Parity and lactation in relation to estrogen receptor negative breast cancer in African American women

Trends in breast cancer incidence by estrogen receptor status in the United States, 2004-2020

Divergent trends of breast cancer incidence by subtype have been reported in the United States and elsewhere; however, it remains unknown whether this trend has continued until the era of the COVID-19 pandemic. Using high-quality population-based cancer registry data, representing 83% of the US population, this study examined breast cancer incidence rates by estrogen receptor (ER) status in women aged 20-84 years from 2004 to 2020. The incidence rate of ER-positive cancer increased by 1.75% per year from 2004 to 2009 (95% confidence interval [CI] = 1.26%-3.15%) and has slowed to a 0.87% annual increase (95% CI = 0.41%-1.03%) from 2009 to 2019, followed by a 10.2% reduction from 2019 to 2020. Trends were generally similar across race and ethnicity, although young women (20-49 years), Asian or Pacific Islander, and Hispanic women experienced steady increases until 2019. The incidence rate of ER-negative cancer decreased by 3.13% annually (95% CI = -4.2% to -2.55%) from 2004 to 2012, and the decrease stabilized from 2012 to 2019 (annual percent change: 0.55%; 95% CI = -1.30% to 0.92%), followed by a 6.0% reduction from 2019 to 2020, with trends generally consistent by age and across racial and ethnic groups. The stabilization of the steep decline in ER-negative cancer suggests a departure from the encouraging trajectories projected in earlier studies. Coupled with the deceleration in the rise of ER-positive cancer, the latest trend signals a potential stabilization in the previous rise of the proportional burden of ER-positive cancer. Understanding the impact of the pandemic on each subtype of breast cancer individually may provide a more comprehensive insight into its long-term sequelae on survival and mortality.

Reproductive characteristics, menopausal status, race and ethnicity, and risk of breast cancer subtypes defined by ER, PR and HER2 status: the Breast Cancer Etiology in Minorities study

BACKGROUND

Associations between reproductive factors and risk of breast cancer differ by subtype defined by joint estrogen receptor (ER), progesterone receptor (PR), and HER2 expression status. Racial and ethnic differences in the incidence of breast cancer subtypes suggest etiologic heterogeneity, yet data are limited because most studies have included non-Hispanic White women only.

METHODS

We analyzed harmonized data for 2,794 breast cancer cases and 4,579 controls, of whom 90% self-identified as African American, Asian American or Hispanic. Questionnaire data were pooled from three population-based studies conducted in California and data on tumor characteristics were obtained from the California Cancer Registry. The study sample included 1,530 luminal A (ER-positive and/or PR-positive, HER2-negative), 442 luminal B (ER-positive and/or PR-positive, HER2-positive), 578 triple-negative (TN; ER-negative, PR-negative, HER2-negative), and 244 HER2-enriched (ER-negative, PR-negative, HER2-positive) cases. We used multivariable unconditional logistic regression models to estimate subtype-specific ORs and 95% confidence intervals associated with parity, breast-feeding, and other reproductive characteristics by menopausal status and race and ethnicity.

RESULTS

Subtype-specific associations with reproductive factors revealed some notable differences by menopausal status and race and ethnicity. Specifically, higher parity without breast-feeding was associated with higher risk of luminal A and TN subtypes among premenopausal African American women. In contrast, among Asian American and Hispanic women, regardless of menopausal status, higher parity with a breast-feeding history was associated with lower risk of luminal A subtype. Among premenopausal women only, luminal A subtype was associated with older age at first full-term pregnancy (FTP), longer interval between menarche and first FTP, and shorter interval since last FTP, with similar OR estimates across the three racial and ethnic groups.

CONCLUSIONS

Subtype-specific associations with reproductive factors overall and by menopausal status, and race and ethnicity, showed some differences, underscoring that understanding etiologic heterogeneity in racially and ethnically diverse study samples is essential. Breast-feeding is likely the only reproductive factor that is potentially modifiable. Targeted efforts to promote and facilitate breast-feeding could help mitigate the adverse effects of higher parity among premenopausal African American women.

Biological Basis of Breast Cancer-Related Disparities in Precision Oncology Era

Precision oncology is based on deep knowledge of the molecular profile of tumors, allowing for more accurate and personalized therapy for specific groups of patients who are different in disease susceptibility as well as treatment response. Thus, onco-breastomics is able to discover novel biomarkers that have been found to have racial and ethnic differences, among other types of disparities such as chronological or biological age-, sex/gender- or environmental-related ones. Usually, evidence suggests that breast cancer (BC) disparities are due to ethnicity, aging rate, socioeconomic position, environmental or chemical exposures, psycho-social stressors, comorbidities, Western lifestyle, poverty and rurality, or organizational and health care system factors or access. The aim of this review was to deepen the understanding of BC-related disparities, mainly from a biomedical perspective, which includes genomic-based differences, disparities in breast tumor biology and developmental biology, differences in breast tumors' immune and metabolic landscapes, ecological factors involved in these disparities as well as microbiomics- and metagenomics-based disparities in BC. We can conclude that onco-breastomics, in principle, based on genomics, proteomics, epigenomics, hormonomics, metabolomics and exposomics data, is able to characterize the multiple biological processes and molecular pathways involved in BC disparities, clarifying the differences in incidence, mortality and treatment response for different groups of BC patients.

Enhancing Mammography and Empowering Solutions for Breast Cancer Disparities

Mammography enables early detection of breast cancer, a critical factor in improving treatment outcomes and breast cancer mortality. Yet, not all women benefit equally, and striking racial disparities in breast cancer mortality persist, with Black women 40% more likely to die from breast cancer compared with non-Hispanic White women. The current issue of Cancer Epidemiology, Biomarkers & Prevention presents three informative reports revealing racial and ethnic variations in mammography's performance in risk stratification, detection, and surveillance. The performance dynamics of mammography across different racial and ethnic groups highlight the urgency for additional research and innovative interventions to ensure equitable breast cancer control. We emphasize a pressing need for a comprehensive evaluation of multilevel influences on the performance and implementation of mammography in racially and ethnically diverse populations, complemented by equally urgent efforts to address factors influencing the risk of aggressive tumor subtypes and timely and effective treatment delivery. See related articles by Kerlikowske et al., p. 1524, Hubbard et al., p. 1531, Nyante et al., p. 1542.

Host, reproductive, and lifestyle factors in relation to quantitative histologic metrics of the normal breast

BACKGROUND

Emerging data indicate that variations in quantitative epithelial and stromal tissue composition and their relative abundance in benign breast biopsies independently impact risk of future invasive breast cancer. To gain further insights into breast cancer etiopathogenesis, we investigated associations between epidemiological factors and quantitative tissue composition metrics of the normal breast.

METHODS

The study participants were 4108 healthy women ages 18-75 years who voluntarily donated breast tissue to the US-based Susan G. Komen Tissue Bank (KTB; 2008-2019). Using high-accuracy machine learning algorithms, we quantified the percentage of epithelial, stromal, adipose, and fibroglandular tissue, as well as the proportion of fibroglandular tissue that is epithelium relative to stroma (i.e., epithelium-to-stroma proportion, ESP) on digitized hematoxylin and eosin (H&E)-stained normal breast biopsy specimens. Data on epidemiological factors were obtained from participants using a detailed questionnaire administered at the time of tissue donation. Associations between epidemiological factors and square root transformed tissue metrics were investigated using multivariable linear regression models.

RESULTS

With increasing age, the amount of stromal, epithelial, and fibroglandular tissue declined and adipose tissue increased, while that of ESP demonstrated a bimodal pattern. Several epidemiological factors were associated with individual tissue composition metrics, impacting ESP as a result. Compared with premenopausal women, postmenopausal women had lower ESP [β (95% Confidence Interval (CI)) = -0.28 (- 0.43, - 0.13); P < 0.001] with ESP peaks at 30-40 years and 60-70 years among pre- and postmenopausal women, respectively. Pregnancy [β (95%CI) vs nulligravid = 0.19 (0.08, 0.30); P < 0.001] and increasing number of live births (P-trend < 0.001) were positively associated with ESP, while breastfeeding was inversely associated with ESP [β (95%CI) vs no breastfeeding = -0.15 (- 0.29, - 0.01); P = 0.036]. A positive family history of breast cancer (FHBC) [β (95%CI) vs no FHBC = 0.14 (0.02-0.26); P = 0.02], being overweight or obese [β (95%CI) vs normal weight = 0.18 (0.06-0.30); P = 0.004 and 0.32 (0.21-0.44); P < 0.001, respectively], and Black race [β (95%CI) vs White = 0.12 (- 0.005, 0.25); P = 0.06] were positively associated with ESP.

CONCLUSION

Our findings revealed that cumulative exposure to etiological factors over the lifespan impacts normal breast tissue composition metrics, individually or jointly, to alter their dynamic equilibrium, with potential implications for breast cancer susceptibility and tumor etiologic heterogeneity.

Distinct Reproductive Risk Profiles for Intrinsic-Like Breast Cancer Subtypes: Pooled Analysis of Population-Based Studies

BACKGROUND

Reproductive factors have been shown to be differentially associated with risk of estrogen receptor (ER)-positive and ER-negative breast cancer. However, their associations with intrinsic-like subtypes are less clear.

METHODS

Analyses included up to 23 353 cases and 71 072 controls pooled from 31 population-based case-control or cohort studies in the Breast Cancer Association Consortium across 16 countries on 4 continents. Polytomous logistic regression was used to estimate the association between reproductive factors and risk of breast cancer by intrinsic-like subtypes (luminal A-like, luminal B-like, luminal B-HER2-like, HER2-enriched-like, and triple-negative breast cancer) and by invasiveness. All statistical tests were 2-sided.

RESULTS

Compared with nulliparous women, parous women had a lower risk of luminal A-like, luminal B-like, luminal B-HER2-like, and HER2-enriched-like disease. This association was apparent only after approximately 10 years since last birth and became stronger with increasing time (odds ratio [OR] = 0.59, 95% confidence interval [CI] = 0.49 to 0.71; and OR = 0.36, 95% CI = 0.28 to 0.46 for multiparous women with luminal A-like tumors 20 to less than 25 years after last birth and 45 to less than 50 years after last birth, respectively). In contrast, parous women had a higher risk of triple-negative breast cancer right after their last birth (for multiparous women: OR = 3.12, 95% CI = 2.02 to 4.83) that was attenuated with time but persisted for decades (OR = 1.03, 95% CI = 0.79 to 1.34, for multiparous women 25 to less than 30 years after last birth). Older age at first birth (Pheterogeneity < .001 for triple-negative compared with luminal A-like breast cancer) and breastfeeding (Pheterogeneity < .001 for triple-negative compared with luminal A-like breast cancer) were associated with lower risk of triple-negative breast cancer but not with other disease subtypes. Younger age at menarche was associated with higher risk of all subtypes; older age at menopause was associated with higher risk of luminal A-like but not triple-negative breast cancer. Associations for in situ tumors were similar to luminal A-like.

CONCLUSIONS

This large and comprehensive study demonstrates a distinct reproductive risk factor profile for triple-negative breast cancer compared with other subtypes, with implications for the understanding of disease etiology and risk prediction.

Neighborhood Contexts and Breast Cancer Among Asian American Women

BACKGROUND

This study examines how neighborhood socioeconomic status (nSES) and ethnic composition are associated with breast cancer risk for Asian American women.

METHODS

We linked individual level data from a population-based case-control study of breast cancer among Asian American women with neighborhood level data in the Greater San Francisco Bay Area (cases: n = 118, controls: n = 390). Multivariable logistic regression models examined the association between nSES, ethnic composition, and odds of having breast cancer.

RESULTS

Asian American women living in neighborhoods with high nSES and high ethnic composition had the highest odds of breast cancer, compared to those living in neighborhoods with high nSES and low ethnic composition (OR = 0.34, 95% CI [0.16-0.75]) or in neighborhoods with low nSES and high ethnic composition (OR = 0.37, 95% CI [0.17-0.83]).

DISCUSSION

Neighborhood socioeconomic and ethnic contexts are associated with breast cancer for Asian American women. We discuss explanations and avenues for future research.

A pooled case-only analysis of obesity and breast cancer subtype among Black women in the southeastern United States

PURPOSE

To evaluate the association between obesity and the relative prevalence of tumor subtypes among Black women with breast cancer (BC).

METHODS

We conducted a pooled case-only analysis of 1,793 Black women with invasive BC recruited through three existing studies in the southeastern US. Multivariable case-only polytomous logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association between obesity, measured by pre-diagnostic body mass index (BMI), and human epidermal growth factor receptor 2 + (HER2 +) and triple negative BC (TNBC) subtype relative to hormone receptor (HR) + /HER2- status (referent).

RESULTS

Among 359 premenopausal women, 55.4% of cases were HR + /HER2 -, 20.1% were HER2 + , and 24.5% were TNBC; corresponding percentages among 1,434 postmenopausal women were 59.3%, 17.0%, and 23.6%. Approximately, 50-60% of both pre- and postmenopausal women were obese (BMI > 30 kg/m²), regardless of BC subtype. We did not observe a significant association between obesity and BC subtype. Among postmenopausal women, class I obesity (BMI 35 + kg/m²) was not associated with the development of HER2 + BC (OR 0.69; 95% CI 0.42-1.14) or TNBC (OR 0.93; 95% CI 0.60-1.45) relative to HR + /HER2- tumors. Corresponding estimates among premenopausal women were 1.03 (95% CI 0.43-2.48) and 1.13 (95% CI 0.48-2.64).

CONCLUSION

In this large study of Black women with BC, there was no evidence of heterogeneity of BMI by BC subtype.

TP53 Pathway Function, Estrogen Receptor Status, and Breast Cancer Risk Factors in the Carolina Breast Cancer Study

BACKGROUND

TP53 and estrogen receptor (ER) both play essential roles in breast cancer development and progression, with recent research revealing cross-talk between TP53 and ER signaling pathways. Although many studies have demonstrated heterogeneity of risk factor associations across ER subtypes, associations by TP53 status have been inconsistent.

METHODS

This case-case analysis included incident breast cancer cases (47% Black) from the Carolina Breast Cancer Study (1993-2013). Formalin-fixed paraffin-embedded tumor samples were classified for TP53 functional status (mutant-like/wild-type-like) using a validated RNA signature. For IHC-based TP53 status, mutant-like was classified as at least 10% positivity. We used two-stage polytomous logistic regression to evaluate risk factor heterogeneity due to RNA-based TP53 and/or ER, adjusting for each other and for PR, HER2, and grade. We then compared this with the results when using IHC-based TP53 classification.

RESULTS

The RNA-based classifier identified 55% of tumors as TP53 wild-type-like and 45% as mutant-like. Several hormone-related factors (oral contraceptive use, menopausal status, age at menopause, and pre- and postmenopausal body mass index) were associated with TP53 mutant-like status, whereas reproductive factors (age at first birth and parity) and smoking were associated with ER status. Multiparity was associated with both TP53 and ER. When classifying TP53 status using IHC methods, no associations were observed with TP53. Associations observed with RNA-based TP53 remained after accounting for basal-like subtype.

CONCLUSIONS

This case-case study found breast cancer risk factors associated with RNA-based TP53 and ER.

IMPACT

RNA-based TP53 and ER represent an emerging etiologic schema of interest in breast cancer prevention research.

Individual- and neighborhood-level socioeconomic status and risk of aggressive breast cancer subtypes in a pooled cohort of women from Kaiser Permanente Northern California

BACKGROUND

Low socioeconomic status (SES) has been associated with a higher risk of aggressive breast cancer (BC) subtypes, but few studies have examined the independent effects of both neighborhood-level socioeconomic status (nSES) and individual-level SES measures.

METHODS

This study included 5547 women from the Pathways and Life After Cancer Epidemiology cohorts who were diagnosed with invasive BC. Generalized estimating equation models were used to examine associations of nSES (a composite score based on income, poverty, education, occupation, employment, rent, and house value) and individual-level SES (income and education) with BC subtypes: luminal B (LumB), Her2-enriched (Her2-e), and triple-negative breast cancer (TNBC) relative to luminal A (LumA). Models controlled for age, race, nativity, stage, days from diagnosis to survey, and study cohort and simultaneously for nSES and individual-level SES.

RESULTS

In fully adjusted models, low nSES was significantly associated with the LumB (odds ratio for quartile 1 vs quartile 4 [ORQ1vQ4 ], 1.31; 95% confidence interval [CI], 1.11-1.54; P for trend = .005) and TNBC subtypes (ORQ1vQ4 , 1.32; 95% CI, 1.02-1.71; P for trend = .037) relative to LumA. Conversely, individual education was significantly associated with only the Her2-e subtype (odds ratio for high school degree or less vs postgraduate, 1.68; 95% CI, 1.03-2.75; P for trend = .030) relative to LumA. Individual income was not significantly associated with any BC subtype.

CONCLUSIONS

nSES and individual-level SES are independently associated with different BC subtypes; specifically, low nSES and individual-level education are independent predictors of more aggressive BC subtypes relative to LumA.

Mediation analysis of racial disparities in triple-negative breast cancer incidence among postmenopausal women

BACKGROUND

Triple-negative breast cancer (TNBC) is disproportionately higher in Black women relative to White women. The objective of this study was to examine to what extent the association between race/ethnicity and risk of TNBC is mediated by potentially modifiable factors.

METHODS

A total of 128,623 Black and White women aged 50-79 years from the Women's Health Initiative were followed for a mean of 15.8 years. 643 incident TNBC cases (92 Black women and 551 White women) were confirmed by medical record review. Mediation analyses were conducted using an approach under a counterfactual framework.

RESULTS

Black women had approximately twofold higher risk of TNBC compared with white women (HR = 1.93, 95% CI 1.52-2.45). We observed that 48% of the racial disparity was mediated by metabolic dysfunction defined by having 3 or more cardiometabolic risk factors including elevated waist circumference, having history of diabetes, high cholesterol and hypertension. The racial disparity was not significantly mediated by other factors studied, including socioeconomic, lifestyle or reproductive factors.

CONCLUSION

Our study observed that approximately half of the racial disparity between postmenopausal Black and White women in TNBC incidence was driven by metabolic dysfunction.

Impact of breast cancer risk factors on clinically relevant prognostic biomarkers for primary breast cancer

Purpose

In addition to impacting incidence, risk factors for breast cancer may also influence recurrence and survival from the disease. However, it is unclear how these factors affect combinatorial biomarkers for aiding treatment decision-making in breast cancer.

Methods

Patients were 8179 women with histologically confirmed invasive breast cancer, diagnosed and treated in a large cancer hospital in Beijing, China. Individual clinicopathological (tumor size, grade, lymph nodes) and immunohistochemical (IHC: ER, PR, HER2, KI67) markers were used to define clinically relevant combinatorial prognostic biomarkers, including the Nottingham Prognostic Index (NPI: combining size, grade, nodes) and IHC4 score (combining ER, PR, HER2, KI67). Odds ratios (ORs) and 95% confidence intervals (CIs) for associations between breast cancer risk factors and quartiles (Q1–Q4) of NPI and IHC4 were assessed in multivariable polytomous logistic regression models.

Results

Overall, increasing parity (OR_trend(95% CI) = 1.20(1.05–1.37);P_trend = 0.007), overweight (OR(95% CI)_{vs normal} = 1.60(1.29–1.98)), and obesity (OR(95% CI) _{vs normal} = 2.12(1.43–3.14)) were associated with higher likelihood of developing tumors with high (Q4) versus low (Q1) NPI score. Conversely, increasing age (OR_trend(95% CI) = 0.75(0.66–0.84);P_trend < 0.001) and positive family history of breast cancer (FHBC) (OR(95% CI) = 0.66(0.45–0.95)) were inversely associated with NPI. Only body mass index (BMI) was associated with IHC4, with overweight (OR(95% CI) _{vs normal} = 0.82(0.66–1.02)) and obese (OR(95% CI) _{vs normal} = 0.52(0.36–0.76)) women less likely to develop high IHC4 tumors. Notably, elevated BMI was associated with higher NPI irrespective of hormone receptor-expression status.

Conclusions

Our findings indicate that factors affecting breast cancer incidence, particularly age, parity, FHBC, and BMI, may impact clinically relevant prognostic biomarkers with implications for surveillance, prognostication, and counseling.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-021-06294-5.

Breast cancer risk factors in relation to molecular subtypes in breast cancer patients from Kenya

BACKGROUND

Few studies have investigated risk factor heterogeneity by molecular subtypes in indigenous African populations where prevalence of traditional breast cancer (BC) risk factors, genetic background, and environmental exposures show marked differences compared to European ancestry populations.

METHODS

We conducted a case-only analysis of 838 pathologically confirmed BC cases recruited from 5 groups of public, faith-based, and private institutions across Kenya between March 2012 to May 2015. Centralized pathology review and immunohistochemistry (IHC) for key markers (ER, PR, HER2, EGFR, CK5-6, and Ki67) was performed to define subtypes. Risk factor data was collected at time of diagnosis through a questionnaire. Multivariable polytomous logistic regression models were used to determine associations between BC risk factors and tumor molecular subtypes, adjusted for clinical characteristics and risk factors.

RESULTS

The median age at menarche and first pregnancy were 14 and 21 years, median number of children was 3, and breastfeeding duration was 62 months per child. Distribution of molecular subtypes for luminal A, luminal B, HER2-enriched, and triple negative (TN) breast cancers was 34.8%, 35.8%, 10.7%, and 18.6%, respectively. After adjusting for covariates, compared to patients with ER-positive tumors, ER-negative patients were more likely to have higher parity (OR = 2.03, 95% CI = (1.11, 3.72), p = 0.021, comparing ≥ 5 to ≤ 2 children). Compared to patients with luminal A tumors, luminal B patients were more likely to have lower parity (OR = 0.45, 95% CI = 0.23, 0.87, p = 0.018, comparing ≥ 5 to ≤ 2 children); HER2-enriched patients were less likely to be obese (OR = 0.36, 95% CI = 0.16, 0.81, p = 0.013) or older age at menopause (OR = 0.38, 95% CI = 0.15, 0.997, p = 0.049). Body mass index (BMI), either overall or by menopausal status, did not vary significantly by ER status. Overall, cumulative or average breastfeeding duration did not vary significantly across subtypes.

CONCLUSIONS

In Kenya, we found associations between parity-related risk factors and ER status consistent with observations in European ancestry populations, but differing associations with BMI and breastfeeding. Inclusion of diverse populations in cancer etiology studies is needed to develop population and subtype-specific risk prediction/prevention strategies.

A Pooled Case-only Analysis of Reproductive Risk Factors and Breast Cancer Subtype Among Black Women in the Southeastern United States

BACKGROUND

We investigated the association between reproductive risk factors and breast cancer subtype in Black women. On the basis of the previous literature, we hypothesized that the relative prevalence of specific breast cancer subtypes might differ according to reproductive factors.

METHODS

We conducted a pooled analysis of 2,188 (591 premenopausal, 1,597 postmenopausal) Black women with a primary diagnosis of breast cancer from four studies in the southeastern United States. Breast cancers were classified by clinical subtype. Case-only polytomous logistic regression models were used to estimate ORs and 95% confidence intervals (CI) for HER2⁺ and triple-negative breast cancer (TNBC) status in relation to estrogen receptor-positive (ER⁺)/HER2^- status (referent) for reproductive risk factors.

RESULTS

Relative to women who had ER⁺/HER2^- tumors, women who were age 19-24 years at first birth (OR, 1.78; 95% CI, 1.22-2.59) were more likely to have TNBC. Parous women were less likely to be diagnosed with HER2⁺ breast cancer and more likely to be diagnosed with TNBC relative to ER⁺/HER2^- breast cancer. Postmenopausal parous women who breastfed were less likely to have TNBC [OR, 0.65 (95% CI, 0.43-0.99)].

CONCLUSIONS

This large pooled study of Black women with breast cancer revealed etiologic heterogeneity among breast cancer subtypes.

IMPACT

Black parous women who do not breastfeed are more likely to be diagnosed with TNBC, which has a worse prognosis, than with ER⁺/HER2^- breast cancer.

Developing a Culturally and Linguistically Targeted Breast Cancer Educational Program for a Multicultural Population

Breast cancer is the most commonly diagnosed cancer among women in the USA. Despite the availability of screening mammograms, significant disparities still exist in breast cancer outcomes of racial/ethnic and sexual/gender minorities. To address these disparities, the Mount Sinai Mobile Breast Health Program in New York City collaborated with local organizations to develop culturally and linguistically appropriate breast cancer education programs aimed at increasing screening mammogram utilization. Literature review of the barriers to mammography screening formed the basis to allow us to draft a narrative presentation for each targeted cultural group: African American, African-born, Chinese, Latina, and Muslim women, as well as LGBTQ individuals. The presentations were then tested with focus groups comprised of gatekeepers and members from local community and faith-based organizations which served the targeted populations. Feedback from focus groups and gatekeepers was incorporated into the presentations, and if necessary, the presentations were translated. Subsequently, the presentations were re-tested for appropriateness and reviewed for consistency in message, design, educational information, and slide sequencing. Our experience demonstrated the importance of collaborating with community organizations to provide educational content that is culturally and linguistically appropriate for minority groups facing barriers to uptake of screening mammography.

Reproductive factors and risk of breast cancer in black South African women

PURPOSE

Breast cancer (BC) is increasing in black South African women, but few studies have investigated its risk factors.

METHODS

We conducted an analysis of reproductive factors and BC risk in the South African Breast Cancer (SABC) study-a population-based case-control study of black South African women from Soweto that included 399 cases and 399 matched controls. Information on lifestyle and reproductive history was obtained by interviews. Conditional logistic regression was used to determine the association of reproductive factors with BC, adjusting for potential confounding factors.

RESULTS

Seventy-five percent of all BC cases were ER+, 66% PR+, 30% HER2+, and 16% TN. None of the reproductive variables were associated with BC overall or by subtype in the overall population, nor in pre- (n = 135 cases) or in post-menopausal women separately. In HIV-negative pre-menopausal women (n = 97 cases), later age at first pregnancy and longer time between menarche and first full-time pregnancy were inversely related to BC risk (OR 0.89 (95% CI 0.82-0.97; and 0.93 95% CI 0.86-1.01, respectively).

CONCLUSION

In this population of black South African women, reproductive factors were not associated with BC risk.

Risk factors for breast cancer development by tumor characteristics among women with benign breast disease

Background

Among women diagnosed with invasive breast cancer, 30% have a prior diagnosis of benign breast disease (BBD). Thus, it is important to identify factors among BBD patients that elevate invasive cancer risk. In the general population, risk factors differ in their associations by clinical pathologic features; however, whether women with BBD show etiologic heterogeneity in the types of breast cancers they develop remains unknown.

Methods

Using a nested case-control study of BBD and breast cancer risk conducted in a community healthcare plan (Kaiser Permanente Northwest), we assessed relationships of histologic features in BBD biopsies and patient characteristics with subsequent breast cancer risk and tested for heterogeneity of associations by estrogen receptor (ER) status, tumor grade, and size. The study included 514 invasive breast cancer cases (median follow-up of 9 years post-BBD diagnosis) and 514 matched controls, diagnosed with proliferative or non-proliferative BBD between 1971 and 2006, with follow-up through mid-2015. Odds ratios (ORs) and 95% confidence intervals (CIs) were obtained using multivariable polytomous logistic regression models.

Results

Breast cancers were predominantly ER-positive (86%), well or moderately differentiated (73%), small (74% < 20 mm), and stage I/II (91%). Compared to patients with non-proliferative BBD, proliferative BBD with atypia conferred increased risk for ER-positive cancer (OR = 5.48, 95% CI = 2.14–14.01) with only one ER-negative case, P-heterogeneity = 0.45. The presence of columnar cell lesions (CCLs) at BBD diagnosis was associated with a 1.5-fold increase in the risk of both ER-positive and ER-negative tumors, with a 2-fold increase (95% CI = 1.21–3.58) observed among postmenopausal women (56%), independent of proliferative BBD status with and without atypia. We did not identify statistically significant differences in risk factor associations by tumor grade or size.

Conclusion

Most tumors that developed after a BBD diagnosis in this cohort were highly treatable low-stage ER-positive tumors. CCL in BBD biopsies may be associated with moderately increased risk, independent of BBD histology, and irrespective of ER status.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01410-1.

In-Vitro Fertilization Impact on the Risk of Breast Cancer: A Review Article

Background

Due to the increasing prevalence of infertility, the number of referrals to infertility treatment centers has also increased. Nowadays, assisted reproductive technology (ART), including in vitro fertilization (IVF), is a treatment for infertility or genetic problems. Considering the possible consequences of this method among women undergoing in vitro fertilization (IVF) and kids conceived by IVF, extensive research has been conducted in this regard.

Methods

Overall, 100 articles were entered into the study, and relevant articles were searched and extracted from PubMed, Springer, and Google Scholar databases. In IVF procedure, medications such as Clomiphene citrate and gonadotropins are used to stimulate and mature follicles and thus increase ovulation.

Results

There are conflicting opinions on this issue. Some findings report a slight increase in cancer risk for hormone-sensitive cancers including breast cancer. The long-term use of IVF medications can increase estrogen hormones and cause excessive expression of genes, resulting in an increased risk of breast cancer, which is one of the most frequent cancers among women.

Conclusion

There are some risks to be aware of, which followed the hypothesis that long IVF treatment process may lead to breast cancer among IVF candidates. Furthermore, the risk of breast cancer may be increased in those women with a positive family history and related inherited genes. Therefore, women candidates for IVF should be informed of the probable implications of the reproductive therapy techniques.

Epidemiology of Basal-like and Luminal Breast Cancers among Black Women in the AMBER Consortium

BACKGROUND

Evidence suggests etiologic heterogeneity among breast cancer subtypes. Previous studies with six-marker IHC classification of intrinsic subtypes included small numbers of black women.

METHODS

Using centralized laboratory results for estrogen receptor (ER), progesterone receptor, HER2, proliferation marker, Ki-67, EGFR, and cytokeratin (CK)5/6, we estimated case-only and case-control ORs for established breast cancer risk factors among cases (n = 2,354) and controls (n = 2,932) in the African American Breast Cancer Epidemiology and Risk (AMBER) consortium. ORs were estimated by ER status and intrinsic subtype using adjusted logistic regression.

RESULTS

Case-only analyses by ER status showed etiologic heterogeneity by age at menarche, parity (vs. nulliparity), and age at first birth. In case-control analyses for intrinsic subtype, increased body mass index and waist-to-hip ratio (WHR) were associated with increased risk of luminal A subtype, whereas older age at menarche and parity, regardless of breastfeeding, were associated with reduced risk. For basal-like cancers, parity without breastfeeding and increasing WHR were associated with increased risk, whereas breastfeeding and age ≥25 years at first birth were associated with reduced risk among parous women. Basal-like and ER^-/HER2⁺ subtypes had earlier age-at-incidence distribution relative to luminal subtypes.

CONCLUSIONS

Breast cancer subtypes showed distinct etiologic profiles in the AMBER consortium, a study of more than 5,000 black women with centrally assessed tumor biospecimens.

IMPACT

Among black women, high WHR and parity without breastfeeding are emerging as important intervention points to reduce the incidence of basal-like breast cancer.

Controlled ovarian hyperstimulation for fertility preservation in women with breast cancer: Practical issues

In Korean women, a westernized lifestyle is associated with an increased risk of breast cancer. Fertility preservation has become an increasingly important issue for women with breast cancer, in accordance with substantial improvements in survival rate after cancer treatment. The methods of controlled ovarian hyperstimulation (COH) for fertility preservation in breast cancer patients have been modified to include aromatase inhibitors to reduce the potential harm associated with increased estradiol levels. Random-start COH and dual ovarian stimulation are feasible options to reduce the total duration of fertility preservation treatment and to efficiently collect oocytes or embryos. Using a gonadotropin-releasing hormone agonist as a trigger may improve cycle outcomes in breast cancer patients undergoing COH for fertility preservation. In young breast cancer patients with BRCA mutations, especially BRCA1 mutations, the possibility of diminished ovarian reserve may be considered, although further studies are necessary. Herein, we review the current literature on the practical issues surrounding COH for fertility preservation in women with breast cancer.

Menstrual and reproductive characteristics and breast cancer risk by hormone receptor status and ethnicity: The Breast Cancer Etiology in Minorities study

We pooled multiethnic data from four population-based studies and examined associations of menstrual and reproductive characteristics with breast cancer (BC) risk by tumor hormone receptor (HR) status [defined by estrogen receptor (ER) and progesterone receptor (PR)]. We estimated odds ratios and 95% confidence intervals using multivariable logistic regression, stratified by age (<50, ≥50 years) and ethnicity, for 5,186 HR+ (ER+ or PR+) cases, 1,365 HR- (ER- and PR-) cases and 7,480 controls. For HR+ BC, later menarche and earlier menopause were associated with lower risk in non-Hispanic whites (NHWs) and Hispanics, and higher parity and longer breast-feeding were associated with lower risk in Hispanics and Asian Americans, and suggestively in NHWs. Positive associations with later first full-term pregnancy (FTP), longer interval between menarche and first FTP and shorter time since last FTP were limited to younger Hispanics and Asian Americans. Except for nulliparity, reproductive characteristics were not associated with risk in African Americans. For HR- BC, lower risk was associated with later menarche, except in African Americans and older Asian Americans and with longer breast-feeding in Hispanics and Asian Americans only. In younger African Americans, HR- BC risk associated with higher parity (≥3 vs. 1 FTP) was increased fourfold in women who never breast-fed, but not in those with a breast-feeding history, suggesting that breast-feeding may mitigate the adverse effect of higher parity in younger African American women. Further work needs to evaluate why menstrual and reproductive risk factors vary in importance according to age and ethnicity.

Relationships between Breast Feeding and Breast Cancer Subtypes: Lessons Learned from Studies in Humans and in Mice

There are differential risk relationships between parity and breast cancer according to estrogen receptor (ER) status, with an increased risk of ER^- disease reduced by breastfeeding. This may be particularly relevant for understanding the higher incidence of ER^- tumors in Black women, who are more likely to be parous and less likely to breastfeed than other U.S. groups. Potential mechanisms for these relationships may include effects of disordered breast involution on inflammatory milieu in the breast as well as epigenetic reprogramming in the mammary gland, which can affect cell fate decisions in progenitor cell pools. In normal breast tissue, parity has been associated with hypermethylation of FOXA1, a pioneer transcription factor that promotes the luminal phenotype in luminal progenitors, while repressing the basal phenotype. In breast tumors, relationships between FOXA1 methylation and parity were strongest among women who did not breastfeed. Here, we summarize the epidemiologic literature regarding parity, breastfeeding, and breast cancer subtypes, and review potential mechanisms whereby these factors may influence breast carcinogenesis, with a focus on effects on progenitor cell pools in the mammary gland.

Divergent breast cancer incidence trends by hormone receptor status in the state of Sarawak, Malaysia

Recent studies from high-risk countries such as the US, Denmark and Ireland have shown rising incidence rates of hormone receptor (HR)-positive and falling rates of HR-negative breast cancers (BC). However, it remains unclear whether a similar pattern occurs in low-risk countries. Detailed clinical and risk factor data were collected from 2,977 female invasive BC patients (≥20 years) in Sarawak General Hospital, Malaysia, representing 93% of the population. The population-at-risk was obtained from the Department of Statistics Malaysia. Secular trends in age-standardized incidence rates were assessed using estimated average annual percent changes. Associations between established BC risk factors and tumor subtypes defined by HR or joint human epidermal growth factor receptor 2 (HR/HER2) status were examined by case-case comparisons using logistic regression. From 2006 to 2015, incidence rates increased for HR-positive cancers by 4.46%/year (95% CI = 2.19-6.78) and decreased for HR-negative cancers by 2.29%/year (95% CI = -4.31 to -0.24). When further stratified by HER2, the most contrasting difference in linear trends was observed between HR+/HER2- and HR-/HER2- subtypes. After controlling for potential confounders, cases with excess body weight (OR_{overweight vs. normal} = 0.82; 95% CI = 0.69-0.98; OR_{obese vs. normal} = 0.62; 95% CI = 0.48-0.80), later age at first birth (OR_{≥26 years vs. <23 years} = 0.82; 95% CI = 0.66-1.02), nulliparity (OR_{nulliparous vs. <23 years} = 0.74; 95% CI = 0.59-0.94) and never-breastfeeding (OR_{never vs. ever} = 0.73; 95% CI = 0.55-0.97) were less frequent among HR-negative cases than among HR-positive cases. Diverging incidence trends by HR expression were similar in Sarawak and Western countries, possibly reflecting changes in the prevalence of risk factors with opposing effects by tumor subtypes in low- and high-risk populations.

The impact of sociodemographic factors and health insurance coverage in the diagnosis and clinicopathological characteristics of breast cancer in Brazil: AMAZONA III study (GBECAM 0115)

PURPOSE

In Brazil, the available cancer registries are deficient in number and quality and, hence, little information is known regarding sociodemographic, clinicopathological characteristics, treatment patterns, and outcomes of breast cancer (BC) patients. We performed the AMAZONA III/ GBECAM 0115 study and in this analysis, we describe patients' characteristics at diagnosis and their association with health insurance type.

METHODS

This is a prospective cohort study developed in 23 sites in Brazil including women with newly diagnosed invasive BC from January 2016 to March 2018. In order to compare healthcare insurance type, we considered patients who were treated under the Brazilian public health system as publicly insured, and women who had private insurance or paid for their treatment as privately insured.

RESULTS

A total of 2950 patients were included in the study. Median age at diagnosis was 53.9 years; 63.1% were publicly insured. The majority of patients (68.6%) had stage II-III breast cancer and ductal carcinoma histology (80.9%). The most common breast cancer subtype was luminal A-like (48.0%) followed by luminal B-HER2 positive-like (17.0%) and triple-negative (15.6%). Luminal A was more frequent in private (53.7% vs. 44.2%, p < .0001) than public, whereas Luminal B HER2-positive (19.2% vs. 14.2%, p = 0.0012) and HER2-positive (8.8% vs. 5.1%, p = 0.0009) were more common in patients with public health system coverage. Only 34% of patients were diagnosed by screening exams. Privately insured patients were more frequently diagnosed with stage I disease when compared to publicly insured patients; publicly insured patients had more stage III (33.5% vs. 14.7%; p-value < 0.0001) disease than privately insured ones. Breast cancer was detected by symptoms more frequently in publicly than in privately insured patients (74.2% vs 25.8%, respectively; p-value < 0.0001).

CONCLUSIONS

Patients with public health coverage were diagnosed with symptomatic disease, later stages and more aggressive subtypes when compared to privately insured patients.

Risk Factor Analysis for Breast Cancer in Premenopausal and Postmenopausal Women of Punjab, India

OBJECTIVE

Amritsar, the second largest town of agrarian state of Punjab, India reports high number of breast cancer cases every year. The present study investigated the etiology of breast cancer using various obesity indices and other epidemiological factors among breast cancer patients residing in and around Amritsar city.

METHODS

In this case control study, risk factors for breast cancer were analyzed in 542 female subjects: 271 females with breast cancer patients and 271 unrelated healthy females matched for age as control females.

RESULTS

Bivariate analysis for risk factors in cases and controls showed a lower risk (OR=0.65, 95% CI 0.43-0.99, p=0.04) in obese cases with BMI≥25kg/m2 as compared to subjects with normal BMI. Risk factor analysis showed that parameter which provided risk for cancer in postmenopausal women was obesity and in premenopausal women was parity. Postmenopausal women with BMI (overweight: OR=0.39, 95% CI 0.17-0.92, p=0.03; obese: OR= 0.26, 95% CI 0.13-0.52, p=0.00), WC (OR=0.17, 95% CI 0.05-0.52, p=0.00) and WHtR (p=0.02) had highr risk. Premenopausal women with 3 or less than 3 children had a higher risk (OR=5.54, 95 % CI 2.75-11.19, p=0.00) than postmenopausal women when compared to women with more than 3 children. Binary logistic regression analysis revealed that low parity (≤3) substantially increased the risk for breast cancer (OR=4.80, 95% CI 2.34-9.85, p=0.00) in premenopausal women.

CONCLUSION

Obesity, parity associated breast cancer risk and reduced breastfeeding cumulatively predispose the premenopausal women of this region to higher risk of breast cancer.
.

Clinicopathological and epidemiological significance of breast cancer subtype reclassification based on p53 immunohistochemical expression

TP53 mutations are common in breast cancer and are typically associated with more aggressive tumor characteristics, but little is known about the clinicopathological and epidemiological relevance of p53 protein expression, a TP53 mutation surrogate, in breast cancer subtypes. In this study of 7226 Chinese women with invasive breast cancer, we defined breast cancer subtypes using immunohistochemical (IHC) measures of hormone receptors and HER2 in conjunction with histologic grade. p53 expression status was then used to further stratify subtypes into p53-positive and p53-negative. Odds ratios (ORs) and 95% confidence intervals (CIs) in case-only logistic regression analyses were used to examine heterogeneity across different subtypes. The frequency of p53 protein expression varied by breast cancer subtype, being lowest in the luminal A-like and highest in the triple-negative and HER2-enriched subtypes (P-value < 0.01). In luminal A-like and B-like/HER2-negative subtypes, p53 positivity was associated with early-onset tumors, high grade, high proliferative index, and basal marker (CK5/6 and EGFR) expression. Further, compared with luminal A-like/p53-negative patients, A-like/p53-positive patients were more likely to be parous [adjusted OR parous vs. nulliparous = 2.67 (1.60, 4.51); P-value < 0.01] and to have breastfed [adjusted OR ever vs. never = 1.38 (1.03, 1.85); P-value = 0.03]. p53 positivity was not associated with examined clinical and risk factors in other tumor subtypes. Overall, these findings suggest that p53 expression, which is readily available in many settings, can be used to identify phenotypes of luminal A-like breast cancer with distinct clinical and epidemiological implications.

A Pooled Analysis of Breastfeeding and Breast Cancer Risk by Hormone Receptor Status in Parous Hispanic Women

BACKGROUND

Data on breastfeeding and breast cancer risk are sparse and inconsistent for Hispanic women.

METHODS

Pooling data for nearly 6,000 parous Hispanic women from four population-based studies conducted between 1995 and 2007 in the United States and Mexico, we examined the association of breastfeeding with risk of breast cancer overall and subtypes defined by estrogen receptor (ER) and progesterone receptor (PR) status, and the joint effects of breastfeeding, parity, and age at first birth. We calculated odds ratios (ORs) and 95% confidence intervals (CIs) using logistic regression.

RESULTS

Among parous Hispanic women, older age at first birth was associated with increased breast cancer risk, whereas parity was associated with reduced risk. These associations were found for hormone receptor positive (HR+) breast cancer only and limited to premenopausal women. Age at first birth and parity were not associated with risk of ER- and PR- breast cancer. Increasing duration of breastfeeding was associated with decreasing breast cancer risk (≥25 vs. 0 months: OR = 0.73; 95% CI = 0.60, 0.89; Ptrend = 0.03), with no heterogeneity by menopausal status or subtype. At each parity level, breastfeeding further reduced HR+ breast cancer risk. Additionally, breastfeeding attenuated the increase in risk of HR+ breast cancer associated with older age at first birth.

CONCLUSIONS

Our findings suggest that breastfeeding is associated with reduced risk of both HR+ and ER- and PR- breast cancer among Hispanic women, as reported for other populations, and may attenuate the increased risk in women with a first pregnancy at older ages.

Parity, breastfeeding, and breast cancer risk by hormone receptor status and molecular phenotype: results from the Nurses' Health Studies

Background

Epidemiologic data suggest that parity increases risk of hormone receptor-negative breast cancer and that breastfeeding attenuates this association. Prospective data, particularly on the joint effects of higher parity and breastfeeding, are limited.

Methods

We investigated parity, breastfeeding, and breast cancer risk by hormone-receptor (estrogen (ER) and progesterone receptor (PR)) and molecular subtypes (luminal A, luminal B, HER2-enriched, and basal-like) in the Nurses’ Health Study (NHS; 1976–2012) and NHSII (1989–2013). A total of 12,452 (ER+ n = 8235; ER− n = 1978) breast cancers were diagnosed among 199,514 women. We used Cox proportional hazards models, adjusted for breast cancer risk factors, to calculate hazard ratios (HR) and 95% confidence intervals (CI).

Results

Parous women had lower risk of ER+ breast cancer (vs. nulliparous, HR = 0.82 [0.77–0.88]); no association was observed for ER− disease (0.98 [0.84–1.13]; P_het = 0.03). Among parous women, breastfeeding was associated with lower risk of ER− (vs. never 0.82 [0.74–0.91]), but not ER+, disease (0.99 [0.94–1.05]; P_het < 0.001). Compared to nulliparous women, higher parity was inversely associated with luminal B breast cancer regardless of breastfeeding (≥ 3 children: ever breastfed, 0.78 [0.62–0.98]; never breastfed, 0.76 [0.58–1.00]) and luminal A disease only among women who had breastfed (≥ 3 children, 0.84 [0.71–0.99]). Basal-like breast cancer risk was suggestively higher among women with higher parity who never breastfed; associations were null among those who ever breastfed.

Conclusions

This study provides evidence that breastfeeding is inversely associated with hormone receptor-negative breast cancers, representing an accessible and cost-effective risk-reduction strategy for aggressive disease subtypes.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1119-y) contains supplementary material, which is available to authorized users.

Breast Cancer Risk After Recent Childbirth: A Pooled Analysis of 15 Prospective Studies

Background

Parity is widely recognized as protective for breast cancer, but breast cancer risk may be increased shortly after childbirth. Whether this risk varies with breastfeeding, family history of breast cancer, or specific tumor subtype has rarely been evaluated.

Objective

To characterize breast cancer risk in relation to recent childbirth.

Design

Pooled analysis of individual-level data from 15 prospective cohort studies.

Setting

The international Premenopausal Breast Cancer Collaborative Group.

Participants

Women younger than 55 years.

Measurements

During 9.6 million person-years of follow-up, 18 826 incident cases of breast cancer were diagnosed. Hazard ratios (HRs) and 95% CIs for breast cancer were calculated using Cox proportional hazards regression.

Results

Compared with nulliparous women, parous women had an HR for breast cancer that peaked about 5 years after birth (HR, 1.80 [95% CI, 1.63 to 1.99]) before decreasing to 0.77 (CI, 0.67 to 0.88) after 34 years. The association crossed over from positive to negative about 24 years after birth. The overall pattern was driven by estrogen receptor (ER)-positive breast cancer; no crossover was seen for ER-negative cancer. Increases in breast cancer risk after childbirth were pronounced when combined with a family history of breast cancer and were greater for women who were older at first birth or who had more births. Breastfeeding did not modify overall risk patterns.

Limitations

Breast cancer diagnoses during pregnancy were not uniformly distinguishable from early postpartum diagnoses. Data on human epidermal growth factor receptor 2 (HER2) oncogene overexpression were limited.

Conclusion

Compared with nulliparous women, parous women have an increased risk for breast cancer for more than 20 years after childbirth. Health care providers should consider recent childbirth a risk factor for breast cancer in young women.

Primary Funding Source

The Avon Foundation, the National Institute of Environmental Health Sciences, Breast Cancer Now and the UK National Health Service, and the Institute of Cancer Research.

Health and Racial Disparity in Breast Cancer

Breast cancer is the most common noncutaneous malignancy and the second most lethal form of cancer among women in the United States. It currently affects more than one in ten women worldwide. The chance for a female to be diagnosed with breast cancer during her lifetime has significantly increased from 1 in 11 women in 1975 to 1 in 8 women (Altekruse, SEER Cancer Statistics Review, 1975-2007. National Cancer Institute, Bethesda, 2010). This chance for a female of being diagnosed with cancer generally increases with age (Howlader et al, SEER Cancer Statistics Review, 1975-2010. National Cancer Institute, Bethesda, 2013). Fortunately, the mortality rate from breast cancer has decreased in recent years due to increased emphasis on early detection and more effective treatments in the White population. Although the mortality rates have declined in some ethnic populations, the overall cancer incidence among African American and Hispanic population has continued to grow. The goal of the work presented in this book chapter is to highlight similarities and differences in breast cancer morbidity and mortality rates among non-Hispanic white and non-Hispanic black populations. This book chapter also provides an overview of breast cancer, racial/ethnic disparities in breast cancer, breast cancer incidence and mortality rate linked to hereditary, major risk factors of breast cancer among minority population, breast cancer treatment, and health disparity. A considerable amount of breast cancer treatment research have been conducted, but with limited success for African Americans compared to other ethnic groups. Therefore, new strategies and approaches are needed to promote breast cancer prevention, improve survival rates, reduce breast cancer mortality, and ultimately improve the health outcomes of racial/ethnic minorities. In addition, it is vital that leaders and medical professionals from minority population groups be represented in decision-making in research so that racial disparity in breast cancer can be well-studied, fully addressed, and ultimately eliminated in breast cancer.

Epidemiology of Breast Cancer in Women

Epidemiologic studies have contributed importantly to current knowledge of environmental and genetic risk factors for breast cancer. Worldwide, breast cancer is an important cause of human suffering and premature mortality among women. In the United States, breast cancer accounts for more cancer deaths in women than any site other than lung cancer. A variety of risk factors for breast cancer have been well-established by epidemiologic studies including race, ethnicity, family history of cancer, and genetic traits, as well as modifiable exposures such as increased alcohol consumption, physical inactivity, exogenous hormones, and certain female reproductive factors. Younger age at menarche, parity, and older age at first full-term pregnancy may influence breast cancer risk through long-term effects on sex hormone levels or by other biological mechanisms. Recent studies have suggested that triple negative breast cancers may have a distinct etiology. Genetic variants and mutations in genes that code for proteins having a role in DNA repair pathways and the homologous recombination of DNA double stranded breaks (APEX1, BRCA1, BRCA2, XRCC2, XRCC3, ATM, CHEK2, PALB2, RAD51, XPD), have been implicated in some cases of breast cancer.

Experiences of Racism and Breastfeeding Initiation and Duration Among First-Time Mothers of the Black Women's Health Study

BACKGROUND

Breastfeeding rates are lower for black women in the USA compared with other groups. Breastfeeding and lactation are sensitive time points in the life course, centering breastfeeding as a health equity issue. In the USA, experiences of racism have been linked to poor health outcomes but racism relative to breastfeeding has not been extensively investigated.

AIMS

This study aims to investigate the association between experiences of racism, neighborhood segregation, and nativity with breastfeeding initiation and duration.

METHODS

This is a prospective secondary analysis of the Black Women's Health Study, based on data collected from 1995 through 2005. Daily and institutional (job, housing, police) racism, nativity, and neighborhood segregation in relation to breastfeeding were examined. Odds ratios and 95% confidence intervals were calculated using binomial logistic regression for the initiation outcomes (N = 2705) and multinomial logistic regression for the duration outcomes (N = 2172).

RESULTS

Racism in the job setting was associated with lower odds of breastfeeding duration at 3-5 months. Racism with the police was associated with higher odds of breastfeeding initiation and duration at 3-5 and 6 months. Being born in the USA or having a parent born in the USA predicted lower odds of breastfeeding initiation and duration. Living in a segregated neighborhood (primarily black residents) as a child was associated with decreased breastfeeding initiation and duration relative to growing up in a predominantly white neighborhood.

CONCLUSION

Experiences of institutionalized racism influenced breastfeeding initiation and duration. Structural-level interventions are critical to close the gap of racial inequity in breastfeeding rates in the USA.

The Effect of Insurance and Race on Breast Cancer Tumor Biology and Short-Term Outcomes

To determine whether low-income status as demonstrated by insurance type has any association with aggressive tumor biology and breast cancer outcomes. Retrospective review of 535 women with new diagnosis of breast cancer from January 2009 to March 2013 was performed. There was no significant association between race and stage at diagnosis. Women with Medicaid/Charity coverage were diagnosed at more advanced stages, more likely to have triple-negative breast cancer (TNBC), and had longer time to treatment. Rate of TNBC was higher in black women and younger patients. There was no significant difference in breast cancer recurrence or survival by race, insurance type, age, or tumor biology. In multivariable analysis, only black race (P = 0.003) and Medicaid/Charity Insurance (P = 0.0008) were the most significant predictors of TNBC. Presentation of aggressive tumor biology and advanced stage is strongly associated with socio-economic factors as reflected by Medicaid funding and lack of insurance.

Reproductive history, breast-feeding and risk of triple negative breast cancer: The Breast Cancer Etiology in Minorities (BEM) study

Few risk factors have been identified for triple negative breast cancer (TNBC) which lacks expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). This more aggressive subtype disproportionately affects some racial/ethnic minorities and is associated with lower survival. We pooled data from three population-based studies (558 TNBC and 5,111 controls) and examined associations of TNBC risk with reproductive history and breast-feeding. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using multivariable logistic regression. For younger women, aged <50 years, TNBC risk was increased two-fold for parous women who never breast-fed compared to nulliparous women (OR = 2.02, 95% CI = 1.12-3.63). For younger parous women, longer duration of lifetime breast-feeding was associated with a borderline reduced risk (≥24 vs. 0 months: OR = 0.52, 95% CI = 0.26-1.04, Ptrend  = 0.06). Considering the joint effect of parity and breast-feeding, risk was increased two-fold for women with ≥3 full-term pregnancies (FTPs) and no or short-term (<12 months) breast-feeding compared to women with 1-2 FTPs and breast-feeding ≥12 months (OR = 2.56, 95% CI = 1.22-5.35). None of these associations were observed among older women (≥50 years). Differences in reproductive patterns possibly contribute to the ethnic differences in TNBC incidence. Among controls aged <50 years, the prevalence of no or short-term breast-feeding and ≥3 FTPs was highest for Hispanics (22%), followed by African Americans (18%), Asian Americans (15%) and non-Hispanic whites (6%). Breast-feeding is a modifiable behavioral factor that may lower TNBC risk and mitigate the effect of FTPs in women under age 50 years.

The protective effect of longer duration of breastfeeding against pregnancy-associated triple negative breast cancer

Parity associated breast cancer (PABC) often diagnosed within the 2-5 years after a full term pregnancy. PABC is usually present with more advanced, poorly differentiated, high-grade cancers that show shorter time to progression and often of the triple negative breast cancer (TNBC) subtype. Data from around the world show that pregnancy-associated TNBC is independently associated with poor survival, underscoring the impact of the pregnant breast microenvironment on the biology and consequently the prognosis of these tumors. Although it is not yet clear, a link between pregnancy-associated TNBCs and lack or shorter duration of breastfeeding (not pregnancy per se) has been proposed. Here, we present epidemiological and experimental evidence for the protective effect of longer duration of lactation against pregnancy-associated TNBCs, and propose a putative molecular mechanism for this protective effect and its effect in eliminating any potential TNBC precursors from the breast by the end of the natural breast involution.

Menstrual and reproductive factors and risk of breast cancer: A case-control study in the Fez region, Morocco

BACKGROUND

Breast cancer is the most common cancer in women worldwide. In the Moroccan context, the role of well-known reproductive factors in breast cancer remains poorly documented. The aim of this study was to explore the relationship between menstrual and reproductive factors and breast cancer risk in Moroccan women in the Fez region.

METHODS

A case-control study was conducted at the Hassan II University Hospital of Fez between January 2014 and April 2015. A total of 237 cases of breast cancer and 237 age-matched controls were included. Information on sociodemographic characteristics, menstrual and reproductive history, family history of breast cancer, and lifestyle factors was obtained through a structured questionnaire. Conditional logistic regression models were used to estimate odds ratios and 95% confidence intervals for breast cancer by menstrual and reproductive factors adjusted for potential confounders.

RESULTS

Early menarche (OR = 1.60, 95% CI: 1.08-2.38) and nulliparity (OR = 3.77, 95% CI: 1.98-7.30) were significantly related to an increased risk of breast cancer, whereas an early age at first full-term pregnancy was associated with a decreased risk of breast cancer (OR = 0.41, 95% CI: 0.25-0.65).

CONCLUSION

The results of this study confirm the role of established reproductive factors for breast cancer in Moroccan women. It identified some susceptible groups at high risk of breast cancer. Preventive interventions and screening should focus on these groups as a priority. These results should be confirmed in a larger, multicenter study.

Type II Diabetes and Incidence of Estrogen Receptor Negative Breast Cancer in African American Women

White women with type II diabetes (T2D) have an estimated 20% increased risk of developing breast cancer. Little is known about associations by breast cancer subtype or among African American (AA) women, who are disproportionately affected by T2D and estrogen receptor negative (ER-) breast cancer. We assessed the relation of T2D to incidence of ER- and ER+ breast cancer in data from the Black Women's Health Study, a prospective cohort of AA women enrolled in 1995 and followed biennially. During 847,934 person-years of follow-up, there were 1,851 incident invasive breast cancers, including 914 ER+ and 468 ER- cases. Multivariable Cox proportional hazards models were used to compute HRs for breast cancer incidence associated with T2D relative to no T2D, controlling for body mass index (BMI) and other potential confounders. The HR for T2D relative to no T2D was 1.18 [95% confidence interval (CI) 1.00-1.40] for overall breast cancer incidence, with the increase accounted for by ER- cancer: HRs were 1.02 (95% CI, 0.80-1.31) for ER+ and 1.43 (95% CI, 1.03-2.00) for ER- cancer. The HR for T2D and ER- breast cancer was highest among nonobese women (1.92; 95% CI, 1.22-3.04). The findings suggest that AA women with T2D are at increased risk of developing ER- breast cancer and that poor metabolic health may be more important than obesity for this subtype. Given the high prevalence of T2D in AA women, the observed association could, in part, explain racial disparities in incidence of ER- breast cancer. Cancer Res; 77(22); 6462-9. ©2017 AACR.

Divergent oestrogen receptor-specific breast cancer trends in Ireland (2004-2013): Amassing data from independent Western populations provide etiologic clues

The aetiology and clinical behaviour of breast cancers vary by oestrogen receptor (ER) expression, HER2 expression and over time. Data from the United States and Denmark show rising incidence rates for ER+ and falling incidence rates for ER- breast cancers. Given that Ireland is a somewhat similar Western population but with distinctive risk exposures (especially for lactation), we analysed breast cancer trends by ER status; and for the first time, by the joint expression of ER±/HER2±. We assessed invasive breast cancers (n = 24,845; 2004-2013) within the population-based National Cancer Registry of Ireland. The population at risk was obtained from the Irish Central Statistics Office (n = 10,401,986). After accounting for missing ER and HER2 data, we assessed receptor-specific secular trends in age-standardised incidence rates (ASRs) with the estimated annual percentage change (EAPC) and corresponding 95% confidence intervals (95% CI). Age-period-cohort models were also fitted to further characterise trends accounting for age, calendar-period and birth-cohort interactions. ASRs increased for ER+ (EAPC: 2.2% per year [95% CI: 0.97, 3.45%/year]) and decreased for ER- cancers (EAPC: -3.43% per year [95% CI: -5.05, -1.78%/year]), as well as for specific age groups at diagnosis (<30-49, 50-64 and ≥65 years). ER+/HER2- cancers rose, ER+/HER2+ cancers were statistically flat and ER-/HER± cancers declined. Secular trends for ER± cancers in Ireland were like those previously observed. Stratification by HER2± expression did not substantively alter ER± trends. The divergence of ER± incidence rates among independent Western populations likely reflects calendar-period and/or risk factor changes with differential effects for ER+ and ER- breast cancers.

Ethnicity and breast cancer characteristics in Kenya

PURPOSE

There are no published data from specific regions of sub-Saharan Africa describing the clinical and pathological characteristics and molecular subtypes of invasive breast cancer by ethnic group. The purpose of this study was to investigate these characteristics among the three major ethno-cultural groupings in Kenya.

METHODS

The study included women with pathologically confirmed breast cancer diagnosed between March 2012 and May 2015 at 11 hospitals throughout Kenya. Sociodemographic, clinical, and reproductive data were collected by questionnaire, and pathology review and immunohistochemistry were performed centrally.

RESULTS

The 846 cases included 661 Bantus (78.1%), 143 Nilotes (16.9%), 19 Cushites (2.3%), and 23 patients of mixed ethnicity (2.7%). In analyses comparing the two major ethnic groups, Bantus were more educated, more overweight, had an older age at first birth, and had a younger age at menopause than Nilotes (p < 0.05 for all comparisons). In analyses restricted to definitive surgery specimens, there were no statistically significant differences in tumor characteristics or molecular subtypes by ethnicity, although the Nilote tumors tended to be larger (OR for ≥ 5 cm vs. < 2 cm: 3.86, 95% CI 0.77, 19.30) and were somewhat more likely to be HER2 enriched (OR for HER2 enriched vs. Luminal A/B: 1.41, 95% CI 0.79, 2.49).

CONCLUSION

This case series showed no significant differences in breast cancer tumor characteristics or molecular subtypes, but significant differences in sociodemographic characteristics and reproductive factors, among the three major ethnic groups in Kenya. We suggest further evaluation of ethnic differences in breast cancer throughout the genetically and culturally diverse populations of sub-Saharan Africa.

Pubertal growth and adult height in relation to breast cancer risk in African American women

Adult height has been positively associated with breast cancer risk. The timing of pubertal growth-as measured by age at menarche and age at attained height-may also influence risk. We evaluated associations of adult height, age at attained height, and age at menarche with incidence of invasive breast cancer in 55,687 African American women in the prospective Black Women's Health Study. Over 20 years, 1,826 invasive breast cancers [1,015 estrogen receptor (ER) positive; 542 ER negative] accrued. We used multivariable Cox proportional hazards regression to estimate hazards ratios (HRs) and 95% confidence intervals (CIs) for associations with breast cancer overall and by ER status, mutually adjusted for the three factors of interest. Adult height was associated with increased risk of ER+ breast cancer (HR for ≥70 inches vs ≤63 inches: 1.44; 95% CI: 1.09, 1.89) but not ER- (corresponding HR: 1.16; 95% CI: 0.78, 1.71) (p heterogeneity = 0.34). HRs for attained height before age 13 versus age >17 were 1.30 (95% CI: 0.96, 1.76) for ER+ and 1.25 (95% CI: 0.80, 1.96) for ER- breast cancer. Results for age at menarche (≤11 vs ≥14 years) were similar for ER+ and ER- breast cancer (HR for breast cancer overall: 1.30; 95% CI: 1.12, 1.50). We confirmed height as a strong risk factor for ER+ breast cancer in African American women and identified early age at attained height as a risk factor for both ER+ and ER- breast cancer, albeit without statistical significance of the latter associations. While adult height and timing of pubertal growth are inter-related, our findings suggest that they may be independent risk factors for breast cancer.

The Premenopausal Breast Cancer Collaboration: A Pooling Project of Studies Participating in the National Cancer Institute Cohort Consortium

Breast cancer is a leading cancer diagnosis among premenopausal women around the world. Unlike rates in postmenopausal women, incidence rates of advanced breast cancer have increased in recent decades for premenopausal women. Progress in identifying contributors to breast cancer risk among premenopausal women has been constrained by the limited numbers of premenopausal breast cancer cases in individual studies and resulting low statistical power to subcategorize exposures or to study specific subtypes. The Premenopausal Breast Cancer Collaborative Group was established to facilitate cohort-based analyses of risk factors for premenopausal breast cancer by pooling individual-level data from studies participating in the United States National Cancer Institute Cohort Consortium. This article describes the Group, including the rationale for its initial aims related to pregnancy, obesity, and physical activity. We also describe the 20 cohort studies with data submitted to the Group by June 2016. The infrastructure developed for this work can be leveraged to support additional investigations. Cancer Epidemiol Biomarkers Prev; 26(9); 1360-9. ©2017 AACR.

Lack of Breastfeeding History in Parous Women with Inflammatory Breast Cancer Predicts Poor Disease-Free Survival

Purpose: Breastfeeding alters the breast microenvironment, and several lines of evidence suggest the breast microenvironment contributes to the clinical phenotype of inflammatory breast cancer. We investigated breastfeeding history as a modifier of locoregional recurrence (LRR), distant metastasis (DM), disease-free survival (DFS), and overall survival (OS) in parous women with inflammatory breast cancer.

Methods: Parous women with inflammatory breast cancer were identified from a prospective registry at The University of Texas MD Anderson Cancer Center. We compared patient and tumor characteristics, LRR, DM, DFS, and OS patients with (BF+) and without (BF-) a history of breastfeeding.

Results: Eighty-two patients were included. At a median follow-up of 50 months, BF+ patients had significantly lower risk of LRR (9.0% vs. 23.6%; p=0.01), a lower risk of DM (26.8% vs. 53.8%; p=0.008), and better DFS (73.1% vs. 48.1%; p=0.006) than BF- patients. On multivariate analysis, BF+ history was associated with significantly lower risk of DM (hazard ratio 0.38, 95% confidence interval 0.15-0.97; p=0.04) and better DFS (hazard ratio 0.37, 95% confidence interval 0.15-0.93; p=0.04) after adjusting for established predictive and prognostic variables. The prognostic significance of breastfeeding may be most pronounced in women with triple-negative IBC.

Conclusion: A lack of breastfeeding history in parous women with inflammatory breast cancer may predict worse prognosis. We speculate that breastfeeding-induced alterations in the breast microenvironment may alter the aggressiveness of inflammatory breast cancer.

Breastfeeding Mode and Risk of Breast Cancer: A Dose-Response Meta-Analysis

BACKGROUND

Breastfeeding reduces women's risk of breast cancer. Since exclusive breastfeeding has a stronger hormonal effect, it could theoretically result in a greater reduction in breast cancer risk than any breastfeeding mode. No meta-analysis has examined breast cancer risk by breastfeeding mode. Research aim: The authors conducted a meta-analysis for breast cancer risk in parous women who breastfed exclusively or in any mode versus parous women who formula fed their infants, and they estimated the summary dose-response association by the accumulated duration of any breastfeeding mode.

METHODS

A systematic review of studies published between 2005 and 2015 analyzing breastfeeding and breast cancer risk in women was conducted in PubMed and EBSCOhost. A meta-analysis ( n = 65 studies) with fixed effects (or random effects, if heterogeneity existed) was carried out stratified by breastfeeding mode and menopausal and parity status. A summary dose-response association was estimated using the generalized least-squares method.

RESULTS

The summary relative risk (SRR) for breast cancer in parous women who breastfed exclusively was 0.72, 95% confidence interval (CI) [0.58, 0.90], versus parous women who had never breastfed. For parous women who breastfed in any mode, the SRR was lower in both premenopausal women (0.86, 95% CI [0.80, 0.93]) and postmenopausal women (0.89, 95% CI [0.83, 0.95]). There was no heterogeneity or publication bias. There is weak evidence of a difference between exclusive and any breastfeeding mode ( p = .08). The summary dose-response curve was nonlinear ( p < .001).

CONCLUSION

Exclusive breastfeeding among parous women reduces the risk of breast cancer compared with parous women who do not breastfeed exclusively.

Alcohol Intake and Breast Cancer Risk in African American Women from the AMBER Consortium

Background: Alcohol is a recognized risk factor for invasive breast cancer, but few studies involve African American women.Methods: The current analysis included 22,338 women (5,108 cases of invasive breast cancer) from the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. The association between number of alcoholic drinks per week (dpw) and breast cancer was estimated using logistic regression, adjusting for potential confounders, and stratifying by breast cancer subtype.Results: Approximately 35% of controls were current drinkers at interview. Women who reported current drinking of ≥14 dpw had an elevated risk of breast cancer compared with light drinkers (>0-<4 dpw) [adjusted OR (ORadj), 1.33; 95% confidence interval (CI), 1.07-1.64]. We observed elevated risk among women drinking ≥7 dpw for ER - [ORadj, 1.31; 95% CI, 1.00-1.72], PR - [ORadj, 1.28; 95% CI, 1.00-1.63], HER2 - [ORadj, 1.36; 95% CI, 1.09-1.70], and triple-negative [ORadj, 1.39; 95% CI, 0.98-2.00] molecular subtype. Among receptor-positive cases, ORs remained elevated but attenuated relative to receptor-negative cases. Sensitivity analysis of age-defined windows of exposure (<30 years, 30-49, 50+ years of age) did not reveal variation in patterns of association. Risk associated with alcohol intake did not vary significantly by oral contraceptive use, smoking status, or menopausal status.Conclusions: Among African American women, similar to women of European descent, drinking ≥7 alcoholic dpw was associated with an increased risk of breast cancer regardless of subtype.Impact: Alcohol intake is a modifiable risk factor for breast cancer, and reduced intake among African American women should be encouraged. Cancer Epidemiol Biomarkers Prev; 26(5); 787-94. ©2017 AACR.