The NICHD Women's Contraceptive and Reproductive Experiences Study: methods and operational results

Pregnancy, abortion, and birth control methods' complicity with breast cancer occurrence

Reproductive factors play significantly important roles in determining the breast cancer (BC) risk. The impact of pregnancy, abortion, and birth control methods on tumor development remains unclear. It has been found that early full-term pregnancies in young women can lower their lifetime risk of developing the type of cancer in question. However, having a first full-term pregnancy at an older age can increase this risk. The relationship between pregnancy and breast cancer (BC) is, however, much more complicated. Both induced and spontaneous abortions lead to sudden changes in hormonal balance, which could cause different effects on sensitive breast epithelial cells, making abortion a potential risk factor for breast cancer. The influence of hormonal contraception on carcinogenesis is not comprehensively understood, and therefore, more exhaustive analysis of existing data and further investigation is needed. This review explores how the mentioned reproductive factors affect the risk of breast cancer (BC), focusing on the molecular mechanisms that contribute to its complexity. By comprehending this intricate network of relationships, we can develop new strategies for predicting and treating the disease.

Web-Based Survey Piloting Process as a Model for Developing and Testing Past Contraceptive Use and Pregnancy History: Cystic Fibrosis Case Study

BACKGROUND

Individuals with complex, chronic diseases are now living longer, making reproductive health an important topic to address in the health care setting. Self-respondent surveys are a feasible way to collect past contraceptive use and pregnancy history to assess contraceptive safety and effectiveness. Because sensitive topics, such as contraception and pregnancy outcomes, can vary across social groups or cultures, piloting questions and evaluating survey administration procedures in the target population are necessary for precise and reliable responses before wide distribution.

OBJECTIVE

This study aimed to develop a precise and reliable survey instrument and related procedures among individuals with cystic fibrosis regarding contraceptive use and obstetrical history.

METHODS

We piloted and tested web-based questions related to contraceptive use and pregnancy history among 50 participants with and those without cystic fibrosis aged 18 to 45 years using a 3-tier process. Findings from each tier informed changes to the questionnaire before testing in the subsequent tier. Tier 1 used cognitive pretesting to assess question understanding and the need for memory prompts. In tier 2, we used test-retest self- and interviewer-administered approaches to assess question reliability, evaluate response missingness, and determine confidence between 2 types of survey administration approaches. In tier 3, we tested the questionnaire for clarity, time to complete, and whether additional prompts were necessary.

RESULTS

In tier 1, respondents suggested improvements to the web-based survey questions and to the written and visual prompts for better recall regarding past contraceptive use. In tier 2, the test-retest reliability between self- and interviewer-administrative procedures of "ever use" contraceptive method questions was similar, with percent absolute agreement ranging between 84% and 100%. When the survey was self-administered, the percentage of missing responses was higher and respondent confidence about month and year when contraceptive methods were used was lower. Most respondents reported that they preferred the self-administered survey because it was more convenient and faster to complete.

CONCLUSIONS

Our 3-tier process to pilot web-based survey questions related to contraceptive and obstetrical history in our complex disease population helped us tailor content and format questions before wide dissemination to our target population. Results from this pilot study informed the subsequent larger study design to include a 10% respondent test-retest self- and interviewer-administered quality control component to better inform imputation procedures of missing data.

A Validated Risk Prediction Model for Breast Cancer in US Black Women

PURPOSE

Breast cancer risk prediction models are used to identify high-risk women for early detection, targeted interventions, and enrollment into prevention trials. We sought to develop and evaluate a risk prediction model for breast cancer in US Black women, suitable for use in primary care settings.

METHODS

Breast cancer relative risks and attributable risks were estimated using data from Black women in three US population-based case-control studies (3,468 breast cancer cases; 3,578 controls age 30-69 years) and combined with SEER age- and race-specific incidence rates, with incorporation of competing mortality, to develop an absolute risk model. The model was validated in prospective data among 51,798 participants of the Black Women's Health Study, including 1,515 who developed invasive breast cancer. A second risk prediction model was developed on the basis of estrogen receptor (ER)-specific relative risks and attributable risks. Model performance was assessed by calibration (expected/observed cases) and discriminatory accuracy (C-statistic).

RESULTS

The expected/observed ratio was 1.01 (95% CI, 0.95 to 1.07). Age-adjusted C-statistics were 0.58 (95% CI, 0.56 to 0.59) overall and 0.63 (95% CI, 0.58 to 0.68) among women younger than 40 years. These measures were almost identical in the model based on estrogen receptor-specific relative risks and attributable risks.

CONCLUSION

Discriminatory accuracy of the new model was similar to that of the most frequently used questionnaire-based breast cancer risk prediction models in White women, suggesting that effective risk stratification for Black women is now possible. This model may be especially valuable for risk stratification of young Black women, who are below the ages at which breast cancer screening is typically begun.

Theory, methods, and operational results of the Young Women's Health History Study: a study of young-onset breast cancer incidence in Black and White women

Purpose

The etiology of young-onset breast cancer (BC) is poorly understood, despite its greater likelihood of being hormone receptor-negative with a worse prognosis and persistent racial and socioeconomic inequities. We conducted a population-based case–control study of BC among young Black and White women and here discuss the theory that informed our study, exposures collected, study methods, and operational results.

Methods

Cases were non-Hispanic Black (NHB) and White (NHW) women age 20–49 years with invasive BC in metropolitan Detroit and Los Angeles County SEER registries 2010–2015. Controls were identified through area-based sampling from the U.S. census and frequency matched to cases on study site, race, and age. An eco-social theory of health informed life-course exposures collected from in-person interviews, including socioeconomic, reproductive, and energy balance factors. Measured anthropometry, blood (or saliva), and among cases SEER tumor characteristics and tumor tissue (from a subset of cases) were also collected.

Results

Of 5,309 identified potentially eligible cases, 2,720 sampled participants were screened and 1,812 completed interviews (682 NHB, 1140 NHW; response rate (RR): 60%). Of 24,612 sampled control households 18,612 were rostered, 2,716 participants were sampled and screened, and 1,381 completed interviews (665 NHB, 716 NHW; RR: 53%). Ninety-nine% of participants completed the main interview, 82% provided blood or saliva (75% blood only), and SEER tumor characteristics (including ER, PR and HER2 status) were obtained from 96% of cases.

Conclusions

Results from the successfully established YWHHS should expand our understanding of young-onset BC etiology overall and by tumor type and identify sources of racial and socioeconomic inequities in BC.

Supplementary Information

The online version of this article contains supplementary material available (10.1007/s10552-021-01461-x).

Breast cancer risk factor evaluation in a Western Himalayan state: A case-control study and comparison with the Western World

Context:

Breast cancer incidence is increasing rapidly in India. The lifestyle, built, genetic makeup, reproductive and breastfeeding patterns are quite different in Indian females when compared to the Western population. Generalizing the Western data to the population residing in the Himalayan region would breed inaccuracies.

Aim:

The aim of our study was to identify risk factors in our own population in a Western Himalayan state of Himachal Pradesh, India.

Subjects and Methods:

A case–control study with 377 cases of invasive breast cancer and 346 hospital-based controls was conducted for 1 year. The data were collected by interviewing the individuals during their visit to hospital using a questionnaire. The data were analyzed using standard statistical techniques using SPSS version 17 software.

Results:

Factors found to have strong association with invasive breast cancer on multivariate analysis are late age at first childbirth >30 years, which is the strongest risk factor associated, late age of menopause > 50 years, high socioeconomic class, and age of female above 50 years.

Conclusion:

In our females, age >50 years, late age of menopause (>50 years), late age at first childbirth (>30 years), and high socioeconomic status were found to be major risk factors associated with breast cancer. Several factors implicated in the Western data were not found to be significant in our study. We need to identify such aspects in reproductive and breastfeeding patterns of women and spread awareness regarding the same.

Pre-diagnosis alcohol consumption and mortality risk among black women and white women with invasive breast cancer

Background

Alcohol consumption is associated with increased risk of breast cancer; however, its association with subsequent risk of breast cancer death is unclear.

Methods

We followed 4523 women with complete information on relevant risk factors for mortality; these women were 35 to 64 years of age when diagnosed with incident invasive breast cancer between 1994 and 1998. During follow up (median, 8.6 years), 1055 women died; 824 died from breast cancer. The information on alcohol consumption before diagnosis was collected shortly after breast cancer diagnosis (average: 5.1 months) during an in-person interview which used a structured questionnaire. Multivariable Cox proportional hazards regression models provided hazard ratios (HRs) and 95% confidence intervals (CIs) for breast cancer-specific mortality, mortality due to causes other than breast cancer, and all-cause mortality associated with alcohol consumption from age 15 years until breast cancer diagnosis and during recent periods of time prior to breast cancer diagnosis.

Results

Average weekly alcohol consumption from age 15 years until breast cancer diagnosis was inversely associated with breast cancer-specific mortality (P_trend = 0.01). Compared to non-drinkers, women in the highest average weekly alcohol consumption category (≥7 drinks/week) had 25% lower risk of breast cancer-specific mortality (HR = 0.75, 95% CI = 0.56–1.00). Breast cancer mortality risk was also reduced among women in the highest average weekly alcohol consumption category in two recent time periods (5-year period ending 2-years prior to breast cancer diagnosis, HR = 0.74, 95% CI = 0.57–0.95; 2-year period immediately prior to breast cancer diagnosis: HR = 0.73, 95% CI = 0.56–0.95). Furthermore, analyses of average weekly alcohol consumption by beverage type from age 15 years until breast cancer diagnosis suggested that wine consumption was inversely associated with breast cancer-specific mortality risk (wine P_trend = 0.06, beer P_trend = 0.24, liquor P_trend = 0.74). No association with any of these alcohol consumption variables was observed for mortality risk due to causes other than breast cancer.

Conclusions

Overall, we found no evidence that alcohol consumption before breast cancer diagnosis increases subsequent risk of death from breast cancer.

CYP2D6-inhibiting medication use and inherited CYP2D6 variation in relation to adverse breast cancer outcomes after tamoxifen therapy

PURPOSE

Tamoxifen is widely used to reduce the risk of breast cancer (BC) recurrence and extend disease-free survival among women with estrogen-sensitive breast cancers. Tamoxifen efficacy is thought to be attributable to its active metabolite, which is formed through a reaction catalyzed by the P450 enzyme, CYP2D6. Inhibition of tamoxifen metabolism as a result of germline genetic variation and/or use of CYP2D6-inhibiting medications ("inhibitors") is hypothesized to increase the risk of adverse BC outcomes among women taking tamoxifen.

METHODS

The present cohort study of 960 women diagnosed with early-stage BC between 1993 and 1999 examined the association between concomitant use of CYP2D6 inhibitors and adjuvant tamoxifen and the risk of adverse BC outcomes (recurrence, second primary BC, BC mortality), both overall and according to CYP2D6 metabolic phenotype.

RESULTS

Six or more months of CYP2D6 inhibitor use concomitant with tamoxifen was not associated with any appreciable increase in risk of recurrence or second primary BC or BC mortality, and there was no clear evidence of variation by CYP2D6 metabolic phenotype.

CONCLUSIONS

These results are consistent with the relatively few other large, population-based studies conducted to date that have not observed an increased risk of adverse BC outcomes associated with CYP2D6 inhibition.

Breast Cancer Diagnostic Methods: Screen-Detected and Clinical Cases. An Italian Survey of Women's Experiences

Aims and Background

The real practice of breast cancer diagnosis and treatment is often very different from guideline recommendations. Screening programs should minimize deviations from “best practice”. The aim of the study was to compare cases detected by screening programs with cases that were not part of the public screening program, analyzing the diagnostic pathways from the first suspected breast problem to therapeutic intervention for breast cancer.

Methods

We interviewed a random sample of 268 women aged 49–70 years in three Italian regions (Lazio, Tuscany, Basilicata) who were treated for breast cancer, stratified by screening participation.

Results

In the nonscreened group, 48% of women were symptomatic and 50% were diagnosed by preventive tests. The proportion of women treated within 30 days of diagnosis was significantly lower in the screened group, 21.3% vs 35.8% (P = 0.0003). The mean number of tests (mammography, ultrasonography, cytology and histology) performed in the screened group was significantly higher than in the nonscreened group, 3.7 vs 2.8 (P = 0.001). The percentage of women treated without a preoperative histological or cytological diagnosis was lower in the screened group than in the nonscreened group, 14% vs 25% (P = 0.024).

Conclusion

Participation in screening programs seems to lead to more appropriate disease management even for breast cancer cases treated at the same hospital.

Body mass index at age 18 years and recent body mass index in relation to risk of breast cancer overall and ER/PR/HER2-defined subtypes in white women and African-American women: a pooled analysis

BACKGROUND

Although it has been well-documented that obesity is associated with decreased risk of premenopausal breast cancer and increased risk of postmenopausal breast cancer, it is unclear whether these associations differ among breast cancer subtypes defined by the tumor protein expression status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2).

METHODS

We evaluated the associations of body mass index (BMI) at age 18 years and recent BMI in relation to risk of breast cancer overall and ER/PR/HER2-defined subtypes, in 6320 women (3934 case-patient participants, 2386 control participants) aged 35-64 years, who participated in one of three population-based case-control studies. We estimated multivariable-adjusted odd ratios (ORs) and corresponding 95% confidence intervals (CIs) using polychotomous unconditional logistic regression methods for case-control comparisons in premenopausal women and postmenopausal women.

RESULTS

BMI at age 18 years was inversely associated with risk of breast cancer, particularly among premenopausal women (≥ 25 vs. < 20 kg/m2, OR = 0.72, 95% CI = 0.53-0.96; per 5 kg/m2 increase, OR = 0.83, 95% CI = 0.73-0.95). This inverse association did not differ across ER/PR/HER2-defined subtypes or by race (white women, African-American women). Recent BMI was not associated with risk of premenopausal breast cancer after adjustment for BMI at age 18 years; nevertheless, the analysis for the joint effects of BMI at age 18 years and recent BMI showed that premenopausal women in the highest categories of the two BMI measures (≥ 25 kg/m2 at age 18 years and ≥ 30 kg/m2 for recent BMI) had 46% lower risk of breast cancer than premenopausal women in the lowest categories of the two BMI measures (< 20 kg/m2 at age 18 years and < 25 kg/m2 for recent BMI; OR = 0.54, 95% CI = 0.38-0.78). Neither measure of BMI was statistically significantly associated with risk of postmenopausal breast cancer.

CONCLUSION

Our findings indicate that high BMI near the end of adolescence decreases risk of all ER/PR/HER2-defined subtypes of premenopausal breast cancer and also suggest that this benefit could be maximized among premenopausal women who consistently have high BMI during their premenopausal years.

Reproductive factors and the risk of triple-negative breast cancer in white women and African-American women: a pooled analysis

BACKGROUND

Early age at menarche, nulliparity, late age at first completed pregnancy, and never having breastfed, are established breast cancer risk factors. However, among breast cancer subtypes, it remains unclear whether all of these are risk factors for triple-negative breast cancer (TNBC).

METHODS

We evaluated the associations of these reproductive factors with TNBC, in 2658 patients with breast cancer (including 554 with TNBC) and 2448 controls aged 20-64 years, who participated in one of the three population-based case-control studies: the Women's Contraceptive and Reproductive Experiences Study, the Women's Breast Carcinoma in situ Study, or the Women's Learning the Influence of Family and Environment Study. We used multivariable polychotomous unconditional logistic regression methods to conduct case-control comparisons among breast cancer subtypes defined by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 expression status.

RESULTS

TNBC risk decreased with increasing duration of breastfeeding (P trend = 0.006), but age at menarche, age at first completed pregnancy, and nulliparity were not associated with risk of TNBC. Parous women who breastfed for at least one year had a 31% lower risk of TNBC than parous women who had never breastfed (odds ratio, OR = 0.69; 95% confidence interval, CI = 0.50-0.96). The association between breastfeeding and risk of TNBC was modified by age and race. Parous African-American women aged 20-44 years who breastfed for 6 months or longer had an 82% lower risk of TNBC than their counterparts who had never breastfed (OR = 0.18, 95% CI = 0.07-0.46).

CONCLUSIONS

Our data indicate that breastfeeding decreases the risk of TNBC, especially for younger African-American women.

Genetic variants in microRNA and microRNA biogenesis pathway genes and breast cancer risk among women of African ancestry

MicroRNAs (miRNA) regulate breast biology by binding to specific RNA sequences, leading to RNA degradation and inhibition of translation of their target genes. While germline genetic variations may disrupt some of these interactions between miRNAs and their targets, studies assessing the relationship between genetic variations in the miRNA network and breast cancer risk are still limited, particularly among women of African ancestry. We systematically put together a list of 822 and 10,468 genetic variants among primary miRNA sequences and 38 genes in the miRNA biogenesis pathway, respectively; and examined their association with breast cancer risk in the ROOT consortium which includes women of African ancestry. Findings were replicated in an independent consortium. Logistic regression was used to estimate the odds ratio (OR) and 95 % confidence intervals (CI). For overall breast cancer risk, three single-nucleotide polymorphisms (SNPs) in miRNA biogenesis genes DROSHA rs78393591 (OR = 0.69, 95 % CI: 0.55-0.88, P = 0.003), ESR1 rs523736 (OR = 0.88, 95 % CI: 0.82-0.95, P = 3.99 × 10(-4)), and ZCCHC11 rs114101502 (OR = 1.33, 95 % CI: 1.11-1.59, P = 0.002), and one SNP in primary miRNA sequence (rs116159732 in miR-6826, OR = 0.74, 95 % CI: 0.63-0.89, P = 0.001) were found to have significant associations in both discovery and validation phases. In a subgroup analysis, two SNPs were associated with risk of estrogen receptor (ER)-negative breast cancer, and three SNPs were associated with risk of ER-positive breast cancer. Several variants in miRNA and miRNA biogenesis pathway genes were associated with breast cancer risk. Risk associations varied by ER status, suggesting potential new mechanisms in etiology.

Contribution of the neighborhood environment and obesity to breast cancer survival: the California Breast Cancer Survivorship Consortium

Little is known about neighborhood attributes that may influence opportunities for healthy eating and physical activity in relation to breast cancer mortality. We used data from the California Breast Cancer Survivorship Consortium and the California Neighborhoods Data System (CNDS) to examine the neighborhood environment, body mass index, and mortality after breast cancer. We studied 8,995 African American, Asian American, Latina, and non-Latina white women with breast cancer. Residential addresses were linked to the CNDS to characterize neighborhoods. We used multinomial logistic regression to evaluate the associations between neighborhood factors and obesity and Cox proportional hazards regression to examine associations between neighborhood factors and mortality. For Latinas, obesity was associated with more neighborhood crowding [quartile 4 (Q4) vs. Q1: OR, 3.24; 95% confidence interval (CI), 1.50-7.00]; breast cancer-specific mortality was inversely associated with neighborhood businesses (Q4 vs. Q1: HR, 0.46; 95% CI, 0.25-0.85) and positively associated with multifamily housing (Q3 vs. Q1: HR, 1.98; 95% CI, 1.20-3.26). For non-Latina whites, lower neighborhood socioeconomic status (SES) was associated with obesity [quintile 1 (Q1) vs. Q5: OR, 2.52; 95% CI, 1.31-4.84], breast cancer-specific (Q1 vs. Q5: HR, 2.75; 95% CI, 1.47-5.12), and all-cause (Q1 vs. Q5: HR, 1.75; 95% CI, 1.17-2.62) mortality. For Asian Americans, no associations were seen. For African Americans, lower neighborhood SES was associated with lower mortality in a nonlinear fashion. Attributes of the neighborhood environment were associated with obesity and mortality following breast cancer diagnosis, but these associations differed across racial/ethnic groups.

Reduced risk of breast cancer associated with recreational physical activity varies by HER2 status

Convincing epidemiologic evidence indicates that physical activity is inversely associated with breast cancer risk. Whether this association varies by the tumor protein expression status of the estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), or p53 is unclear. We evaluated the effects of recreational physical activity on risk of invasive breast cancer classified by the four biomarkers, fitting multivariable unconditional logistic regression models to data from 1195 case and 2012 control participants in the population-based Women’s Contraceptive and Reproductive Experiences Study. Self-reported recreational physical activity at different life periods was measured as average annual metabolic equivalents of energy expenditure [MET]-hours per week. Our biomarker-specific analyses showed that lifetime recreational physical activity was negatively associated with the risks of ER-positive (ER+) and of HER2-negative (HER2−) subtypes (both P_trend ≤ 0.04), but not with other subtypes (all P_trend > 0.10). Analyses using combinations of biomarkers indicated that risk of invasive breast cancer varied only by HER2 status. Risk of HER2–breast cancer decreased with increasing number of MET-hours of recreational physical activity in each specific life period examined, although some trend tests were only marginally statistically significant (all P_trend ≤ 0.06). The test for homogeneity of trends (HER2– vs. HER2+ ) reached statistical significance only when evaluating physical activity during the first 10 years after menarche (P_homogeneity = 0.03). Our data suggest that physical activity reduces risk of invasive breast cancers that lack HER2 overexpression, increasing our understanding of the biological mechanisms by which physical activity acts.

Genomic investigation of etiologic heterogeneity: methodologic challenges

Background

The etiologic heterogeneity of cancer has traditionally been investigated by comparing risk factor frequencies within candidate sub-types, defined for example by histology or by distinct tumor markers of interest. Increasingly tumors are being profiled for molecular features much more extensively. This greatly expands the opportunities for defining distinct sub-types. In this article we describe an exploratory analysis of the etiologic heterogeneity of clear cell kidney cancer. Data are available on the primary known risk factors for kidney cancer, while the tumors are characterized on a genome-wide basis using expression, methylation, copy number and mutational profiles.

Methods

We use a novel clustering strategy to identify sub-types. This is accomplished independently for the expression, methylation and copy number profiles. The goals are to identify tumor sub-types that are etiologically distinct, to identify the risk factors that define specific sub-types, and to endeavor to characterize the key genes that appear to represent the principal features of the distinct sub-types.

Results

The analysis reveals strong evidence that gender represents an important factor that distinguishes disease sub-types. The sub-types defined using expression data and methylation data demonstrate considerable congruence and are also clearly correlated with mutations in important cancer genes. These sub-types are also strongly correlated with survival. The complexity of the data presents many analytical challenges including, prominently, the risk of false discovery.

Conclusions

Genomic profiling of tumors offers the opportunity to identify etiologically distinct sub-types, paving the way for a more refined understanding of cancer etiology.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2288-14-138) contains supplementary material, which is available to authorized users.

Pregnancy-associated breast cancer in women from Shanghai: risk and prognosis

Breast cancer (BC) has been associated with pregnancy if diagnosed within 5-10 years after delivery (pregnancy-associated BC, PABC). PABC carries a poor prognosis compared to sporadic BC in Western populations. Data are limited regarding PABC in Asian populations, where longer periods of breastfeeding, higher birth rates and a lower median age of BC at diagnosis have been noted, all of which are known to influence prognosis. We used two datasets of women treated for early BC in Shanghai 1990-2012 (n = 10,161 and n = 7,411). For the analysis of BC risk after pregnancy we compared the distribution of pregnancy in our dataset to that in Shanghai using age-specific fertility rates. For disease-free survival (DFS) evaluation, we restricted our data to women ≤45 years. Women <30 years had a significantly elevated BC risk within 5 years of completing a pregnancy compared to women who had not been pregnant in the previous 5 years. In women aged 20-24 the relative risk (RR) was 3.33 (P = 0.012), and for women aged 25-29 the RR was 1.76 (P = 0.0074). For women >30, the RR was decreased. Patients with PABC had a higher risk of recurrence or death (hazard ratio (HR) for DFS 1.72, P = 0.019) compared to women with non-PABC by univariable analysis. Age was eliminated from the multivariable model by backward selection, resulting in tumor stage (3 versus 1, HR 3.08, P < .001) and recent pregnancy (HR 1.62, P < 0.05) as significant independent prognosticators. Having had a full-term pregnancy in the previous 5 years was associated with a 62 % increased risk of recurrence. We show that recent full-term pregnancy significantly elevates BC risk in women <30 in Shanghai, and that women diagnosed with PABC have a particularly adverse prognosis. Health care providers and women in Asian populations should be made aware of these results.

A comprehensive examination of breast cancer risk loci in African American women

Genome-wide association studies have identified 73 breast cancer risk variants mainly in European populations. Given considerable differences in linkage disequilibrium structure between populations of European and African ancestry, the known risk variants may not be informative for risk in African ancestry populations. In a previous fine-mapping investigation of 19 breast cancer loci, we were able to identify SNPs in four regions that better captured risk associations in African American women. In this study of breast cancer in African American women (3016 cases, 2745 controls), we tested an additional 54 novel breast cancer risk variants. Thirty-eight variants (70%) were found to have an association with breast cancer in the same direction as previously reported, with eight (15%) replicating at P < 0.05. Through fine-mapping, in three regions (1q32, 3p24, 10q25), we identified variants that better captured associations with overall breast cancer or estrogen receptor positive disease. We also observed suggestive associations with variants (at P < 5 × 10(-6)) in three separate regions (6q25, 14q13, 22q12) that may represent novel risk variants. Directional consistency of association observed for ∼65-70% of currently known genetic variants for breast cancer in women of African ancestry implies a shared functional common variant at most loci. To validate and enhance the spectrum of alleles that define associations at the known breast cancer risk loci, as well as genome-wide, will require even larger collaborative efforts in women of African ancestry.

Quantitative measures of estrogen receptor expression in relation to breast cancer-specific mortality risk among white women and black women

Introduction

The association of breast cancer patients’ mortality with estrogen receptor (ER) status (ER + versus ER-) has been well studied. However, little attention has been paid to the relationship between the quantitative measures of ER expression and mortality.

Methods

We evaluated the association between semi-quantitative, immunohistochemical staining of ER in formalin-fixed paraffin-embedded breast carcinomas and breast cancer-specific mortality risk in an observational cohort of invasive breast cancer in 681 white women and 523 black women ages 35-64 years at first diagnosis of invasive breast cancer, who were followed for a median of 10 years. The quantitative measures of ER examined here included the percentage of tumor cell nuclei positively stained for ER, ER Histo (H)-score, and a score based on an adaptation of an equation presented by Cuzick and colleagues, which combines weighted values of ER H-score, percentage of tumor cell nuclei positively stained for the progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) results. This is referred to as the ER/PR/HER2 score.

Results

After controlling for age at diagnosis, race, study site, tumor stage, and histologic grade in multivariable Cox proportional hazards regression models, both percentage of tumor cell nuclei positively stained for ER (P_trend = 0.0003) and the ER H-score (P_trend = 0.0004) were inversely associated with breast cancer-specific mortality risk. The ER/PR/HER2 score was positively associated with breast cancer-specific mortality risk in women with ER + tumor (P_trend = 0.001). Analyses by race revealed that ER positivity was associated with reduced risk of breast cancer-specific mortality in white women and black women. The two quantitative measures for ER alone provided additional discrimination in breast cancer-specific mortality risk only among white women with ER + tumors (both P_trend ≤ 0.01) while the ER/PR/HER2 score provided additional discrimination for both white women (P_trend = 0.01) and black women (P_trend = 0.03) with ER + tumors.

Conclusions

Our data support quantitative immunohistochemical measures of ER, especially the ER/PR/HER2 score, as a more precise predictor for breast cancer-specific mortality risk than a simple determination of ER positivity.

Colorectal cancer morbidity in Poland and Japan in the years 1999-2006 - a comparison

INTRODUCTION

The frequency of colorectal cancer (CRC) is dependent on sex and age. The illness more often affects men than women, and a considerable increase in morbidity is noted after 65 years of age. The aim of the study was to assess the influence of various risk factors on CRC morbidity, statistical data from countries varied in cultural, socioeconomic and biological terms need to be studied. Poland and Japan can serve as examples of such contrasts.

MATERIAL AND METHODS

The basis for the analysis of CRC morbidity was statistical data from Poland and Japan gathered in the period 1999-2006. They were expressed in absolute numbers and were related to the total morbidity, as well as morbidity according to sex and age.

RESULTS

In the years 1999-2006, the total morbidity in Japan was on average 2.3 times higher than in Poland. The value was 2.5 times higher among men and 2.1 times among women when compared to Poland. In both countries morbidity is closely related to age and it reaches a peak between 65 and 74 years of age. Although the change in morbidity over the period was the same for Poland and Japan, there are considerable differences concerning the sex of the patients.

CONCLUSIONS

There is a substantial increase in CRC morbidity in both countries, especially among elderly people, which may point to the predominant influence of environmental factors and population aging in both countries. The much higher increase in morbidity among Polish men when compared to Polish women, not observed in the Japanese population, requires further study.

Obesity and mortality after breast cancer by race/ethnicity: The California Breast Cancer Survivorship Consortium

We investigated body size and survival by race/ethnicity in 11,351 breast cancer patients diagnosed from 1993 to 2007 with follow-up through 2009 by using data from questionnaires and the California Cancer Registry. We calculated hazard ratios and 95% confidence intervals from multivariable Cox proportional hazard model-estimated associations of body size (body mass index (BMI) (weight (kg)/height (m)(2)) and waist-hip ratio (WHR)) with breast cancer-specific and all-cause mortality. Among 2,744 ascertained deaths, 1,445 were related to breast cancer. Being underweight (BMI <18.5) was associated with increased risk of breast cancer mortality compared with being normal weight in non-Latina whites (hazard ratio (HR) = 1.91, 95% confidence interval (CI): 1.14, 3.20), whereas morbid obesity (BMI ≥ 40) was suggestive of increased risk (HR = 1.43, 95% CI: 0.84, 2.43). In Latinas, only the morbidly obese were at high risk of death (HR = 2.26, 95% CI: 1.23, 4.15). No BMI-mortality associations were apparent in African Americans and Asian Americans. High WHR (quartile 4 vs. quartile 1) was associated with breast cancer mortality in Asian Americans (HR = 2.21, 95% CI: 1.21, 4.03; P for trend = 0.01), whereas no associations were found in African Americans, Latinas, or non-Latina whites. For all-cause mortality, even stronger BMI and WHR associations were observed. The impact of obesity and body fat distribution on breast cancer patients' risk of death may vary across racial/ethnic groups.

A conceptual and methodological framework for investigating etiologic heterogeneity

Cancer has traditionally been studied using the disease site of origin as the organizing framework. However, recent advances in molecular genetics have begun to challenge this taxonomy, as detailed molecular profiling of tumors has led to discoveries of subsets of tumors that have profiles that possess distinct clinical and biological characteristics. This is increasingly leading to research that seeks to investigate whether these subtypes of tumors have distinct etiologies. However, research in this field has been opportunistic and anecdotal, typically involving the comparison of distributions of individual risk factors between tumors classified on the basis of candidate tumor characteristics. The purpose of this article is to place this area of investigation within a more general conceptual and analytic framework, with a view to providing more efficient and practical strategies for designing and analyzing epidemiologic studies to investigate etiologic heterogeneity. We propose a formal definition of etiologic heterogeneity and show how classifications of tumor subtypes with larger etiologic heterogeneities inevitably possess greater disease risk predictability overall. We outline analytic strategies for estimating the degree of etiologic heterogeneity among a set of subtypes and for choosing subtypes that optimize the heterogeneity, and we discuss technical challenges that require further methodologic research. We illustrate the ideas by using a pooled case-control study of breast cancer classified by expression patterns of genes known to define distinct tumor subtypes.

Mortality risk of black women and white women with invasive breast cancer by hormone receptors, HER2, and p53 status

Background

Black women are more likely than white women to have an aggressive subtype of breast cancer that is associated with higher mortality and this may contribute to the observed black-white difference in mortality. However, few studies have investigated the black-white disparity in mortality risk stratified by breast cancer subtype, defined by estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) status. Furthermore, it is not known whether additional consideration of p53 protein status influences black-white differences in mortality risk observed when considering subtypes defined by ER, PR and HER2 status.

Methods

Four biomarkers were assessed by immunohistochemistry in paraffin-embedded breast tumor tissue from 1,204 (523 black, 681 white) women with invasive breast cancer, aged 35–64 years at diagnosis, who accrued a median of 10 years’ follow-up. Multivariable Cox proportional hazards regression models were fit to assess subtype-specific black-white differences in mortality risk.

Results

No black-white differences in mortality risk were observed for women with triple negative (ER-negative [ER-], PR-, and HER2-) subtype. However, older (50–64 years) black women had greater overall mortality risk than older white women if they had been diagnosed with luminal A (ER-positive [ER+] or PR+ plus HER2-) breast cancer (all-cause hazard ratio, HR, 1.88; 95% confidence interval, CI, 1.18 to 2.99; breast cancer-specific HR, 1.51; 95% CI, 0.83 to 2.74). This black-white difference among older women was further confined to those with luminal A/p53- tumors (all-cause HR, 2.22; 95% CI, 1.30 to 3.79; breast cancer-specific HR, 1.89; 95% CI, 0.93 to 3.86). Tests for homogeneity of race-specific HRs comparing luminal A to triple negative subtype and luminal A/p53- to luminal A/p53+ subtype did not achieve statistical significance, although statistical power was limited.

Conclusions

Our findings suggest that the subtype-specific black-white difference in mortality risk occurs mainly among older women diagnosed with luminal A/p53- breast cancer, which is most likely treatable. These results further suggest that factors other than subtype may be relatively more important in explaining the increased mortality risk seen in older black women.

A genome-wide scan for breast cancer risk haplotypes among African American women

Genome-wide association studies (GWAS) simultaneously investigating hundreds of thousands of single nucleotide polymorphisms (SNP) have become a powerful tool in the investigation of new disease susceptibility loci. Haplotypes are sometimes thought to be superior to SNPs and are promising in genetic association analyses. The application of genome-wide haplotype analysis, however, is hindered by the complexity of haplotypes themselves and sophistication in computation. We systematically analyzed the haplotype effects for breast cancer risk among 5,761 African American women (3,016 cases and 2,745 controls) using a sliding window approach on the genome-wide scale. Three regions on chromosomes 1, 4 and 18 exhibited moderate haplotype effects. Furthermore, among 21 breast cancer susceptibility loci previously established in European populations, 10p15 and 14q24 are likely to harbor novel haplotype effects. We also proposed a heuristic of determining the significance level and the effective number of independent tests by the permutation analysis on chromosome 22 data. It suggests that the effective number was approximately half of the total (7,794 out of 15,645), thus the half number could serve as a quick reference to evaluating genome-wide significance if a similar sliding window approach of haplotype analysis is adopted in similar populations using similar genotype density.

Pain in long-term breast cancer survivors: the role of body mass index, physical activity, and sedentary behavior

Although pain is common among post-treatment breast cancer survivors, studies that are longitudinal, identify a case definition of clinically meaningful pain, or examine factors contributing to pain in survivors are limited. This study describes longitudinal patterns of pain in long-term breast cancer survivors, evaluating associations of body mass index (BMI), physical activity, sedentary behavior with mean pain severity and above-average pain. Women newly diagnosed with stages 0-IIIA breast cancer (N = 1183) were assessed, on average, 6 months (demographic/clinical characteristics), 30 months (demographics), 40 months (demographics, pain), 5 years (BMI, physical activity, and sedentary behavior), and 10 years (demographics, pain, BMI, physical activity, and sedentary behavior) post-diagnosis. This analysis includes survivors who completed pain assessments 40 months post-diagnosis (N = 801), 10 years post-diagnosis (N = 563), or both (N = 522). Above-average pain was defined by SF-36 bodily pain scores ≥1/2 standard deviation worse than age-specific population norms. We used multiple regression models to test unique associations of BMI, physical activity, and sedentary behavior with pain adjusting for demographic and clinical factors. The proportion of survivors reporting above-average pain was higher at 10 years than at 40 months (32.3 vs. 27.8 %, p < 0.05). Approximately one-quarter of survivors reported improved pain, while 9.0 % maintained above-average pain and 33.1 % reported worsened pain. Cross-sectionally at 10 years, overweight and obese survivors reported higher pain than normal-weight survivors and women meeting physical activity guidelines were less likely to report above-average pain than survivors not meeting these guidelines (p < 0.05). Longitudinally, weight gain (>5 %) was positively associated, while meeting physical activity guidelines was inversely associated, with above-average pain (OR, 95 % CI = 1.76, 1.03-3.01 and 0.40, 0.20-0.84, respectively) (p < 0.05). Weight gain and lack of physical activity place breast cancer survivors at risk for pain long after treatment ends. Weight control and exercise interventions should be tested for effects on long-term pain in these women.

Examination of ancestral informative markers and self-reported race with tumor characteristics of breast cancer among Black and White women

African American (AA) women have a higher mortality from breast cancer (BC) compared to European American (EA) women. This may be due to the higher proportion of AA women with tumors that are diagnosed at more advanced stages and are characterized as being estrogen receptor negative (ER-)/progesterone receptor negative (PR-). Our study sought to determine whether self-reported race and percent African ancestry were associated with BC tumor characteristics. In a multi-center, population-based case-control study of BC, we determined percent African ancestry using ancestry informative markers (AIM) among women self-reporting race as AA or Black. BC tumor characteristics were associated with self-reported race (including a 30 % reduction in ER+/PR+ tumors [95 % confidence interval [CI]: 0.6-0.9] and a 1.5-fold increased risk of high grade [95 % CI: 1.2-1.9] for AA women compared to EA women). AIMs among AA women were not associated with BC tumor characteristics (AA women with ≥95 % versus <80 % African ancestry, odds ratio [OR] = 1.0 for ER+/PR+ [95 % CI: 0.6-1.8] and OR = 0.9 for high-grade tumors [95 % CI: 0.6-1.4]). Similar findings were observed for BC stage. While BC subtypes were associated with self-reported race, BC subtypes were not associated with percent African ancestry. These study results suggest that subtle differences in percent African ancestry are less important than the overall presence of African ancestry in relation to BC tumor characteristics.

Estrogen-related genes and their contribution to racial differences in breast cancer risk

Racial differences in breast cancer risk, including the risks of hormone receptor subtypes of breast cancer, have been previously reported. We evaluated whether variation in genes related to estrogen metabolism (COMT, CYP1A1, CYP1B1, CYP17A1, CYP19A1, ESR1, GSTM1, GSTP1, GSTT1, HSD17B1, SULT1A1, and UGT1A1) contributes to breast cancer risk and/or racial differences in risk within the CARE study, a multi-centered, population-based case-control study of breast cancer. Genetic variation was assessed as single nucleotide polymorphisms (SNPs), haplotypes, and SNP-hormone therapy (HT) interactions within a subset of 1,644 cases and 1,451 controls, including 949 Black women (493 cases and 456 controls), sampled from the CARE study population. No appreciable associations with breast cancer risk were detected for single SNPs or haplotypes in women overall. We detected SNP-HT interactions in women overall within CYP1B1 (rs1800440; p (het) = 0.003) and within CYP17A1 (rs743572; p (het) = 0.009) in which never users of HT were at a decreased risk of breast cancer, while ever users were at a non-significant increased risk. When investigated among racial groups, we detected evidence of an SNP-HT interaction with CYP1B1 in White women (p value = 0.02) and with CYP17A1 in Black women (p value = 0.04). This analysis suggests that HT use may modify the effect of variation in estrogen-related genes on breast cancer risk, which may affect Black and White women to a different extent.

Fatigue, inflammation, and ω-3 and ω-6 fatty acid intake among breast cancer survivors

PURPOSE

Evidence suggests that inflammation may drive fatigue in cancer survivors. Research in healthy populations has shown reduced inflammation with higher dietary intake of ω-3 polyunsaturated fatty acids (PUFAs), which could potentially reduce fatigue. This study investigated fatigue, inflammation, and intake of ω-3 and ω-6 PUFAs among breast cancer survivors.

METHODS

Six hundred thirty-three survivors (mean age, 56 years; stage I to IIIA) participating in the Health, Eating, Activity, and Lifestyle Study completed a food frequency/dietary supplement questionnaire and provided a blood sample assayed for C-reactive protein (CRP) and serum amyloid A (30 months after diagnosis) and completed the Piper Fatigue Scale and Short Form-36 (SF-36) vitality scale (39 months after diagnosis). Analysis of covariance and logistic regression models tested relationships between inflammation and fatigue, inflammation and ω-3 and ω-6 PUFA intake, and PUFA intake and fatigue, controlling for three incremental levels of confounders. Fatigue was analyzed continuously (Piper scales) and dichotomously (SF-36 vitality ≤ 50).

RESULTS

Behavioral (P = .003) and sensory (P = .001) fatigue scale scores were higher by increasing CRP tertile; relationships were attenuated after adjustment for medication use and comorbidity. Survivors with high CRP had 1.8 times greater odds of fatigue after full adjustment (P < .05). Higher intake of ω-6 relative to ω-3 PUFAs was associated with greater CRP (P = .01 after full adjustment) and greater odds of fatigue (odds ratio, 2.6 for the highest v lowest intake; P < .05).

CONCLUSION

Results link higher intake of ω-3 PUFAs, decreased inflammation, and decreased physical aspects of fatigue. Future studies should test whether ω-3 supplementation may reduce fatigue among significantly fatigued breast cancer survivors.

Oral contraceptive formulation and risk of breast cancer

BACKGROUND

While evidence on the association between oral contraceptive (OC) use and breast cancer generally suggests little or no increased risk, the question of whether breast cancer risk varies by OC formulation remains controversial. Few studies have examined this issue because large samples and extensive OC histories are required.

STUDY DESIGN

We used data from a multicenter, population-based, case-control investigation. Women aged 35-64 years were interviewed. To explore the association between OC formulation and breast cancer risk, we used conditional logistic regression to derive adjusted odds ratios, and we used likelihood ratio tests for heterogeneity to assess whether breast cancer risk varied by OC formulation. Key OC exposure variables were ever use, current or former use, duration of use and time since last use. To strengthen inferences about specific formulations, we restricted most analyses to the 2282 women with breast cancer and the 2424 women without breast cancer who reported no OC use or exclusive use of one OC.

RESULTS

Thirty-eight formulations were reported by the 2674 women who used one OC; most OC formulations were used by only a few women. We conducted multivariable analyses on the 10 formulations that were each used by at least 50 women and conducted supplemental analyses on selected formulations of interest based on recent research. Breast cancer risk did not vary significantly by OC formulation, and no formulation was associated with a significantly increased breast cancer risk.

CONCLUSIONS

These results add to the small body of literature on the relationship between OC formulation and breast cancer. Our data are reassuring in that, among women 35-64 years of age, we found no evidence that specific OC formulations increase breast cancer risk.

Long-term use of continuous-combined estrogen-progestin hormone therapy and risk of endometrial cancer

The daily administered dose of progestin in continuous-combined estrogen-progestin therapy is provided to counteract the proliferative effect of estrogen on the postmenopausal endometrium. However, there remains some uncertainty as to whether use of such a combined regimen, over the long term, is associated with an altered risk of endometrial cancer. We pooled data from four population-based case-control studies of endometrial cancer in western Washington State. Cases, ages 45-74, were diagnosed between 1985 and 2005. Using logistic regression with the adjustment for confounding factors, women who had exclusively used continuous-combined estrogen-progestin therapy (90 endometrial cancer cases, 227 controls) were compared with women who had never used any type of hormone therapy (774 cases, 1,116 controls). Associations with duration and recency of use were evaluated overall and within strata defined by body mass index. Long-term use of continuous-combined estrogen-progestin therapy (≥10 years) was associated with a reduced risk of endometrial cancer (OR = 0.37, 95% CI: 0.21-0.66). This association was most pronounced in women with a body mass index ≥30 kg/m(2) (OR = 0.19, 95% CI: 0.05-0.68). Associations did not differ according to recency of use. These results suggest that long duration of use of continuous-combined estrogen-progestin therapy is associated with a reduced risk of endometrial cancer.

Pregnancy history and risk of endometrial cancer

BACKGROUND

Epidemiologic studies are consistent in finding that women who have had at least one birth are less likely to develop endometrial cancer. Less clear is whether timing of pregnancies during reproductive life influences risk, and the degree to which incomplete pregnancies are associated with a reduced risk.

METHODS

We evaluated pregnancy history in relation to endometrial cancer risk using data from a series of 4 population-based endometrial cancer case-control studies of women 45-74 years of age (1712 cases and 2134 controls) during 1985-2005 in western Washington State. Pregnancy history and information on other potential risk factors were collected by in-person interviews.

RESULTS

Older age at first birth was associated with a reduced risk of endometrial cancer after adjustment for number of births and age at last birth (test for trend P = 0.004). The odds ratio comparing women at least 35 years of age at their first birth with those younger than 20 years was 0.34 (95% confidence interval = 0.14-0.84). Age at last birth was not associated with risk after adjustment for number of births and age at first birth (test for trend P = 0.830). Overall, a history of incomplete pregnancies was not associated with endometrial cancer risk to any appreciable degree.

CONCLUSIONS

In this study, older age at first birth was more strongly associated with endometrial cancer risk than was older age at last birth. To date, there remains some uncertainty in the literature on this issue.

Obesity and survival among black women and white women 35 to 64 years of age at diagnosis with invasive breast cancer

PURPOSE

To evaluate the effect of obesity on survival among black women and white women with invasive breast cancer and to determine whether obesity explains the poorer survival of black women relative to white women.

PATIENTS AND METHODS

We observed 4,538 (1,604 black, 2,934 white) women who were 35 to 64 years of age when diagnosed with incident invasive breast cancer between 1994 and 1998. Multivariate Cox regression models were used to examine the effect of body mass index (BMI, in kilograms per square meter) 5 years before diagnosis on risk of death from any cause and from breast cancer.

RESULTS

During a median of 8.6 years of follow-up, 1,053 women died (519 black, 534 white), 828 as a result of breast cancer (412 black, 416 white). Black women were more likely to die than white women (multivariate-adjusted relative risk [RR], 1.33; 95% CI, 1.16 to 1.53). Compared with women with BMI of 20 to 24.9 kg/m(2), those who were obese (BMI ≥ 30 kg/m(2)) had a greater risk of all-cause mortality (RR, 1.23; 95% CI, 1.04 to 1.47) and breast cancer-specific mortality (RR, 1.20; 95% CI, 0.99 to 1.46). These associations were observed among white women (all-cause RR, 1.54; 95% CI, 1.21 to 1.96; breast cancer RR, 1.46; 95% CI, 1.11 to 1.92), but not among black women (all-cause RR, 1.03; 95% CI, 0.81 to 1.29; breast cancer RR, 1.02; 95% CI, 0.79 to 1.33).

CONCLUSION

Obesity may play an important role in mortality among white but not black patients with breast cancer. It is unlikely that differences in obesity distributions between black women and white women account for the poorer survival of black women.

Fine-mapping of breast cancer susceptibility loci characterizes genetic risk in African Americans

Genome-wide association studies (GWAS) have revealed 19 common genetic variants that are associated with breast cancer risk. Testing of the index signals found through GWAS and fine-mapping of each locus in diverse populations will be necessary for characterizing the role of these risk regions in contributing to inherited susceptibility. In this large study of breast cancer in African-American women (3016 cases and 2745 controls), we tested the 19 known risk variants identified by GWAS and replicated associations (P < 0.05) with only 4 variants. Through fine-mapping, we identified markers in four regions that better capture the association with breast cancer risk in African Americans as defined by the index signal (2q35, 5q11, 10q26 and 19p13). We also identified statistically significant associations with markers in four separate regions (8q24, 10q22, 11q13 and 16q12) that are independent of the index signals and may represent putative novel risk variants. In aggregate, the more informative markers found in the study enhance the association of these risk regions with breast cancer in African Americans [per allele odds ratio (OR) = 1.18, P = 2.8 × 10(-24) versus OR = 1.04, P = 6.1 × 10(-5)]. In this detailed analysis of the known breast cancer risk loci, we have validated and improved upon markers of risk that better characterize their association with breast cancer in women of African ancestry.

Polymorphisms in nucleotide excision repair genes and endometrial cancer risk

BACKGROUND

Exposure to estrogens increases the risk of endometrial cancer. Certain estrogen metabolites can form bulky DNA adducts, which are removed via nucleotide excision repair (NER), and the ability to carry out this repair might be related to endometrial cancer risk.

METHODS

We examined 64 tag and functional single-nucleotide polymorphisms (SNPs) in the NER genes ERCC1, ERCC2 (XPD), ERCC3 (XPB), ERCC4 (XPF), ERCC5 (XPG), LIG1, XPA, and XPC in a population-based case-control study in Washington state, with 783 endometrial cancer cases and 795 controls.

RESULTS

The presence of ERCC5 rs4150386 C, LIG1 rs3730865 C, XPA rs2808667 T, or XPC rs3731127 T alleles was associated with risk of endometrial cancer, with respective age-, county-, and reference year-adjusted per-allele ORs and 95% CIs of 0.68 (0.53-0.87, P = 0.002), 1.46 (1.02-2.10, P = 0.04), 0.71 (0.52-0.97, P = 0.03), and 1.57 (1.13-2.17, P = 0.007), respectively.

CONCLUSIONS

Certain ERCC5, LIG1, XPA, and XPC genotypes might influence endometrial cancer risk.

IMPACT

Because of multiple redundancies in DNA repair pathways (and therefore a low prior probability) and the large number of associations examined, false-positive findings are likely. Further characterization of the relation between variation in NER genes and endometrial cancer risk is warranted.

A review of body size and breast cancer risk in Hispanic and African American women

Obesity is an epidemic in the United States, especially among Hispanics and African Americans. Studies of obesity and breast cancer risk have been conducted primarily in non-Hispanic whites. There have been few studies of the association between body mass index (BMI) or weight gain and the risk of breast cancer in minorities, and the results have been inconsistent. Because most studies are conducted primarily in non-Hispanic whites, the etiology of breast cancer in minorities is not well understood. The authors of the current report reviewed the literature on the association between obesity, weight, and weight gain and breast cancer in minorities using a combination of the Medical Subject Heading (MeSH) terms "obesity," "body mass index," "weight," "weight gain," "Hispanic," and "African American." Only publications in English and with both risk estimates and 95% confidence intervals were considered. Forty-five studies of body size and breast cancer risk in non-Hispanic whites were identified. After an exhaustive search of the literature, only 3 studies of body size and breast cancer were conducted in Hispanic women were identified, and only 8 such studies in African American women were identified. The results were inconsistent in both race/ethnicity groups, with studies reporting positive, inverse, and null results. Thus, as obesity rates among Hispanics and African Americans continue to rise, there is an urgent need to identify the roles that both obesity and adult weight gain play in the development of breast cancer in these minorities. Additional studies are needed to provide more understanding of the etiology of this disease and to explain some of the disparities in incidence and mortality.

Genetic variation in proinflammatory cytokines IL6, IL6R, TNF-region, and TNFRSF1A and risk of breast cancer

Proinflammatory cytokines are associated with age-related diseases including arthritis and heart disease. IL6 and TNF also play key roles in estrogen modulation in older women. We explored whether variation in IL6 and TNF genes influenced the risk of breast cancer in samples that differed by age group: <44 years (228 cases and 271 controls), 45-64 years (426 cases and 396 controls), and 65+ years (228 cases and 239 controls). Samples were drawn from population-based case-control studies conducted in Seattle. Age-adjusted odds ratios (ORs) were calculated to evaluate the risk associated with variants in IL6, IL6R, TNF, and TNFRSF1A. There was a significantly increased risk of breast cancer associated with one or more C>T alleles at IL6 rs2069861 among subjects in the oldest age group (OR 1.8, 95% CI 1.1-2.9), but no overall increased risk of breast cancer associated with any IL6 or IL6R variants in the combined data. There were significantly elevated risks of breast cancer among women 45-64 years old associated with a UTR 5' flanking SNP LTA rs2009658 C>G allele (OR 1.5, 95% CI 1.1-1.9) and a nonsynonomous coding SNP TNFRSF1A rs767455 T>C allele (OR 1.3, 95% CI 1.1-1.6); these two variants were also elevated in the combined data (OR 1.3, 95% CI 1.1-1.5 and OR 1.2, 95% CI 1.1-1.4, respectively). This study supports a modest association between a variant in IL6 and breast cancer among older women and TNF-related variants and breast cancer among middle-aged women. Further evaluation of these genes in other studies is warranted.

Enhanced statistical tests for GWAS in admixed populations: assessment using African Americans from CARe and a Breast Cancer Consortium

While genome-wide association studies (GWAS) have primarily examined populations of European ancestry, more recent studies often involve additional populations, including admixed populations such as African Americans and Latinos. In admixed populations, linkage disequilibrium (LD) exists both at a fine scale in ancestral populations and at a coarse scale (admixture-LD) due to chromosomal segments of distinct ancestry. Disease association statistics in admixed populations have previously considered SNP association (LD mapping) or admixture association (mapping by admixture-LD), but not both. Here, we introduce a new statistical framework for combining SNP and admixture association in case-control studies, as well as methods for local ancestry-aware imputation. We illustrate the gain in statistical power achieved by these methods by analyzing data of 6,209 unrelated African Americans from the CARe project genotyped on the Affymetrix 6.0 chip, in conjunction with both simulated and real phenotypes, as well as by analyzing the FGFR2 locus using breast cancer GWAS data from 5,761 African-American women. We show that, at typed SNPs, our method yields an 8% increase in statistical power for finding disease risk loci compared to the power achieved by standard methods in case-control studies. At imputed SNPs, we observe an 11% increase in statistical power for mapping disease loci when our local ancestry-aware imputation framework and the new scoring statistic are jointly employed. Finally, we show that our method increases statistical power in regions harboring the causal SNP in the case when the causal SNP is untyped and cannot be imputed. Our methods and our publicly available software are broadly applicable to GWAS in admixed populations.

Missing genetic information in case-control family data with general semi-parametric shared frailty model

Case-control family data are now widely used to examine the role of gene-environment interactions in the etiology of complex diseases. In these types of studies, exposure levels are obtained retrospectively and, frequently, information on most risk factors of interest is available on the probands but not on their relatives. In this work we consider correlated failure time data arising from population-based case-control family studies with missing genotypes of relatives. We present a new method for estimating the age-dependent marginalized hazard function. The proposed technique has two major advantages: (1) it is based on the pseudo full likelihood function rather than a pseudo composite likelihood function, which usually suffers from substantial efficiency loss; (2) the cumulative baseline hazard function is estimated using a two-stage estimator instead of an iterative process. We assess the performance of the proposed methodology with simulation studies, and illustrate its utility on a real data example.

Does hormone therapy counter the beneficial effects of physical activity on breast cancer risk in postmenopausal women?

Studies consistently demonstrate that physical activity is inversely associated with postmenopausal breast cancer. Whether this association is stronger among non-hormone users or former users of menopausal hormone therapy (HT) is of interest given the marked decline in HT use since 2002. The Women's Contraceptive and Reproductive Experiences Study, a population-based case-control study of invasive breast cancer, recruited white women and black women ages 35-64 years and collected histories of lifetime recreational physical activity and HT use including estrogen-alone therapy (ET) and estrogen plus progestin therapy (EPT). Among postmenopausal women (1,908 cases, 2,013 control participants), breast cancer risk declined with increasing levels of lifetime physical activity among never HT users; among short-term HT users (fewer than 5 years); and among current ET users; P (trend) values ranged from 0.004 to 0.016. In contrast, physical activity had no significant association with risk among long-term and past HT users and among current EPT users. No statistical evidence of heterogeneity was demonstrated for duration or currency of HT use. Breast cancer risk decreases with increasing lifetime physical activity levels among postmenopausal women who have not used HT, have used HT for less than 5 years, or are current ET users, yet this study was unable to demonstrate statistically that HT use modifies the relationship between physical activity and breast cancer. With profound changes in HT use occurring since 2002, it will be important in future studies to learn whether or not any association between physical activity and breast cancer among former HT users is a function of time since last HT use.

Breast cancer risk and ovariectomy, hysterectomy, and tubal sterilization in the women's contraceptive and reproductive experiences study

Removal or impairment of ovaries before menopause may affect a woman's breast cancer risk by altering her cumulative exposure to ovarian hormones. The Women's Contraceptive and Reproductive Experiences Study, a population-based, multicenter case-control study of incident invasive breast cancer, recruited women aged 35-64 years (4,490 cases and 4,611 controls) who provided data on ovariectomy, hysterectomy, and tubal sterilization during in-person interviews. Controls were frequency-matched to cases by age, race, and study site. Unconditional logistic regression analysis was used. Women who had not undergone premenopausal reproductive surgery were the referent group. Bilateral ovariectomy was associated with reduced breast cancer risk overall (odds ratio (OR) = 0.59, 95% confidence interval (CI): 0.50, 0.69) and among women <45 years of age (ORs ranged from 0.31 to 0.52), but not among those who were older at surgery. It was also associated with a reduced risk for estrogen and progesterone receptor-positive tumors (OR = 0.63, 95% CI: 0.52, 0.75) but not receptor-negative tumors. Hysterectomy with ovarian conservation (OR = 0.83, 95% CI: 0.72, 0.96) and hysterectomy with partial ovary removal (OR = 0.73, 95% CI: 0.59, 0.91) were also associated with lower risk. No association with breast cancer risk was observed with tubal sterilization only or partial ovariectomy without hysterectomy. Reproductive organ surgeries may alter ovarian hormone levels, thereby affecting breast cancer risk.

Age-related variation in the relationship between menopausal hormone therapy and the risk of dying from breast cancer

Multiple past studies have reported a reduced risk of breast cancer-related mortality (BCM) in relation to pre-diagnostic use of hormone therapy (HT); however, the extent to which this reduction is due to heightened screening or tumor biology is unknown. Using a population-based cohort of 1,911 post-menopausal women diagnosed with invasive breast cancer at ages 45-79 from 1993 to 1999, we investigated the extent to which the reduced risk in BCM observed in relation to HT might be explained by screening patterns or tumor features. Estrogen-progestin therapy (EPT) use was associated with a decreased risk of BCM (after adjustment for age, study, mammography, stage, and treatment), but only among older women (ever use: ≥ 65 years: HR = 0.45 [95% CI 0.26-0.80]; <65 years: HR = 1.03 [95% CI 0.60-1.79]). Estrogen-alone therapy (ET) use was not associated with risk of BCM (ever use: ≥ 65 years: HR = 0.76 [95% CI 0.51-1.12]; <65 years: HR = 1.20 [95% CI 0.71-2.02]). HT users had a much greater frequency of mammography (P value <0.001). EPT use was associated with tumor characteristics related to improved prognosis in older women after adjustment for screening, including an inverse association with poorly differentiated tumors (OR = 0.57 [95% CI 0.38-0.85]) and an association with lobular tumors (OR = 1.68 [95% CI 1.07-2.65]). Beyond the influence of EPT use on screening uptake, these data indicate that the improved survival associated with pre-diagnostic EPT use may be due in part to the development of more favorable tumor characteristics.

Benign breast disease

Benign breast diseases are among the most common diagnoses that the busy obstetrician-gynecologist will see in practice. Moreover, breast cancer will undoubtedly be diagnosed numerous times in an obstetrician-gynecologist's career. An ability to accurately and promptly diagnose both benign and malignant breast diseases is within the purview of the generalist obstetrician-gynecologist. A thorough understanding of benign breast diseases, including appropriate diagnostic techniques, is vitally important in well-women care. In addition, a working knowledge of breast cancer risk factors with the ability to identify women at high risk and either refer or initiate risk reduction methods is equally important. This review outlines common benign breast diseases stratified by future risk of breast cancer and discusses appropriate management after diagnosis.

The potential for enhancing the power of genetic association studies in African Americans through the reuse of existing genotype data

We consider the feasibility of reusing existing control data obtained in genetic association studies in order to reduce costs for new studies. We discuss controlling for the population differences between cases and controls that are implicit in studies utilizing external control data. We give theoretical calculations of the statistical power of a test due to Bourgain et al (Am J Human Genet 2003), applied to the problem of dealing with case-control differences in genetic ancestry related to population isolation or population admixture. Theoretical results show that there may exist bounds for the non-centrality parameter for a test of association that places limits on study power even if sample sizes can grow arbitrarily large. We apply this method to data from a multi-center, geographically-diverse, genome-wide association study of breast cancer in African-American women. Our analysis of these data shows that admixture proportions differ by center with the average fraction of European admixture ranging from approximately 20% for participants from study sites in the Eastern United States to 25% for participants from West Coast sites. However, these differences in average admixture fraction between sites are largely counterbalanced by considerable diversity in individual admixture proportion within each study site. Our results suggest that statistical correction for admixture differences is feasible for future studies of African-Americans, utilizing the existing controls from the African-American Breast Cancer study, even if case ascertainment for the future studies is not balanced over the same centers or regions that supplied the controls for the current study.

This paper discusses and provides unique insight into an important problem raised by the current state of genetic studies into disease susceptibility, namely whether we can reuse genetic data from participants genotyped as controls in one study when cases (people with a disease of interest) are obtained from other studies, or whether each new study needs its own controls. We are interested in whether studies where cases and controls are sampled differently will give correct answers and are as powerful statistically as when new control data is also genotyped. Because of the huge investments made recently in large scale genotyping of cases and controls for various diseases, this is a timely question. This question is especially important in understanding the genetic causes of disease in as-yet relatively understudied population groups, such as African-Americans, in order to speed up progress when this is possible. We give theoretical results about the power of studies that reuse existing control genotypes based on statistical considerations. We also provide analysis of real data from a major study of the genetic causes of breast cancer in African-American women in order to shed practical light upon this issue.

A case-control study of body mass index and breast cancer risk in white and African-American women

OBJECTIVE

Large body size has been associated with decreased risk of breast cancer in premenopausal women but with increased risk in postmenopausal women. Limited information is available about African-American women and differences by estrogen and progesterone receptor status.

METHODS

We analyzed data from the Women's Contraceptive and Reproductive Experiences Study among 3,997 white and African-American breast cancer case patients diagnosed in 1994 to 1998 and 4,041 control participants ages 35 to 64 years. We calculated multivariate odds ratios (OR) as measures of relative risk of breast cancer associated with self-reported body mass index (BMI) at age 18 and 5 years before diagnosis (recent BMI).

RESULTS

Risk tended to decrease with increasing BMI at age 18 years in all women [OR(BMI > or = 25 kg/m(2) versus < 20 kg/m(2)) = 0.76; 95% confidence interval (CI), 0.63-0.90; P(trend) = 0.005] and with recent BMI in premenopausal women (OR(BMI > or = 35 kg/m(2) versus < 25 kg/m(2)) = 0.81; 95% CI, 0.61-1.06; P(trend) = 0.05), unmodified by race. Among postmenopausal white but not African-American women, there was an inverse relation between recent BMI and risk. High recent BMI was associated with increased risk of estrogen receptor- and progesterone receptor-positive tumors among postmenopausal African-American women (OR(BMI > or = 35 kg/m(2) versus < 25 kg/m(2)) = 1.83; 95% CI, 1.08-3.09; P(trend) = 0.03).

CONCLUSION

Among women at age 35 to 64 years, BMI at age 18 years is inversely associated with risk of breast cancer, but association with recent BMI varies by menopause status, race, and hormone receptor status.

IMPACT

Our findings indicate that studies of BMI and breast cancer should consider breast cancer subtypes.

Hormone therapy and fatal breast cancer

PURPOSE

Among unanswered questions is whether menopausal use of estrogen therapy (ET) or estrogen-plus-progestin therapy (CHT) increases risk of developing fatal breast cancer i.e., developing and dying of breast cancer. Using a population-based case-control design, we estimated incidence rate ratios of fatal breast cancer in postmenopausal hormone therapy (HT) users compared to non-users by type, duration, and recency of HT use.

METHODS

HT use prior to breast cancer diagnosis in 278 women who died of breast cancer within 6 years of diagnosis (cases) was compared with use in 2224 controls never diagnosed with breast cancer using conditional logistic regression. Measures taken to address potential bias and confounding inherent in case-control studies included collecting and adjusting for detailed data on demographic and other factors potentially associated both with HT use and breast cancer.

RESULTS

Fifty-six per cent of cases and 68% of controls reported HT use. Among current 3+ year HT users, odds ratios and 95% confidence intervals for death were 0.83 (0.50, 1.38) and 0.69 (0.44, 1.09), respectively, for exclusive use of CHT or of ET, and were 0.94 (0.59, 1.48) and 0.70 (0.45, 1.07) for any use of CHT or of ET regardless of other hormone use.

CONCLUSION

Point estimates suggest no increased risk of fatal breast cancer with HT use, although 50% increases in risk in longer-term current CHT users cannot be ruled out.

A frailty-model-based approach to estimating the age-dependent penetrance function of candidate genes using population-based case-control study designs: an application to data on the BRCA1 gene

The population-based case-control study design is perhaps one of, if not the most, commonly used designs for investigating the genetic and environmental contributions to disease risk in epidemiological studies. Ages at onset and disease status of family members are routinely and systematically collected from the participants in this design. Considering age at onset in relatives as an outcome, this article is focused on using the family history information to obtain the hazard function, i.e., age-dependent penetrance function, of candidate genes from case-control studies. A frailty-model-based approach is proposed to accommodate the shared risk among family members that is not accounted for by observed risk factors. This approach is further extended to accommodate missing genotypes in family members and a two-phase case-control sampling design. Simulation results show that the proposed method performs well in realistic settings. Finally, a population-based two-phase case-control breast cancer study of the BRCA1 gene is used to illustrate the method.

Use of four biomarkers to evaluate the risk of breast cancer subtypes in the women's contraceptive and reproductive experiences study

Epidemiologic studies suggest that some hormone-related risk factors in breast cancer differentially influence risk for disease subtypes classified by the status of the estrogen and progesterone receptors (ER/PR). However, it remains unclear whether human epidermal growth factor receptor 2 (HER2) or p53 expression status further differentiates these exposure-risk group associations. We evaluated the associations of oral contraceptive (OC) use and reproductive factors with incident invasive breast cancer subtypes among 1,197 population-based cases and 2,015 controls from the Los Angeles County or Detroit components of the Women's Contraceptive and Reproductive Experiences Study. Case-control comparisons by ER/PR/HER2/p53 status were conducted by multivariable polychotomous unconditional logistic regression methods. We found that OC use was not associated with any breast cancer subtype as defined by ER/PR/HER2/p53 status, except for a 2.9-fold increased risk of so-called triple-negative tumors (ER(-)/PR(-)/HER2(-)) among women of 45 to 64 years of age who started OC use before age 18. Parity was associated with a decreased risk of luminal A (ER(+) or PR(+), HER2(-)), luminal B (ER(+) or PR(+)/HER2(+)), and ER(-)/PR(-)/HER2(+) tumors. Age at first full-term pregnancy was positively associated with luminal A tumors among older women. Neither of these reproductive factors was associated with triple-negative tumors. Long duration of breast-feeding lowered the risk of triple-negative and luminal A tumors. p53 status did not define further differential risk patterns. Our findings offer evidence of differences in the hormone-related risk factors between triple-negative cancers and other ER/PR/HER2-defined subtypes of breast cancer.

Breast cancer receptor status: do results from a centralized pathology laboratory agree with SEER registry reports?

We investigated the extent to which estrogen receptor (ER) and progesterone receptor (PR) status results from a centralized pathology laboratory agree with ER and PR results from community pathology laboratories reported to two Surveillance, Epidemiology and End Results (SEER) registries (Los Angeles County and Detroit) and whether statistical estimates for the association between reproductive factors and breast cancer receptor subtypes differ by the source of data. The agreement between the centralized laboratory and SEER registry classifications was substantial for ER (kappa = 0.70) and nearly so for PR status (kappa = 0.60). Among the four subtypes defined by joint ER and PR status, the agreement between the two sources was substantial for the two major breast cancer subtypes (ER-/PR-, kappa = 0.69; ER+/PR+, kappa = 0.62) and poor for the two rarer subtypes (ER+/PR-, kappa = 0.30; ER-/PR+, kappa = 0.05). Estimates for the association between reproductive factors (number of full-term pregnancies, age at first full-term pregnancy, and duration of breastfeeding) and the two major subtypes (ER+/PR+ and ER-/PR-) differed minimally between the two sources of data. For example, parous women with at least four full-term pregnancies had 40% lower risk for ER+/PR+ breast cancer than women who had never been pregnant [centralized laboratory, odds ratio, 0.60 (95% confidence interval, 0.39-0.92); SEER, odds ratio, 0.57 (95% confidence interval, 0.38-0.85)]; no association was observed for ER-/PR- breast cancer (both P(trend) > 0.30). Our results suggest that conclusions based on SEER registry data are reasonably reliable for ER+/PR+ and ER-/PR- subtypes.

An admixture scan in 1,484 African American women with breast cancer

African American women with breast cancer present more commonly with aggressive tumors that do not express the estrogen receptor (ER) and progesterone receptor (PR) compared with European American women. Whether this disparity is the result of inherited factors has not been established. We did an admixture-based genome-wide scan to search for risk alleles for breast cancer that are highly differentiated in frequency between African American and European American women, and may contribute to specific breast cancer phenotypes, such as ER-negative (ER-) disease. African American women with invasive breast cancer (n = 1,484) were pooled from six population-based studies and typed at approximately 1,500 ancestry-informative markers. We investigated global genetic ancestry and did a whole genome admixture scan searching for breast cancer-predisposing loci in association with disease phenotypes. We found a significant difference in ancestry between ER+PR+ and ER-PR- women, with higher European ancestry among ER+PR+ individuals, after controlling for possible confounders (odds ratios for a 0 to 1 change in European ancestry proportion, 2.84; 95% confidence interval, 1.13-7.14; P = 0.026). Women with localized tumors had higher European ancestry than women with non-localized tumors (odds ratios, 2.65; 95% confidence interval, 1.11-6.35; P = 0.029). No genome-wide statistically significant associations were observed between European or African ancestry at any specific locus and breast cancer, or in analyses stratified by ER/PR status, stage, or grade. In summary, in African American women, genetic ancestry is associated with ER/PR status and disease stage. However, we found little evidence that genetic ancestry at any one region contributes significantly to breast cancer risk or hormone receptor status.