigations are needed to explore the underlying mechanism.Despite advancements in the management of cancer, some patients still face a poor prognosis due to local tumor recurrence or distant metastasis.Therefore, novel biomarkers are necessary to predict the prognoses accurately and formulate follow-up strategies based on the stratification of risks for UC patients.Tumor-related immune responses in tumor micro-environment serve as immunological surveillance and contribute to antitumor immune responses, which are closely associated with patients' tumor outcomes (34).Therefore, certain immune-inflammatory indicators, such as C-reactive protein (CRP) (35), plateletlymphocyte ratio (PLR) (36), neutrophil-lymphocyte ratio (NLR) (37), lymphocyte-monocyte ratio (LMR) (38), albumin (39), and plasma fibrinogen levels (40), have been reported as potential biomarkers for diagnosing and predicting the prognosis of tumor patients.The findings of this meta-analysis indicate that plasma fibrinogen serves as a valuable prognostic biomarker, enabling the identification of high-risk UC patients prior to treatment and subsequently enhancing their tumor outcomes.Esumi et al. (41) also reported that inhibiting coagulation events by using r-hirudin, a highly specific thrombin inhibitor, significantly inhibited lung metastasis in an animal model.Thus, the administration of anticoagulants may potentially mitigate hematogenous metastasis in UC patients exhibiting elevated levels of plasma fibrinogen.Although our study comprehensively assessed the prognostic value of the preoperative plasma fibrinogen in UCs with no obvious heterogeneity and bias, it had certain limitations.Firstly, some of the included studies only enrolled a small number of patients, which might introduce confounder bias.However, excluding these studies did not significantly affect the overall estimation.Secondly, our focus was primarily on the postsurgical outcomes, thereby excluding consideration of other treatment modalities.Consequently, this led to a paucity of data within the studies included.Additionally, our meta-analysis included a limited number of studies.However, our meta-analysis exhibited no significant heterogeneity and publication bias.Besides, sensitivity analysis confirmed that our findings were stable and reliable.Finally, all the studies included in this meta-analysis were retrospective observational studies with inherent structural defects; therefore, we cannot draw definitive conclusions regarding how preoperative plasma fibrinogen influences oncologic outcomes.
In conclusion, the findings of our meta-analysis indicate a significant association between elevated preoperative plasma fibrinogen levels and unfavorable tumor outcomes in UCs.While further studies are needed, our findings suggested that elevated preoperative plasma fibrinogen could serve as a potential prognostic biomarker for UC patients and may influence clinical decision-making.

FIGURE 1 Flow
FIGURE 1Flow diagram of the study selection process.

TABLE 1
Characteristics of all 10 studies included in the meta-analysis.

TABLE 2
HR values for OS according to subgroup analysis.

TABLE 3
HR values for RFS according to subgroup analysis.

TABLE 4
HR values for CSS and PFS., cancer-specific survival; PFS, progression free survival; HR, hazard ratio; CI, confidence interval; P H , P for heterogeneity.