EPIDEMIOLOGICAL ANALYSIS OF THE INCIDENCE OF EARLY-ONSET NON-HODGKIN LYMPHOMA STRATIFIED BY COUNTRY AND CONTINENT

Non-Hodgkin lymphoma (NHL) comprises a heterogeneous group of lymphoid malignancies with diverse clinical behaviors and histological subtypes. Although more commonly diagnosed in older adults, a considerable number of cases occur in individuals under 50 years, herein defined as early-onset non-Hodgkin lymphoma (EO-NHL). These early-onset cases may differ biologically and epidemiologically from those diagnosed later in life and can significantly affect quality of life, productivity, and long-term outcomes. Identifying global epidemiological trends in EO-NHL may clarify underlying genetic predispositions, infectious exposures (such as HIV or EBV), and environmental and socioeconomic factors contributing to disparities in incidence and diagnosis. To analyze the global incidence of EO-NHL (ages 0-49) in 2022, stratified by country, continent, United Nations (UN) region, Human Development Index (HDI), and World Bank income classification, and to explore potential genetic, environmental, and socioeconomic factors in specific populations. This is a descriptive epidemiological study based on data extracted from the Cancer Today platform of the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO). Incidence estimates for NHL in individuals aged 0-49 years in 2022 were analyzed. The age-standardized rate (ASR, per 100,000 inhabitants) was used for comparisons. Stratifications were made by geographic (country, continent, and UN region), socioeconomic (HDI), and economic (World Bank income classification) parameters to identify patterns and disparities. A total of 120,037 new cases were identified globally in 2022, with an ASR of 1.9 per 100,000. The highest ASRs were observed in Malawi (6.3), Zimbabwe (6.1), Trinidad and Tobago (5.4), and other sub-Saharan African and small island countries. Bhutan and São Tomé and Príncipe reported zero cases. North America had the highest continental ASR (3.7), followed by Oceania (3.3), Europe (2.7), Africa (2.5), Latin America (2.1), and Asia (1.4). UN regional analysis revealed the highest rates in Southern Europe (3.5), Australia-New Zealand (3.4), and Melanesia (3.3); the lowest occurred in Eastern Asia (1.4), Polynesia (1.4), South-Central Asia (1.1), and Micronesia (0.8). HDI stratification showed very high HDI countries with an ASR of 2.8, compared to 2.0 in low, 1.7 in high, and 1.4 in medium HDI nations. Regarding income level, high-income countries had the highest ASR (3.0), followed by low- (2.2), upper-middle- (1.8), and lower-middle-income nations (1.5). Brazil reported 3,153 cases, with an ASR of 1.7, below both the global and South American (2.0) averages. The global burden of EO-NHL is unevenly distributed, reflecting complex interactions between environmental exposures, infections, genetics, and health system capacity. Some of the highest ASRs are found in African nations, possibly linked to HIV prevalence and endemic infections, whereas developed countries exhibit higher incidence rates, likely due to better diagnostic access and registry systems. Conversely, underreporting and limited diagnostic capabilities may underestimate incidence in low-resource settings. The findings highlight the necessity of strengthening cancer surveillance, improving access to early diagnosis and care, and investing in research on EO- NHL etiology, particularly in high-incidence and underserved regions.