Breast cancer characteristics in low- and middle-income countries: An umbrella review

Breast cancer presents significant challenges in low- and middle-income countries (LMICs) due to disparities in healthcare access and outcomes. This umbrella review synthesizes data on breast cancer characteristics-age at diagnosis, staging, and molecular subtypes-to guide targeted healthcare strategies in LMICs. Our umbrella review was conducted following PRISMA 2020 and JBI guidelines. Systematic reviews from 2009 to 2024 were sourced from PubMed, Google Scholar, and Cochrane. Reviews were assessed with AMSTAR 2, and only those rated moderate or higher were included. Data synthesis and meta-analyses were performed using R. From 1165 records, 35 systematic reviews met initial criteria; nine were included in the final synthesis, representing 305 primary studies (195 relevant to LMICs). Of those, 50 % were hospital-based and 22 % population-based, limiting the generalizability of the data and the importance of promoting more population-based studies. The overall quality of systematic reviews was variable, with only a few meeting high standards. Geographic analysis revealed a significant underrepresentation of high-quality reviews in sub-Saharan Africa and Latin America. Age at diagnosis varied: sub-Saharan Africa (45-52 years), Middle East (36-56 years), and Latin America (∼49-53 years). Advanced-stage diagnoses (stages III and IV) were common, worsening prognostic outcomes. Molecular subtype analysis indicated a predominance of luminal A but highlighted treatment challenges due to limited targeted therapy access. The results emphasize a pressing need to enhance the availability and quality of primary data, including both hospital-based and population-based studies, particularly in underrepresented regions like sub-Saharan Africa and Latin America. Addressing these gaps with rigorous, locally focused studies is essential for improving breast cancer prevention, diagnosis, and treatment. Enhancing methodological standards and expanding research in these areas will be crucial to bridging global breast cancer outcomes disparities.