Introduction: Leukemia is the most frequent neoplasia in children; in our country it is the main cause of medical attention in children with cancer. The are different risk factors associated with the development of this kind of cancer.
Objective: To identify which of the already known factors described in the literature associated with the development of leukemia are most frequent in the pediatric population of Mexico City.
Material and methods: A protective case-control study was carried out using prevalent and incident cases. In two third level hospitals of Mexico City, a total of 81 children who had been diagnosed as suffering from different kind of leukemia, confirmed by biopsy of bone marrow, were select and studied. The control were 154 children from two different sources: 77 of them came from the same hospital where the cases received medical care, the selection criteria was not to have any kind of neoplasia; and 77 came from the same community where those diagnosed children cases lived, the selection criteria for this group was that they were healthy children. Both cases and community controls were visited at home and interview to complete precoded questionnaire with the different variables of the study. The information from the hospital controls was obtained during the time they stayed in the hospital. Odds ratio (OR's) for the different associations were calculated, as well as its confidence intervals at 95% (IC) accord to Cornfield and unconditioned logistic regression was carried out to control confounding variables.
Results: OR greater than 1 was found in those with familiar cancer background 1.93 (1.2-3.63); the mother being exposed to X-ray during pregnancy 1.89 (0.84-4.22); previous abortions before the child with leukemia was born 2.44 (1-06-5.68); being born from full term birth 2.42 (0.47-16.65); being born with weight greater that 3500 g 2.21 (1.04-4.33); being exposed to fertilizers 4.73 (1.04-24.14) and insecticides 1.93 (1.05-3.56). OR smaller than 1 was found in those who have been in a hospital because of an infectious disease during the first year of life 0.57 (0.17-1.74); to have suffered from chicken pox 0.59 (0.32-1.08). No association to parent's age or job was found. Multivariated analysis shows that the exposure to insecticide is the most important risk factor associated with the development of leukemia in children.
Conclusions: We obtained positive associations to different risk factors described in the literature, having found that exposure to fertilizers is the most important risk factor and finding no association with the parent's occupation. This leads to the need of carrying out further studies to investigate, in more detail, the occupation of the father to confirm whether or not this is a risk factor.