BackgroundWorldwide, acute leukemia is the most common type of childhood cancer. It is particularly common in the Hispanic populations residing in the United States, Costa Rica, and Mexico City. The objective of this study was to determine the incidence of acute leukemia in children who were diagnosed and treated in public hospitals in Mexico City.MethodsIncluded in this study were those children, under 15 years of age and residents of Mexico City, who were diagnosed in 2006 and 2007 with leukemia, as determined by using the International Classification of Childhood Cancer. The average annual incidence rates (AAIR), and the standardized average annual incidence rates (SAAIR) per million children were calculated. We calculated crude, age- and sex-specific incidence rates and adjusted for age by the direct method with the world population as standard. We determined if there were a correlation between the incidence of acute leukemias in the various boroughs of Mexico City and either the number of agricultural hectares, the average number of persons per household, or the municipal human development index for Mexico (used as a reference of socio-economic level).ResultsAlthough a total of 610 new cases of leukemia were registered during 2006-2007, only 228 fit the criteria for inclusion in this study. The overall SAAIR was 57.6 per million children (95% CI, 46.9-68.3); acute lymphoblastic leukemia (ALL) was the most frequent type of leukemia, constituting 85.1% of the cases (SAAIR: 49.5 per million), followed by acute myeloblastic leukemia at 12.3% (SAAIR: 6.9 per million), and chronic myeloid leukemia at 1.7% (SAAIR: 0.9 per million). The 1-4 years age group had the highest SAAIR for ALL (77.7 per million). For cases of ALL, 73.2% had precursor B-cell immunophenotype (SAAIR: 35.8 per million) and 12.4% had T-cell immunophenotype (SAAIR 6.3 per million). The peak ages for ALL were 2-6 years and 8-10 years. More than half the children (58.8%) were classified as high risk. There was a positive correlation between the average number of persons per household and the incidence of the pre-B immunophenotype (Pearson's r, 0.789; P = 0.02).ConclusionsThe frequency of ALL in Mexico City is among the highest in the world, similar to those found for Hispanics in the United States and in Costa Rica.

To evaluate the usefulness of flow cytometric detection of intracellular antigens (Ags) in establishing proper lineage affiliation and its contribution to the diagnosis of acute leukemia, we studied 100 consecutive patients in whom acute leukemia was diagnosed between January 1997 and July 1998. Immunological classification was assessed using a three-line panel of monoclonal antibodies for phenotypic characterization of leukemic blast cells as proposed at the First Latin American Consensus Conference for Flow Cytometric Immunophenotyping of Leukemia. We found 74 cases of B-cell lineage acute lymphoblastic leukemia (ALL), seven cases of T-cell ALL, and 19 cases of acute myeloid leukemia (AML). In this study cytoplasmic (cy) CD79a, cyCD22, cyCD3, and cyMPO were highly sensitive, specific B, T, and myeloid markers that were expressed in virtually all cases of B and T cell ALL and in all subtypes of AML. Applied in combination with immunophenotyping this knowledge led to improvement in diagnostic precision and refinement of immunological classification, ensuring the selection of the most appropriate therapy for the patients studied. In conclusion, intracellular Ags detection was of utmost importance in establishing correct lineage affiliation in cases lacking expression of B, T, or myeloid surface Ags or disclosing equivocal or ambiguous immunophenotypic features and in identifying biphenotypic acute leukemia. In combination with FAB morphology and immunophenotyping, we were able to reliably classify all patients with acute leukemia in this study. Am. J. Hematol. 68:69-74, 2001.

BACKGROUND: For a child to develop acute leukaemia (AL), environmental exposure may not be sufficient: interaction with a susceptibility factor to the disease, such as Down syndrome (DS), may also be necessary. We assessed whether breastfeeding and early infection were associated with the risk of developing AL in children with DS. METHODS: Children with DS in Mexico City, and either with or without AL, were the cases (N ¼ 57) and controls (N ¼ 218), respectively. Population was divided in children with AL and with acute lymphoblastic leukaemia (ALL) and also in children p6 and 46 years old. RESULTS: Breastfeeding and early infections showed moderate (but not significant) association for AL, whereas hospitalisation by infection during the first year of life increased the risk: odds ratios (confidence interval 95%) were 0.84 (0.43 -1.61), 1.70 (0.82 -3.52); and 3.57 (1.59 -8.05), respectively. A similar result was obtained when only ALL was analysed. CONCLUSION: We found that breastfeeding was a protective factor for developing AL and ALL, and during the first year of life, infections requiring hospitalisation were related to a risk for developing the disease in those children with DS 46 years of age. These data do not support the Greaves's hypothesis of early infection being protective for developing ALL.

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The role of malnutrition at diagnosis as a predictor of early mortality in Mexican leukemia children remains controversial. The objective of present study was to investigate whether malnutrition was a predictor of early mortality during the first year of treatment in Mexican acute lymphoblastic leukemia (ALL) children through the first population-based study. A total of 794 newly diagnosed ALL pediatric patients from public hospitals of Mexico City were enrolled. A multivariate Cox proportional hazards regression model was constructed and adjusted by patient's age at diagnosis, gender, hospital of treatment, and socioeconomic status. Early mortality was high (12.1%) and malnutrition by different indicators was not associated with mortality at induction phase and at 6th month; a high risk of dying (RR = 2.08; 95% CI: 1.08-4.01) was observed in the group of malnourished children with a high-risk ALL.