Off-label use of sodium cantharidinate and vitamin B6 injection in cancer: a protocol for a systematic review and meta-analysis.

Background: In China, sodium cantharidinate/vitamin B6 (SC/VB6) injection has been approved since 2002 for the treatment of lung cancer and primary liver cancer. In addition to these authorized indications, clinical application of SC/VB6 is also common in various other types of cancer. However, there is a lack of comprehensive understanding on this topic. Thus, this systematic review and meta-analysis aims to consolidate evidence regarding the efficacy and safety of off-label use of SC/VB6 in oncology.

Methods: International databases including PubMed, Embase, Cochrane Library, Web of Science, and CINAHL Plus, as well as Chinese databases including China National Knowledge Infrastructure (CNKI), Chinese Biomedical Literature Database (CBM), and Wanfang, will be searched from the inception to 31 December 2024. Comparative studies that evaluated the add-on effect of SC/VB6 to conventional cancer treatments against the use of conventional treatments alone will be considered in the scope of this review. The primary outcomes are objective response rate and performance status. Secondary outcomes are disease control rate (DCR), progression-free survival (PFS), disease-free survival (DFS), overall survival (OS), and adverse events (AEs). Depending on heterogeneity, data will be synthesized using either the Mantel-Haenszel fixed-effect or the DerSimonian and Laird random-effect model. Subgroup analyses will be conducted for the following variables: type of cancer, study design, SC/VB6 dosage, treatment duration, and combined therapies, provided that each subgroup contains at least two studies. Sensitivity analyses will be performed on efficacy outcomes. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) will be utilized to appraise the overall quality of evidence.

Discussion: This review will encompass both randomized controlled trials (RCTs) and cohort studies, thereby enabling us to synthesize and assess evidence across experimental and real-world observational settings. Our findings will contribute to a better understanding on the benefit-risk profile regarding the off-label use of SC/VB6 in oncology, guiding the trajectory of future research, and offering a robust scientific foundation to inform clinical and regulatory decision-making process.

Systematic review registration: PROSPERO CRD42024504977.