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Introduction: Epidemiological studies around the world on acute leukemia (AL) and risk factors in infants are scarce. Infant AL has been proposed to originate in utero, which facilitates its study by establishing a short exposure time in pregnant women to environmental and dietary factors that could contribute to the risk of or protection against leukemia. We hypothesized that maternal diet during pregnancy may be an important factor involved in AL in offspring. Methods: We conducted a hospital-based case-control study from 2010 to 2019 on maternal diet during pregnancy in nine high-specialty public hospitals of different health institutions that diagnose and offer treatment to children with AL in Mexico City. Cases (n=109) were children ≤24 months of age with de novo diagnosis of AL, and controls (n=252) were children obtained in hospitals from second-level medical care matched for age, sex, and health institution. Maternal diet during pregnancy was obtained by a semiquantitative food frequency questionnaire. Unconditional logistic regression models were used to assess the association between food groups and infant AL. Potential confounders were assessed by constructing directed acyclic graphs (DAGs) with Dagitty software in which adjusted options were identified for the construction of unconditional logistic regression models. Results: Cases were slightly predominantly female (52.3%). The years of education of the mother in cases and controls was 0-9 on average, and those who reported smoking cigarettes and consuming alcohol during pregnancy did so at a low frequency. Regarding the mother's diet, the main findings were that the consumption of allium vegetables during pregnancy was inversely associated with AL for medium and high consumption (OR=0.26, 95% CI 0.14-0.46; P-trend< 0.001). In contrast, the high consumption of high-fat dairy products had a positive association with AL (OR=2.37, 95% CI 1.30-4.34; P-trend<0.001). No association was found between consumption of topoisomerase II inhibitor foods during pregnancy and AL. Conclusion: The results suggest that maternal intake during pregnancy of allium vegetables, specifically garlic, is inversely associated with the development of AL in children ≤24 months old. On the other hand, consumption of high-fat dairy products is positively associated with AL in children ≤24 months old.

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PURPOSE: We analyzed the epidemiologic characteristics of different types of non-Hodgkin Lymphoma (NHL), excluding Burkitt Lymphoma, in 2 Mexican regions with different socioeconomic status. MATERIALS AND METHODS: In this surveillance study, we analyzed the incidence rates (cases per million children/year) of different types of NHL according to the ICCC3, registered in 1996-2015, from 2 different socioeconomic regions in Mexico: central and southern, with higher and lower status, respectively. RESULTS: The principal NHL subgroups were precursor (IIb1), mature B cell (IIb2), mature T/NK cell, and no other specification (NOS; 42.3%, 15.8%, 14.1%, and 27.8%, respectively). In both regions, the overall incidence rates were similar (central=5.3, 95% confidence interval [CI], 4.6-6.1 vs. southern=6.3, 95% CI, 4.6-8.4); also, there were no differences by types (precursor cell LNH, 2.3 vs. 2.5; mature B cell, 0.9 vs. 0.8; mature T/NK cells, 0.8 vs. 0.8; and NOS, 1.4 vs. 2.3). In both regions, a decreasing trend was found (central= -0.17%, 95% CI, -0.03 to -0.3, P=0.04; southern= -0.32%, 95% CI, -0.07 to -0.57, P=0.02), with major reduction of NHL NOS from 1996 to 2000. In both regions, men predominated (2.1:1). CONCLUSIONS: Socioeconomic status did not influence the incidence rates of NHL. In this study, we found a reduction of NHL NOS, possibly due to better typing.

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BACKGROUND: Mexico City has one of the highest incidences and mortality rates of acute lymphoblastic leukemia (ALL) in the world and a high frequency of early relapses (17%) and early mortality (15%). Otherwise, childhood overweight and obesity are reaching epidemic proportions. They have been associated with poor outcomes in children with ALL. The aim of present study was to identify if overweight and obesity are predictors of early mortality and relapse in Mexican children with ALL. METHODS: A multicenter cohort study was conducted. ALL children younger than 15 years old were included and followed-up during the first 24 months after diagnosis. Overweight and obesity were classified according World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) criteria. Early mortality and early relapses were the main outcomes. RESULTS: A total of 1070 children were analyzed. Overweight/obesity at diagnosis were predictors of early mortality (WHO: HR = 1.4, 95%CI:1.0-2.0; CDC: HR = 1.6, 95%CI:1.1-2.3). However, no associations between overweight (WHO: HR = 1.5, 95%CI:0.9-2.5; CDC: HR = 1.0; 95% CI:0.6-1.6) and obesity (WHO: HR = 1.5, 95%CI:0.7-3.2; CDC: HR = 1.4; 95%CI:0.9-2.3) with early relapse were observed. CONCLUSIONS: Overweight and obese patients embody a subgroup with high risk of dying during leukemia treatment.

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Acute lymphoblastic leukemia is the most common type of childhood cancer worldwide. Mexico City has one of the highest incidences and mortality rates of this cancer. It has previously been recognized that chromosomal translocations are important in cancer etiology. Specific fusion genes have been considered as important treatment targets in childhood acute lymphoblastic leukemia (ALL). The present research aimed at the identification and characterization of novel fusion genes with potential clinical implications in Mexican children with acute lymphoblastic leukemia. The RNA-sequencing approach was used. Four fusion genes not previously reported were identified: CREBBP-SRGAP2B, DNAH14-IKZF1, ETV6-SNUPN, ETV6-NUFIP1. Although a fusion gene is not sufficient to cause leukemia, it could be involved in the pathogenesis of the disease. Notably, these new translocations were found in genes encoding for hematopoietic transcription factors which are known to play an important role in leukemogenesis and disease prognosis such as IKZF1, CREBBP, and ETV6. In addition, they may have an impact on the prognosis of Mexican pediatric patients with ALL, with the potential to be included in the current risk stratification schemes or used as therapeutic targets.

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Following publication of the original article [1], the author reported her name has been erroneously spelled as Blanca E. Pelcastre. The full name is Blanca E. Pelcastre-Villafuerte.

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BACKGROUND: Although acute lymphoblastic leukemia (ALL) 5 years survival in minors has reached 90%, socioeconomic differences have been reported among and within countries. Within countries, the difference has been related to the socioeconomic status of the parents, even in the context of public health services with universal coverage. In Mexico, differences in the mortality of children with cancer have been reported among sociodemographic zones. The Instituto Mexicano del Seguro Social (IMSS), the country's main social security institution, has reported socioeconomic differences in life expectancy within its affiliated population. Here, the socioeconomic inequalities in the survival of children (< 15 years old) enrolled in the IMSS were analyzed. METHODS: Five-year survival data were analyzed in cohorts of patients diagnosed with ALL during the period 2007-2009 in the two IMSS networks of medical services that serve 7 states of the central region of Mexico. A Cox proportional risk model was developed and adjusted for the socioeconomic characteristics of family, community of residence and for the clinical characteristics of the children. The slope of socioeconomic inequality of the probability of dying within five years after the diagnosis of ALL was estimated. RESULTS: For the 294 patients studied, the 5 years survival rate was 53.7%; the median survival was 4.06 years (4.9 years for standard-risk diagnosis; 2.5 years for high-risk diagnosis). The attrition rate was 12%. The Cox model showed that children who had been IMSS-insured for less than half their lives had more than double the risk of dying than those who had been insured for their entire lives. CONCLUSIONS: We did not find evidence of socioeconomic inequalities in the survival of children with ALL associated with family income, educational and occupational level of parents. However, we found a relevant gradient related social security protection: the longer children's life insured by social security, the higher their probability of surviving ALL was. These results add evidence of the effectiveness of social security, as a mechanism of wealth redistribution and a promoter of social mobility. Extending these social security benefits to the entire Mexican population could promote better health outcomes.

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La mortalidad por cáncer en niños mexicanos no ha disminuido a los niveles informados en países desarrollados. Una explicación frecuentemente declarada es el alto porcentaje (57.3 %) de pacientes diagnosticados en estadios avanzados (III/IV), atribuible a errores en la sospecha o en la metodología empleada, consideración dudosa si se toma en cuenta que el tiempo de diagnóstico y la proporción de estadios avanzados en México son semejantes a los de países desarrollados. En la mayoría de los niños con cáncer, los días transcurridos desde el primer síntoma a momento del diagnóstico oncológico no correlacionan con el estadio clínico y tampoco con la probabilidad de supervivencia. El éxito en la supervivencia depende en gran medida del tratamiento integral (específico y de la atención a las complicaciones). Esta visión obliga a estrategias dirigidas principalmente a invertir más recursos en opciones terapéuticas eficaces y eficientes, capacitación oncológica integral del equipo de salud (médicos, enfermeras, técnicos), tecnologías diagnósticas, fomento a la colaboración interinstitucional e internacional y apoyo socioeconómico a las familias durante el proceso terapéutico.Cancer mortality in Mexican children has not decreased to the levels reported in developed countries. A commonly proposed explanation is the high percentage (53.7%) of patients diagnosed at advanced stages (III/IV), which is attributed to erroneous assumptions or mistakes in the diagnostic approach ­a questionable consideration taking into account that both time to diagnosis and the proportion of advanced stage cases in Mexico are similar to those in developed countries. In most cancer cases in children, the number of days elapsed from the moment of the first symptom to the cancer diagnosis is not correlated with clinical stage, and neither with the probability of survival. Survival success largely depends on comprehensive treatment (specific and for the care of complications). This view calls for strategies mainly aimed at spending more resources on efficacious and efficient therapeutic strategies, comprehensive oncology training of healthcare personnel (physicians, nurses and technicians), diagnostic technologies, promotion of interinstitutional and international collaboration and socioeconomic support to families during the therapeutic process.

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In Mexico, due to the high rates of diabetes, overweight, and obesity, there has also been noted an increased newborn weight, which may be contributing to the elevated incidence rate of childhood acute leukemia (AL). We conducted a case-control study in public hospitals of Mexico City aimed to know whether a greater weight at birth is associated with a higher risk of developing leukemia. We included incident cases with acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) diagnosed between 2010 and 2015. Controls were frequency-matched to the cases by age, sex, and health institution. Logistic regression analysis was performed adjusting risks by child's sex, overcrowding index, birth order, and mother's age at the time of pregnancy. Adjusted odds ratios (aORs) and 95% confidence intervals were calculated. A total of 1455 cases and 1455 controls were included. An evident association between ALL and child's birthweight ≥2500 g was found (aOR 2.06; 95% CI: 1.59, 2.66) and also, in those with birthweight ≥3500 g (aOR 1.19; 95% CI: 1.00, 1.41). In AML patients with birthweight ≥2500 g and ≥3500 g, an aOR of 1.77 (95% CI: 1.07, 2.94) and 1.42 (95% CI: 1.03-1.95) was observed, respectively. No association was noticed with either type of AL and a birthweight ≥4000 g. To sum up, we found a moderate association between not having a low birthweight and an increased risk of acute leukemias. Birthweight ≥3500 g was also a risk factor for both types of leukemia. This suggests that a greater birthweight may increase the risk of acute leukemias in Mexican children.

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Measurement is essential in epidemiology, and this is why detailed knowledge of the different measures that are estimated in this discipline is necessary, since information interpretation and, most importantly, the decisions made in the care of patients depend on it. This article describes the three main groups of measures in epidemiology: frequency, association and potential impact; examples and instructions for their calculation are also provided. Incidence and prevalence are the most significant frequency measures, and can be obtained when both morbidity and mortality of diseases are studied. In descriptive epidemiology these measures are fundamental and involve studying how the disease is distributed in the population, in particular, the incidence according to the individual, place and time. The measures of association that are used in analytical epidemiology, such as prevalence ratio, odds ratio and relative risk, are also detailed. In addition, attributable risk, population and etiological fractions of exposed subjects and measures of potential impact are addressed. In general, it is important to consider that the relevance of calculating the frequency, association and potential impact measures depends on the study design.

En epidemiología es primordial la medición, por ello es necesario un conocimiento detallado de las diferentes medidas que se estiman en esta disciplina, porque de esto depende la interpretación de la información y, lo más importante, las decisiones que se tomen en la atención de los pacientes. En este artículo se describen los tres principales grupos de medidas en epidemiología: frecuencia, asociación e impacto potencial; se dan ejemplos y se indica cómo deben calcularse. La incidencia y la prevalencia son las medidas de frecuencia más significativas y pueden obtenerse cuando se estudia la morbilidad y mortalidad de las enfermedades; en la epidemiología descriptiva son fundamentales e implican estudiar cómo se distribuye la enfermedad en la población, en particular, la incidencia según la persona, lugar y el tiempo. También se detallan las medidas de asociación que se emplean en la epidemiología analítica, como la razón de prevalencias, razón de momios y el riesgo relativo. Además, se abordan el riesgo atribuible, las fracciones poblacionales y etiológicas en expuestos y las medidas de impacto potencial. En general es importante considerar que la pertinencia de calcular las medidas de frecuencia, de asociación y de impacto potencial depende del diseño de estudio.

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We analyzed clinical and epidemiological characteristics of Burkitt lymphoma (BL) in two defined socioeconomic regions in Mexico: high socioeconomic region (HSER; with two political jurisdictions) and low socioeconomic region (LSER; with three jurisdictions). Of the 63 cases registered in the Childhood Cancer Registry (1996-2013), 45 (71.4%) were from HSER and 18 (28.6%) from LSER. The incidence was higher in the LSER (3.1 vs. 1.4 cases per million children/year). The sporadic form and Stages III/IV predominated in both regions. Only one post-renal transplant (HSER) was found. The male/female ratio was higher in the LSER (5.0 vs. 1.4). The peak incidence was in the 1-4 age group for LSER, and in the 5-9 age group for HSER. This difference in the sporadic BL by socioeconomic regions may be related to different exposure factors.

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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.

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INTRODUCTION: Acute myeloid leukemias represent the second most common childhood leukemia subtype. In Mexico, there are few studies on descriptive epidemiology for this disease. AIMS: To report acute myeloid leukemia incidence for children less than 15 years of age in the Metropolitan Area of the Valley of Mexico for a period of five years (2010-2014) and to analyze whether there are differences in the incidence of acute myeloid leukemia by regions. MATERIAL AND METHODS: A descriptive study was conducted in nine public hospitals in Mexico City. The crude annual average incidence rate and adjusted average annual incidence rate were calculated. RESULTS: A total of 190 patients with diagnosis of de novo acute myeloid leukemia were analyzed. Male sex (57.2%) and acute myeloid leukemia-M3 subtype (25.3%) were more frequent. The adjusted average annual incidence rates for Mexico City and for the Metropolitan Area of the Valley of Mexico were 8.18 and 7.74 per million children under 15 years old, respectively. CONCLUSIONS: It seems that childhood acute myeloid leukemia incidence is increasing in Mexico City, which makes the identification of associated risk factors imperative.

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OBJECTIVE: To identify the cancer incidence and mortality in Mexican Social Security Institute beneficiary (MSSI-B) children during 1996-2013. MATERIALS AND METHODS: Both cancer cases (n=4 728) and deaths (n=2 378) were analyzed in MSSI-B children who were registered in five states of the Mexican Republic. The incidence and mortality trends and the incidences (rate x 1 000 000 children / year) of the type of cancer, age, sex, and place of residence were obtained. RESULTS: For both indicators (incidence and mortality), there was a downward trend for the period of 1996-2001 and a stable trend for 2002-2013. This occurred in the overall mortality and incidence trends of the Estado de México and Chiapas and in the leukemia and the acute lymphoid subgroups. The annual overall incidence was 128 cases per 1 000 000 children. Leukemia, lymphomas, and central nervous system tumors were the principal cancer groups. CONCLUSIONS: Cancer mortality for the period of 2002-2013 did not diminish. Interinstitutional and/or international research should be designed to improve the care of these children.

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Abstract Objective: To identify the cancer incidence and mortality in Mexican Social Security Institute beneficiary (MSSI-B) children during 1996-2013. Materials and methods: Both cancer cases (n=4 728) and deaths (n=2 378) were analyzed in MSSI-B children who were registered in five states of the Mexican Republic. The incidence and mortality trends and the incidences (rate x 1 000 000 children / year) of the type of cancer, age, sex, and place of residence were obtained. Results: For both indicators (incidence and mortality), there was a downward trend for the period of 1996-2001 and a stable trend for 2002-2013. This occurred in the overall mortality and incidence trends of the Estado de México and Chiapas and in the leukemia and the acute lymphoid subgroups. The annual overall incidence was 128 cases per 1 000 000 children. Leukemia, lymphomas, and central nervous system tumors were the principal cancer groups. Conclusions: Cancer mortality for the period of 2002-2013 did not diminish. Interinstitutional and/or international research should be designed to improve the care of these children.

Resumen Objetivo: Mostrar la incidencia y mortalidad por cáncer en niños derechohabientes del Instituto Mexicano del Seguro Social (DH-IMSS) (periodo 1996-2013). Material y métodos: Se analizaron los casos (n=4 728) y las muertes (n=2 378) por cáncer en niños DH-IMSS registrados en cinco estados de la República mexicana. Se obtuvo la tendencia de la incidencia y mortalidad y la incidencia por tipo de cáncer, edad, sexo y lugar de residencia. Resultados: Para ambos indicadores (incidencia y mortalidad) hubo tendencia a la disminución para el periodo 1996-2001 y estabilidad para 2002-2013; esto sucedió para la tendencia global, para el Estado de México y Chiapas, para las leucemias y para el subgrupo de las linfoide agudas. La incidencia global fue de 128 x 1 000 000 niños/año; las leucemias, tumores del sistema nervioso central y linfomas fueron los principales grupos de cáncer. Conclusiones: La mortalidad por cáncer para el periodo 2002-2013 no ha disminuido; deben diseñarse investigaciones interinstitucionales e internacionales para mejorar la atención médica de estos niños.

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BACKGROUND AND AIMS: Occupational exposure of parents to carcinogens is of great interest in the etiology of leukemias. Evidence of the impact of such exposure on infants or small children is scarce. Here we estimated whether occupational exposure of parents to carcinogens could be a risk factor for leukemias in their children. METHODS: Cases of acute leukemia (AL) in infants ≤24 months old diagnosed in Mexico City (1998-2013) were included in a population-based, case-control study. Each of the 195 cases was matched with at least one healthy child (n = 369). For each of four exposure windows studied, the degree of exposure to carcinogens was determined for both parents by using a validated occupational exposure index. An unconditional logistic regression was carried out. RESULTS: Odds ratios (OR) and the 95% confidence intervals (CI) of the overall occupational exposure for parents during the four exposure windows indicated no association with risk of AL in their children. Pre-conception, the OR by the father 0.77 (0.49-1.21), by the mother 1.03 (0.50-2.11); during pregnancy, father 0.66 (0.38-1.15), mother 1.79 (0.46-6.90); during breastfeeding, father 0.75 (0.43-1.30), mother 0.96 (0.21-4.30); and after birth, father 0.74 (0.45-1.22), mother 0.90 (0.24-3.32). The statistical power of the sample size to identify an OR ≥2 and an exposure of ≥10% among controls was 78%. CONCLUSIONS: These data support the idea that parents' occupational exposure during any of the periods studied was not a risk factor contributing to the etiology of AL in infants ≤24 months of age.

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BACKGROUND: Incidence rates of the histologic subtypes of Hodgkin lymphoma (HL) differed with socioeconomic conditions. MATERIALS AND METHODS: HL cases from the Register of Childhood Cancer (below 15 y of age) for 2 socioeconomic regions were analyzed. Central region has a high socioeconomic index; and the southern region a low index. The incidence rates (cases per million children/year) were estimated according to histologic subtypes, age groups, sex, clinical stages, time to diagnosis, and overall survival by regions. RESULTS: The overall incidence was greater in the south (6.8 vs. 4.6), principally due to higher incidence of mixed cellularity subtype (3.8 vs. 1.0). In the south, the highest incidence was found in the 5- to 9-year-old group (9.2), whereas in the central region it was found in the 10- to 14-year-old group (7.4). There was a delay of ∼3 weeks in the time to diagnosis (P=0.36) in the south, but no difference in the percentage of advanced stages, adjusted by histologic subtype (61%, III and IV). The overall survival was 71%, differences were identified only for mixed cellularity cases (center=89.2 vs. south=61.5%, P=0.03). CONCLUSIONS: Incidences of HL subtypes differed in relation to socioeconomic conditions in Mexico. In the south, the incidence of mixed cellularity was higher and there was an earlier peak of presentation.

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PURPOSE: We reviewed the childhood lymphomas epidemiological data for the Mexico City metropolitan area (MCMA). METHODS: Data analysis from children (0-14 years old) diagnosed with lymphoma during the period 1996-2010 was performed at the Mexican Childhood Cancer Registry. Histological subtype was determined according to the International Classification of Childhood Cancer 3 (ICCC-3). Age-adjusted incidence rates were calculated per 1,000,000 children/year by age, gender, and ICCC-3 subtype; trends, by average annual percent change (AAPC). RESULTS: A total of 328 lymphoma cases included in the study had an incidence rate of 11.8, showing a decreasing trend [AAPC: -3.5; CI 95% (-5.9, -1.0)], primarily due to non-Hodgkin lymphomas (NHL) and Hodgkin lymphoma (HL) mixed cellularity subtype. NHL had the major incidence (5.8), with the precursor cell subtype being the most frequent (38.3%). Nodular sclerosis was the most frequent HL subtype. The incidence of Burkitt lymphoma was low (1.3). During the study period, there was an important reduction in the not-otherwise-specified subtype of NHL, which translated into a relative increase in the IIb3 subtype [AAPC: 7.3 (1.2, 13.8)]. Low incidences of NHL and of HL and NHL were found for < 1-year-olds and for 10- to 14-year-olds, respectively. Incidence rates for children in the MCMA, particularly the < 1 and 10-14 age groups, were lower than those for developed countries. The overall male/female ratio was 2.3. CONCLUSIONS: There was a trend toward a reduced incidence, for some lymphoma subtypes, in particular for NOS lymphomas, which may be the result of improvement in diagnostic techniques.

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Publishing a research is one of the most important achievements for a researcher, since it is one of the tools to evaluate his scientific work. This achievement has a three-dimensional commitment: the personal commitment, the commitment with the population from which the data were obtained, and the commitment to the institution where he works. Therefore, publishing in the Revista Médica del Instituto Mexicano del Seguro Social should be a priority and an honor for a researcher of this Institution, since he is working with it to provide solutions to medical problems that affect their beneficiaries.

Publicar una investigación es uno de los logros más importantes para un investigador, pues es un instrumento para evaluar su trabajo científico. Este logro conlleva un compromiso tridimensional: el compromiso personal, el compromiso con la población de la que se obtienen los datos y el compromiso con la institución en donde trabaja. Por ende, publicar en Revista Médica del Instituto Mexicano del Seguro Social debe ser una prioridad y un orgullo para un investigador de esta institución, pues colabora con ella para solucionar los problemas médicos que aquejan a sus derechohabientes.

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Mexico has one of the highest incidences of childhood leukemia worldwide and significantly higher mortality rates for this disease compared with other countries. One possible cause is the high prevalence of gene rearrangements associated with the etiology or with a poor prognosis of childhood acute lymphoblastic leukemia (ALL). The aims of this multicenter study were to determine the prevalence of the four most common gene rearrangements [ETV6-RUNX1, TCF3-PBX1, BCR-ABL1, and MLL rearrangements] and to explore their relationship with mortality rates during the first year of treatment in ALL children from Mexico City. Patients were recruited from eight public hospitals during 2010-2012. A total of 282 bone marrow samples were obtained at each child's diagnosis for screening by conventional and multiplex reverse transcription polymerase chain reaction to determine the gene rearrangements. Gene rearrangements were detected in 50 (17.7%) patients. ETV6-RUNX1 was detected in 21 (7.4%) patients, TCF3-PBX1 in 20 (7.1%) patients, BCR-ABL1 in 5 (1.8%) patients, and MLL rearrangements in 4 (1.4%) patients. The earliest deaths occurred at months 1, 2, and 3 after diagnosis in patients with MLL, ETV6-RUNX1, and BCR-ABL1 gene rearrangements, respectively. Gene rearrangements could be related to the aggressiveness of leukemia observed in Mexican children.

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BACKGROUND: In Mexico City, the incidence of childhood acute lymphoblastic leukemia (ALL) is one of the highest in the world; epidemiologic evidence suggests that infectious agents could be involved in the genesis of this disease. Early transmitted oncogenic retroviruses infecting lymphocytes are important candidates. METHODS: PCR-based assays were used to screen viral genomic sequences of human T-cell lymphotrophic virus, type 1 (HTLV1) and mouse mammary tumor virus (MMTV)-like virus (MMTV-LV) in leukemic cells from 67 pediatric patients with ALL. RESULTS: Viral genomic sequences were not detected in any sample by neither standard nor nested PCR. CONCLUSIONS: Because of the methodologic strictness and high statistical power of the study, these results suggest that HTLV1 and MMTV-LV are not involved in the genesis of childhood ALL in Mexican children. IMPACT: To our knowledge, this is the first work exploring the direct participation of HTLV1 and MMTV-LV retroviruses in childhood ALL development.

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