Incidence and time trends of childhood lymphomas: findings from 14 Southern and Eastern European cancer registries and the Surveillance, Epidemiology and End Results, USA.

Purpose: To describe epidemiologic patterns of childhood (0-14 years) lymphomas in the Southern and Eastern European (SEE) region in comparison with the Surveillance, Epidemiology and End Results (SEER), USA, and explore tentative discrepancies.
Methods: Childhood lymphomas were retrieved from 14 SEE registries (n = 4,702) and SEER (n = 4,416), diagnosed during 1990-2014; incidence rates were estimated and time trends were evaluated.
Results: Overall age-adjusted incidence rate was higher in SEE (16.9/10 ⁶ ) compared to SEER (13.6/10 ⁶ ), because of a higher incidence of Hodgkin (HL, 7.5/10 ⁶ vs. 5.1/10 ⁶ ) and Burkitt lymphoma (BL, 3.1 vs. 2.3/10 ⁶ ), whereas the incidence of non-Hodgkin lymphoma (NHL) was overall identical (5.9/10 ⁶ vs. 5.8/10 ⁶ ), albeit variable among SEE. Incidence increased with age, except for BL which peaked at 4 years; HL in SEE also showed an early male-specific peak at 4 years. The male preponderance was more pronounced for BL and attenuated with increasing age for HL. Increasing trends were noted in SEER for total lymphomas and NHL, and was marginal for HL, as contrasted to the decreasing HL and NHL trends generally observed in SEE registries, with the exception of increasing HL incidence in Portugal; of note, BL incidence trend followed a male-specific increasing trend in SEE.
Conclusions: Registry-based data reveal variable patterns and time trends of childhood lymphomas in SEE and SEER during the last decades, possibly reflecting diverse levels of socioeconomic development of the populations in the respective areas; optimization of registration process may allow further exploration of molecular characteristics of disease subtypes.