Social inequalities in cancer incidence, survival and mortality: An umbrella review

Abstract Background An increasing number of systematic reviews investigating differences in cancer burden by social factors such as race, ethnicity, and socioeconomic status have been published in recent years. Our study aims to evaluate the strength and quality of evidence from systematic reviews investigating associations between social factors and cancer incidence, survival, and mortality to help policy-makers reduce existing social inequalities in the burden of cancer. Methods Our study is a pre-registered umbrella review (PROSPERO; CRD42024552884). We systematically searched Medline, Scopus, Web of Science, CINAHL, PsycINFO, the Cochrane Library, the JBI EBP database, and Epistemonikos without date restrictions for published systematic reviews with or without meta-analyses on June 17, 2024. The search identified 15,542 records, which were reduced to 7,421 after deduplication. We are currently screening studies to include systematic reviews of cohort or case-control studies that examined associations between one or more social factors (gender, race/ethnicity, education, occupation, socioeconomic status, place of residence, religion, social capital) and cancer outcomes. Study screening, data extraction, and quality appraisal will be done in duplicate using pre-piloted forms. The strength of evidence of reported associations between social factors and cancer outcomes will be assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) criteria. Before data synthesis, we will assess the degree of overlap between primary studies in the eligible reviews by creating citation matrices and calculating corrected covered area indices. Following this, we will narratively summarize associations (for systematic reviews without meta-analyses) and pool the risk estimates for individual social factors and cancer outcomes (for reviews with meta-analyses) using random-effects meta-analysis models. We will have preliminary results ready by November 2024. Key messages • Our umbrella review aims to evaluate the strength and quality of evidence from systematic reviews which have examined social inequalities in cancer incidence, survival, and mortality. • This high-level evidence synthesis can help policy-makers better plan and target interventions to reduce the existing social inequalities in the burden of cancer.