To reduce these incident cancer cases, improvement of smoking control policies and extension of colorectal cancer screening should be the two priorities in cancer prevention for the next years.

Persons with Down syndrome (DS) uniquely have an increased frequency of leukemias but a decreased total frequency of solid tumors. The distribution and frequency of specific types of brain tumors have never been studied in DS. We evaluated the frequency of primary neural cell embryonal tumors and gliomas in a large international data set. The observed number of children with DS having a medulloblastoma, central nervous system primitive neuroectodermal tumor (CNS-PNET) or glial tumor was compared to the expected number. Data were collected from cancer registries or brain tumor registries in 13 countries of Europe, America, Asia and Oceania. The number of DS children with each category of tumor was treated as a Poisson variable with mean equal to 0.000884 times the total number of registrations in that category. Among 8,043 neural cell embryonal tumors (6,882 medulloblastomas and 1,161 CNS-PNETs), only one patient with medulloblastoma had DS, while 7.11 children in total and 6.08 with medulloblastoma were expected to have DS. (p 0.016 and 0.0066 respectively). Among 13,797 children with glioma, 10 had DS, whereas 12.2 were expected. Children with DS appear to be specifically protected against primary neural cell embryonal tumors of the CNS, whereas gliomas occur at the same frequency as in the general population. A similar protection against neuroblastoma, the principal extracranial neural cell embryonal tumor, has been observed in children with DS. Additional genetic material on the supernumerary chromosome 21 may protect against embryonal neural cell tumor development.

The aim of this study was to estimate the incidence of leukaemias and lymphomas in children according to the International Classification of Childhood Cancer third edition (ICCC-3) in the population covered by the Girona, Valencia, and Zaragoza population-based cancer registries and compare it with the incidence rates in other European countries. All haematological malignancies (HMs) registered between 1993 and 2002 in children below 15 years of age were included in the study. Pathological and haematological diagnoses were reviewed, recoded according to International Classification of Diseases for Oncology-3 and reclassified on the basis of ICCC-3. Sex and age-adjusted incidence rates were calculated, using the world population as standard. Five hundred and seventy-one HMs were registered in the Girona, Valencia and Zaragoza Cancer Registries during the study period. According to ICCC-3, precursor cell leukaemias were the most frequent HMs in children and constituted 60% of all HMs (an age-adjusted incidence rate of 42.7 per million children-years). The second most frequent childhood HM was Hodgkin lymphoma (11.2% of all HMs), yielding an age-adjusted standardized incidence rate of 6.3 per million children-years. With regard to myeloid lineage, acute myeloid leukaemias were the most frequent with a rate of 7.9 per million children-years. The standardized incidence rates for lymphoid leukaemia (1.19) and Burkitt lymphoma (3.94) were statistically higher than the rates observed in Europe. Compared with European data, Spain has a high incidence of lymphoid leukaemias and lymphomas. In particular, a high incidence of Burkitt lymphoma was observed. The causes of this geographical variation are still unknown.