Incidence of malignant neoplasms in children attending Social Security Hospitals in Mexico City.

An increase in neoplasms in Mexican children has been reported. In 1991, the incidence in children from Mexico City (MC) was 70 (x 10(6) child/year), although this rate might be underestimated. The aim of the present study was to estimate the incidence of malignant neoplasms in children resident in MC attending Social Security (SS) hospitals. This study was a retrospective hospital survey. All records of childhood malignant neoplasms diagnosed between 1992 and 1993 in the two SS hospitals which attend childhood neoplasms in MC were reviewed. Histopathological diagnoses were reevaluated and incidence rates (x 10(6) child/ year) in terms of age, sex, and place of residence were estimated. A total of 667 cases were found for the period of study, of which 199 corresponded to residents of MC. The neoplasms with highest prevalence were leukemias (39.2%), lymphomas (17.6%), and central nervous system tumors (12.6%). A general incidence of 94.3 was found, which was highest in children under 5 years of age. Leukemias had an incidence of 36.4, lymphomas of 15.2, and central nervous system tumors of 12.0. Prevalence was higher in boys (male/female ratio of 1.6). As for the place of residence, the highest incidence corresponded to children living in the southern areas of MC. Eighty percent of the leukemias were acute lymphoblastic, while 54% of solid neoplasms were classified as stages III and IV. In conclusion, the incidence of malignant neoplasms in children resident in MC treated at SS hospitals is consistent with that found worldwide, and also with the Latin American pattern.

[Risk factors associated with the development of leukemia in children]. / Factores de riesgo asociados al desarrollo de leucemia en niños.

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.

[Residence close to high-tension electric power lines and its association with leukemia in children]. / Residencia cercana a fuentes eléctricas de alta tensión y su asociación con leucemia en niños.

INTRODUCTION: There are different risk factors which have been related to the presence of leukemia in children. In the past years one of these factors has become relevant, the risk of living in an area near to high electric voltage lines, generators of electromagnetic fields of low frequency (EMF), which can cause development of leukemia in children. OBJECTIVE: To learn whether living in an area close to EMF generator sources, electric transformers, high electric voltage distribution or transmission lines and electric substations, is a risk factor in the development of leukemia in children living in Mexico City. MATERIAL AND METHODS: A projective study of case-control was accomplished. The cases were obtained from hospitals of the third level. The diagnosis of leukemia in its different varieties was confirmed through biopsy of bone marrow. The controls were selected in the same hospital from inpatients and outpatients with different problems, except neoplasia. A total sample of 81 cases and 77 controls was analyzed. The residence of the controls and cases were visited using a questionnaire coded with the different study variables. To diminish the memory bias in relation to EMF, the subjects were shown different pictures pointing out the different sources of exposures, which were asked. Having obtained the information, different odds ratios (OR) were calculated for the different associations, as well as the confidence intervals at 95% and an unconditioned logistic regression was accomplished to know the adjusted OR. RESULTS: There were no differences between the cases and controls according to the relative who gave the information, the current age of children, the parents's age, the social class and the parent's occupation. It was found that all the generating sources of EMF, which were involved in the study, had and OR above 1. Being the highest, the ones living near the distribution or transmission wires of high voltage with an OR of 2.63 (1.26-5.36) and 2.5 (0.97-6.67) respectively. When the distance of exposure was controlled, the highest OR was for distribution lines (OR 2.12; 0.79-5.85). When the analysis was applied to persons who have moved from the residence, it was found that the OR was above 1 in all the associations, the highest being the distribution wires and with the distance the highest was the electric substations. Furthermore, the multivariate analysis showed that the risk continued only for the distribution wires. CONCLUSIONS: The EMF exposure was found positive, however this is not very precise, that is why it is necessary to carry out other studies to confirm the existence of the association and correct possible biases which could appear during the research.