Incidence and Survival Rates in European Children With Retinoblastoma

Abstract

Retinoblastoma (Rb) is the most common primary intraocular malignancy in children and is second in total worldwide prevalence to uveal melanoma. Incidence rates of Rb and survival rates among patients with Rb vary substantially by country. 1 In their epidemiological registry-based study, Virgili and colleagues 2 address the survival and health care burden of children with Rb in Europe from 2000 to 2013. They report that the incidence of Rb within most European countries remained stable at 4 cases per 1 million person-years aged 0 to 14, with an expected overall 5-year survival rate of 97.8%. Cancer registries are extensively used to provide valuable incidence and prevalence data. However, in tumors like Rb, registry data may be particularly subject to bias. Rb is a tumor that may be hereditable and multicentric, and it may not always be confirmed histologically. In addition, Rb is treated with a variety of treatment approaches, all of which make it difficult to systematically capture all data in the epidemiological registry. For example, in this European study, only 28.4% of cases where laterality was reported were noted to be bilateral, which is lower than the expected rate (40%). This may be due in part to the limitations of the registry. It is likely that some patients who initially were reported as unilateral but later developed Rb in the fellow eye did not have their laterality status updated.Another bias of the registry data can be exemplified with the data from Bulgaria, where the 5-year Rb survival rate appears to be less than 70%, compared with the 97.8% survival rate observed in Europe overall. While it is possible that the actual survival rate is lower in Bulgaria, the lower rate could be related to ascertainment bias. However, lower survival rates are generally observed in Eastern European countries.An important issue related to worse outcomes in the study is the impact of migration on the overall results, and the authors briefly mention treatment migration in their discussion. Migration or referral from 1 European country to another could be associated with the registry statistics if a patient is counted twice or is counted in the country to which they were referred. Late referral of Rb cases from resource-limited countries without Rb centers, such as some areas in Africa, to centers of excellence in central Europe could also affect observed survival rates. Finally, the methodology did not address patients' ethnicity and nationality of origin, which might be important because of the different waves of migration from the Middle East and North Africa into Europe. If children of migrants arrived at a European country with advanced Rb, these patients might be counted as from that European country, altering the interpretation of incidence rates and outcomes for the country in which the child was treated. Statistics from the 2024 World Migration Report 3 show that Germany, France, Poland, and Turkey were the European coun-