Early-onset cancer in Latin America: incidence trends, evidence gaps and clinical implications.

BACKGROUND: Early-onset cancers (EOC), defined as cancers diagnosed before age 50, have increased worldwide; however epidemiological evidence from Latin America and the Caribbean (LAC) remains limited. This scoping review aimed to synthesize population-based studies reporting on the incidence trends and temporal changes in EOC across LAC, while also identifying associated risk factors when reported. METHODS: We conducted a scoping review following the JBI Manual for Evidence Synthesis and PRISMA-ScR guidelines. We searched systematically MEDLINE/PubMed, Embase, Cochrane Library, Scopus, Web-of-Science, LILACS, and complementary sources from database inception to June 12, 2025, with an updated search on December 30, 2025. No language or date restrictions were applied. Eligible studies reported incidence rates or case counts among adults aged 19-49 years. Data were extracted using standardized forms and synthesized descriptively. The methodological strength of the included studies was appraised through hierarchical classification of levels of evidence. The review protocol was prospectively registered in the Open Science Framework (OSF; registration number: OSF.IO/TZ67D). FINDINGS: Of 4426 records, 28 studies from 11 of 33 LAC countries were included, with Brazil contributing nearly half. Most studies were classified as level IV and VI evidence. Breast, colorectal, cervical, and thyroid cancers were most frequently evaluated. Incidence trends were observed for early-onset breast cancer in Brazil (AAPC 5.22%) and for thyroid cancer in Puerto Rico (APC 5,3), alongside rising incidence rates reported in Argentina and Ecuador. Colorectal cancer showed heterogeneous patterns, with increasing trends in Brazil and Uruguay (APC 3.10% in men), but declining incidence in Peru. For cervical cancer, squamous cell carcinoma incidence declined, whereas adenocarcinoma increased in some settings. Substantial heterogeneity in study design and reliance on hospital-based data, combined with limited geographic coverage, restricted comparability across countries. INTERPRETATION: EOC are increasing in parts of LAC, but regional surveillance remains fragmented. Strengthening population-based cancer registries and regional collaboration are essential to address this emerging public health challenge. FUNDING: This study was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil, under public Call MCTI/CNPq N. 18/2024 - Track 2: individual research project for researchers with up to 10 years since PhD (Grand Number: 403483/2024-7), as well as by a CNPq Research Productivity Fellowship (Process Number: 311427/2023-5), both to Dr. Luís Carlos Lopes-Júnior (L.C.L.J).