The role of antiangiogenic agents in the treatment of gastric cancer: A systematic review and meta-analysis

Tumor vessel normalization and immunotherapy in gastric cancer

Gastric cancer (GC) is a common malignant tumor, and patients with GC have a low survival rate due to limited effective treatment methods. Angiogenesis and immune evasion are two key processes in GC progression, and they act synergistically to promote tumor progression. Tumor vascular normalization has been shown to improve the efficacy of cancer immunotherapy, which in turn may be improved through enhanced immune stimulation. Therefore, it may be interesting to identify synergies between immunomodulatory agents and anti-angiogenic therapies in GC. This strategy aims to normalize the tumor microenvironment through the action of the anti-vascular endothelial growth factor while stimulating the immune response through immunotherapy and prolonging the survival of GC patients.

Tumor progression-dependent angiogenesis in gastric cancer and its potential application

Despite improvements in the early diagnosis, prognosis and therapeutic strategies for gastric cancer (GC), human GC remains one of the most frequently diagnosed malignant tumors in the world, and the survival rate of GC patients remains very poor. Thus, a suitable therapeutic strategy for GC is important for prolonging survival. Both tumor cells themselves and the tumor microenvironment play an important role in tumorigenesis, including angiogenesis, inflammation, immunosuppression and metastasis. Importantly, these cells contribute to gastric carcinogenesis by altering the angiogenic phenotype switch. The development, relapse and spreading of tumors depend on new vessels that provide the nutrition, growth factors and oxygen required for continuous tumor growth. Therefore, a state of tumor dormancy could be induced by blocking tumor-associated angiogenesis. Recently, several antiangiogenic agents have been identified, and their potential for the clinical management of GC has been tested. Here, we provide an up-to-date summary of angiogenesis and the angiogenic factors associated with tumor progression in GC. We also review antiangiogenic agents with a focus on the anti-vascular endothelial growth factor receptor (VEGFR)-mediated pathway for endothelial cell growth and their angiogenesis ability in GC. However, most antiangiogenic agents have reported no benefit to overall survival (OS) compared to chemotherapy alone in local or advanced GC. In phase III clinical trials, only ramucirumab (anti-VEGFR blocker) and apatinib (VEGFR-TKI blocker) have reported an improved median overall response rate and prolonged OS and progression-free survival outcomes as a 2nd-line agent combined with chemotherapy treatment in advanced GC. By providing insights into the molecular mechanisms of angiogenesis associated with tumor progression in GC, this review will hopefully aid the optimization of antiangiogenesis strategies for GC therapy in combination with chemotherapy and adjuvant treatment.

The Use of (Network) Meta-Analysis in Clinical Oncology

Meta-analysis is important in oncological research to provide a more reliable answer to a clinical research question that was assessed in multiple studies but with inconsistent results. Pair-wise meta-analysis can be applied when comparing two treatments at once, whereas it is possible to compare multiple treatments at once with network meta-analysis (NMA). After careful systematic review of the literature and quality assessment of the identified studies, there are several assumptions in the use of meta-analysis. First, the added value of meta-analysis should be evaluated by examining the comparability of study populations. Second, the appropriate comparator in meta-analysis should be chosen according to the types of comparisons made in individual studies: (1) Experimental and comparator arms are different treatments (A vs. B); (2) Substitution of a conventional treatment by an experimental treatment (A+B vs. A+C); or (3) Addition of an experimental treatment (A+B vs. B). Ideally there is one common comparator treatment, but when there are multiple common comparators, the most efficacious comparator is preferable. Third, treatments can only be adequately pooled in meta-analysis or merged into one treatment node in NMA when considering likewise mechanism of action and similar setting in which treatment is indicated. Fourth, for both pair-wise meta-analysis and NMA, adequate assessment of heterogeneity should be performed and sub-analysis and sensitivity analysis can be applied to objectify a possible confounding factor. Network inconsistency, as statistical manifestation of violating the transitivity assumption, can best be evaluated by node-split modeling. NMA has advantages over pair-wise meta-analysis, such as clarification of inconsistent outcomes from multiple studies including multiple common comparators and indirect effect calculation of missing direct comparisons between important treatments. Also, NMA can provide increased statistical power and cross-validation of the observed treatment effect of weak connections with reasonable network connectivity and sufficient sample-sizes. However, inappropriate use of NMA can cause misleading results, and may emerge when there is low network connectivity, and therefore low statistical power. Furthermore, indirect evidence is still observational and should be interpreted with caution. NMA should therefore preferably be conducted and interpreted by both expert clinicians in the field and an experienced statistician. Finally, the use of meta-analysis can be extended to other areas, for example the identification of prognostic and predictive factors. Also, the integration of evidence from both meta-analysis and expert opinion can improve the construction of prognostic models in real-world databases.

Efficacy and safety of apatinib as second-line therapy for advanced gastric cancer: a single-center observational study

Apatinib has been proven to be effective and safe among patients in the third-line treatment of advanced gastric cancer in phase II and III trials. We aimed to evaluate its efficacy and safety in second-line practice, and to explore the factors associated with efficacy. Between April 2015 and May 2017, a total of 23 patients with advanced gastric adenocarcinoma or adenocarcinoma of gastroesophageal junction were enrolled and followed up retrospectively after failing the first line of systemic therapy. The median progression-free survival was 4.43 months (95% confidence interval: 1.63-7.22) and the median overall survival was 9.11 months (95% confidence interval: 8.22-9.99). Two patients achieved a partial response and 14 patients achieved stable disease. The disease control rate was 69.6% and the objective response rate was 8.7%. The most common adverse events over grade 3 were hypertension (8.7%) and thrombocytopenia (8.7%). No treatment-related death was documented during the drug administration. Apatinib is an effective regimen for the second-line treatment of advanced gastric and gastroesophageal cancer with manageable toxicity.

Efficacy and safety for Apatinib treatment in advanced gastric cancer: a real world study

Apatinib has been proved to be effective and safe among patients in gastric cancer in Phase II and III Trials. We aimed to evaluate its efficacy and safety in real world practice, and to explore factors associated with efficacy. Between January 2015 and February 2017, totally 36 patients with advanced gastric adenocarcinoma or adenocarcinoma of gastroesophageal junction (GEJ) were enrolled and followed up retrospectively after failing at least two lines of systemic therapy. The mPFS was 2.65 months (95%CI 1.66–3.54), and mOS was 5.8 months (95%CI 4.77–6.83). Two patients achieved partial response, and nineteen achieved stable disease. The disease control rate (DCR) was 58.3%, and objective response rate (ORR) was 5.6%. Common grade adverse events were hypertension (38.9%), proteinuria (36.1%), and neutropenia (33.3%). And the most common adverse events over grade 3 were hand-foot syndrome (8.3%), anemia (5.6%), and diarrhea (5.6%). No treatment-related death was documented during the drug administration. Exploratory analyses indicated patients treated with antiangiogenic therapy previously were more likely to benefit from apatinib.

Erratum: The role of antiangiogenic agents in the treatment of gastric cancer: A systematic review and meta-analysis: Erratum

[This corrects the article DOI: 10.1097/MD.0000000000006301.].