Abstract P5-08-11: Urinary arsenic metabolites and risk of breast cancer molecular subtypes in northern Mexican women

Background/Aim: For many years, the presence of arsenic (As) in drinking water of some areas in Northern Mexico has been a major concern. As levels have ranged from 71 to 600 μg/L. We have recently reported that women residing in Northern Mexico, with higher urinary monomethyl arsenic acid percentage (%MMA) had an increased breast cancer (BC) risk (MMA% ORQ5vs.Q1=2.63; 95%CI: 1.89, 3.66; p for trend <0.001) (López-Carrillo et al., 214).

Breast tumor subtypes with distinctive biology and treatment responses are defined by the immunohistochemical expression of estrogen and progesterone receptors (HR) and human epidermal growth factor receptor 2 (HER2). Epidemiological evidence suggests that BC risk factors (i.e. breastfeeding, parity, menarche, etc.) may vary by tumor pathology.We assessed if %MMA is associated with a particular BC molecular subtype.

Methods: A population based case–control study was performed from 2007 to 2011 in five states of Northern Mexico. Incident cases were identified from main public tertiary hospitals in the study area. A total of 499 patients with histopathologically confirmed BC and molecular subtype status available information were identified. Controls were healthy women, with no history of cancer, matched 1:1 by age.

Tumor marker information for estrogen receptor (ER), progesterone receptor (PR) and HER2 was obtained from medical records. ER+ and PR+ was based on >=1% cell staining. HER2+ status was determined when at least 30% of protein overexpression was observed in the tumor cell. Cases were assigned to one of three tumor marker categories: HR+ (ER+ and/or PR+ and HER2-), HER+ (regardless of ER or PR status) and TNBC (ER-, PR-, and HER2-).

Urinary concentrations (μg/L) of species As3+, As5+, MMA5+, DMA5+, and arsenobetaine (AsB) were determined by high-performance liquid chromatography ICP-MS. Detection limits were As3+: 0.12; As5+: 0.20; MMA5+: 0.12; DMA5+: 0.08; AsB: 0.08. Results were reported by g of creatinine. Total As was calculated by using both the sum of iAs, MMA, DMA plus or minus AsB concentration (TAs or TAs-AsB, respectively). iAs was calculated as the sum of trivalent (As3+) and pentavalent (As5+). %iAs, %MMA and %DMA species were estimated using TAs-AsB as denominator.

Using logistic regression models, the associations between BC molecular subtypes and MMA% and DMA% was estimated according to the observed quintile distribution among controls. Based on the median value of each quintile a lineal trend was assessed accordingly.

Results.The mean age of cases and controls was around 54 years with 51 years of residence in the study zone. In the entire population, TAs ranged from 0.47 to 303.29 μg/L (0.45 to 1683.83 μg/g creatinine). HR+ BC patients were 57%, HER2 23% and TNBC 20%. These figures are similar to those reported among other groups of Mexican cancer patients. After controlling by key BC factors, %MMA remained as a significant risk factor for BC only for HR+. HER2+ and TNBC tumors were not significantly associated with urinary As metabolites.

Conclusion: Our results suggest that increased BC risk related to As exposure is not mediated by HER2 expression. This is the first report on As exposure and breast cancer subtypes which requires further confirmation.

Citation Format: López-Carrillo L, Gamboa-Loira B, Cebrián ME. Urinary arsenic metabolites and risk of breast cancer molecular subtypes in northern Mexican women [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-08-11.

Dietary and genetic determinants of homocysteine levels among Mexican women of reproductive age

OBJECTIVE

To evaluate the independent and joint effects of dietary folate, vitamin B(12) consumption and methylenetetrahydrofolate reductase (MTHFR) polymorphisms (677C>T and 1298A>C) on the circulating folate and homocysteine (Hcy) levels among Mexican women of reproductive age.

DESIGN

A cross-sectional, population-based study.

SUBJECTS

The first 130 healthy non-pregnant women (aged 16-34 years) who agreed to participate in a reproductive cohort in Morelos, Mexico.

MAIN OUTCOME MEASUREMENTS

Dietary intakes of vitamin B(12) and folate were estimated using a semiquantitative food frequency questionnaire. MTHFR 677C>T and 1298A>C polymorphisms were ascertained using the PCR-based method. Serum levels of Hcy and folate were determined using high-performance liquid chromatography and radioimmunoassay, respectively.

RESULTS

Genotype frequencies for the MTHFR 677C>T polymorphism were 21.5% (CC), 52.3% (CT) and 26.2% (TT) among Mexican women. Of the population, 22% had the MTHFR 1298AC genotype, while no individual carried the 1298CC genotype. We observed an increased level of Hcy among carriers of the 677TT genotype, compared to carriers of the 677CC genotype. The highest level of Hcy was observed among MTHFR 677TT carriers with low B(12) intake (<2.0 microg/day), which resulted with a significant interaction (P=0.01).

CONCLUSION

Vitamin B(12) is an important determinant of Hcy levels in Mexico. Supplementation of folic acid with vitamin B(12) may be preferable when the MTHFR 677T variant allele is prevalent.

Genetic polymorphisms and activity of PON1 in a Mexican population

Human paraoxonase (PON1) plays a role in detoxification of organophosphorus (OP) compounds by hydrolyzing the bioactive oxons, and in reducing oxidative low-density lipoproteins, which may protect against atherosclerosis. Some PON1 polymorphisms have been found to be responsible for variations in catalytic activity and expression and have been associated with susceptibility to OP poisoning and vascular diseases. Both situations are of public health relevance in Mexico. Therefore, the aim of this study was to evaluate PON1 phenotype and the frequencies of polymorphisms PON1 -162, -108, 55, and 192 in a Mexican population. The studied population consisted of unrelated individuals (n = 214) of either gender, 18-52 years old. Serum PON1 activity was assayed using phenylacetate and paraoxon as substrates. PON1 variants, -162, 55, and 192, were determined by real-time PCR using the TaqMan System, and PON1 -108 genotype by PCR-RFLP. We found a wide interindividual variability of PON1 activity with a unimodal distribution; the range of enzymatic activity toward phenylacetate was 84.72 to 422.0 U/mL, and 88.37 to 1645.6 U/L toward paraoxon. All four PON1 polymorphisms showed strong linkage disequilibrium (D% >90). PON1 polymorphisms -108, 55, and 192 were independently associated with arylesterase activity; whereas the activity toward paraoxon was related only with PON1 192 polymorphism, suggesting that this polymorphism is determinant to infer PON1 activity. A better understanding of the phenotype and genotypes of PON1 in Mexican populations will facilitate further epidemiological studies involving PON1 variability in OP poisoning and in the development of atherosclerosis.

Organophosphorous pesticide exposure alters sperm chromatin structure in Mexican agricultural workers

Our objective was to evaluate alterations in sperm chromatin structure in men occupationally exposed to a mixture of organophosphorus pesticides (OP) because these alterations have been proposed to compromise male fertility and offspring development. Chromatin susceptibility to in situ acid-induced denaturation structure was assessed by the sperm chromatin structure assay (SCSA). Urinary levels of alkylphosphates (DAP) were used to assess exposure. Diethylthiophosphate (DETP) was the most frequent OP metabolite found in urine samples indicating that compounds derived from thiophosphoric acid were mainly used. Chromatin structure was altered in most samples. About 75% of semen samples were classified as having poor fertility potential (>30% of Percentage of DNA Fragmentation Index [DFI%]), whereas individuals without OP occupational exposure showed average DFI% values of 9.9%. Most parameters of conventional semen analysis were within normality except for the presence of immature cells (IGC) in which 82% of the samples were above reference values. There were significant direct associations between urinary DETP concentrations and mean DFI and SD-DFI but marginally (P = 0.079) with DFI%, after adjustment for potential confounders, including IGC. This suggests that OP exposure alters sperm chromatin condensation, which could be reflected in an increased number of cells with greater susceptibility to DNA denaturation. This study showed that human sperm chromatin is a sensitive target to OP exposure and may contribute to adverse reproductive outcomes. Further studies on the relevance of protein phosphorylation as a possible mechanism by which OP alter sperm chromatin are required.

Serum levels of beta-hexachlorocyclohexane, hexachlorobenzene and polychlorinated biphenyls and breast cancer in Mexican women

Information on the association between exposure to beta-hexachlorocyclohexane (beta-HCH), hexachlorobenzene (HCB) or polychlorinated biphenyls (PCBs) and the incidence of breast cancer is inconclusive. However, exposure to such compounds is a public health concern in Mexico and is subject to recent regulation. Serum levels of beta-HCH, HCB and PCBs were analysed in 95 histologically confirmed breast cancer cases and 95 hospital controls, 20-79 years of age, from Mexico City, enrolled between March 1994 and April 1996. After adjusting for established risk factors, there was no evidence of a relationship between beta-HCH, HCB and PCBs and breast cancer risk (OR for beta-HCH tertile 3 versus tertile 1: 1.05 95% CI 0.46-2.40; OR for HCB tertile 3 versus tertile 1: 0.46 95% CI 0.20-1.07; OR for PCBs 1.31 95% CI 0.33-5.21 for the high category of exposure). This study lends no support to the case for a role for beta-HCH, HCB or PCBs in breast cancer aetiology.

Breast-feeding and serum p,p'DDT levels among Mexican women of childbearing age: a pilot study

For almost 50 years, millions of Mexicans have been directly and/or indirectly exposed to (1,1,1-trichloro-2,2-bis[p-chlorophenyl]ethane) (p,p'DDT). The potential related health outcomes of this exposure are of international concern. The objective of the study was to determine the effect of breast-feeding on serum levels of 1,1-dichloro-2; 2'-bis(p-chlorophenyl)ethylene (p,p'DDE) and p,p'DDT in women of childbearing age who were residents of the state of Morelos, Mexico. In March 1999, we examined a sample of 24 women, ages 21 to 36 years, who came with their children to the outpatient facility of a county Health Center in the state of Morelos. The geometric mean for p,p'DDE was 21.8 ng/ml+/-2.58 (GSD) and 2.9 ng/ml+/-2.84 for p,p'DDT. For each month of breast-feeding we observed similar significant decreases for both p,p'DDE (beta=-0.0403 per log concentration unit, P=0.001) and p,p'DDT (beta=-0.0309, P=0.03) serum levels, adjusted by mothers' age and number of children. The adjusted half-life estimate for p,p'DDE serum levels was 17 months. It was concluded that breast-feeding leads to rapid removal of p,p'DDT from the body (<2 year half-life) compared to nonlactational elimination rates (<5 year half-life). In this population, serum p,p'DDE levels were similar to those found 20 years ago in the United States.

Food sources of phytoestrogens and breast cancer risk in Mexican women

We analyzed the intake of selected foods that contain phytoestrogens in relation to breast cancer (BC) risk using data from a hospital-based case-control study performed in Mexico City from 1994 to 1995. A total of 198 women with BC, aged 21-79 years, were individually age matched to an identical number of women with no breast disease. By a direct interview, information on socioeconomic characteristics and diet was obtained. A semiquantitative questionnaire was used to estimate the frequency of consumption of 95 foods. The effect of selected foods that contain phytoestrogens on BC risk was estimated using logistic regression models. The adjusted odds ratio for the consumption of more than one slice of onion per day and BC was 0.27 (95% confidence interval = 0.16-0.47), with a statistically significant trend (p < 0.001). This protective effect remained after adjustment for known risk factors of BC. Among premenopausal women, there was also a protective and significant effect due to the intake of lettuce and spinach and nonsignificant protective effects for the consumption of apples and herbal tea. Additional studies aimed at evaluating the potential protective effect of particular phytoestrogens on BC risk are needed.

Epidemiologic panorama of stomach cancer mortality in Mexico

BACKGROUND

Annually, there are more than 6 million deaths from a type of malignant neoplasia worldwide. In developing countries, the highest rates of incidence of malignant neoplasias are uterine cervical cancer, stomach, lung, esophagus, pharynx, and liver cancers. Recent estimates on the incidence of cancer worldwide show that, in 1990, stomach cancer (SC) was the second most frequent type of cancer (900,000 new cases annually). Rates of incidence have decreased consistently in nearly all areas of the world. In Mexico, however, rates of incidence and mortality have increased gradually between 1980 and 1997; in 1995, 4,685 people died of SC in Mexico. This report presents a descriptive analysis of SC mortality in Mexico.

METHODS

A mortality database edited from the electronic files of the National Institute of Informatics, Statistics and Geography (INEGI) in Mexico was used; population denominators were edited by the Mexican National Population Council (Conapo). Adjusted mortality rates, taking as standard of reference the population of Mexico City by sex, year, and 10-year age groups were calculated as well as the sex ratio for the 1980-1997 period. To evaluate the magnitude of risks by state, the standardized mortality ratio (SMR) was calculated; prematurity was evaluated through the potential lost-life years index (PLLYI). The analysis was carried out using the Excel and Stata 5.0 software programs.

RESULTS

During the years from 1980 to 1997, in Mexico the total number of deaths from SC was 76,315. The male:female ratio was 1.2:1.0. SMR by state showed that the states of Yucatán, Sonora, Zacatecas, Michoacán, and Chiapas had higher mortality rates. The PLLYI was higher for males in the states of Chiapas, Sonora, Chihuahua, Zacatecas, and Southern Baja California, and higher for females in Chiapas, Oaxaca, Yucatán, Puebla, and Campeche.

CONCLUSIONS

World statistics on mortality caused by SC suggest a decreasing trend. Findings for this study show an increase in the adjusted mortality rates by SC during the 1980-1997 period in Mexico. However, when analyzing the different indicators that reveal risks, magnitude, and prematurity of mortality, there is a differential trend in mortality by sex that includes regional patterns probably related to different socioeconomic levels.

[Identification of malignant breast lesions in Mexico]

OBJECTIVE

To evaluate the modes of detection of breast malignancies in Mexico City and to estimate the number of patients diagnosed in advanced stages.

MATERIAL AND METHODS

This cross-sectional study was conducted between 1994 and 1996, among 256 women with a histological diagnosis of breast cancer, at three tertiary level public hospitals in Mexico City. Personal interviews were conducted to collect data on reproductive characteristics, clinical history, and breast cancer modes of detection. Data analysis consisted of percentages, odds ratios, and 95% confidence intervals.

RESULTS

Ninety percent of women sought medical care after identifying a breast lump by themselves. Only 10% of patients had a stage-I tumor; all 27 cases first identified by a physician were in stage II-B and higher.

CONCLUSIONS

An increasing trend of breast cancer mortality in Mexico City will persist, unless a greater proportion of tumors in situ is detected; this would require enhancing breast cancer screening programs and conducting an intense educational intervention among women at risk.

[Lead elimination by traditional curing]

OBJECTIVE

To evaluate traditional acidic curing as a preventive method for reducing lead content of glazed ceramic ware.

MATERIAL AND METHODS

In 27 ceramic ware pieces from four states in Mexico, the level of residual lead was determined through atomic absorption spectrophotometry after four washings with acetic acid 3%.

RESULTS

The lead content of the vinegar washing diminished proportionally with the number of washings, although it remained highly above the permissible levels of this metal (2.5-7.0 p.p.m.).

CONCLUSIONS

Traditional acidic curing of glazed ceramic ware is not a useful preventive measure for reducing lead exposure.

The epidemiology of Her-2/neu and P53 in breast cancer

Breast cancer is an etiologically heterogeneous disease with marked geographical variations. Joint consideration of the relationship between specific molecular alterations and known or suspected epidemiologic risk factors for this disease should help distinguish subgroups of women that are at elevated risk of developing breast cancer. In this article, we present a comprehensive literature review of the etiologic and prognostic roles of Her-2/neu and P53 among women. In addition, we discuss the advantages and limitations of using biomarkers in epidemiological studies. We conclude that more research is needed to understand the complex relationships between genetic alterations and etiologic risk factors for breast cancer.

[Strategies for teaching self-examination of the breast to women in reproductive age]

OBJECTIVE

To develop an effective strategy to inform Mexican women between 12 and 47 years of age about breast cancer (BC) and train them to perform breast self-examination (BSE).

MATERIAL AND METHODS

Between April, 1996 and July, 1998, two different strategies to teach BSE were designed and evaluated in Cuernavaca, State of Morelos, Mexico. These strategies included teaching materials and were based on opinions of women participating in the first stage of this study. Both strategies consisted of the presentation of a leaflet and a video. The first strategy was delivered by a public health nurse in charge of leading the session. The second one was presented by a BC survivor. This second strategy included slides and silicon breast models. These two strategies were then compared to a third one, consisting of a primary care nurse handling out a leaflet and showing a video, based on Health Secretariat's guidelines. In total, 149 women were trained. They were randomly assigned to any one of these three strategies. The effectiveness of the teaching strategies was determined by assessing the changes in the women's knowledge of BC and BSE, as well as in their ability to identify the largest number of lumps on a natural size silicon breast, before and after training. Statistical analysis included Student's t test, variance analysis, McNemar's chi 2, Pearson's chi 2, and multiple linear regression.

RESULTS

With all three strategies, there was an increase of approximately 30% in women's knowledge of BC and BSE as well as in their ability to detect lumps. Although at the beginning of the training only one out of every 20 women were able to identify more than three lumps in the silicon model, by the end between 3 and 4 of every 10 women were able to do this, with values of p < 0.05. Some factors determine women's learning of both BSE and information about BC as well as their ability to identify lumps.

CONCLUSIONS

Teaching BSE with any of the strategies evaluated could be included in an integral program to educate Mexican women on breast cancer prevention and early detection. The appropriate and monthly practice of BSE is linked both to a decrease in the amount of time elapsing between the identification of suspect signs and the demand for medical care, such as requesting a clinical breast examination, which entails identifying small tumors when BC is present.

Nutrient intake and gastric cancer in Mexico

In contrast to the decreasing trends observed in most countries, gastric-cancer mortality has remained at about the same level in Mexico throughout the last 40 years. As part of a study carried out in the metropolitan area of Mexico City, an assessment of nutrient intake and gastric cancer is presented here. The study population comprised 220 cases of gastric cancer and 752 population-based controls. Our results showed 70 to 80% reduction in the risk of developing this tumor, associated with the intake of polyunsaturated fat, fiber and vitamin E; and this effect was independent of the histological type of the tumor (i.e., intestinal or diffuse). On the other hand, an increased risk of gastric cancer was related to the consumption of saturated fat (OR(Q4vs.Q1) = 4.37, 95% CI 1.89-10.12) and, cholesterol (OR(Q4vs.Q1) = 2.39, 95% CI 1.23-4.64), but such effects were restricted to the intestinal type of gastric cancer. In the whole study population, mono-unsaturated fat intake increased the risk for gastric cancer, and a marginally significant increasing trend was observed for protein consumption. The findings from this study add information about the role of specific nutrients in the etiology of gastric cancer.

Nutrient intake and gastric cancer in Mexico

In contrast to the decreasing trends observed in most countries, gastric-cancer mortality has remained at about the same level in Mexico throughout the last 40 years. As part of a study carried out in the metropolitan area of Mexico City, an assessment of nutrient intake and gastric cancer is presented here. The study population comprised 220 cases of gastric cancer and 752 population-based controls. Our results showed 70 to 80% reduction in the risk of developing this tumor, associated with the intake of polyunsaturated fat, fiber and vitamin E; and this effect was independent of the histological type of the tumor (i.e., intestinal or diffuse). On the other hand, an increased risk of gastric cancer was related to the consumption of saturated fat (OR(Q4vs.Q1) = 4.37, 95% CI 1.89-10.12) and, cholesterol (OR(Q4vs.Q1) = 2.39, 95% CI 1.23-4.64), but such effects were restricted to the intestinal type of gastric cancer. In the whole study population, mono-unsaturated fat intake increased the risk for gastric cancer, and a marginally significant increasing trend was observed for protein consumption. The findings from this study add information about the role of specific nutrients in the etiology of gastric cancer.

Intrauterine lead exposure and preterm birth

The objective of this study was to determine the risk of preterm birth in relation to umbilical cord blood lead levels (UCL) among primiparous and multiparous women. A case-cohort study was performed in Mexico City during 1995. A total of 459 full-term births was compared with 161 preterm births (before 37 gestational weeks). Mothers were interviewed before the delivery about their reproductive histories and other related factors of preterm birth. Lead was determined by atomic absorption spectrophotometry. Lead levels were higher in primiparous women who had a preterm birth than in primiparous women with a full-term birth (9.77+/-2.0 microgram/dl vs 8.24+/-2.15 microgram/dl); this difference was marginally significant. After adjusting for other known preterm birth risk factors, the frequency of preterm birth was almost three times higher among women who had UCL levels greater or equal to 5.1 microgram/dl compared to those who had UCL levels lower than 5.1 microgram/dl. This difference was not observed among multiparous women. Our results suggest that intrauterine lead exposure may be associated with preterm birth in first deliveries but not in subsequent ones.

The adipose tissue to serum dichlorodiphenyldichloroethane (DDE) ratio: some methodological considerations

Dichlorodiphenyldichloroethane (DDE) adipose tissue level has been regarded as a preferred indicator of accumulated human exposure to DDT; however, blood sera are more feasible to obtain and analyze than adipose tissue samples. Inconsistent and scarce information exists in relation to the adipose tissue/serum DDE ratio. As a part of a hospital-based case-control study performed in Mexico City from 1994 to 1996, 198 paired serum and adipose tissue samples were obtained from 72 women with histologically confirmed breast cancer and 126 women with benign breast disease. Both adipose tissue and serum DDE levels were determined by gas-liquid chromatography and reported as ppb lipid weight (ng/g) as well as wet basis (ng/ml). Results showed that the adipose tissue/serum DDE ratio (ADSE) varies according to the type of information (lipid vs wet basis, arithmetic vs geometric means) used for its estimation. ADSE gets a value near 1 (1.1) only when the geometric DDE levels in lipid basis are used for its estimation. The correlation between DDE serum and adipose tissue levels was found (r=0.364, P<0.001). The ADSE did not vary by disease status, nor was it altered by parity, history of breast-feeding, and other reproductive characteristics. We endorse the use of venipuncture instead of biopsy as a way to estimate DDT body burden levels in further research.

[Is cancer preventable?]

Cancer prevention is possible when the causes and risk factors for this disease are known and can be avoided. Lung, breast, stomach and cervical cancers are those with the highest incidence internationally. Smoking, diet, physical activity and certain viruses are factors that have potential for modification, and they determine most of the cancers in the world. To reduce cancer risk, the following is recommended at the individual level: increasing fruit and vegetable consumption, decreasing consumption of red meats, animal fats and alcoholic beverages, avoiding smoking, exercising regularly and avoiding weight gain. Health education, restrictions as to where smoking is prohibited and establishing taxes on tobacco consumption are the principal strategies for designing population prevention programs.

Dietary factors and the risk of gastric cancer in Mexico City

Dietary factors play an important role in gastric cancer risk but have not been investigated extensively in Mexico. The authors conducted a population-based case-control study of gastric cancer in the Mexico City, Mexico, metropolitan area in 1989-1990. A total of 220 patients with histologically confirmed gastric adenocarcinomas were interviewed. Controls were an age-stratified random sample of residents of the Mexico City metropolitan area. The dietary questionnaire was a 70-item semiquantitative food frequency adapted for the Mexican diet. Odds ratios were calculated for quartiles of consumption of food groups and were adjusted for age, gender, calories, chili pepper intake, cigarette smoking, socioeconomic status, added salt, and history of peptic ulcer disease. There was approximately a threefold increased risk of gastric cancer for frequent consumption (highest quartile) of both fresh meat (odds ratio (OR) = 3.1) and processed meat (OR = 3.2). Odds ratios were also significantly elevated for frequent consumption of dairy products (OR = 2.7) and fish (OR = 2.2). The authors observed a decreasing gradient of risk with increasing frequency of vegetable consumption due to a significant inverse trend for the yellow and orange vegetables. High intake of citrus fruits showed a slight inverse association. Consumption of salty snacks more than twice per month was associated with an 80 percent increased risk, and there was a significant positive trend. These findings are consistent with many studies around the world that indicate important roles for salt, processed meats, and vegetable consumption in gastric cancer risk.

Levels of dichloro-dyphenyl-trichloroethane (DDT) metabolites in maternal milk and their determinant factors

To document the levels and the determinants of dichloro-dyphenyl-trichloroethane (DDT) metabolites in maternal milk, we conducted a cohort study of 50 adult females who lived in Mexico City. We measured social and dietary characteristics via interview. Levels of DDT metabolites were determined by gas-liquid chromatography. The mean values (lipid milk basis) were 0.162 ppm p,p'-DDT; 0.138 ppm o,p'-DDT; and 0.594 ppm 2,2(bis)p-chlorophyenyl-1-1-dichloroethylene (DDE). The main determinants of DDT metabolites were maternal age, lifetime lactation, history of living in an agricultural area, and consumption of salted meat and fish. We estimated that 6.0% of the breast-fed babies had daily intakes of DDT above the level of 0.005 mg/kg d recommended by the World Health Organization/Food and Agriculture Organization of the United Nations (WHO/FAO). Health-outcomes research among children is needed, and investigators should design or adjust current surveillance programs.

Alcohol consumption and gastric cancer in Mexico

This paper presents an assessment of alcohol consumption, including the popular Mexican liquor tequila, in relation to the incidence of gastric cancer. We conducted a population-based case-control study in Mexico City, with 220 gastric cancer cases and 752 population-based controls. A food frequency questionnaire was used to measure consumption of alcohol and other dietary items. Grams of ethanol were estimated by the Food Intake Analysis System 3.0 software. After adjustment for known risk factors, wine consumption was positively associated with the risk of developing gastric cancer (OR=2.93; CI 95% 1.27-6.75) in the highest category of wine consumption, corresponding to at least 10 glasses of wine per month, with a significant trend (p=0.005). This association remained among intestinal (OR=2.16; CI 95% 0.68-6.92, p-value for trend=0.031 ) and diffuse (OR=4.48; CI 95% 1.44-13.94, p-value for trend=0.018 ) gastric cancer cases. A borderline significant trend between GC risk and total ethanol intake was observed (p=0.068). Consumption of beer and distilled alcoholic beverages including brandy, rum, and tequila was not associated with GC risk. The results indicate the need to focus on the study of the potential effects of different types of wine, with emphasis on components other than ethanol regarding the incidence of gastric cancer, even among populations with moderate to low levels of alcohol consumption.

Histological types of gastric cancer in Mexico

BACKGROUND

Gastric cancer is the second leading cause of malignant tumours in Mexico. The distribution of the histological types of this tumour has not been estimated from a population-based representative sample.

METHODS

The histological types of gastric cancer according to the Lauren classification and selected socio-demographic characteristics for 220 patients from different socioeconomic levels are reported. The study population represents 66% of all new gastric cancer cases during 1989-1990 reported to the Mexico City Cancer Registry. The patients attended four public hospitals, seven social security hospitals and four private hospitals in Mexico City. A second histological diagnosis was performed by one pathologist.

RESULTS

No specific histological type of gastric cancer predominated since the estimated distribution for intestinal gastric cancer was 44.5%, for diffuse gastric cancer 43.2% (and the remaining 12.3% corresponded to indeterminate tumours). The distribution of intestinal and diffuse gastric cancer did not vary significantly according to socioeconomic level or medical care unit and it showed a clear relationship with gender, the intestinal type of gastric cancer being more common among males.

CONCLUSIONS

Mexico may not have been affected by the gastric cancer epidemic at the beginning of the twentieth century but the available information and the results of this study are only useful to demonstrate that, currently, no histological type of gastric cancer (according to Lauren's classification) predominates significantly in this country.

Dichlorodiphenyltrichloroethane serum levels and breast cancer risk: a case-control study from Mexico

Some, but not all, epidemiological studies have suggested that dichlorodiphenyltrichloroethane (DDT) may play a role in the development of breast cancer. These investigations have been conducted in countries where this substance has been banned for at least 20 years. We conducted a study in Mexico, a country in which DDT is still being used to control malaria. In a hospital-based case-control study, we compared 141 histologically confirmed cases of breast cancer with 141 age-matched controls (+/-3 years). All subjects were identified at three referral hospitals of Mexico City between March 1994 and April 1996. Reproductive histories and other variables were obtained by structured interviews, DDT/DDE levels were determined in serum by gas-liquid chromatography. The arithmetic mean of serum DDE in lipid basis was 562.48 +/- 676.18 ppb (range, 10.24-4661.44) for the cases and 505.46 +/- 567.22 ppb (range, 0.004 to 4361.75) for the controls, but this difference was not statistically significant. The age-adjusted odds ratios for breast cancer regarding the serum level of DDE were 0.69 (95% confidence interval, 0.38-1.24) and 0.97 (confidence interval, 0.55-1.70) for the contrasts between tertile 1 (lowest level) and tertiles 2 and 3, respectively. These estimates were unaffected by adjustment for body mass, accumulated time of breast-feeding and menopause, and other breast cancer risk factors. These results do not lend support to the hypothesis that DDT is causally related to breast cancer at the body-burden levels found in our study population but do not exclude the possibility that higher levels of exposure could still play a role in the etiology of this tumor.

Validity and reproducibility of cytologic diagnosis in a sample of cervical cancer screening centers in Mexico

OBJECTIVE

To evaluate the diagnostic precision of the cervical cytology (smear) in a sample of 16 cervical cancer screening centers (CCSCs) from the Mexican Ministry of Health and Mexican Institute for Social Security CCSCs distributed across the country.

STUDY DESIGN

Each center received a batch of 90 cytologic specimens with a random positive prevalence of 1.5-36%. Positive cases were always histologically confirmed. The "gold standard" was an expert pathologist certified by the Mexican Board of Pathology.

RESULTS

Our results show that cytologic diagnosis validity and reproducibility vary greatly within and between institutions. The false negative rate (FNR) varied between 10% and 54%, independent of the prevalence of positive cases.

CONCLUSION

Quality control of diagnostic precision is central to the consistency of results obtained at CCSCs. In Mexico the high FNR calls for governmental regulation of cytopathology policies and methods, such as through national and international accreditation of cytotechnology programs. In order to decrease the FNR, developing countries must frame managerial development strategies to streamline the cervical cancer screening program, including continuing education, improvement of operation processes in CCSCs, internal and external quality control of cytopathology laboratories and cervical sampling procedures, and standardization of diagnostic criteria.

Prevalence and determinants of lead intoxication in Mexican children of low socioeconomic status

This paper reports on the prevalence of lead poisoning in children between 1 and 5 years of age living in a marginal area to the north of Mexico City and also includes an evaluation of sources of exposure to this metal in the same area. The results show that 67.5% of the children studied have blood lead (PbB) levels > or = 10 micrograms/100 ml. Twenty-one percent of these children (1987) had PbB levels that required medical evaluation (> or = 20 micrograms/100 ml- < or = 40 micrograms/100 ml), and 112 children needed medical treatment (PbB > or = 40 micrograms/100 ml). In addition, the study found that the probability of higher blood lead levels (> or = 20 micrograms/dl) corresponds to children whose mothers use lead-glazed pottery dishes (OR = 2.80; CI 95%, 1.55-5.07) and to children who habitually bite colored pencils (OR = 2.05; CI 95%, 1.13-3.71) compared, respectively, with children whose mothers do not use that type of dishes and children who do not bite pencils. Our results provide baseline information for estimating the impact and costs of population-based interventions aimed at these populations and also confirm the need to strengthen health education programs to promote the reduction of lead exposure in the general population.

[Reproducibility of a questionnaire for studying climacteric]

OBJECTIVE

This study evaluated the reproducibility of a questionnaire concerned with the clinical and epidemiological aspects of menopause.

MATERIAL AND METHODS

The study population consisted of a hundred perimenopausal Mexican women seeking care at gynecology and obstetric health care services. Their participation was voluntary and they answered the same questionnaire two times with a 15-30 day lag between each application.

RESULTS

The Kappa coefficient was high (0.81-1.0) for categorical variables such as: type of menstrual cycles, type of menopause, breast-feeding, use of estrogen during menopause and use of hormonal contraceptives. The Kappa coefficient was moderate (0.7-0.8) for symptoms related to menopause such as hot flashes, sweating, painful coitus, vaginal dryness and a decrease in libido. Mean differences were calculated for continuous variables such as age at menarche, age at menopause, time using estrogen and the duration of breast-feeding, the majority had a value of zero and 95% confidence intervals for these mean differences included the null value. The questionnaire also included other characteristics such as tobacco consumption and a short food frequency questionnaire, which showed high concordance (Kappa 0.7-1.0).

CONCLUSIONS

The results of this study show that this questionnaire has a high level of reproducibility and can be useful as a research tool to explore menopause in Mexican women.

Exercise and reproductive factors as predictors of bone density among osteoporotic women in Mexico City

We examined the association between physical activity and reproductive factors with bone density among 313 Mexican women, aged 26-83 years. Bone mineral density (BMD) was measured with a HOLOGIC QRD 1000 w, DXA densitometer at the lumbar spine and femoral region. We explored the relation between BMD and parity, age, body mass index (BMI), type of menopause, and level of exercise. Multiple regression models examining determinants of bone density at the lumbar and femoral regions showed that increasing age and lack of exercise were statistically significant predictors of bone demineralization. The number of pregnancies also had a deletereous effect on bone density, especially for lumbar spine, as well as BMI <20 kg/m2. Our results suggest that physical activity, parity, and BMI are important determinants of bone density in this population.

Is DDT use a public health problem in Mexico?

We review the potential impact of DDT on public health in Mexico. DDT production and consumption patterns in Mexico during the last 20 years are described and compared with those in the United States. In spite of the restrictions on DDT use in antimalaria campaigns in Mexico, use of DDT is still higher than in other Latin American countries. We analyzed information from published studies to determine accumulated levels of this insecticide in blood, adipose tissue, and breast milk samples from Mexican women. Current lipid-adjusted DDE levels from women living in Mexico City are 6.66 ppb in mammary adipose tissue and 0.594 ppm in total breast milk. Finally, the methodological limitations of existing epidemiological studies on DDT exposure and breast cancer are discussed. We conclude that DDT use in Mexico is a public health problem, and suggest two solutions: identification of alternatives for the control of malaria and educational intervention to reduce DDT exposure. We also recommend strengthening epidemiological studies to evaluate the association between accumulated DDT levels in adipose tissue and breast cancer incidence among Mexican women.

Age of natural menopause among women in Mexico City

OBJECTIVES

The average age of menopause among women in Mexico City was calculated, considering their reproductive and socio-demographic characteristics. The information was obtained from a population-based control group from a case-controlled study of gynecologic cancer.

METHODS

Interviews were carried out with 1005 women resident in Mexico City chosen at random from a sample using the housing sample framework of the Mexico General Directorate of Epidemiology, 472 of whom had undergone a natural menopause.

RESULTS

The most important results include an average age for menopause in this population of 46.5 +/- 5 years (95% C.I. 46-48) with a median of 47. Groups of women with an average early menopause were those with no formal education (1.6 years), low socio-economic level (1.3 years, P < 0.05), nulliparas (2.6 years, P < 0.05), those who had never breastfed (2.2 years, P < 0.05) and those who had not used contraceptive hormones (1.7 years, P < 0.05).

CONCLUSION

This phenomenon must be documented in Mexico because of its strong links with the morbidity and mortality of the growing number of women who are reaching advanced ages and whose survival is calculated at 30 years after menopause.

[Breast cancer. A historical account, present and future]

This essay describes the different theoretical constructions of breast cancer models, such as the biological, hygienist-preventive and epidemiological. An anecdotal account of the Hippocratic model is also presented. This disease will be one of the major challenges posed by noncommunicable diseases in coming years, due to a significant increase of life expectancy and to a decrease of the overall annual growth rate-resulting in the ageing of the population-, as well as to lifestyle changes-particularly the considerable decrease of fertility rates and breastfeeding practices-, and to the poor efficiency and effectiveness of breast cancer screening programs. In this context, one of the main challenges for breast cancer control is to secure the multidisciplinary approach offered by public health. After analyzing the different models, we favor the sociomedical model as the one that incorporates several areas of knowledge to formulate an effective response to breast cancer.

[Reproductive risk factors and sexual history associated with cervical cancer in Mexico]

Uterine cervical cancer is one of the principal public health problems in Mexico. The national mortality rate for cervical cancer in 1991 is estimated at 9.5 per 100,000 women, representing 4,194 deaths. In the period from August 1990 to December 1992, a case-control study was carried out that included 630 cases of histologically confirmed cervical cancer in eight Mexico City hospitals (two for people with no social security cover, four of the social security system and two private). As controls, 1,005 women were chosen from a random sampling of houses in the Mexico City metropolitan area. The main cervical cancer risk factors found in this study, adjusted for a multivariate model, were multiple normals births (with five births OR of 1.93 and 95% C.I. of 1.22-2.73) and a history of two or more sex partners (the OR with four or more sex partners was 5.56 and a C.I. of 2.3-13.4). In addition, there was an estimated lower risk of disease related to starting a sex life after 25 years of age (OR 0.41 with C.I. of 0.25-0.69) and to having cesareans as compared versus one normal birth (OR 0.28 and C.I. of 0.13-0.61). The information obtained is relevant since it identifies Mexican women with a high-risk of developing cervical cancer which can be used in planning programs for the early detection of cancer in this population.

[Beliefs about chili pepper consumption and health in Mexico City]

Eating chili peppers is a cultural tradition in Mexico. Controversial characteristics have been empirically associated to chili pepper consumption and human health. In this paper, the beliefs about the health impacts of chili pepper consumption in two independent groups of Mexico City residents are described. The results confirm, on the one hand, that there is a wide variety of health benefits and damages associated with chili pepper consumption, but on the other hand, that the levels of chili pepper consumption are not related to beliefs about its human health impact.

[NAFTA: a challenge and an opportunity for environmental health. The case of the maquila industry]

The three countries that have signed the North American Free Trade Agreement (NAFTA) have focused particular interest and concern on the potential impact that this agreement will have on the environmental health, based on the premise that economical development should not detriment neither the environment nor the human health. In this paper, the NAFTA is presented as an opportunity to improve environmental and occupational health in Mexico and assumes that the study of the potential impact of NAFTA could help to find the solutions of the former and actual environmental health problems. From this perspective, the north-border maquila industry is analyzed as a case study for the purpose of identifying and predicting the impact of NAFTA on environmental and the occupational health. Preventive as well as control measurements are suggested. The general characteristics of the U.S.-Mexico border and the maquila industry are presented. The lack of both social investment and urban planning along with population and economical growth are described. An explanation of the impact that these factors have had on the environmental and occupational problems is discussed. Special emphasis is given to the human health problems including that of water, air and soil contamination by industrial toxic residues. Also, some possible health impact of NAFTA are outlined. Finally a sustainable developmental intervention is suggested, based on NAFTA as an opportunity to take advantage of coming structural changes that will improve the environmental health conditions at the northern-border and in the entire country.

[Health risk control for organophosphate pesticides in Mexico: challenges under the Free Trade Treaty]

This paper discusses recent trends concerning the commercialization of pesticides in Mexico and focuses on organophosphates and their potential health risk impact. It points out the existing lack of knowledge on health effects associated to chronic exposure to organophosphate pesticides. A need for both toxicological and epidemiologic studies of chronic exposure is identified. Regulatory programs for pesticides in Mexico and the United States are also compared. The paper also addresses the possibility of effective enforcement of environmental and health regulations in Mexico as a result of more rigorous surveillance under NAFTA.

[Evaluation of a program for the early detection of cancer of the uterine cervix in Mexico City. A populational-based epidemiologic study of cases and controls]

Cervical cancer is still an important public health problem in Mexico; in spite of the development of various programs aimed at lowering mortality due to this disease, impact has not yet been achieved. In this study we present an evaluation of the Early Detection Program for Cervical Cancer in Mexico City. The authors carried out a case-control study with a populational base, in which a sample of cases obtained in eight hospitals and a sample of controls representative of the general population were included. We report a protective effect attributed to the program. The women with complete cytology showed 2.4 times less risk of cervical cancer. Nevertheless the effect of the program at a populational level is still limited because it covers only 20 per cent of the cases in the population. The results indicate the need for developing operative research programs in order to increase the demand for and the quality and efficiency of preventive services.

[Dietary fiber and gastro-intestinal tumors, implications for the Mexican population]

Certain nutrients serve as individual influences in the development or protection against chronic and/or degenerative diseases. Specifically, it has been observed that the abundant consumption of dietetic fiber is a protective factor against tumors of the digestive system. Many scientific articles have reported mechanisms by which dietetic fibers exert an important protective effect for colon cancer and in lesser degree against cancer of the stomach and rectum. In Mexico during 1990, neoplasms were the second cause of general mortality for the persons over the age of 65 years. The Fourth National Report of Cancer in Mexico revealed that tumors of the digestive tube were the third most frequent type of neoplasm in the country and that stomach cancer had the greatest incidence among cancers which affect this system. To date, we do not know how much the urban immigration and the consequent changes in food patterns have acted as cofactors for the increase in this type of tumors. During the seventies, a number of national and regional nutritional surveys showed that the Mexican population had a high consumption of fiber, as part of the traditional diet, comprised primarily of tortilla and beans. At the present time, the national dietary patterns have changed; the increasing consumption of high energy foods with a low nutritional value is associated with much less ingestion of dietary fiber. This article points out that the population may have additional digestive cancer risks, due to new food consumption patterns which have reduced the availability of dietary fiber.

Chili pepper consumption and gastric cancer in Mexico: a case-control study

Laboratory studies indicate that capsaicin, the hot-tasting component of chili peppers, may be carcinogenic. A population-based case-control study was conducted in Mexico City during 1989-1990 to evaluate the relation between chili pepper consumption and gastric cancer risk. The study included 220 incident cases and 752 controls randomly selected from the general population. Information was collected by interview. Chili pepper consumers were at high risk for gastric cancer compared with nonconsumers (age- and sex-adjusted odds ratio = 5.49, 95% confidence interval (CI) 2.72-11.06). Among consumers, there was a highly significant trend of increasing risk with increasing self-rated level of consumption (low, medium, and high) (p = 2 x 10(-7). The odds ratio for high-level consumers compared with nonconsumers was 17.11 (95% CI 7.78-37.59). However, when consumption was measured as frequency per day, a significant trend among consumers was not observed. Multivariable adjustment increased the magnitude of the chili pepper-gastric cancer association, but a significant trend among consumers (measured as frequency per day) was still not observed. Chili pepper consumption may be a strong risk factor for gastric cancer, but further studies are needed to test this hypothesis.

[Research in Mexico on the health impact of environmental chemical pollutants]

This paper is intended to offer a qualitative and quantitative diagnosis on publications concerned with human health impact of exposure to environmental chemical pollutants in Mexico. The review of these subjects included scientific papers on studies carried out in Mexico, published both in Mexican and international journals. The articles were analyzed according to the following criteria: chemical pollutants, type of study and institution that conducted it, study population, design, and analysis of data. The article concludes that publications in this field are scarce. Moreover, this review showed that there is little diversity, limited methodology and an unequal distribution of the human and material resources for research. All this indicates a rudimentary level of scientific knowledge in Mexico regarding public health implications of chemical pollutants.

[Reproductive risk factors and uterine cervix cancer in Mexico City]

An epidemiological case control study nested in the Early Cancer Detection program of the Health Ministry in Mexico City was carried out to evaluate the principal reproductive risk factors associated with uterine cervix cancer. Information from 12,741 gynecological cytologies reported to the National Cancer Registry, during the period between January 2 to March 31, 1987 was studied. In this population group the most important reproductive risk factors associated with uterine cervix cancer were: multiple births (seven or more births, OR = 3.24, IC 95% = 2.20-4.76), initiation of active sex life before 14 years (OR = 1.53, 95% IC = 1.13-2.08) and late menarche (in the group with menarche after 17 year of ages OR = 3.22, 95% IC = 1.06-9.77). In relation to the Early Cancer Detection program, an important number of women made use of the program when they showed symptoms. The prevalence among women who had at least one symptom was 43.09 per cent. Women with a tumor at the cervical level at the time of the cytology were 7.76 times more likely to have of uterine cervix cancer (95% IC = 4.84-13.15). Symptoms such as dysfunctional bleeding (OR 2.79, IC 95% = 1.90-4.12), metrorrhagia (OR 2.66, 95% IC 1.83-3.86) and bloody leukorrhea (OR 2.64, 95% IC 2.05-3.38) can be relevant findings in women at high risk. The attributable fraction of higher exposure in the presence of gynecological signs and symptoms is the cervical tumor, with 87.46 per cent.(ABSTRACT TRUNCATED AT 250 WORDS)