title: Spatial analysis of childhood cancer: a case/control study.
abstract: BACKGROUND
  Childhood cancer was the leading cause of death among children aged 1-14 years for 2012 in Spain. Leukemia has the highest incidence, followed by tumors of the central nervous system (CNS) and lymphomas (Hodgkin lymphoma, HL, and Non-Hodgkin's lymphoma, NHL). Spatial distribution of childhood cancer cases has been under concern with the aim of identifying potential risk factors.
  
  
  OBJECTIVE
  The two objectives are to study overall spatial clustering and cluster detection of cases of the three main childhood cancer causes, looking to increase etiological knowledge.
  
  
  METHODS
  We ran a case-control study. The cases were children aged 0 to 14 diagnosed with leukemia, lymphomas (HL and NHL) or CNS neoplasm in five Spanish regions for the period 1996-2011. As a control group, we used a sample from the Birth Registry matching every case by year of birth, autonomous region of residence and sex with six controls. We geocoded and validated the address of the cases and controls. For our two objectives we used two different methodologies. For the first, for overall spatial clustering detection, we used the differences of K functions from the spatial point patterns perspective proposed by Diggle and Chetwynd and the second, for cluster detection, we used the spatial scan statistic proposed by Kulldorff with a level for statistical significance of 0.05.
  
  
  RESULTS
  We had 1062 cases of leukemia, 714 cases of CNS, 92 of HL and 246 of NHL. Accordingly we had 6 times the number of controls, 6372 controls for leukemia, 4284 controls for CNS, 552 controls for HL and 1476 controls for NHL. We found variations in the estimated empirical D(s) for the different regions and cancers, including some overall spatial clustering for specific regions and distances. We did not find statistically significant clusters.
  
  
  CONCLUSIONS
  The variations in the estimated empirical D(s) for the different regions and cancers could be partially explained by the differences in the spatial distribution of the population; however, according to the literature, we cannot discard environmental hazards or infections agents in the etiology of these cancers.
authors.affiliation: Environmental Epidemiology and Cancer Unit, National Centre for Epidemiology, Instituto de Salud Carlos III - ISCIII, Madrid, Spain; Consortium for Biomedical Research in Epidemiology & Public Health (CIBER en Epidemiología y Salud Pública-CIBERESP), Madrid, Spain.
authors.forename: Rebeca
authors.initials: R
authors.lastname: Ramis
authors.affiliation: Consortium for Biomedical Research in Epidemiology & Public Health (CIBER en Epidemiología y Salud Pública-CIBERESP), Madrid, Spain.
authors.forename: Diana
authors.initials: D
authors.lastname: Gómez-Barroso
authors.affiliation: Consortium for Biomedical Research in Epidemiology & Public Health (CIBER en Epidemiología y Salud Pública-CIBERESP), Madrid, Spain; Public Health Division of Gipuzkoa, BIODonostia Research Institute, Department of Health of the regional Government of the Basque Country, Donostia, Spain.
authors.forename: Ibon
authors.initials: I
authors.lastname: Tamayo
authors.affiliation: Environmental Epidemiology and Cancer Unit, National Centre for Epidemiology, Instituto de Salud Carlos III - ISCIII, Madrid, Spain; Consortium for Biomedical Research in Epidemiology & Public Health (CIBER en Epidemiología y Salud Pública-CIBERESP), Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: García-Pérez
authors.affiliation: Rare Disease Research Institute (Instituto de Investigación de Enfermedades Raras-IIER), Instituto de Salud Carlos III - ISCIII, Madrid, Spain; Consortium for Biomedical Research in Rare Diseases (Centro de Investigación Biomédica en Red de Enfermedades Raras-CIBERER), Madrid, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Morales
authors.affiliation: Registro Español de Tumores Infantiles (RETI-SEHOP), Universidad de Valencia, Valencia, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Pardo Romaguera
authors.affiliation: Environmental Epidemiology and Cancer Unit, National Centre for Epidemiology, Instituto de Salud Carlos III - ISCIII, Madrid, Spain; Consortium for Biomedical Research in Epidemiology & Public Health (CIBER en Epidemiología y Salud Pública-CIBERESP), Madrid, Spain.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: López-Abente
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D005260:Female; D005843:Geography; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009369:Neoplasms / Q000453:epidemiology*; D013030:Spain / Q000453:epidemiology; D062206:Spatial Analysis