Breast Cancer Population Attributable Risk Proportions Associated with Body Mass Index and Breast Density by Race/Ethnicity and Menopausal Status

BACKGROUND

Overweight/obesity and dense breasts are strong breast cancer risk factors whose prevalences vary by race/ethnicity. The breast cancer population attributable risk proportions (PARP) explained by these factors across racial/ethnic groups are unknown.

METHODS

We analyzed data collected from 3,786,802 mammography examinations (1,071,653 women) in the Breast Cancer Surveillance Consortium, associated with 21,253 invasive breast cancers during a median of 5.2 years follow-up. HRs for body mass index (BMI) and breast density, adjusted for age and registry were estimated using separate Cox regression models by race/ethnicity (White, Black, Hispanic, Asian) and menopausal status. HRs were combined with observed risk-factor proportions to calculate PARPs for shifting overweight/obese to normal BMI and shifting heterogeneously/extremely dense to scattered fibroglandular densities.

RESULTS

The prevalences and HRs for overweight/obesity and heterogeneously/extremely dense breasts varied across races/ethnicities and menopausal status. BMI PARPs were larger for postmenopausal versus premenopausal women (12.0%-28.3% vs. 1.0%-9.9%) and nearly double among postmenopausal Black women (28.3%) than other races/ethnicities (12.0%-15.4%). Breast density PARPs were larger for premenopausal versus postmenopausal women (23.9%-35.0% vs. 13.0%-16.7%) and lower among premenopausal Black women (23.9%) than other races/ethnicities (30.4%-35.0%). Postmenopausal density PARPs were similar across races/ethnicities (13.0%-16.7%).

CONCLUSIONS

Overweight/obesity and dense breasts account for large proportions of breast cancers in White, Black, Hispanic, and Asian women despite large differences in risk-factor distributions.

IMPACT

Risk prediction models should consider how race/ethnicity interacts with BMI and breast density. Efforts to reduce BMI could have a large impact on breast cancer risk reduction, particularly among postmenopausal Black women.

Abstract P2-10-05: A breast cancer multi-racial/ethnic polygenic risk score for improved personalized breast cancer screening

Background: Polygenic risk scores (PRS) integrate risk information from breast cancer associated SNPs (single nucleotide polymorphism). The risk scores have mostly been developed in populations of European ancestry, and have been shown to improve risk prediction over standard breast cancer risk models in these populations. The ability of the PRS to personalize screening is currently being studied. We included PRS as a component of breast cancer risk assessment in the WISDOM Study, a trial of personalized vs. annual breast cancer screening. In order to account for race/ethnicity in PRS risk assessment, we developed a race/ethnicity calibrated and inclusive PRS risk score that we incorporated here into the Gail model to determine impact on risk stratification.

Methods: We constructed two different PRS for each race/ethnicity: For Caucasian populations, we constructed two PRS based on SNPs discovered in European-ancestry populations. One PRS was based on 167 SNPs (PRS-167) and the other based on 313 SNPs (PRS-313) from the Breast Cancer Association Consortium studies as previously published. For each of the Asian-, Hispanic- and African-ancestry populations we added additional ancestry specific SNPs to the PRS-167 or the PRS-313, that were literature curated or our own identified race/ethnicity SNPs that we validated to provide independent risk prediction for their ancestry group: Asian added 10 or 4 additional SNPs, Hispanic 2 SNPs, and African 8 and 12 SNPs, respectively to each model. We tested this approach using datasets from several case-control studies of multiple racial/ethnic populations and compared discrimination of the models using area under the receiver operating characteristic curve (AUROC). Furthermore, we applied our multi-racial/ethnic PRS-313 in a sample of ~3000 multi-racial/ethnic women from the Athena Breast Screening Registry, case-control sampled by Gail score to be at elevated (Gail >1.67) or average (Gail≤1.67) risk, to evaluate the impact of our multi-ethnic adjustment on risk stratification.

Results: A multi-race/ethnicity adjusted PRS-313 and PRS-167 plus ethnicity specific SNPs has moderate-high discriminatory power with AUROCs of 0.65 and 0.64, respectively. The specificity of our PRS-167 in the different race/ethnicity ancestries performs relatively well in Asian (AUROC 0.59) and Hispanic (AUROC 0.63) populations, but less so in African-ancestry (AUROC 0.56). Incorporating multi-race/ethnicity PRS into Gail model selected women, resulted in 20% of average-risk women transitioning to risk above 1.67%, and conversely, 38% of elevated risk patients were reclassified to average risk.

Conclusion: We constructed a PRS risk score that can be applied to multi-ethnic populations and found moderate-high discrimination. Additional work is needed for the African-ancestry population. The addition of a multi-race/ethnicity SNP model to risk classification based on the Gail model significantly changes risk stratification and clinical care recommendations due to down- or up-reclassification of women at average versus elevated risk.

Citation Format: Sarah Theiner, Donglei Hu, Scott Huntsman, Yiwey Shieh, Laura Fejerman, Irene Acerbi, Sarah D Sawyer, Paige Kendall, Wei Zheng, Dezheng Huo, Olufunmilayo I Olopade, Christopher Haiman, Karla Kerlikowske, Steven Cummings, Ester John, Gabriela Torres-Mejia, Lawrence H Kushi, Denise Wolf, Jeffery A Tice, David A Pearce, Laura Esserman, Athena Breast Health Network Investigators and Advocate Partners, Laura J van ‘t Veer, Elad Ziv. A breast cancer multi-racial/ethnic polygenic risk score for improved personalized breast cancer screening [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-10-05.

Abstract P1-08-04: Withdrawn

This abstract was withdrawn by the authors.

Citation Format: Trabert B, Bauer DC, Brinton LA, Buist DS, Cauley JA, Dallal CM, Gierach GL, Falk RT, Hue TF, Lacey, Jr. JV, LaCroix AZ, Tice JA, Xu X. Withdrawn [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-04.

Breast Density and Risk of Invasive Breast Cancer among Older Women Undergoing Mammography: The Breast Cancer Surveillance Consortium Cohort Study

This study examined whether breast density is associated with risk of breast cancer in women age ≥65 years undergoing screening mammography in community practice. Methods: We used prospective cohort data between 1996 and 2012 from the Breast Cancer Surveillance Consortium (BCSC). We calculated separate cumulative incidence models for breast cancer incidence according to Breast Imaging Reporting and Data System (BI-RADS) breast density for women ages 65–74 and ages ≥75. Multivariable Cox proportional hazards regression models were fitted to determine the risk of invasive breast cancer adjusted for BCSC registry, race/ethnicity, BMI, hormone therapy use and benign breast disease. Results: Among the 403,268 women included in the study, approximately 40% were ages ≥75. The annual incidence rate of invasive breast cancer increased with increasing breast density among women ages 65–74 [BI- RADS fatty breasts: 2.2% (95% CI, 2.1%–2.4%) vs. heterogeneously or extremely dense breasts: 4.7% (95% CI, 4.6%–4.9%)] and women ages 75+ [BI-RADS fatty breasts: 2.3% (95% CI, 2.1%–2.5%) vs. heterogeneously or extremely dense: 4.3% (95% CI, 4.1%–4.5%)]. Women with BI-RADS fatty breasts had a decreased risk of breast cancer among women ages 65–74 [HR: 0.66 (95% CI: 0.58%–0.78%) and women ages ≥75 [HR: 0.73 (95% CI: 0.62%–0.87%). Women with BI-RADS heterogeneously or extremely dense breasts were found to have increased risk of breast cancer among women ages 65–74 [HR: 1.39 (95% CI: 1.28%–1.51%)] and women ages ≥75 [HR: 1.23 (95% CI: 1.10%–1.37%)]. Conclusions: Older women with higher BI-RADS density had a significantly increased risk of breast cancer. These findings add further evidence that breast density continues to be associated with an increased risk of breast cancer, even among women age ≥75 years.

Abstract P5-09-05: A model with polygenic risk score and mammographic density predicts interval cancers

Introduction:

Interval breast cancers present with clinical symptoms following a normal screening mammogram. They are associated with unfavorable biological features and with dense breasts. Models predictive of aggressive phenotypes may facilitate tailored screening for women at elevated risk of interval cancers. Polygenic risk scores (PRS) represent the cumulative effects of multiple single nucleotide polymorphisms (SNPs) and can be used to risk-stratify women. In prior reports, PRS is preferentially associated with screen-detected rather than interval cancers. We investigated methods to refine the PRS to preferentially predict interval cancers, and tested the performance of the PRS in joint models with mammographic breast density (MBD).

Methods:

We used data from 1058 breast cancer cases from The Cancer Genome Atlas (TCGA) as the discovery set for our PRS. We selected 107 SNPs from genomewide association studies of breast cancer risk for testing against tumor status at last follow-up in TCGA. Presence of tumor indicated recurrence, progression, or positive margins after resection. Women with tumor present at <100 days of follow-up were excluded. Suggestive associations (p<0.2) were used to construct a PRS, calculated as the sum across all SNPs of the per-allele log-odds ratio multiplied by the number of risk alleles for each SNP. We tested the performance of the PRS in a nested case-control dataset with 471 cases (102 interval cancers, 369 screen detected) and 496 controls from the California Pacific Medical Center Research Institute cohort. Logistic regression was used to evaluate the association between PRS, MBD and interval cancers. Area under the receiver operating characteristic (AUROC) curve was used to measure discrimination.

Results:

Of 107 SNPs, 23 had suggestive associations with presence of tumor at last follow-up in TCGA. The 23-SNP PRS discriminated between women with interval cancers and controls, with AUROC 0.57 (95% CI 0.51-0.63). With the inclusion of MBD in the model, the AUROC was 0.68 (95% CI 0.62-0.74). Women in the highest PRS quintile had an unadjusted 2.07-fold odds (95% CI 1.05-4.07) of developing interval cancers compared with women in the lowest quintile; adjustment for MBD did not change the point estimate. The PRS also discriminated between women with interval and screen-detected cancers, although the findings did not reach statistical significance (AUROC 0.55, 95% CI 0.48-0.61). With the inclusion of MBD in the model, the AUROC was 0.63 (95% CI 0.57-0.69).

Discussion:

A PRS associated with presence of tumor at last follow-up was independently predictive of interval cancers relative to controls. Models with PRS and MBD discriminated between interval and screen-detected cancers, although MBD provided most of the predictive power. Our findings are limited by the size and low number of recurrences in TCGA. It is possible that tumor status largely reflects treatment received, and may only partially represent the biological pathways of interval cancers. Our results suggest that SNPs may potentially identify women at risk for developing interval breast cancer, although further validation is required.

Citation Format: Shieh Y, Hu D, Huntsman S, Ma L, Gard CC, Leung JWT, Tice JA, Cummings SR, Kerlikowske K, Ziv E. A model with polygenic risk score and mammographic density predicts interval cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-09-05.

Abstract 2623: Common genetic variants associated with breast cancer risk used in the Athena study to enhance models identifying women for breast cancer chemoprevention

Background: The U.S. Preventive Services Task Force recommends that women with a >3% five-year risk of developing breast cancer consider taking selective estrogen receptor modifiers (SERMs) or aromatase inhibitors (AIs) to reduce their risk. Polygenic risk score (PRS), calculated by adding the individual breast cancer risk association for each common genetic variant (SNP), has been found to predict women at low- to high-risk of breast cancer. We analyze associations between SNP risk alleles and known breast cancer risk factors (ethnicity, family history of breast cancer and number of biopsies); furthermore, we quantify the likely impact on chemoprevention recommendations by adding the PRS to known risk models in a subset of women participating in the University of California 100,000 women Athena Breast Health Network.

Methods: Our research cohort included 838 women with no previous diagnosis of breast cancer from the University of California, San Francisco, and was enriched for women determined to be at elevated risk for developing breast cancer by the Gail model. A panel of 75 breast cancer risk SNPs were evaluated on saliva and blood samples (Akesogen Inc; COGS oncochip array). The PRS for each patient was calculated by converting the odds ratio for each SNP into a likelihood ratio (LR) and combining LR's across SNPs. Breast Cancer Surveillance Consortium (BCSC), Gail, BCSC-PRS and Gail-PRS scores (risk models incorporating PRS within a Bayesian framework), were evaluated for each patient. Associations between variables were assessed using t-test or ANOVA. A threshold of p<0.05 was used to assess significance.

Results: Women in this study carry an average of 65 risk allele SNPs (of 150, 2 per locus). By ANOVA, there is a statistically significant association between the SNPs risk allele count and ethnicity (p = 0.014), with a trend towards association with a family history of a first-degree relative with breast cancer (p = 0.053). PRS is significantly associated with a family history breast cancer (p = 0.031); neither SNP allele count nor PRS associates with previous biopsy status.

We found by adding PRS that 12% (86/707) and 13% (104/776) of patients with a prior BCSC or Gail score <3% five-year risk, respectively, changed classifications and would be eligible for chemoprevention. Conversely, 37% (36/98) and 36% (22/62) of patients with a BCSC or Gail score of >3% five-year risk, respectively, changed classifications by adding PRS and would no longer be eligible for chemoprevention.

Conclusion: The addition of SNP based PRS to BCSC and Gail models significantly changes how women are classified and as a result changes whether risk reducing agents are recommended.

PRS will be combined with BCSC and genetic test results for 9 breast cancer genes to calculate a women's breast cancer risk in the PCORI-funded Athena WISDOM study of 100,000 women, comparing risk-based vs. annual mammography screening.

Citation Format: Sarah Theiner, Sarah D. Sawyer, Paige Kendall, Alexandra S. Perry, Denise Wolf, Scott Huntsman, Bo Pan, Jeffery A. Tice, David A. Pearce, Thomas Cink, Laura Esserman, Elad Ziv, Laura van ‘t Veer. Common genetic variants associated with breast cancer risk used in the Athena study to enhance models identifying women for breast cancer chemoprevention. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2623.

Abstract P6-02-08: Breast cancer screening in the precision medicine era

We are entering the era of precision medicine in which cancer screening, prevention and treatment will be tailored to each individual. The progress made in this field is due, in part, to advances in our understanding of cancer risk and tumor biology. The challenge before us is to harness this knowledge and apply it in the clinical setting. Breast cancer screening provides an excellent opportunity to test the value of precision medicine in the real world. In this report we describe the process of designing a model of personalized breast cancer screening.

Methods

Risk factors were selected that have the greatest impact, have been validated and can be measured across a population. A risk model was selected that is highly calibrated, has been validated in a large screening cohort and is easy to apply in a large population of women. An expert committee was convened that set risk thresholds for stratifying women into groups that will be recommended to undergo biennial, annual or every six month screening. Risk thresholds and screening schedules are in accordance with the United States Preventive Services Task Force breast cancer screening recommendations.

Results

Risk factors: Age, race/ethnicity, personal history of breast biopsies and benign breast disease, family history, breast density and breast cancer-associated genetic mutations and single nucleotide polymorphisms (SNPs) were chosen as the risk factors that will be used to determine breast cancer risk. Risk model: The Breast Cancer Surveillance Consortium risk model will be used to calculate a woman's 5-year risk and will be modified by a polygenic risk score based on 81 SNPs. Risk thresholds: Women will be recommended to undergo biennial screening mammography when they reach the age of 50 or have the risk of an average 50 year-old woman (1.3% 5-year risk). Women will be advised to undergo annual screening if they are at increased risk of developing an interval cancer (women in their forties with extremely dense breasts and women at increased risk of developing estrogen receptor negative breast cancer based on their SNPs). Women will be recommended to undergo annual mammography and annual MRI if they are found to be gene mutation positive, have the risk of a BRCA1 mutation carrier (6% 5-year risk) or have a history of mantle radiation.

Discussion

Selecting the appropriate risk factors and risk model and determining risk thresholds are key components of designing a personalized breast cancer screening model. Personalized screening may be the way forward, but this can only be determined within the setting of a randomized controlled trial. We will conduct such a trial to determine if personalized screening is as safe as, less morbid than, more preferred by women than and enables prevention when compared to annual screening. The WISDOM (Women Informed to Screen Depending on Measures of risk) study will compare risk-based screening to annual screening within the Athena Breast Health Network with support from the Patient-Centered Outcomes Research Institute. Our intent is that this trial will provide us with the data that we need to determine the safest and most effective way to screen women for breast cancer in the era of precision medicine.

Citation Format: Thompson CK, Fiscalini AS, Donnellan P, Kaplan CP, Madlensky L, Eklund M, Ziv E, van't Veer LJ, Tice JA, Esserman LJ. Breast cancer screening in the precision medicine era. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-02-08.

Estrogen receptor alpha haplotypes and breast cancer risk in older Caucasian women

Life-long exposure to estrogen is an established risk factor for breast cancer development. The underlying mechanism has been suggested to be the binding of estrogen-to-estrogen receptors in mammary tissue, which in turn promotes the proliferation and differentiation of breast tissue. Polymorphisms and haplotypes in estrogen receptor alpha (ESR1) have been reportedly associated with breast cancer risk; however, the results are not fully consistent. In this study, we investigated breast cancer risk associated with genotypes and haplotypes resulting from four ESR1 single nucleotide polymorphisms (SNPs), rs746432, rs2234693, rs9340799, and rs1801132. Genotyping has been performed on 393 breast cancer cases and 790 randomly selected controls in 1,183 Caucasian women over age 65 from the Study of Osteoporotic Fractures (SOF). We observed an allelic protective effect for SNP rs9340799 with an estimated odds ratio (OR) of 0.82 (95% CI = 0.68-1.00; P = 0.04) after adjustment for age, BMI and hip BMD. A protective effect of this SNP has been reported before in several different studies. We did not replicate the previously reported C-C-A-G haplotype association to breast cancer-the C-C-A-G haplotype from these SNPs was rare in this study (estimated frequency below 0.001% in cases and controls). No other statistically significant associations were observed between ESR1 haplotypes from the same four SNPs and the risk of breast cancer in older Caucasian women.

Phytoestrogens and healthy aging: gaps in knowledge. A workshop report

There is an increasing public interest in foods and dietary supplements containing phytoestrogens for the maintenance of health. A workshop was convened to assess evidence for the potential benefits of phytoestrogen-containing foods or supplements on diseases or conditions affecting older populations. Preclinical, clinical, and epidemiologic data on the cardiovascular system, various cancers, bone diseases, and menopausal symptoms were the focus of the discussions. Research on the basis of consumer food choices as well as a presentation from the FDA regarding approval of the use of soy foods to reduce the risk of cardiovascular disease were also presented. Based on the information presented, isoflavone-containing soy foods may have favorable effects on the cardiovascular system, but major knowledge gaps still exist regarding effects ofphytoestrogen supplements on bone diseases, various cancers, menopausal symptoms, and cognitive function.

Cost-effectiveness of vitamin therapy to lower plasma homocysteine levels for the prevention of coronary heart disease: effect of grain fortification and beyond

CONTEXT

A high homocysteine level has been identified as an independent modifiable risk factor for coronary heart disease (CHD) events and death. Since January 1998, the US Food and Drug Administration has required that all enriched grain products contain 140 microg of folic acid per 100 g, a level considered to decrease homocysteine levels.

OBJECTIVES

To examine the potential effect of grain fortification with folic acid on CHD events and to estimate the cost-effectiveness of additional vitamin supplementation (folic acid and cyanocobalamin) for CHD prevention.

DESIGN AND SETTING

Cost-effectiveness analysis using the Coronary Heart Disease Policy Model, a validated, state-transition model of CHD events in adults aged 35 through 84 years. Data from the third National Health and Nutrition Examination Survey (NHANES III) were used to estimate age- and sex-specific differences in homocysteine levels.

INTERVENTION

Hypothetical comparison between a diet that includes enriched grain products projected to increase folic acid intake by 100 microg/d with the same diet without folic acid fortification; and a comparison between vitamin therapy that consists of 1 mg of folic acid and 0.5 mg of cyanocobalamin and the diet that includes grains fortified with folic acid.

MAIN OUTCOME MEASURES

Incidence of myocardial infarction and death from CHD, quality-adjusted life-years (QALYs) saved, and medical costs.

RESULTS

Grain fortification with folic acid was predicted to decrease CHD events by 8% in women and 13% in men, with comparable reductions in CHD mortality. The model projected that, compared with grain fortification alone, treating all patients with known CHD with folic acid and cyanocobalamin over a 10-year period would result in 310 000 fewer deaths and lower costs. Over the same 10-year period, providing vitamin supplementation in addition to grain fortification to all men aged 45 years or older without known CHD was projected to save more than 300 000 QALYs, to save more than US $2 billion, and to be the preferred strategy. For women without CHD, the preferred vitamin supplementation strategy would be to treat all women older than 55 years, a strategy projected to save more than 140 000 QALYs over 10 years.

CONCLUSIONS

Folic acid and cyanocobalamin supplementation may be cost-effective among many population subgroups and could have a major epidemiologic benefit for primary and secondary prevention of CHD if ongoing clinical trials confirm that homocysteine-lowering therapy decreases CHD event rates.

Relation of serum ascorbic acid to mortality among US adults

PURPOSE

To examine the relation between serum ascorbic acid (SAA), a marker of dietary intake (including supplements), and cause-specific mortality.

SUBJECTS AND METHODS

We analyzed data from a probability sample of 8,453 Americans age > or = 30 years at baseline enrolled in the Second National Health and Nutrition Examination Survey (NHANES II), who were followed for mortality endpoints. We calculated relative hazard ratios as measures of disease association comparing the mortality rates in three biologically relevant SAA categories.

RESULTS

Participants with normal to high SAA levels had a marginally significant 21% to 25% decreased risk of fatal cardiovascular disease (CVD) (p for trend = 0.09) and a 25% to 29% decreased risk of all-cause mortality (p for trend <0.001) compared to participants with low levels. Because we determined that gender modified the association between SAA levels and cancer death, we analyzed these associations stratified by gender. Among men, normal to high SAA levels were associated with an approximately 30% decreased risk of cancer deaths, whereas such SAA levels were associated with an approximately two-fold increased risk of cancer deaths among women. This association among women persisted even after adjustment for baseline prevalent cancer and exclusion for early cancer death or exclusion for prevalent cancer.

CONCLUSIONS

Low SAA levels were marginally associated with an increased risk of fatal CVD and significantly associated with an increased risk for all-cause mortality. Low SAA levels were also a risk factor for cancer death in men, but unexpectedly were associated with a decreased risk of cancer death in women. If the association between low SAA levels and all-cause mortality is causal, increasing the consumption of ascorbic acid, and thereby SAA levels, could decrease the risk of death among Americans with low ascorbic acid intakes.

What if Americans ate less fat? A quantitative estimate of the effect on mortality

Americans consume an average of 37% of their energy intake as fat. Many authorities recommend restricting fat intake to 30% of energy intake to reduce the rates of coronary heart disease and perhaps of cancers of the breast, colon, and prostate. Based on the assumptions that underlie those recommendations, we estimated the effect of this dietary change on mortality. If all Americans restricted their intake of dietary fat by reducing consumption of saturated fat and accompanying dietary cholesterol, the corresponding reductions in serum cholesterol levels could reduce coronary heart disease mortality rates by 5% to 20%, depending on age. If the relationship between dietary fat and cancer is as strong as has been observed in some studies, the proportional effects on mortality from fat-related cancers could be even greater, although the absolute effects--given the lower mortality rates--would be smaller. Overall, if the assumptions are correct, about 42,000 of the 2.3 million deaths that would have occurred in adults each year in the United States could be deferred. This 2% benefit, equivalent to an increase in average life expectancy of 3 to 4 months, would accrue chiefly to people over the age of 65 years. If recent concerns about the possibly harmful effects of cholesterol lowering on mortality from noncardiovascular causes--which mainly affect younger persons--are valid, these relatively modest benefits would be overestimates of the actual effect.