Childhood acute lymphoblastic leukemia survival and spatial analysis of socio-environmental risks in Mexico

Background

Acute lymphoblastic leukemia (ALL) etiology remains largely unknown; incidence patterns by age, sex, and geographical distribution suggest a potential environmental role.

Aim

To identify ALL clusters from four contrasting urban areas of Mexico and to characterize the sources of environmental carcinogens.

Methods

Hospital-based ALL cases (n = 443) diagnosed in children <19 years old from the Metropolitan Zones of Merida and San Luis Potosi, the State of Mexico, and Tijuana were analyzed (2015-2020). ALL cases were coded according to the International Classification of Diseases for Oncology. ALL clusters were identified by Kernel Density, and excess risk was estimated. Data of particulate matter ≤2.5 µm (PM2.5) concentrations measured by community-monitoring stations were analyzed. Geocoded datasets of benzene, polycyclic aromatic hydrocarbons, and PM2.5 sources were analyzed to characterize patterns of exposure in ALL clusters.

Results

The survival rate for ALL ranged from 61.5% to 78.6%. Seven ALL clusters with excess risk (RR 1.4-2.3, p < 0.05) were identified. The carcinogen sources included artisanal brick kilns, gas stations, cement works, carpentry, paint, and chemical manufacturing establishments. PM2.5 levels ranged from 15 µg/m3 to 37 µg/m3 among study areas.

Conclusion

ALL clusters were identified at the community level; the excess risk could be explained by small-scale carcinogen sources. The levels of PM2.5 in outdoor air ranged from 3 to 6 times above the World Health Organization (WHO) air quality guidelines. Healthcare providers must raise awareness of the increased risk of ALL in children living near sources of environmental carcinogens; cancer control and prevention strategies must be steered from a multi-sectoral and multi-action perspective to protect children's health.

Cancer Incidence in Merida, Mexico 2015-2018: First Report from the Population-based Cancer Registry

BACKGROUND

Cancer registries are essential for monitoring cancer burden and patterns, and document changes in time for cancer control. Hereby, we present the first results of four years of the Merida population-based cancer registry in Mexico.

METHODS

The registry collects data on all new cancers diagnosed since 2015 using both active and passive methods including a total of 104 information sources. Definitions and coding follow international standards. Using CanReg5 software, age-standardized incidence rates (ASR/100,000 person years) were computed by direct method using the world standard population.

RESULTS

A total of 5684 new cancer cases were registered during 2015-2018, 2321 in males and 3363 in females corresponding to age-adjusted incidence rates (ASR per 100,000) of 128.5, and 153.1, respectively. Most frequent cancers among males were prostate cancer (ASR 29.8), lymphomas (ASR 10.9) and colorectal cancer (ASR 9.7) while among females it was breast cancer (ASR 49.3), cervical cancer (ASR 17.5) and corpus uteri (ASR 11.5). Childhood cancers (0-14 year) represented 2.9% of all cancers, with leukemias accounting for 52% of the new cases. Overall, 87.6% of new cases were microscopically verified.

CONCLUSIONS

The data reported provide information on the cancer profile in Merida. Prostate and breast cancer are the main incident cancers. Cervical cancers present high rates among women, while lymphomas and liver cancer data merit further exploration. Efforts to support the Merida cancer registry as well as other registries in Mexico need to be pursued in order to have locally recorded data to support cancer control measures.

Circulating Levels of Sex Steroid Hormones and Gastric Cancer

BACKGROUND AND AIMS

Men develop gastric cancer more frequently than women, yet little is known about the mechanisms underlying this sex difference. Sex steroid hormones may influence gastric cancer risk. We therefore assessed whether major circulating adrenal precursors, androgens and estrogens were associated with gastric cancer in a high-risk Mexican population.

METHODS

Blood samples were collected at time of diagnosis from 50 noncardia gastric cancer patients and 50 histologically confirmed non-atrophic gastritis controls. Serum levels of estradiol, testosterone and dehydroepiandrosterone (DHEA) measured with a validated mass spectrometry method were categorized in tertiles as low (T1), middle (T2), and high (T3). Unconditional logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CI), adjusting for age, sex, and education.

RESULTS

Levels of DHEA were inversely associated with gastric cancer (p-trend per tertile increase: <0.0001), with adjusted ORs (95% CI) of T2 and T3 (vs. T1) of 0.25 (0.09-0.70) and 0.10 (0.03-0.34), respectively. Levels of estradiol and testosterone were not significantly associated with gastric cancer.

CONCLUSIONS

Our study provides evidence that higher concentration of circulating DHEA may be associated with lower risk of noncardia gastric cancer. Longitudinal studies are needed to evaluate the temporality of this association and investigate mechanisms of disease pathogenesis.

Implementation of the population-based cancer registry in the city of Mérida, Mexico: process and early results

OBJECTIVE

To briefly describe the process of establishment and preliminary results of the Mérida Population-based Cancer Registry (Mérida-PBCR).

MATERIALS AND METHODS

Mérida-PBCR started in 2016 as a research project in the IMSS, with a gradual increase in its information sources. It covers a population of 908 536 inhabitants. Data collection is active and passive, international standards are used; CanReg5 software enables data entry, storage and analysis.

RESULTS

Current data include 71.5% of sources. For the period 2015- 2016, a total of 2 623 new cancer cases were registered, the majority of these (60.1%) among females. 81.5% of the cases had morphological verification. Prostate (17.4%), colorectal (8.5%) and stomach (8.1%) cancers were the most common among males, and breast (31.6%), cervix (12%) and corpus uteri (7.6%) cancers, the most common among females. Ageadjusted cancer incidence rates (per 100 000) for all sites combined were 114.9 among males and 145.1 among females.

CONCLUSIONS

The implementation of the Mérida-PBCR has followed particular parameters, with important efforts to include new information sources. Although the data are still preliminary and must be interpreted with great caution, the main cancers follow a similar pattern to that of the national and regional estimates.

Increased expression of deleted in malignant brain tumors (DMBT1) gene in precancerous gastric lesions: Findings from human and animal studies

Helicobacter pylori infection triggers a cascade of inflammatory stages that may lead to the appearance of non-atrophic gastritis, multifocal atrophic, intestinal metaplasia, dysplasia, and cancer. Deleted in malignant brain tumors 1 (DMBT1) belongs to the group of secreted scavenger receptor cysteine-rich proteins and is considered to be involved in host defense by binding to pathogens. Initial studies showed its deletion and loss of expression in a variety of tumors but the role of this gene in tumor development is not completely understood. Here, we examined the role of DMBT1 in gastric precancerous lesions in Caucasian, African American and Hispanic individuals as well as in the development of gastric pathology in a mouse model of H. pylori infection. We found that in 3 different populations, mucosal DMBT1 expression was significantly increased (2.5 fold) in individuals with dysplasia compared to multifocal atrophic gastritis without intestinal metaplasia; the increase was also observed in individuals with advanced gastritis and positive H. pylori infection. In our animal model, H. pylori infection of Dmbt1-/- mice resulted in significantly higher levels of gastritis, more extensive mucous metaplasia and reduced Il33 expression levels in the gastric mucosa compared to H. pylori-infected wild type mice. Our data in the animal model suggest that in response to H. pylori infection DMBT1 may mediate mucosal protection reducing the risk of developing gastric precancerous lesions. However, the increased expression in human gastric precancerous lesions points to a more complex role of DMBT1 in gastric carcinogenesis.

ARID5B, CEBPE and PIP4K2A Germline Genetic Polymorphisms and Risk of Childhood Acute Lymphoblastic Leukemia in Mexican Patients: A MIGICCL Study

BACKGROUND AND AIMS

Childhood acute lymphoblastic leukemia (ALL) is the leading cause of childhood cancer-related deaths worldwide. Multiples studies have shown that ALL seems to be originated by an interaction between environmental and genetic susceptibility factors. The ARID5B polymorphisms are among the most reproducible ALL associated-risk alleles in different populations. The aim of the present study was to examine the contribution of ARID5B, CEBPE, and PIP4K2 risk alleles for the development of ALL in children from Mexico City and Yucatan, Mexico.

METHODS

A study was conducted with a total of 761 unrelated subjects. Two hundred eighty five ALL cases (111 from Yucatan and 174 from Mexico City) and 476 healthy subjects. Genotyping included the rs7088318 (PIP4K2A), rs10821936 (ARID5B), rs7089424 (ARID5B) and rs2239633 (CEBPE) polymorphisms.

RESULTS

Associations between ALL and rs10821936 and rs7089424 ARID5B SNPs were found (OR = 1.9, 95% CI (1.5-2.4) and OR = 2.0, 95% CI (1.6-2.5), respectively). Moreover, a higher risk was observed in the homozygous risk genotypes of carriers from Mexico City (OR = 3.1, 95% CI (2.0-4.9) and OR 3.1, CI 95% (2.0-4.8), respectively). Otherwise, the rs7088318 (PIP4K2A) and rs2239633 (CEBPE) polymorphisms were not associated with ALL risk.

CONCLUSIONS

Our analysis suggests that ARID5B confers risk for childhood ALL in a Mexican population.

Analysis of Thiopurine S-Methyltransferase Deficient Alleles in Acute Lymphoblastic Leukemia Patients in Mexican Patients

BACKGROUND AND AIMS

It has been demonstrated that heterozygote and homozygote thiopurine S-methyltransferase (TPMT) mutant allele carriers are at high risk to develop severe and potentially fatal hematopoietic toxicity after treatment with standard doses of 6-mercaptopurine (6-MP) and methotrexate (MX). Those drugs are the backbone of acute lymphoblastic leukemia (ALL) and several autoimmune disease treatments. We undertook this study to determine the frequency of the TPMT deficient alleles in children with ALL and non-ALL subjects from Mexico City and Yucatan, Mexico.

METHODS

We included 849 unrelated subjects, of which 368 ALL children and 342 non-ALL subjects were from Mexico City, and 60 ALL cases and 79 non-ALL individuals were from Yucatan. Genotyping of the rs1800462, rs1800460 and rs1142345 SNPs was performed by 5'exonuclease technique using TaqMan probes (Life Technologies Foster City, CA).

RESULTS

The mutant TPMT alleles were present in 4.8% (81/1698 chromosomes) and only 0.2% were homozygote TPMT*3A/TPMT*3A. We did not find statistically significant differences in the distribution of the mutant alleles between patients from Mexico City and Yucatan in either ALL cases or non-ALL. Nonetheless, the TPMT*3C frequency in ALL patients was higher than non-ALL subjects (p = 0.03). To note, the null homozygous TPMT*3A/TPMT*3A genotype was found in 2.5% of the non-ALL subjects.

CONCLUSIONS

TPMT mutant alleles did not exhibit differential distribution between both evaluated populations; however, TPMT*3C is overrepresented in ALL cases in comparison with non-ALL group. Assessing the TPMT mutant alleles could benefit the ALL children and those undergoing 6-MP and MX treatment.

Evidence of Epstein-Barr virus association with gastric cancer and non-atrophic gastritis

Different lines of evidence support an association between Epstein-Barr virus (EBV) and gastric cancer (GC). The main understood risk factor to develop GC is infection by Helicobacter pylori (H. pylori), which triggers a local inflammatory response critical for progression from gastritis to GC. The role of EBV in early inflammatory gastric lesions has been poorly studied. A recent study proposed a cutoff value of 2000 EBV particles to identify patients with increased chances of infection of the gastric epithelium, which may favor the inflammatory process. To better understand the role of EBV in cancer progression, we analyzed 75 samples of GC, 147 control samples of non-tumor gastric tissue derived from GC patients and 75 biopsies from patients with non-atrophic gastritis (NAG). A first-round PCR was used for EBV detection in tumor and non-tumor controls and a more sensitive nested PCR for gastritis samples; both PCRs had lower detection limits above the proposed cutoff value. With this strategy 10.67% of GC, 1.3% of non-tumor controls and 8% of gastritis samples were found positive. An EBER1 in situ hybridization showed EBV infection of epithelial cells in GC and in a third of NAG samples, while in the other NAGs infection was restricted to the mononuclear cell infiltrate. EBV-positive GCs were enriched in lace and cribriform patterns, while these rare patterns were not observed in EBV negative samples. Our results support a role for EBV in GC and early precursor lesions, either as directly oncogenic infecting epithelial cells or indirectly as an inflammatory trigger.

13C-urea breath test for the diagnosis of Helicobacter pylori infection in children: a systematic review and meta-analysis

BACKGROUND

The (13) C-urea breath test ((13) C-UBT) is a safe, noninvasive and reliable method for diagnosing H. pylori infection in adults. However, the test has shown variable accuracy in the pediatric population, especially in young children. We aimed to carry out a systematic review and meta-analysis to evaluate the performance of the (13) C-UBT diagnostic test for H. pylori infection in children.

METHODS

We conducted a systematic review of the PubMed, Embase and Liliacs databases including studies from January 1998 to May 2009. Selection criteria included studies with at least 30 children and reporting the comparison of (13) C-UBT against a gold standard for H. pylori diagnosis. Thirty-one articles and 135 studies were included for analysis. Children were stratified in subgroups of <6 and ≥6 years of age, and we considered variables such as type of meal, cutoff value, tracer dose, and delta time for the analysis.

DISCUSSION

The (13) C-UBT performance meta-analyses showed 1, good accuracy in all ages combined (sensitivity 95.9%, specificity 95.7%, LR+ 17.4, LR- 0.06, diagnostic odds ratio (DOR) 424.9), 2, high accuracy in children >6 years (sensitivity 96.6%, specificity 97.7%, LR+ 42.6, LR- 0.04, DOR 1042.7), 3, greater variability in accuracy estimates and on average a few percentage points lower, particularly specificity, in children ≤6 years (sensitivity 95%, specificity 93.5%, LR+ 11.7, LR- 0.12, DOR 224.8). Therefore, the meta-analysis shows that the (13) C-UBT test is less accurate for the diagnosis of H. pylori infection in young children, but adjusting cutoff value, pretest meal, and urea dose, this accuracy can be improved.

Seroepidemiology of giardiasis in Mexico

Prevalence of antibodies against Giardia duodenalis was determined by enzyme-linked immunosorbent assay in serum samples from a national serologic survey of Mexico that included all geographic areas and socioeconomic and demographic data for each person sampled. The country was divided into four regions on the basis of development (high, medium high, medium low, and low). Of 3,461 serum samples tested, 1,914 (55.3%) were positive for IgG antibodies against Giardia duodenalis. Seropositivity was age-specific; the probability of seropositivity increased 4.9-fold (95% confidence interval [CI] = 3.16-7.64) in adolescents 10-19 years of age, 8.0-fold (95% CI = 5.19-12.53) in young adults 20-39 years of age, and 12.6-fold (95% CI = 7.93-20.28) in adults more than 40 years of age. Giardia duodenalis seropositivity was associated with male sex (odds ratio = 1.40, 95% CI = 1.22-1.61). No association was found between seropositivity and socioeconomic variables or regional development status.

Antibody-based detection tests for the diagnosis of Helicobacter pylori infection in children: a meta-analysis

Background

Numerous serologic tests are available for the diagnosis of H. pylori infection in children. Common designs of antibody-based detection tests are ELISA and Western Blot (WB). For developing countries with limited laboratory resources and access, ELISA would be the preferred method because of its simplicity, lower cost and speed. Although in adults ELISA has proven to be highly accurate in diagnosing H. pylori infection; in children, it has shown variable accuracy.

Methods/Findings

We conducted a systematic review and meta-analysis to assess the accuracy of antibody-based detection tests for the diagnosis of H. pylori infection in children. Selection criteria included participation of at least 30 children and the use of a gold standard for H. pylori diagnosis. In a comprehensive search we identified 68 studies. Subgroup analyses were carried out by technique, immunoglobulin class, and source of test (commercial and in-house). The results demonstrated: 1) WB tests showed high overall performance, sensitivity 91.3% (95% CI, 88.9–93.3), specificity 89% (95% CI, 85.7–91.9), LR+ 8.2 (95% CI, 5.1–13.3), LR− 0.06 (95% CI, 0.02–0.16), DOR 158.8 (95% CI, 57.8–435.8); 2) ELISA-IgG assays showed low sensitivity 79.2% (95% CI, 77.3–81.0) and high specificity (92.4%, 95% CI, 91.6–93.3); 3) ELISA commercial tests varied widely in performance (test for heterogeneity p<0.0001); and 4) In-house ELISA with whole-cell antigen tests showed the highest overall performance: sensitivity 94% (95% CI, 90.2–96.7), specificity 96.4% (95% CI, 94.2–97.9), LR+ 19.9 (95% CI, 7.9–49.8), LR− 0.08 (95% CI, 0.04–0.15) DOR 292.8 (95% CI, 101.8–841.7).

Conclusions/Significance

WB test and in-house ELISA with whole-cell antigen tests are the most reliable tests for the diagnosis of H. pylori infection in children. Antigens obtained from local strains of the community could partially explain the good overall accuracy of the in-house ELISA. Because of its cost and technical demands, in-house ELISA might be more suitable for use in developing countries.

A primary Helicobacter pylori infection does not protect against reinfection in children after eradication therapy

BACKGROUND

Helicobacter pylori infection is one of the most common chronic infections in the world, and is acquired mainly during childhood. It is not clear to which extent a primary infection protects the child from reinfection. Our aim was to determine the possible protection conferred by a primary infection against H. pylori reinfection in children.

METHODS

A follow-up study with 120 children distributed in two cohorts; the first included 80 children without previous H. pylori infection (primo-infection cohort); the second included 40 infected children successfully eradicated (reinfection cohort). Cohorts were monitored during 2 years with urea-breath-test (UBT) at 3, 6, 9, 12, 18 and 24 months for the acquisition of H. pylori infection. We compared the rate of reinfection in eradicated children with the rate of infection in children without previous infection. H. pylori infection during the follow-up was analyzed and compared between cohorts using chi2 and survival curves. A questionnaire was performed for the evaluation of possible risk factors for infection in both cohorts.

RESULTS

No significant differences in rates of primo-infection or reinfection were found; 17 (21.2%) primo-infections and 10 (25%) reinfections were documented. Most of the primo-infections (14/17) occurred in the first year of follow-up. In contrast, reinfection episodes occurred more frequently during the second year (6/10). In both cohorts, most infections were transient. Risk factors were similar for both, primo and reinfection cohorts.

CONCLUSION

A primary infection does not protect from reinfection in the population of children studied.