Fibroblast Activation Protein Overexpression in Gastrointestinal Tumors: Protocol for a Systematic Review and Meta-analysis

BACKGROUND: A hallmark of gastrointestinal cancer, especially pancreatic cancer, is the dense stromal tumor microenvironment in which cancer-associated fibroblasts (CAFs) represent the major stromal cell type. Preclinical studies have demonstrated that depletion of fibroblast activation protein (FAP)–positive CAFs results in increased survival. OBJECTIVE: We present the protocol for a systematic review and meta-analysis that aim to assess the currently available evidence on the effect of FAP expression on survival and clinical characteristics in gastrointestinal cancers. METHODS: The literature search and data analysis will be conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) 2020 statement. The databases PubMed/MEDLINE, Web of Science Core Collection, Cochrane Library, and ClinicalTrials.gov will be searched via their respective online search engines. A meta-analysis comparing patients with and without FAP overexpression with the following outcomes will be performed: postoperative survival (overall and median survival; 1-, 2-, 3-, and 5-year survival rates), histological differentiation (grading), local tumor invasion, lymph node metastases, and distant metastases. Odds ratios will be calculated for binary data, and weighted mean differences and relative SD differences will be determined for continuous data. The 95% CI, heterogeneity measures, and statistical significance will be reported for each outcome. The chi-square and Kruskal-Wallis tests will be used to evaluate statistical significance. A P value of <.05 will be considered statistically significant. RESULTS: Database searches will commence in April 2023. The meta-analysis will be completed by December 2023. CONCLUSIONS: In recent years, several publications on FAP overexpression in gastrointestinal tumors have been published. The only published meta-analysis on this topic dates to 2015. It included 15 studies on various solid tumors and only 8 studies focusing exclusively on gastrointestinal tumors. The expected results of the present analysis will provide new evidence on the prognostic value of FAP in gastrointestinal tumors and thereby support health care professionals and patients in their decision-making. TRIAL REGISTRATION: PROSPERO CRD42022372194; https://tinyurl.com/352ae8b8 INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/45176