Systematic review and meta-analysis of vascular endothelial growth factor as a biomarker for malignant pleural effusions

Immune modulation in malignant pleural effusion: from microenvironment to therapeutic implications

Immune microenvironment and immunotherapy have become the focus and frontier of tumor research, and the immune checkpoint inhibitors has provided novel strategies for tumor treatment. Malignant pleural effusion (MPE) is a common end-stage manifestation of lung cancer, malignant pleural mesothelioma and other thoracic malignancies, which is invasive and often accompanied by poor prognosis, affecting the quality of life of affected patients. Currently, clinical therapy for MPE is limited to pleural puncture, pleural fixation, catheter drainage, and other palliative therapies. Immunization is a new direction for rehabilitation and treatment of MPE. The effusion caused by cancer cells establishes its own immune microenvironment during its formation. Immune cells, cytokines, signal pathways of microenvironment affect the MPE progress and prognosis of patients. The interaction between them have been proved. The relevant studies were obtained through a systematic search of PubMed database according to keywords search method. Then through screening and sorting and reading full-text, 300 literatures were screened out. Exclude irrelevant and poor quality articles, 238 literatures were cited in the references. In this study, the mechanism of immune microenvironment affecting malignant pleural effusion was discussed from the perspectives of adaptive immune cells, innate immune cells, cytokines and molecular targets. Meanwhile, this study focused on the clinical value of microenvironmental components in the immunotherapy and prognosis of malignant pleural effusion.

Long-Term Survival of American Joint Committee on Cancer 8th Edition Staging Descriptors for Clinical M1a Non-Small Cell Lung Cancer

BACKGROUND

The American Joint Committee on Cancer (AJCC) 8th edition TNM staging manual for non-small cell lung cancer (NSCLC) M1a descriptors includes tumors presenting with malignant pleural or pericardial effusion (ie, M1a-Effusion), pleural or pericardial nodule(s) (ie, M1a-Pleural), or separate tumor nodule(s) in a contralateral lobe (ie, M1a-Contralateral).

RESEARCH QUESTION

Is M1a NSCLC presenting with malignant pleural or pericardial effusion associated with worse survival compared with other types of M1a NSCLC?

STUDY DESIGN AND METHODS

Patients with cT1-4, N0-3, M1a NSCLC (satisfying a single M1a descriptor of M1a-Effusion, M1a-Pleural, or M1a-Contralateral), according to AJCC eighth edition staging criteria, in the National Cancer Database from 2010 to 2015 were included. Overall survival was evaluated by using Kaplan-Meier analysis, multivariable-adjusted Cox proportional hazards modeling, and propensity score matching.

RESULTS

Of the 25,716 patients who met study eligibility criteria, 12,756 (49.6%) presented with M1a-Effusion tumors, 3,589 (14.0%) with M1a-Pleural tumors, and 9,371 (36.4%) with M1a-Contralateral tumors. In multivariable-adjusted analysis, compared to M1a-Effusion tumors, both M1a-Pleural tumors (hazard ratio, 0.68; 95% CI, 0.64-0.71; P < .001) and M1a-Contralateral tumors (hazard ratio, 0.66; 95% CI, 0.64-0.69; P < .001) were associated with better overall survival. No significant differences were found in overall survival between patients with M1a-Pleural tumors vs M1a-Contralateral tumors. In a propensity score-matched analysis of 5,581 patients with M1a-Effusion tumors and 5,581 patients with other M1a tumors (ie, M1a-Contralateral or M1a-Effusion), those with M1a-Effusion tumors had worse 5-year overall survival than patients with other M1a tumors (M1a-Effusion 6.4% [95% CI, 5.7-7.1] vs M1a-Other 10.6% [95% CI, 9.7-11.5]; P < .001).

INTERPRETATION

In this national analysis of AJCC 8th edition cT1-4, N0-3, M1a NSCLC, tumors with malignant pleural or pericardial effusion were associated with worse overall survival than tumors with either pleural or contralateral pulmonary nodules. These findings may be taken into consideration for the upcoming ninth edition of the AJCC lung cancer staging guidelines.

Malignant pleural disease

Malignant pleural disease represents a growing healthcare burden. Malignant pleural effusion affects approximately 1 million people globally per year, causes disabling breathlessness and indicates a shortened life expectancy. Timely diagnosis is imperative to relieve symptoms and optimise quality of life, and should give consideration to individual patient factors. This review aims to provide an overview of epidemiology, pathogenesis and suggested diagnostic pathways in malignant pleural disease, to outline management options for malignant pleural effusion and malignant pleural mesothelioma, highlighting the need for a holistic approach, and to discuss potential challenges including non-expandable lung and septated effusions.

Malignant Pleural Effusions in the Era of Immunotherapy and Antiangiogenic Therapy

Malignant pleural effusions (MPE) have historically been associated with a poor prognosis, and patients often require a series of invasive procedures and hospitalizations that significantly reduce quality of life at the terminus of life. However, advances in the management of MPE have coincided with the era of immunotherapies, and to a lesser extent, antiangiogenic therapies for the treatment of lung cancer. Landmark studies have shown these drugs to improve overall survival and progression-free survival in patients with lung cancer, but a paucity of phase III trial data exists for the impact of immune checkpoint inhibitors (ICI) on lung cancers associated with MPE. This review will focus on the leading studies investigating the impact of ICI and antiangiogenic therapies in patients with lung cancer and MPE. The diagnostic and prognostic values of vascular endothelial growth factor and endostatin expression levels in malignancy will also be discussed. These advancements are changing the paradigm of MPE management from palliation to treatment for the first time since 1767 when MPE was first reported. The future holds the promise of durable response and extended survival in patients with MPE.

Trial Protocol: Reaccumulation rate of pleural effusions after therapeutic aspiration: An observational cohort study to determine baseline factors associated with rate of pleural fluid reaccumulation following therapeutic aspiration in patients with malignant pleural effusion attending a pleural clinic (REPEAT)

Background

Malignant pleural effusion (MPE) is the build-up of pleural fluid in the space between the lung and chest wall due to advanced cancer. It is treated initially by large volume drainage (therapeutic aspiration). If the fluid reaccumulates, a definitive procedure is performed. There is wide variation in rate of reaccumulation. Patients with rapid reaccumulation often attend hospital as an emergency. Conversely, patients with slow reaccumulation do not need a definitive procedure and may experience cancelled or unnecessary procedures. This study aims to create and validate a multivariable prediction model to predict how quickly pleural fluid will reaccumulate in patients with MPE following therapeutic aspiration.

Research question

Can we predict how quickly pleural fluid will reaccumulate in patients with MPEs?

Methods

A total of 200 patients with known or suspected MPE attending for therapeutic aspiration will be recruited from 5-10 UK hospitals over 20 months. Patients will be enrolled prior to undergoing aspiration. Following this, they will undergo chest X-ray, which will be repeated one week later (treatment as usual). Rate of reaccumulation will be calculated based on change of size of the effusion seen on X-ray. Data will be collected on common clinical biomarkers e.g., size of effusion on pre-aspiration chest X-ray, volume of fluid drained. This data will be analysed to create a clinical score.A further validation cohort of 40 patients will be enrolled in parallel with creation of the score.

Anticipated impact

The ability to predict rate of reaccumulation of MPE will enable patients and clinicians to make better informed treatment decisions. For patients with predicted rapid reaccumulation, a definitive procedure could be offered as first-line treatment, rather than a therapeutic aspiration. This will prevent emergency hospital admissions and decrease number of procedures. By contrast, patients whose effusions will recur slowly may avoid an unnecessary procedure.

Factors Affecting Rate of Pleural Fluid Accumulation in Patients with Malignant Pleural Effusions

Purpose of Review

Malignant pleural effusions (MPEs) are initially treated with thoracocentesis but usually reaccumulate. There is wide variation in the rate of recurrence. Those with rapid recurrence could benefit from early definitive treatment, whilst those with slower recurrences may not. Here, we discuss pleural fluid homeostasis, MPE pathophysiology, and factors associated with reaccumulation.

Recent Findings

Few studies have investigated markers of MPE reaccumulation. Suggested features of rapid reaccumulation include lactate dehydrogenase, effusion size, positive cytology, and dyspnoea. Vascular endothelial growth factor (VEGF) correlates with MPE size and treatment response, but its association with reaccumulation rate is unknown. Some anti-VEGF therapies have shown promise in MPE management.

Summary

Further work is needed to validate hypothesised biomarkers of rapid recurrence and to characterise other biomarkers, such as VEGF. The Reaccumulation rate of Malignant Pleural Effusions After Therapeutic Aspiration (REPEAT) study aims to address these gaps in the literature and is currently in recruitment.

The Effect of Pleural Effusion on Prognosis in Patients with Non-Small Cell Lung Cancer Undergoing Immunochemotherapy: A Retrospective Observational Study

Objectives: Combined immune checkpoint inhibitor (ICI) therapy and chemotherapy has become the standard treatment for advanced non-small-cell lung cancer (NSCLC). Pleural effusion (PE) is associated with poor outcomes among patients with NSCLC undergoing chemotherapy. However, minimal data exists on PE for patients undergoing combined ICI and chemotherapy. Therefore, we investigated how PE affects survival outcomes in patients with NSCLC undergoing this combined therapy. Methods: We identified patients with advanced NSCLC undergoing chemotherapy and ICI therapy from the Okayama Lung Cancer Study Group−Immune Chemotherapy Database (OLCSG−ICD) between December 2018 and December 2020; the OLCSG−ICD includes the clinical data of patients with advanced NSCLC from 13 institutions. Then, we analyzed the treatment outcomes based on the presence of PE. Results: We identified 478 patients who underwent combined ICI therapy and chemotherapy; 357 patients did not have PE, and 121 patients did have PE. Patients with PE had significantly shorter progression-free survival (PFS) and overall survival (OS) than those without PE (median PFS: 6.2 months versus 9.1 months; p < 0.001; median OS: 16.4 months versus 27.7 months; p < 0.001). The negative effect of PE differed based on the patient’s programmed cell death-ligand 1 (PD-L1) expression status; with the effect being more evident in patients with high PD-L1 expression. In addition, PFS and OS did not differ between patients who did and did not undergo bevacizumab treatment; thus, bevacizumab-containing regimens did not improve the survival outcomes for patients with PE. Conclusion: PE is associated with poor outcomes among patients with NSCLC undergoing combined ICI therapy and chemotherapy.

Treatment of malignant pleural effusion in non-small cell lung cancer with VEGF-directed therapy

BACKGROUND

Vascular endothelial growth factor (VEGF) is a critical regulator of malignant pleural effusion (MPE) in non-small-cell lung cancer (NSCLC). Bevacizumab (BEV) and apatinib (APA) are novel VEGF blockers that inhibit lung cancer cell proliferation and the development of pleural effusion.

METHODS

In this study, we established Lewis lung cancer (LLC) xenograft mouse models to compare the therapeutic effect of APA and BEV in combination with cisplatin (CDDP) against MPE. The anti-tumour and anti-angiogenic effects of this combination therapy were evaluated by ¹⁸F-FDG PET/CT imaging, TUNEL assay and Immunohistochemistry.

RESULTS

The triple drug combination significantly prolonged the overall survival of the tumour-bearing mice by reducing MPE and glucose metabolism and was more effective in lowering VEGF/soluble VEGFR-2 levels in the serum and pleural exudates compared to either of the monotherapies. Furthermore, CDDP + APA + BEV promoted in vivo apoptosis and decreased microvessel density.

CONCLUSIONS

Mechanistically, LLC-induced MPE was inhibited by targeting the VEGF-MEK/ERK pathways. Further studies are needed to establish the synergistic therapeutic effect of these drugs in NSCLC patients with MPE.KEY MESSAGESCombined treatment of MPE with apatinib, bevacizumab and cisplatin can prolong the survival time of mice, reduce the content of MPE, decrease the SUV_max of thoracic tumour tissue, down-regulate the content of VEGF and sVEGFR-2 in serum and pleural fluid, and promote the apoptosis of tumour cells. Angiogenesis and MPE formation can be inhibited by down-regulation of HIF-1α, VEGF, VEGFR-2, MEK1 and MMP-2 molecular signalling pathway proteins.

Efficacy of osimertinib in epidermal growth factor receptor-mutated non-small-cell lung cancer patients with pleural effusion

Background

Osimertinib is a standard first-line treatment for advanced non-small-cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations. Although malignant pleural effusion (PE) is a common clinical problem in NSCLC, information about the efficacy of osimertinib in patients with PE is limited, especially regarding its efficacy in EGFR T790M-negative patients with PE remains unclear.

Methods

We retrospectively reviewed the medical records of patients with NSCLC harboring EGFR mutations who were treated with osimertinib in our institution between May 2016 and December 2020.

Results

A total of 63 patients with EGFR mutated NSCLC were treated with osimertinib; 33 (12 with PE) had no EGFR T790M mutation, while 30 (12 with PE) had EGFR T790M mutation. In EGFR T790M-negative NSCLC, the progression-free survival (PFS) of the patients with PE was comparable to that of the patients without PE (median PFS 19.8 vs. 19.8 months, p = 0.693). In EGFR T790M- positive NSCLC, the PFS and overall survival (OS) of the patients with PE were significantly shorter than those of the patients without PE (median PFS 16.8 vs. 8.3 months, p = 0.003; median OS 44.9 vs. 14.2 months, p = 0.007). In the multivariate analysis, the presence of PE was independently associated with shorter PFS and OS in EGFR T790M-positive NSCLC patients, but not EGFR T790M-negative patients.

Conclusions

These data suggest the efficacy of osimertinib may differ between EGFR T790M-positive and -negative NSCLC patients with PE.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09701-2.

Accelerated Wound Healing and Keratinocyte Proliferation through PI3K/Akt/pS6 and VEGFR2 Signaling by Topical Use of Pleural Fluid

Impaired wound healing is an ongoing issue that cancer patients undergoing chemotherapy or radiotherapy face. Our previous study regarding lung-cancer-associated pleural fluid (LCPF) demonstrated its propensity to promote endothelial proliferation, migration, and angiogenesis, which are crucial features during cutaneous wound healing. Therefore, the current study aimed to investigate the effect of pleural fluid on cutaneous wound closure in vitro and in vivo using HaCaT keratinocytes and a full-thickness skin wound model, respectively. Both heart-failure-associated pleural fluid (HFPF) and LCPF were sequentially centrifuged and filtered to obtain a cell-free status. Treatment with HFPF and LCPF homogeneously induced HaCaT proliferation with cell cycle progression, migration, and MMP2 upregulation. Western blotting revealed increased PI3K/Akt phosphorylation and VEGFR2/VEGFA expression in HaCaT cells. When treated with the PI3K inhibitor, LCPF-induced keratinocyte proliferation was attenuated with decreased pS6 levels. By applying the VEGFR2 inhibitor, LCPF-induced keratinocyte proliferation was ameliorated by pS6 and MMP2 downregulation. The effect of LCPF-induced cell junction rearrangement was disrupted by co-treatment with a VEGFR2 inhibitor. Compared with a 0.9% saline dressing, LCPF significantly accelerated wound closure and re-epithelization when used as a dressing material in a full-thickness wound model. Histological analysis revealed increased neo-epidermis thickness and dermis collagen synthesis in the LCPF-treated group. Furthermore, LCPF treatment activated basal keratinocytes at the wound edge with the upregulation of Ki-67, VEGFA, and MMP2. Our preliminaries provided the benefit of wet dressing with pleural fluid to improve cutaneous wound closure through enhanced re-epithelization and disclosed future autologous application in cancer wound treatment.

The Meta-Analysis of Bevacizumab Combined with Platinum-Based Treatment of Malignant Pleural Effusions by Thoracic Perfusion

Objective

To evaluate the safety of bevacizumab combined with platinum-based thoracic perfusion for treating lung cancer-related malignant pleural effusion (MPE) through meta-analysis.

Methods

The CNKI, PubMed, Cochrane Library, Embase, Chinese Science and Technology Journal Database (VIP), and Wanfang Databases were searched for randomized controlled trials (RCTs) of bevacizumab combined with platinum-based thoracic perfusion for the treatment of MPE. The references included in the articles were manually searched for additional studies. A meta-analysis of the RCTs was conducted using the RevMan 5.3 application.

Results

A total of 8 studies involving 540 patients (271 cases in the test group and 269 cases in the control group) were included in the meta-analysis. The test group had a significantly greater risk of elevated blood pressure as well as a higher rate of complete remission (CR) compared to the control group (P < 0.05). In contrast, the incidence of partial remission (PR) was only slightly higher in the test group (P > 0.05), and the risks of leukopenia, vomiting or nausea, rhinorrhea, diarrhea, gastrointestinal bleeding or hemoptysis, proteinuria, abnormal kidney and liver function, arrhythmia, and rashes were not significantly different between the test and control groups (P > 0.05).

Conclusion

Bevacizumab combined with platinum-based thoracic perfusion can achieve CR of MPE in patients with advanced lung cancer without significantly increasing the risk of adverse effects. The rate of PR was similar for the combination treatment and platinum-based infusion.

Exploring the value of pleural fluid biomarkers for complementary pleural effusion disease examination

OBJECTIVE

Pleural fluid biomarkers are beneficial for the complementary diagnosis of pleural effusion etiologies. This study focuses on the multidimensional evaluation of deep learning to investigate the pleural effusion biomarkers value and the diagnostic utility of combining these markers, in distinguishing pleural effusion etiologies.

METHODS

Pleural effusion were divided into three groups according to the diagnosis and treatment guidelines: malignant pleural effusion (MPE), parapneumonic effusion (PPE), and congestive heart failure (CHF). First, the value of the biomarker was analyzed by a receiver operating characteristic (ROC) curve. Then by utilizing deep learning and entropy weight method (EWM), the clinical value of biomarkers was computed multidimensionally for complementary diagnosis of pleural effusion diseases.

RESULTS

There were significant differences in the six biomarkers, TP, ADA, CEA, CYFRA211, NSE, MNC% (p < 0.05) and no significant differences in three physical characteristics including color, transparency, specific gravity and six other biomarkers such as WBC, PNC%, MTC%, pH level, GLU, LDH (p > 0.05) among the three pleural effusion groups. The comprehensive test of pleural fluid biomarkers based on deep learning is of high accuracy. The clinical value of cytomorphology biomarkers WBC, MNC %, PNC %, MTC % was higher among pleural fluid biomarkers.

CONCLUSION

The clinical value of multi-dimensional analysis of biomarkers by deep learning and entropy weight method is different from the ROC curve analysis. It is suggested that during the clinical examination process, more attention should be paid to the cell morphology biomarkers, but the physical properties of the pleural fluid are less clinical significance.

Validation of Calprotectin As a Novel Biomarker For The Diagnosis of Pleural Effusion: a Multicentre Trial

Discriminating between malignant pleural effusion (MPE) and benign pleural effusion (BPE) remains difficult. Thus, novel and efficient biomarkers are required for the diagnosis of pleural effusion (PE). The aim of this study was to validate calprotectin as a diagnostic biomarker of PE in clinical settings. A total of 425 patients were recruited, and the pleural fluid samples collected had BPE in 223 cases (53.7%) or MPE in 137 patients (33%). The samples were all analysed following the same previously validated clinical laboratory protocols and methodology. Calprotectin levels ranged from 772.48 to 3,163.8 ng/mL (median: 1,939 ng/mL) in MPE, and 3,216-24,000 ng/mL in BPE (median: 9,209 ng/mL; p < 0.01), with an area under the curve of 0.848 [95% CI: 0.810-0.886]. For a cut-off value of ≤ 6,233.2 ng/mL, we found 96% sensitivity and 60% specificity, with a negative and positive predictive value, and negative and positive likelihood ratios of 96%, 57%, 0.06, and 2.4, respectively. Multivariate analysis showed that low calprotectin levels was a better discriminator of PE than any other variable [OR 28.76 (p < 0.0001)]. Our results confirm that calprotectin is a new and useful diagnostic biomarker in patients with PE of uncertain aetiology which has potential applications in clinical practice because it may be a good complement to cytological methods.

Meta-analysis of associations of vascular endothelial growth factor protein levels and -634G/C polymorphism with systemic lupus erythematosus susceptibility

BACKGROUND

The purpose of this study was to detect the effects of vascular endothelial growth factor (VEGF) on systemic lupus erythematosus (SLE) risk.

METHODS

Associated studies were extracted from the China Biological Medicine Database (CBM), and PubMed on June 10, 2018, and applicable investigations were pooled and analyzed by meta-analysis using RevMan 5.3.

RESULTS

VEGF levels was associated with SLE risk (mean differences (MD) =196.02, 95% CI: 135.29-256.75, P < 0.00001), and VEGF levels was associated with active SLE risk (MD =77.51, 95% CI: 10.98-144.05, P = 0.02). We also found that VEGF levels was associated with SLE developing into lupus nephritis (LN) risk (MD =223.16, 95% CI: 144.38-301.93, P < 0.00001). However, VEGF -634G/C gene polymorphism (rs2010963) was not associated with SLE risk.

CONCLUSIONS

VEGF levels was associated with SLE risk, active SLE risk and SLE developing into LN risk. However, there was no an association between VEGF -634G/C gene polymorphism and SLE risk.

Malignant pleural effusion as a predictor of the efficacy of anti-PD-1 antibody in patients with non-small cell lung cancer

Background

The aim of this study was to evaluate the usefulness of the presence of malignant pleural effusion (MPE) as a negative predictor of anti‐PD‐1 antibody efficacy.

Methods

A retrospective review of patients with advanced or recurrent non‐small cell lung cancer treated with an anti‐PD‐1 antibody between December 2015 and March 2018 at the National Cancer Center Hospital, Japan, was conducted. Progression‐free survival (PFS) and overall survival (OS) were compared between patients with and without MPE. Additional survival analysis according to PD‐L1 expression status was conducted. Univariate and multivariate analyses were performed.

Results

A total of 252 patients were identified before the commencement of anti‐PD‐1 antibody treatment: 33 with MPE and 219 without MPE. PFS and OS were significantly shorter in patients with MPE than in patients without MPE (median PFS 3.0 vs. 5.8 months, hazard ratio [HR] 1.7, P = 0.014; median OS 7.9 vs. 15.8 months, HR 2.1, P = 0.001). In patients with PD‐L1 expression in ≥ 1% of their tumor cells, the PFS of patients with MPE was significantly shorter than of patients without MPE (median PFS 3.1 vs. 6.5 months, HR 2.0, 95% confidence interval 1.0–3.5; P = 0.021). The presence of MPE was independently associated with a shorter PFS and OS in multivariate analysis.

Conclusion

The presence of MPE in patients administered an anti‐PD‐1 antibody is associated with shorter PFS and OS, regardless of the presence of PD‐L1 expression ≥ 1% of tumor cells.

The role of VEGF in the diagnosis and treatment of malignant pleural effusion in patients with non‑small cell lung cancer (Review)

Malignant pleural effusion (MPE) is a severe medical condition, which can result in breathlessness, pain, cachexia and reduced physical activity. It can occur in almost all types of malignant tumors; however, lung cancer is the most common cause of MPE, accounting for ~1/3 of clinical cases. Although there are numerous therapeutic approaches currently available for the treatment of MPE, none are fully effective and the majority can only alleviate the symptoms of the patients. Vascular endothelial growth factor (VEGF) has now been recognized as one of the most important regulatory factors in tumor angiogenesis, which participates in the entire process of tumor growth through its function to stimulate tumor angiogenesis, activate host vascular endothelial cells and promote malignant proliferation. Novel drugs targeting VEGF, including endostar and bevacizumab, have been developed and approved for the treatment of various tumors. Data from recent clinical studies have demonstrated that drugs targeting VEGF are effective and safe for the clinical management of MPE. Therefore, VEGF‑targeting represents a promising novel strategy for the diagnosis and treatment of MPE. The present review summarized recent advances in the role of VEGF in the pathogenesis, diagnosis and clinical management of MPE in patients with non‑small cell lung cancer.

Systematic review and meta-analysis of vascular endothelial growth factor as a biomarker for malignant pleural effusions

Conventional methods may fail to identify the cause of pleural effusion (PE), thus establishing reliable biomarkers is deemed necessary. This study aimed at examining the role of vascular endothelial growth factor (VEGF) as a biomarker in the differentiation between malignant and benign PEs in adults. A comprehensive literature search in PubMed (Medline), Scopus (ELSEVIER), and Cochrane Central Register of Controlled Trials (CENTRAL) databases was conducted using keywords. We included studies that evaluated pleural and/or serum levels of VEGF among patients presenting with undiagnosed PE and the association between these levels and the final diagnosis. We performed a meta‐analysis to calculate the summary effect using the random effects model. Statistical analysis was performed with the statistical package for meta‐analysis Comprehensive Meta‐Analysis. Twenty studies were included in the systematic review, while 11 of them in the meta‐analysis. Pleural fluid VEGF levels among patients with malignant PE were increased by 1.93 ng/mL as compared to patients with benign PE (95% CI: 1.32–2.54, Q = 173, df (Q): 10, I² = 94.2%, P < 0.05). Serum VEGF levels among patients with malignant PE were increased respectively by 1.90 ng/mL (95% CI: 0.93–2.88, Q = 182, df (Q): 6, I² = 96.7%, P < 0.05). This study showed that malignant PEs were associated with higher levels of both pleural fluid and serum VEGF. VEGF appears to represent a promising biomarker for the differential diagnosis between benign and malignant PEs.