Radiation and other environmental exposures and breast cancer

ATM in breast and brain tumors: a comprehensive review

The ATM gene is mutated in the syndrome, ataxia-telangiectasia (AT), which is characterized by predisposition to cancer. Patients with AT have an elevated risk of breast and brain tumors Carrying mutations in ATM, patients with AT have an elevated risk of breast and brain tumors. An increased frequency of ATM mutations has also been reported in patients with breast and brain tumors; however, the magnitude of this risk remains uncertain. With the exception of a few common mutations, the spectrum of ATM alterations is heterogeneous in diverse populations, and appears to be remarkably dependent on the ethnicity of patients. This review aims to provide an easily accessible summary of common variants in different populations which could be useful in ATM screening programs. In addition, we have summarized previous research on ATM, including its molecular functions. We attempt to demonstrate the significance of ATM in exploration of breast and brain tumors and its potential as a therapeutic target.

A Geographic Analysis about the Spatiotemporal Pattern of Breast Cancer in Hangzhou from 2008 to 2012

BACKGROUND

Breast cancer (BC) is the most common female malignant tumor. Previous studies have suggested a big incidence disparity among different cities in China. The present work selected a typical city, Hangzhou, to study BC incidence disparity within the city.

METHODS

Totally, 8784 female breast cancer cases were obtained from the Hangzhou Center for Disease Control and Prevention during the period 2008-2012. Analysis of Variance and Poisson Regression were the statistical tools implemented to compare incidence disparity in the space-time domain (reference group: township residents during 2008, area: subdistrict, town, and township, time frame: 2008-2012), space-time scan statistics was employed to detect significant spatiotemporal clusters of BC compared to the null hypothesis that the probability of cases diagnosed at a particular location was equal to the probability of cases diagnosed in the whole study area. Geographical Information System (GIS) was used to generate BC spatial distribution and cluster maps at the township level.

RESULTS

The subdistrict populations were found to have the highest and most stable BC incidence. Although town and township populations had a relatively low incidence, it displayed a significant increasing trend from 2008 to 2012. The BC incidence distribution was spatially heterogeneous and clustered with a trend-surface from the southwest low area to the northeast high area. High clusters were located in the northeastern Hangzhou area, whereas low clusters were observed in the southwestern area during the time considered.

CONCLUSIONS

Better healthcare service and lifestyle changes may be responsible for the increasing BC incidence observed in towns and townships. One high incidence cluster (Linping subdistrict) and two low incidence clusters (middle Hangzhou) were detected. The low clusters may be attributable mainly to developmental level disparity, whereas the high cluster could be associated with other risk factors, such as environmental pollution.

Mediterranean diet for breast cancer prevention and treatment in postmenopausal women

Breast cancer has become a big oncological concern both in Poland and most countries around the world. Epidemiological studies show that women who are directly in danger of suffering from breast cancer are mainly postmenopausal women. Due to the seriousness of the problem more attention is devoted to preventative measures that should be undertaken. That is why, Mediterranean diet and its beneficial effects on health started to be discussed. This diet contains antioxidants and shows anti-inflammatory properties which are crucial in breast cancer prevention. Its components are fish, olive oil, unrefined cereals, herbs, fruits and vegetables. In 1960s there was research done on the influence of low fat diet, as a preventative measure, on coronary artery disease. In 1980s, an interest in this diet grew and there was a great come-back to the origins of the diet. It led to estimation of its influence on cardiological and cancer diseases. Many positive effects were observed among people living in the Mediterranean area as far as health qualities of the diet are concerned. Mediterranean diet was compared with high fat diet of people living in Northern Europe and the USA. It seems to create new dietary recommendations as a preventative measure in breast cancer disease. The following article presents most recent data on the importance of Mediterranean diet as a prevention against breast cancer.

Breast cancer in the Arctic--changes over the past decades

The purpose of this study is to review the current literatures on breast cancer (BC) in the Arctic, especially the trends in incidence during the last decades and the possible explanations. The design of this study is a literature review. The scientific literature concerning BC were reviewed, especially focusing on the Arctic and the special conditions that exist in this region. Breast cancer incidence is increasing all over the world, including in the Arctic. The enormous transition in health conditions and lifestyle in the Arctic might be contributing to the known risk factors. In Greenland, the age at menarche has diminished by 3 years during the course of 100 years, and the number of children per women as well as the duration of breastfeeding is decreasing. Obesity and intake of saturated fat is increasing and the intake of traditional food rich in unsaturated fat and vitamin D decreasing. Smoking and alcohol consumption in the Arctic has been relatively high but is now decreasing. More focus on genetic susceptibility in relation to BC has identified the specific BRCA1 founder mutation in the Greenlandic population, which might appear to be an important risk factor. However, the known established risk factors alone cannot account for the increasing trend observed. Studies suggest that environmental contaminants such as persistent organic pollutants (POPs) including perfluorinated compounds increase the risk of BC possibly in conjunction with certain genetic polymorphisms involved in carcinogen activation. The lipophilic POPs such as polychlorinated biphenyls and organochlorine pesticides are found at very high levels in the Arctic population. Several factors can explain the increasing incidence of BC in the Arctic. The transition in lifestyle and health conditions unfortunately increases the known risk factors of BC. Moreover, the population of the Arctic might show up to be especially vulnerable because of the contemporary high burden of POPs and genetic susceptibility.

Quality of life factor as breast cancer risks

BACKGROUND

Numerous studies have observed risk factors for breast cancer. We investigated the association between quality life factors as breast cancer risks in a case-control study in industrial Zenica- Doboj Canton in Bosnia and Herzegovina.

METHODS

The case-control study was included 200 women, 100 without (control subjects) and 100 women with diagnosed breast cancer. We used questionnaires about breast cancer risks" as study tool. Logistic regression was used to compute odds ratios (ORs) and 95% confidence intervals (CI) and a full assessment of confounding was included in analysis.

RESULTS

Breast cancer was positive associated with increasing age of life (from 45 years and more; OR= 1.25); further relative breast cancer history (OR= 4.42; 95%CI, 0.483-4.043); exposure to CT (OR=2.02; 95%CI, 1,254-3.261); never birth child (OR= 1.394; 95%CI, 0.808-2,407); used replacement hormonal therapy (OR= 1.826; 95%CI, 1.637-10.590); arrival time of menstruation (OR=2.651; 95%CI, 1.303-1.571); length of smoking status (OR=1.534; 95%CI, 0.756-3.098), alcohol consumption (OR=1.728; 95% CI, 0.396-7.533); exposure to CT per year (p=0.009), routine physical inactivity (p=0.009) and replacement hormones treatment (p=0.036).

CONCLUSION

Inverse associations of breast cancer and poverty, arival time of menopause were observed. The link between breast cancer and a distant-cousin- degree family history of breast cancer was inverse association with breast cancer too. These results provide further evidence that, for most women, physical activity may reduce the risk of invasive breast cancer.

Female breast cancer in relation to exposure to medical iatrogenic diagnostic radiation during life

AIM OF THE STUDY

Exposure to radiation and aging are the leading causes of breast cancer among female patients. We aimed to investigate and assess the relationship between exposure to medical, diagnostic and iatrogenic radiation and breast cancer using a questionnaire among 100 newly diagnosed female breast cancer patients and 100 control female subjects without cancer.

MATERIAL AND METHODS

A case control study using a family ambulatory based survey was conducted among 200 female patients from all municipalities of Zenica-Doboj Canton. New cases of breast cancer among subjects of experimental groups (n = 100) were diagnosed between 1 January 2003 and 31 December 2007 using the institutional clinical procedure for breast cancer diagnosis. Data were obtained using a self-rated questionnaire on radiation as a breast carcinogen. Data analysis was performed using SPSS version 19.0.

RESULTS

There were no significant differences between the two groups and their subgroups for individual data and demographics except for prevalence of decreased family financial situation (practical poverty) among subjects with breast cancer in relation to control subjects (31%: 17% among control subjects; p = 0.001). Female patients who are exposed to iatrogenic radiation before the 3(rd) year of life (OR = 1.29; 95% CI: 0.839-1.985) and those who are exposed to CT more than twice per year are more than twice as likely to have breast carcinoma (OR = 2.02; 95% CI: 1.254-3.261) compared to control subjects. Poverty and low family income are vulnerability factors associated with elevated levels of breast carcinoma. This result is not in accordance with prior study results.

CONCLUSIONS

It is necessary to develop an adequate registration system of iatrogenic exposure to radiation for each patient of any age, particularly for children aged < 3 years and for CT iatrogenic exposure.

Mutagen sensitivity, tobacco smoking and breast cancer risk: a case-control study

Given the high incidence of breast cancer and that more than half of cases remain unexplained, the need to identify risk factors for breast cancer remains. Deficiencies in DNA repair capacity have been associated with cancer risk. The mutagen sensitivity assay (MSA), a phenotypic marker of DNA damage response and repair capacity, has been consistently shown to associate with the risk of tobacco-related cancers.

METHODS

In a case-control study of 164 women with breast cancer and 165 women without the disease, we investigated the association between mutagen sensitivity and risk of breast cancer using bleomycin as the mutagen.

RESULTS

High bleomycin sensitivity (>0.65 breaks per cell) was associated with an increased risk of breast cancer, with an adjusted odds ratio of 2.8 [95% confidence interval (CI) = 1.7-4.5]. Risk increased with greater number of bleomycin-induced chromosomal breaks (P(trend) = 0.01). The association between bleomycin sensitivity and breast cancer risk was greater for women who were black, premenopausal and ever smokers. Our data also suggest that bleomycin sensitivity may modulate the effect of tobacco smoking on breast cancer risk. Among women with hypersensitivity to bleomycin, ever smokers had a 1.6-fold increased risk of breast cancer (95% CI = 0.6-3.9, P for interaction between tobacco smoking and bleomycin sensitivity = 0.32).

CONCLUSIONS

Increased bleomycin sensitivity is significantly associated with an increased risk of breast cancer in both pre- and postmenopausal women. Our observation that the effect of tobacco smoking on breast cancer risk may differ based on mutagen sensitivity status warrants further investigation.

The breast cancer and the environment research centers: transdisciplinary research on the role of the environment in breast cancer etiology

OBJECTIVES

We introduce and describe the Breast Cancer and the Environment Research Centers (BCERC), a research network with a transdisciplinary approach to elucidating the role of environmental factors in pubertal development as a window on breast cancer etiology. We describe the organization of four national centers integrated into the BCERC network.

DATA SOURCES

Investigators use a common conceptual framework based on multiple levels of biologic, behavioral, and social organization across the life span. The approach connects basic biologic studies with rodent models and tissue culture systems, a coordinated multicenter epidemiologic cohort study of prepubertal girls, and the integration of community members of breast cancer advocates as key members of the research team to comprise the network.

DATA EXTRACTION

Relevant literature is reviewed that describes current knowledge across levels of organization. Individual research questions and hypotheses in BCERC are driven by gaps in our knowledge that are presented at genetic, metabolic, cellular, individual, and environmental (physical and social) levels.

DATA SYNTHESIS

As data collection on the cohort, animal experiments, and analyses proceed, results will be synthesized through a transdisciplinary approach.

CONCLUSION

Center investigators are addressing a large number of specific research questions related to early pubertal onset, which is an established risk factor for breast cancer. BCERC research findings aimed at the primary prevention of breast cancer will be disseminated to the scientific community and to the public by breast cancer advocates, who have been integral members of the research process from its inception.

Common single-nucleotide polymorphisms in DNA double-strand break repair genes and breast cancer risk

The proteins involved in homologous recombination are instrumental in the error-free repair of dsDNA breakages, and common germ-line variations in these genes are, therefore, potential candidates for involvement in breast cancer development and progression. We carried out a search for common, low-penetrance susceptibility alleles by tagging the common variation in 13 genes in this pathway in a two-stage case-control study. We genotyped 100 single-nucleotide polymorphisms (SNP), tagging the 655 common SNPs in these genes, in up to 4,470 cases and 4,560 controls from the SEARCH study. None of these tagging SNPs was associated with breast cancer risk, with the exception of XRCC2 rs3218536, R188H, which showed some evidence of a protective association for the rare allele [per allele odds ratio, 0.89; 95% confidence intervals (95% CI), 0.80-0.99; P trend = 0.03]. Further analyses showed that this effect was confined to a risk of progesterone receptor positive tumors (per rare allele odds ratio, 0.78; 95% CI, 0.66-0.91; P trend = 0.002). Several other SNPs also showed receptor status-specific susceptibility and evidence of roles in long-term survival, with the rare allele of BRIP1 rs2191249 showing evidence of association with a poorer prognosis (hazard ratio per minor allele, 1.20; 95% CI, 1.07-1.36; P trend = 0.002). In summary, there was little evidence of breast cancer susceptibility with any of the SNPs studied, but larger studies would be needed to confirm subgroup effects.

A comparison of trends in incidence and mortality rates of breast cancer, incidence to mortality ratio and stage at diagnosis between Arab and Jewish women in Israel, 1979–2002

In Israel, breast cancer is the most common malignancy in women, but there are large intra-population differences. The aim of this study was to compare the incidence and mortality, incidence to mortality rate ratio and stage at diagnosis of breast cancer between Arab and Jewish women in Israel. Data on all cases of breast cancer, stage at diagnosis and mortality were obtained from the National Cancer Registry and the Central Bureau of Statistics. Trends in age-specific and age-adjusted incidence and mortality rates, rate ratios and stage at diagnosis were examined for Arab and Jewish women during 1979-2002. Five-year survival rates for 1995-1999 were compared by stage. Among Arab women, age-adjusted incidence rates increased by 202.1%, from 14.1 per 100,000 in 1979-1981 to 42.6 in 2000-2002. Among Jewish women, the rates increased by 45.7%, from 71.1 per 100,000 women in 1979-1981 to 103.6 in 2000-2002. Incidence to mortality rate ratio increased for both population groups, but it is still lower among Arab women. In every age group, Arab women were more likely to be diagnosed at a more advanced stage of the disease. The rise in breast cancer incidence and mortality rates and the later stage of diagnosis among Arab women emphasize the urgent need for increasing early detection of breast cancer in the Arab population by improving rates of compliance with screening mammography.

Genetic polymorphism of XRCC3 Thr241Met and breast cancer risk: case-control study in Korean women and meta-analysis of 12 studies

To evaluate the relationship of genetic polymorphism in XRCC3 Thr(241)Met and the risk of breast cancer, a hospital-based case-control study was conducted in Korea. Histologically confirmed breast cancer cases (n = 574) and controls (n = 502) with no present or previous history of cancer were recruited from several teaching hospitals in Seoul during 1995-2001. Information on demographic characteristics and other information were collected by interviewed questionnaire. Genetic polymorphisms of XRCC3 Thr(241)Met (C > T) was determined by single base extention assay. The frequency of Thr/Thr, Thr/Met, and Met/Met genotype were 89.4, 10.4, 0.2% in cases and 92.3, 7.7, 0.0% in controls, respectively. Genotype distribution in controls fit well to the Hardy-Weinberg equilibrium (P = 0.74). XRCC3 codon 241 Thr/Met or Met/Met genotype moderately increased the risk of breast cancer (OR = 1.4, 95% CI: 0.87-2.33), but not significant in this study. In the results of meta-analysis using twelve reports, however, Thr/Met or Met/Met genotype increased the risk of breast cancer (OR = 1.08, 95%CI: 1.00-1.17). In conclusion, although the genetic polymorphism of XRCC3 Thr(241)Met was unlikely to have a substantial overall association in Korean women, the meta-analysis of studies, including ours, provided that Thr/Met and Met/Met was weakly increased the risk of breast cancer compare to Thr/Thr genotype.

The role of xenoestrogenic compounds in the development of breast cancer

Lifetime exposure to endogenous steroidal estrogens is an established risk factor for breast cancer, and exposures to other estrogenic and antiestrogenic compounds might also modify the risk of breast cancer. It has been hypothesized that synthetic estrogenic industrial pollutants such as organochlorine compounds and plant-derived estrogenic compounds also modify breast cancer risks; however, recent studies show that levels of organochlorine pollutants are similar in breast cancer patients and controls. There is evidence that synthetic and plant-derived estrogens are selective estrogen receptor modulators, which implies that these compounds can induce tissue-specific, time- and dose-dependent estrogenic or antiestrogenic responses. Therefore, the effects of synthetic or plant-derived estrogens on the incidence of breast cancer depend on both the levels and the timing of exposure to these compounds, particularly during stages of mammary gland development that are extremely sensitive to hormone levels.

Polymorphisms in DNA double-strand break repair genes and risk of breast cancer: two population-based studies in USA and Poland, and meta-analyses

The double-strand break DNA repair pathway has been implicated in breast carcinogenesis. We evaluated the association between 19 polymorphisms in seven genes in this pathway (XRCC2, XRCC3, BRCA2, ZNF350, BRIP1, XRCC4, LIG4) and breast cancer risk in two population-based studies in USA (3,368 cases and 2,880 controls) and Poland (1,995 cases and 2,296 controls). These data suggested weak associations with breast cancer risk for XRCC3 T241M and IVS7-14A>G (pooled odds ratio (95% confidence interval): 1.18 (1.04-1.34) and 0.85 (0.73-0.98) for homozygous variant vs wild-type genotypes, respectively), and for an uncommon variant in ZNF350 S472P (1.24 (1.05-1.48)), with no evidence for study heterogeneity. The remaining variants examined had no significant relationships to breast cancer risk. Meta-analyses of studies in Caucasian populations, including ours, provided some support for a weak association for homozygous variants for XRCC3 T241M (1.16 (1.04-1.30); total of 10,979 cases and 10,423 controls) and BRCA2 N372H (1.13 (1.10-1.28); total of 13,032 cases and 13,314 controls), and no support for XRCC2 R188H (1.06 (0.59-1.91); total of 8,394 cases and 8,404 controls). In conclusion, the genetic variants evaluated are unlikely to have a substantial overall association with breast cancer risk; however, weak associations are possible for XRCC3 (T241M and IVS7-14A>G), BRCA2 N372H, and ZNF350 S472P. Evaluation of potential underlying gene-gene interactions or associations in population subgroups will require even larger sample sizes.

Polymorphisms in DNA repair genes, medical exposure to ionizing radiation, and breast cancer risk

An epidemiologic study was conducted to determine whether polymorphisms in DNA repair genes modify the association between breast cancer risk and exposure to ionizing radiation. Self-reported exposure to ionizing radiation from medical sources was evaluated as part of a population-based, case-control study of breast cancer in African-American (894 cases and 788 controls) and White (1,417 cases and 1,234 controls) women. Genotyping was conducted for polymorphisms in four genes involved in repair of radiation-induced DNA damage, the double-strand break repair pathway: X-ray cross-complementing group 3 (XRCC3) codon 241 Thr/Met, Nijmegen breakage syndrome 1 (NBS1) codon 185 Glu/Gln, X-ray cross-complementing group 2 (XRCC2) codon 188 Arg/His, and breast cancer susceptibility gene 2 (BRCH2) codon 372 Asn/His. Allele and genotype frequencies were not significantly different in cases compared with controls for all four genetic polymorphisms, and odds ratios for breast cancer were close to the null. Combining women with two, three, and four variant genotypes, a positive association was observed between breast cancer and number of lifetime mammograms (P(trend) < 0.0001). No association was observed among women with zero or one variant genotype (P = 0.86). Odds ratios for radiation treatments to the chest and number of lifetime chest X-rays were slightly elevated but not statistically significant among women with two to four variant genotypes. The study has several limitations, including inability to distinguish between diagnostic and screening mammograms or reliably classify prediagnostic mammograms and chest X-rays in cases. Prospective studies are needed to address whether common polymorphisms in DNA repair genes modify the effects of low-dose radiation exposure from medical sources.

Correlation between nutritional biomarkers and breast cancer: a case-control study

A case-control study to explore associations between retinoids, tocopherols, total and beta-carotenes and breast cancer was conducted by analysing concentrations of these biomarkers in adipose tissue, cheek cells and plasma. A total of 414 French-Canadians in Montreal with new diagnoses of breast cancer were age-matched to 429 population-based controls. Subjects were interviewed using a questionnaire, and biological samples from 287 cases and 112 controls were collected within 3 months of the diagnosis. Mean beta carotene concentrations in cheek cells were significantly lower among controls. Odds ratios (ORs) from logistic regression analysis were used to compare higher and lower tercile concentrations. Significant positive associations were observed in adipose tissue for retinoid [OR=2.11; 95% CI (1.09-4.08)] and beta carotene [OR=3.18; 95% CI (1.70-5.93)]; in cheek cells for beta carotene [OR=2.22; 95% CI (1.21-4.50)] and for total carotenes [OR=2.94; 95% CI (1.59-5.42)] and in plasma for beta carotene [OR=1.53; 95% CI (0.80-2.93)] and total carotenes [OR=1.04; 95% CI (0.53-2.05)]. Among the control groups, significant Pearson correlations were observed between cheek cells and adipose tissue for total carotenes (r=0.27; p=0.01) and cheek cells and plasma (r=0.22; p=0.04). In contrast to previous works, this study shows that high concentrations of retinoids and carotenes in adipose tissue and cheek cells are associated with increased risk of breast cancer. However, all these studies are limited by small sample size. Although our study tested a limited number of controls, important associations were observed. These results suggest that the effect of disease on biomarkers is fundamental to the interpretation of epidemiological data. We suggest either that the high levels of these biomarkers found in cancer patients in this study may be due to the disease process that affects the pharmacokinetics of the biomarker or that the disease causes a change in dietary habits. In addition, in studies involving the application of biomarkers to cancer epidemiology it is imperative that a typical biomarker concentration is not associated with breast cancer risk before further examination of the methodological limitations of epidemiological studies investigating this relationship. Therefore, sample size, selection bias, information bias, and confounding should be considered in the design of studies investigating the aetiological relationship between biomarkers and breast cancer.

Residential mobility in the California Teachers Study: implications for geographic differences in disease rates

BACKGROUND

Especially for cancers with long latency periods, such as breast cancer, the issue of residential mobility hinders ecologic analyses seeking to examine the role of environmental contaminants in chronic disease etiology. This study describes and evaluates characteristics associated with residential mobility in a sub-sample of the California Teachers Study (CTS) cohort.

METHODS

In 2000, lifetime residential histories were collected for a sub-sample of 328 women enrolled in the CTS; women's degree of residential mobility and associated factors were analyzed.

RESULTS

While most women moved many times during their lives (average = 8.9), the average number of years at their residence when they enrolled in the study was reasonably long (15.1 years). Age strongly predicted duration at current residence but was not related to the number of lifetime residences. After adjusting for age, California-born women and women living in high socioeconomic status (SES) neighborhoods were significantly more residentially stable. Agreement between self-reported urbanization of recent residences and that based on census data of the geocoded residences was very good (80% concordant). Among women currently living in urban areas, an average of 43.3 years, or 77%, of their lifetimes were spent in urban residences; among women currently living in a rural area, an average of 37.3 years, or 67% of their lifetimes were spent in rural residences.

CONCLUSIONS

This suggests that analyses of incidence rates based on current residence, while not capturing a woman's full exposure history, may reasonably reflect some aspect of longer term chronic exposures, especially those related to urbanization, at least in professional women.

Double-Strand Break Repair Gene Polymorphisms and Risk of Breast or Ovarian Cancer

Deficiencies in DNA repair have been hypothesized to increase cancer risk and excess cancer incidence is a feature of inherited diseases caused by defects in DNA damage recognition and repair. We investigated, using a case-control design, whether the double-strand break repair gene polymorphisms RAD51 5' untranslated region -135 G > C, XRCC2 R188H G > A, and XRCC3 T241M C > T were associated with risk of breast or ovarian cancer in Australian women. Sample sets included 1,456 breast cancer cases and 793 age-matched controls ages under 60 years of age, 549 incident ovarian cancer cases, and 335 controls of similar age distribution. For the total sample and the subsample of Caucasian women, there were no significant differences in genotype distribution between breast cancer cases and controls or between ovarian cancer cases and combined control groups. The crude odds ratios (OR) and 95% confidence intervals (95% CI) associated with the RAD51 GC/CC genotype frequency was OR, 1.10; 95% CI, 0.80-1.41 for breast cancer and OR, 1.22; 95% CI, 0.92-1.62 for ovarian cancer. Similarly, there were no increased risks associated with the XRCC2 GA/AA genotype (OR, 0.98; 95% CI, 0.76-1.26 for breast cancer and OR, 0.93; 95% CI, 0.69-1.25 for ovarian cancer) or the XRCC3 CT/TT genotype (OR, 0.92; 95% CI, 0.77-1.10 for breast cancer and OR, 0.87; 95% CI, 0.71-1.08 for ovarian cancer). Results were little changed after adjustment for age and other measured risk factors. Although there was little statistical power to detect modest increases in risk for the homozygote variant genotypes, particularly for the rare RAD51 and XRCC2 variants, the data suggest that none of these variants play a major role in the etiology of breast or ovarian cancer.

Residential proximity to agricultural pesticide use and incidence of breast cancer in the California Teachers Study cohort

We examined the association between residential proximity to agricultural pesticide use and breast cancer incidence among members of the California Teachers Study cohort, a large study of professional school employees with extensive information on breast cancer risk factors, followed for cancer incidence since 1995. We identified 1552 invasive breast cancer cases, diagnosed between 1996 and 1999, among 114,835 cohort members. We used California Pesticide Use Reporting data to select pesticides for analysis based on use volume, carcinogenic potential, and exposure potential; a Geographic Information System was used to estimate pesticide applications within a half-mile radius of subjects' residences. We applied Cox proportional hazard models to estimate hazard rate ratios (HR) for selected pesticides, adjusting for age, race, and socioeconomic status. We saw no association between residential proximity to recent agricultural pesticide use and invasive breast cancer incidence. HR estimates for the highest compared to the lowest exposure categories for groups of agents were as follows: probable or likely carcinogens (1.07, 95% confidence interval (CI): 0.86-1.32), possible or suggestive carcinogens (1.06, 95% CI: 0.87-1.29), mammary carcinogens (1.15, 95% CI: 0.90-1.48), and endocrine disruptors (1.03, 95% CI: 0.86-1.25). HR estimates for other groups and individual pesticides did not differ from unity, nor was there a trend for any groupings of or individual pesticides examined. Stratifying by menopausal status or family history of breast cancer did not substantially affect our results. Our analyses suggest that breast cancer incidence is not elevated in areas of recent, high agricultural pesticide use in California.

ATM and genome maintenance: defining its role in breast cancer susceptibility

The ATM gene is mutated in ataxia-telangiectasia (A-T), a genetic instability syndrome characterized by increased cancer risk, as well as other features. Recent studies have shown that the ATM protein kinase plays a critical role in maintaining genome integrity by activating a biochemical chain reaction that in turn leads to cell cycle checkpoint activation and repair of DNA damage. ATM targets include well-known tumor suppressor genes such as p53 and BRCA1, both of which play an important role in predisposition to breast cancer. Studies of A-T families have consistently reported an increased risk of breast cancer in women with one mutated ATM gene, but so far an increased frequency of ATM mutations has not been found in women with breast cancer. Some specific missense and protein truncating variants of ATM have been reported to confer increased breast cancer risk, but the magnitude of this risk remains uncertain. A more comprehensive analysis of ATM is needed in large case-control studies, and in multiple-case breast cancer families.

Study design: evaluating gene-environment interactions in the etiology of breast cancer - the WECARE study

INTRODUCTION

Deficiencies in cellular responses to DNA damage can predispose to cancer. Ionizing radiation can cause cluster damage and double-strand breaks (DSBs) that pose problems for cellular repair processes. Three genes (ATM, BRCA1, and BRCA2) encode products that are essential for the normal cellular response to DSBs, but predispose to breast cancer when mutated.

DESIGN

To examine the joint roles of radiation exposure and genetic susceptibility in the etiology of breast cancer, we designed a case-control study nested within five population-based cancer registries. We hypothesized that a woman carrying a mutant allele in one of these genes is more susceptible to radiation-induced breast cancer than is a non-carrier. In our study, 700 women with asynchronous bilateral breast cancer were individually matched to 1400 controls with unilateral breast cancer on date and age at diagnosis of the first breast cancer, race, and registry region, and counter-matched on radiation therapy. Each triplet comprised two women who received radiation therapy and one woman who did not. Radiation absorbed dose to the contralateral breast after initial treatment was estimated with a comprehensive dose reconstruction approach that included experimental measurements in anthropomorphic and water phantoms applying patient treatment parameters. Blood samples were collected from all participants for genetic analyses.

CONCLUSIONS

Our study design improves the potential for detecting gene-environment interactions for diseases when both gene mutations and the environmental exposures of interest are rare in the general population. This is particularly applicable to the study of bilateral breast cancer because both radiation dose and genetic susceptibility have important etiologic roles, possibly by interactive mechanisms. By using counter-matching, we optimized the informativeness of the collected dosimetry data by increasing the variability of radiation dose within the case-control sets and enhanced our ability to detect radiation-genotype interactions.

Molecular epidemiology of sporadic breast cancer. The role of polymorphic genes involved in oestrogen biosynthesis and metabolism

The major known risk factors for female breast cancer are associated with prolonged exposure to increased levels of oestrogen. The predominant theory relates to effects of oestrogen on cell growth. Enhanced cell proliferation, induced either by endogenous or exogenous oestrogens, increases the number of cell divisions and thereby the possibility for mutation. However, current evidence also supports a role for oxidative metabolites, in particular catechol oestrogens, in the initiation of breast cancer. As observed in drug and chemical metabolism, there is considerable interindividual variability (polymorphism) in the conjugation pathways of both oestrogen and catechol oestrogens. These person-to-person differences, which are attributed to polymorphisms in the genes encoding for the respective enzymes, might define subpopulations of women with higher lifetime exposure to hormone-dependent growth promotion, or to cellular damage from particular oestrogens and/or oestrogen metabolites. Such variation could explain a portion of the cancer susceptibility associated with reproductive effects and hormone exposure. In this paper the potential role of polymorphic genes encoding for enzymes involved in oestrogen biosynthesis (CYP17, CYP19, and 17beta-HSD) and conversion of the oestrogen metabolites and their by-products (COMT, CYP1A1, CYP1B1, GSTM1, GSTM3, GSTP1, GSTT1 and MnSOD) in modulating individual susceptibility to breast cancer are reviewed. Although some of these low-penetrance genes appeared as good candidates for risk factors in the etiology of sporadic breast cancer, better designed and considerably larger studies than the majority of the studies conducted so far are evidently needed before any firm conclusions can be drawn.

Carcinogenic and endocrine disrupting effects of cigarette smoke and risk of breast cancer

BACKGROUND

Results of epidemiological studies, assessing the relation between smoking and breast cancer, have been inconclusive. Our aim was to assess the carcinogenic and possibly antioestrogenic effects of cigarette smoke on risk of breast cancer.

METHODS

We sent a questionnaire to 1431 women younger than age 75 years who had breast cancer and were listed on the population-based British Columbia cancer registry between June 1, 1988, and June 30, 1989. We also sent questionnaires to 1502 age-matched controls, randomly selected from the 1989 provincial voters list. We obtained information on all known and suspected risk factors for breast cancer, and on lifetime smoking, alcohol consumption, and occupational history. We assessed the effect of smoking separately for premenopausal and postmenopausal women, adjusting for confounding variables.

FINDINGS

318 premenopausal women and 340 controls replied. Risk of breast cancer was significantly increased (adjusted odds ratio 1.69, 95% CI 1.13-2.51) in women who had been pregnant and who started to smoke within 5 years of menarche, and in nulliparous women who smoked 20 cigarettes daily or more (7.08, 1.63-30.8) and had smoked for 20 cumulative pack-years or more (7.48, 1.59-35.2). Postmenopausal women (700 breast cancer and 685 controls) whose body-mass index increased from age 18 to current and who started to smoke after a first fullterm pregnancy had a significantly reduced risk of breast cancer (0.49, 0.27-0.89).

INTERPRETATION

Our results suggest that cigarette smoke exerts a dual action on the breast, with different effects in premenopausal and postmenopausal women. Our observations reinforce the importance of smoking prevention, especially in early adolescence, and draw attention to the timing of exposure in relation to susceptibility and refractory windows in the design of studies to investigate associations between environmental carcinogens or putative endocrine disruptors and risk of breast cancer.

The value of adjuvant treatment in young women with breast cancer

The postoperative management of breast cancer is an ever-changing field. Young patients, in particular, have attracted recent interest as it has become apparent that age alone is a poor prognostic indicator for breast cancer. Adjuvant therapies indisputably delay breast cancer recurrence and save lives, and should be considered for all young patients. Chemotherapy is increasingly being considered appropriate for all women under the age of 35 years, regardless of other risk factors, but poses the particularly difficult problem of infertility for these young women. As the additional benefits of anthracyclines and taxanes in the adjuvant setting become clear, chemotherapy regimens are also becoming increasingly intensive and the risk of myocardial damage and leukaemia should not be ignored. The benefits of chemotherapy need to be weighed against the possible dangers, and therapy should be individualised according to cancer pathology and patient circumstance. Tamoxifen should be given for 5 years to all women whose cancer is estrogen receptor positive, regardless of whether the patient has received chemotherapy. If chemotherapy is not given, the addition of luteinising hormone-releasing hormone (LHRH) agonists to tamoxifen in patients with estrogen receptor positive breast cancers appears to be beneficial. The addition of LHRH agonists to chemotherapy and tamoxifen is currently being evaluated in randomised trials. Radiotherapy should be given after breast conservation surgery, and should include the axilla if nodes are involved and the axilla has not been surgically cleared. Chest wall radiotherapy should be considered following mastectomy in young women considered at high risk of local recurrence, but the long-term morbidity and mortality of local radiation therapy, which is increased in young women, needs to be considered.

Active and passive smoking in breast cancer: prospective results from the Nurses' Health Study

BACKGROUND

The role of active and passive smoking in breast cancer remains controversial.

METHODS

Using data collected in the prospective Nurses' Health Study, we examined the influence of active and passive smoking on the incidence of invasive breast cancer. The analysis was based on women responding to the 1982 questionnaire, which included questions on passive smoking exposure. Information on active smoking was collected in biennial questionnaires. A total of 78,206 women were followed prospectively from 1982 until June 1996.

RESULTS

Of these women, 3,140 reported a diagnosis of invasive breast cancer during follow-up. Compared with never active smoking, relative risks (RR) of breast cancer were 1.04 (95% CI = 0.94-1.15) for current active smoking and 1.09 (95% CI = 1.00-1.18) for past active smoking. The RR for regular passive exposure at work and at home was 0.90 (95% CI = 0.67-1.22). For active smoking, a modest increase in risk was confined to women who began smoking before the age of 17 (RR = 1.19; 95% CI = 1.03-1.37).

CONCLUSION

Results suggest that passive smoking is unrelated to breast cancer. However, results for active smoking are compatible with a small increase in risk when smoking is initiated at young ages.

Characterization of a major aromatic DNA adduct detected in human breast tissues

A bulky DNA adduct (Spot 1) was previously detected in normal adjacent breast tissues of 41% (36/87) of women with breast cancer and in none (0/29) of the noncancer controls by (32)P-postlabeling. To characterize this adduct, it was chromatographically compared with DNA adduct profiles generated in several in vitro and in vivo experimental systems. First, MCF-7 cells were exposed to a number of chemical carcinogens, that is, benzo[a]pyrene (B[a]P), 4-OH-B[a]P, 9-OH-B[a]P, 11-OH-B[a]P, B[a]P-trans-4,5-dihydrodiol, 1-nitropyrene, 6-nitrochrysene, dibenzo[a,l]pyrene, benzo[c]phenanthrene, dibenzo[a,h]anthracene, 3-methylcholanthrene, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. Spot 1 was detected as a minor adduct in cells treated with B[a]P but not other compounds. Second, to determine whether Spot 1 is derived from lipid peroxidation products or estrogen metabolites, it was compared with adduct profiles of cells or DNAs exposed to 17beta-estradiol, 4-hydroxy estradiol, 4-hydroxynonenal, or oxidized oat oil. Spot 1 was not detectable in these samples. In addition, Spot 1 did not comigrate with the 1,N(2)-ethenodeoxyguanosine adduct standard. Third, to explore the mechanism of Spot 1 formation, it was compared with adduct profiles detected in DNA or mononucleotides reacted with BPDE, 1-OH-7,8-dihydrodiol of B[a]P, and 3-OH-7,8-dihydrodiol of B[a]P as well as in rats orally treated with B[a]P. Spot 1 comigrated with a minor adduct in BPDE-treated DNA during anion exchange rechromatography but these two adducts were separated by partition chromatography. Spot 1 also behaved in a manner that was very similar to that of the polar B[a]P adducts detected in rat liver, but the two adducts were separated by HPLC. Fourth, Spot 1 was compared with CD1 mice exposed to 7H-benzo[c]fluorene (B[c]F). Spot 1 from some patients comigrated with a major adduct induced by B[c]F. Finally, we found that the presence of Spot 1 in human breast tissues was not related to smoking status but, rather, with CYP1A1 MspI polymorphism. The CYP1A1 mutant carriers had a significantly higher frequency of this adduct than did the wild-type genotypes. Furthermore, individuals with Spot 1 had a significantly higher staining intensity for BPDE-PAH adducts in their tissue sections than those without it. These results demonstrate that this major bulky DNA adduct detected in human breast tissues is related to PAH exposure.

Breast cancer, occupation, and exposure to electromagnetic fields among Swedish men

BACKGROUND

Investigations of breast cancer among men may provide clues for environmental and occupational risk factors that may be difficult to study in women, because of confounding or effect modification from reproductive female characteristics. The objective was to estimate occupation-specific risks of male breast cancer and to assess the effect of occupational exposure to extremely low-frequency magnetic fields (ELFMF).

METHODS

Standardized incidence ratios were computed for the period 1971-1989 among Swedish men who were 25-59 years of age at start of follow-up and gainfully employed in 1970. Log-linear Poisson models were fitted to adjust for geographical area. A job exposure matrix was used to classify occupational ELFMF exposure.

RESULTS

A marked and consistent excess risk was found for machinery repairers. Increased relative risks based on few cases were also noted for librarians/archivists/curators, bank employees, non-specified clerical workers, metal processing workers, tanners/fur dressers, policemen, and custom surveillance officials. The relative risk among subjects with an estimated ELFMF exposure above the first quartile (0.12 microT) was 1.31 (95% confidence interval = 0.94-1.81), without a clear exposure-response pattern. Indications of an exposure-response relationship were found in workers with intermittent ELFMF exposure.

CONCLUSIONS

The findings give no clear evidence for an etiological role of ELFMF in the development of breast cancer in men, but suggest that large variations in exposure over the work-day may be associated with an increased risk.

Tumour biology of a breast cancer at least partly reflects the biology of the tissue/epithelial cell of origin at the time of initiation - a hypothesis

A hypothesis is presented suggesting that initiation of breast epithelial cell freezes the cell at least partly according to the development/differention of cell at the time of initiation. Tumour biology will mimic the physiology of normal cell development at the time of initiation and this is preserved at least partly onwards. Also preferentially, tumours will develop from the cell type that is proliferating at the time of initiation. This may explain the overrepresentation of different types of histology in breast cancer in relation to age of the woman. The development of each tumour may follow at least partly a distinct pathway of evolution.

Evaluation and treatment of BRCA-positive patients

The recent discovery of the breast cancer-associated genes BRCA1 and BRCA2 has now made it possible to identify individuals who are at a very high risk for the future development of breast cancer. To some extent, however, society has fallen victim to its molecular genetic technology. The significance of these discoveries to the detection, treatment, and prevention of breast cancer cannot be overstated. Nevertheless, the appropriate administration and interpretation of BRCA genetic testing and the treatment of BRCA-positive patients remain controversial issues. Complexities of BRCA testing require that such genetic screening be restricted to selected high-risk patients and that test results be interpreted by a knowledgeable molecular geneticist. Although no medical prophylaxis has been demonstrated to be of benefit in BRCA-positive patients, recent evidence suggests that a prophylactic mastectomy, with or without reconstruction, is a reasonable treatment option that substantially reduces cancer risk.

High-risk occupations for breast cancer in the Swedish female working population

OBJECTIVES

The purpose of this study was to estimate, for the period 1971 through 1989, occupation-specific risks of breast cancer among Swedish women employed in 1970.

METHODS

Age-period standardized incidence ratios were computed. Log-linear Poisson models were fitted, with geographical area and town size taken into account. Risks were further adjusted for major occupational group, used as a proxy for socioeconomic status. Risk estimators were also calculated for women reporting the same occupation in 1960 and 1970.

RESULTS

Most elevated risks among professionals, managers, and clerks were reduced when intragroup comparisons were carried out, indicating the confounding effect of socioeconomic status. Excess risks were found for pharmacists, teachers of theoretical subjects, schoolmasters, systems analysts and programmers, telephone operators, telegraph and radio operators, metal platers and coaters, and hairdressers and beauticians, as well as for women working in 1960 and 1970 as physicians, religious workers, social workers, bank tellers, cost accountants, and telephonists.

CONCLUSIONS

While the high risks observed among professional, administrative, and clerical workers might be related to lower birth rates and increased case detection, excess risks found for telephone workers and for hairdressers and beauticians deserve further attention.

Assessing individual risk for breast cancer: risky business

There is increasing demand for prediction of individual women's risk for breast cancer from women, clinicians, researchers, and health planners. Risk assessment for breast cancer is the process of identifying characteristics of an individual woman that are relevant to her risk, and combining those characteristics into a quantitative or qualitative risk profile. This article reviews and compares available methods of predicting risk, discusses benefits and drawbacks to the methods, and compares risk estimates for several hypothetical subjects using the different methods. Current and future uses for risk assessment are described. Risk assessment, while a promising tool for research now, and for clinical areas in the future, is still too imprecise for accurate prediction of breast cancer occurrence in individuals.

Breast cancer following treatment for Hodgkin's disease: the need for screening in a young population. Australasian Radiation Oncology Lymphoma Group (AROLG)

Several recent publications have highlighted the issue of an increased risk of breast cancer in women treated with radiotherapy, chemotherapy, or combined modality therapy for Hodgkin's disease. The risk is greatest in women 30 years or younger at the time of treatment. In the Australasian Radiation Oncology Lymphoma Group database, 60% of women fell into this age category. This article reviews the available data pertaining to induction of breast cancer by radiotherapy for Hodgkin's disease. Breast examination should now be an integral part of the long term follow up for these women. There is also a case for the use of screening mammography. Any breast mass developing subsequent to treatment for Hodgkin's disease should be regarded with a high index of clinical suspicion and, accordingly, biopsies should be performed in the majority of cases, even when mammography is negative.

Studying environmental influences and breast cancer risk: suggestions for an integrated population-based approach

Increased attention has focused in recent years on environmental exposures which may elevate risk of human breast cancer. Following a brief introduction to the topic, we present a summary of recent evidence regarding the role of chlorinated hydrocarbons (e.g. pesticides), occupational exposures (e.g. electromagnetic fields), dietary factors, and other hydrocarbons (e.g. tobacco). Next, we present suggestions for additional measurements which may help to clarify the contribution of environmental factors, including individual and ecologic level exposure histories, polymorphisms in carcinogen-metabolizing enzymes, and interactions among environmental exposures, breast tumor characteristics, and other risk factors for breast cancer. Finally, we discuss how a population-based approach may be used to integrate these sources of information and could provide new clues regarding the role of environmental influences in breast cancer.

Epidemiology and primary prevention of cancers of the breast, endometrium, and ovary. A brief overview

Cancers of the breast, endometrium, and ovary account for 41% of incident cancers among women. Many risk factors for breast cancer have been identified, but most are associated with only modest elevations in risk. Also, of all the risk factors identified, few are likely to be affected by intervention programs. The pathogenesis of breast cancer is not well understood, but estrogen and possibly estrogen plus progesterone are likely to be etiologically involved. For endometrial cancer, a major etiologic pathway is exposure to estrogen without cyclic exposure to progesterone. Most of the established risk factors for endometrial cancer appear to affect risk at least in part through this pathway. Only a few risk factors for ovarian cancer have been identified. The two most commonly suggested etiologic mechanisms for ovarian cancer are (a) that suppression of ovulation reduces risk and (b) that suppression of pituitary gonadotropins reduces risk. Each hypothesis is consistent with some, but not all, of the data. Prospects for the primary prevention of these cancers are discouraging at present because few of the risk factors identified to date are readily subject to modification, especially for breast cancer, and the underlying etiologies of these cancers are not well understood, particularly for breast and ovarian cancers.