Parity, lactation, and breast cancer subtypes in African American women: results from the AMBER Consortium

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.

Psychosocial stressors and breast cancer gene expression in the Black Women's Health Study

PURPOSE

Prior studies indicate that the physiologic response to stress can affect gene expression. We evaluated differential gene expression in breast cancers collected from Black women with high versus low exposure to psychosocial stressors.

METHODS

We analyzed tumor RNA sequencing data from 417 Black Women's Health Study breast cancer cases with data on early life trauma and neighborhood disadvantage. We conducted age-adjusted differential gene expression analyses and pathway analyses. We also evaluated Conserved Transcriptional Response to Adversity (CTRA) contrast scores, relative fractions of immune cell types, T cell exhaustion, and adrenergic signaling. Analyses were run separately for estrogen receptor positive (ER+; n = 299) and ER- (n = 118) cases.

RESULTS

Among ER+ cases, the top differentially expressed pathways by stress exposure were related to RNA and protein metabolism. Among ER- cases, they were related to developmental biology, signal transduction, metabolism, and the immune system. Targeted analyses indicated greater immune pathway enrichment with stress exposure for ER- cases, and possible relevance of adrenergic signaling for ER+ cases. CTRA contrast scores did not differ by stress exposure, but in analyses of the CTRA components, ER- breast cancer cases with high neighborhood disadvantage had higher pro-inflammatory gene expression (p = 0.039) and higher antibody gene expression (p = 0.006) compared to those with low neighborhood disadvantage.

CONCLUSION

There are multiple pathways through which psychosocial stress exposure may influence breast tumor biology. Given the present findings on inflammation and immune response in ER- tumors, further research to identify stress-induced changes in the etiology and progression of ER- breast cancer is warranted.

Disparities in Breast Cancer Care-How Factors Related to Prevention, Diagnosis, and Treatment Drive Inequity

Breast cancer survival has increased significantly over the last few decades due to more effective strategies for prevention and risk modification, advancements in imaging detection, screening, and multimodal treatment algorithms. However, many have observed disparities in benefits derived from such improvements across populations and demographic groups. This review summarizes published works that contextualize modern disparities in breast cancer prevention, diagnosis, and treatment and presents potential strategies for reducing disparities. We conducted searches for studies that directly investigated and/or reported disparities in breast cancer prevention, detection, or treatment. Demographic factors, social determinants of health, and inequitable healthcare delivery may impede the ability of individuals and communities to employ risk-mitigating behaviors and prevention strategies. The disparate access to quality screening and timely diagnosis experienced by various groups poses significant hurdles to optimal care and survival. Finally, barriers to access and inequitable healthcare delivery patterns reinforce inequitable application of standards of care. Cumulatively, these disparities underlie notable differences in the incidence, severity, and survival of breast cancers. Efforts toward mitigation will require collaborative approaches and partnerships between communities, governments, and healthcare organizations, which must be considered equal stakeholders in the fight for equity in breast cancer care and outcomes.

Clinical characteristics and pathologic complete response (pCR) rate after neoadjuvant chemotherapy in postpartum women with breast cancer

PURPOSE

Breast cancer (BC) is currently the leading cause of death in women worldwide. Studies have confirmed that pregnancy is an independent factor affecting the survival of BC patients. BC found during pregnancy, lactation, or shortly after delivery is what we used to think of as pregnancy-associated breast cancer (PABC). The current expert definition of this concept is not uniform; however, there is growing evidence that postpartum breast cancer (PPBC) differs from other types of BC in terms of both biological features and prognosis, with a slightly different focus on diagnosis and treatment. With the increase of female reproductive age population and changes in fertility policies in China, patients with PPBC are receiving increasing attention. Here, we systematically analyzed the clinicopathological characteristics and chemotherapeutic response of patients with PPBC. We retrospectively analyzed the clinicopathological data, molecular subtypes, chemotherapy regimens, and pathological complete remission (pCR) rates of 1343 patients with non-metastatic BC at Harbin Medical University Cancer Hospital from January 1, 2012 to May 31, 2023. The categorical data were compared by chi-square test and Fisher exact test using logistic regression model. Predictor variables with P < 0.05 in the univariate analysis were included in the multivariate regression analysis to investigate the relationship between different age groups and pCR.

RESULTS

A total of 714 patients were eligible for analysis in this study, and 667 patients had a history of pregnancy, 40 (5.6%) of whom were PPBC patients. When diagnosed with BC, patients with PPBC were younger, more likely to undergo breast-conserving surgery (BCS), and more likely to achieve pCR (P < 0.05). In molecular typing, human epidermal growth factor receptor 2 (HER-2)-positive and triple-negative breast cancer (TNBC) were more frequent. In the entire cohort, HER-2 expression and delivery status were independent predictors of pCR rates in BC patients after neoadjuvant chemotherapy (NAC).

CONCLUSION

Our findings suggest that postpartum status is an independent predictor of pCR attainment in BC patients. PPBC is more sensitive to chemotherapy than other patients.We need to pay more attention to this group and achieve individualized treatment, which will help us treat BC better and provide new targets and blueprints for our clinical therapy.

Risk factors for the development of triple-negative breast cancer versus non-triple-negative breast cancer: a case-control study

The risk factors for breast cancer have been defined in several studies but there is deficient data for specific subtypes. We report here the pathological characteristics of a breast cancer cohort and risk factors for patients with triple-negative disease. In this case-control study, a prospective breast cancer cohort was evaluated for demographic, reproductive, obesity-related and other risk factors using a validated questionnaire. Tumors were characterized for routine pathological characteristics and immunohistochemical markers of basal-like breast cancer. Patients with triple-negative breast cancer (TNBC) constituted cases and those with non-TNBC were controls. Odds ratios (OR) were calculated for each risk factor and independent associations were tested in an unconditional logistic regression analysis. Between 2011 and 2014, 1146 patients were recruited, of whom 912 [TNBC 266 (29.1%), non-TNBC 646 (70.9%)] with sufficient pathology material were analysed. Reproductive factors of parity, breastfeeding, age-at-menarche, age at first full-term pregnancy and oral contraceptive use were not significantly associated with TNBC. Higher body mass index (BMI > 24.9 vs ≤ 24.9, OR 0.89, 95%CI 0.63-1.24, p = 0.49) was not significantly associated while lesser waist circumference (> 80 cm vs ≤ 80 cm, OR 0.64, 95%CI 0.45-0.9, p = 0.012) and lower waist-to-hip ratio were significantly associated (> 0.85 vs ≤ 0.85, OR 0.72, 95%CI 0.51-1.0, p = 0.056), with TNBC. History of tobacco use was not significantly associated while lower socio-economic status was borderline associated with TNBC (socio-economic category > 5 versus ≤ 5, OR 0.73, 95%CI 0.50-1.06, p = 0.106). No factor was significant after adjustment for covariates. Central obesity seems to be preferentially associated with non-TNBC, and lower socio-economic status with TNBC in India, while most other conventional risk factors of breast cancer show no significant association with TNBC versus non-TNBC.

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.

Association of reproductive risk factors and breast cancer molecular subtypes: a systematic review and meta-analysis

BACKGROUND

Associations between reproductive factors and breast cancer (BC) risk vary by molecular subtype (i.e., luminal A, luminal B, HER2, and triple negative/basal-like [TNBC]). In this systematic review and meta-analysis, we summarized the associations between reproductive factors and BC subtypes.

METHODS

Studies from 2000 to 2021 were included if BC subtype was examined in relation to one of 11 reproductive risk factors: age at menarche, age at menopause, age at first birth, menopausal status, parity, breastfeeding, oral contraceptive (OC) use, hormone replacement therapy (HRT), pregnancy, years since last birth and abortion. For each reproductive risk factor, BC subtype, and study design (case-control/cohort or case-case), random-effects models were used to estimate pooled relative risks and 95% confidence intervals.

RESULTS

A total of 75 studies met the inclusion criteria for systematic review. Among the case-control/cohort studies, later age at menarche and breastfeeding were consistently associated with decreased risk of BC across all subtypes, while later age at menopause, later age of first childbirth, and nulliparity/low parity were associated with increased risk of luminal A, luminal B, and HER2 subtypes. In the case-only analysis, compared to luminal A, postmenopausal status increased the risk of HER2 and TNBC. Associations were less consistent across subtypes for OC and HRT use.

CONCLUSION

Identifying common risk factors across BC subtypes can enhance the tailoring of prevention strategies, and risk stratification models can benefit from subtype specificity. Adding breastfeeding status to current BC risk prediction models can enhance predictive ability, given the consistency of the associations across subtypes.

Associations of breast cancer etiologic factors with stromal microenvironment of primary invasive breast cancers in the Ghana Breast Health Study

Background

Emerging data suggest that beyond the neoplastic parenchyma, the stromal microenvironment (SME) impacts tumor biology, including aggressiveness, metastatic potential, and response to treatment. However, the epidemiological determinants of SME biology remain poorly understood, more so among women of African ancestry who are disproportionately affected by aggressive breast cancer phenotypes.

Methods

Within the Ghana Breast Health Study, a population-based case-control study in Ghana, we applied high-accuracy machine-learning algorithms to characterize biologically-relevant SME phenotypes, including tumor-stroma ratio (TSR (%); a metric of connective tissue stroma to tumor ratio) and tumor-associated stromal cellular density (Ta-SCD (%); a tissue biomarker that is reminiscent of chronic inflammation and wound repair response in breast cancer), on digitized H&E-stained sections from 792 breast cancer patients aged 17-84 years. Kruskal-Wallis tests and multivariable linear regression models were used to test associations between established breast cancer risk factors, tumor characteristics, and SME phenotypes.

Results

Decreasing TSR and increasing Ta-SCD were strongly associated with aggressive, mostly high grade tumors (p-value < 0.001). Several etiologic factors were associated with Ta-SCD, but not TSR. Compared with nulliparous women [mean (standard deviation) = 28.9% (7.1%)], parous women [mean (standard deviation) = 31.3% (7.6%)] had statistically significantly higher levels of Ta-SCD (p-value = 0.01). Similarly, women with a positive family history of breast cancer [FHBC; mean (standard deviation) = 33.0% (7.5%)] had higher levels of Ta-SCD than those with no FHBC [mean (standard deviation) = 30.9% (7.6%); p-value = 0.01]. Conversely, increasing body size was associated with decreasing Ta-SCD [mean (standard deviation) = 32.0% (7.4%), 31.3% (7.3%), and 29.0% (8.0%) for slight, moderate, and large body sizes, respectively, p-value = 0.005]. These associations persisted and remained statistically significantly associated with Ta-SCD in mutually-adjusted multivariable linear regression models (p-value < 0.05). With the exception of body size, which was differentially associated with Ta-SCD by grade levels (p-heterogeneity = 0.04), associations between risk factors and Ta-SCD were not modified by tumor characteristics.

Conclusions

Our findings raise the possibility that epidemiological factors may act via the SME to impact both risk and biology of breast cancers in this population, underscoring the need for more population-based research into the role of SME in multi-state breast carcinogenesis.

Breast cancer subtype and clinical characteristics in women from Peru

Introduction

Breast cancer is a heterogeneous disease, and the distribution of the different subtypes varies by race/ethnic category in the United States and by country. Established breast cancer-associated factors impact subtype-specific risk; however, these included limited or no representation of Latin American diversity. To address this gap in knowledge, we report a description of demographic, reproductive, and lifestyle breast cancer-associated factors by age at diagnosis and disease subtype for The Peruvian Genetics and Genomics of Breast Cancer (PEGEN-BC) study.

Methods

The PEGEN-BC study is a hospital-based breast cancer cohort that includes 1943 patients diagnosed at the Instituto Nacional de Enfermedades Neoplásicas in Lima, Peru. Demographic and reproductive information, as well as lifestyle exposures, were collected with a questionnaire. Clinical data, including tumor Hormone Receptor (HR) status and Human Epidermal Growth Factor Receptor 2 (HER2) status, were abstracted from electronic medical records. Differences in proportions and mean values were tested using Chi-squared and one-way ANOVA tests, respectively. Multinomial logistic regression models were used for multivariate association analyses.

Results

The distribution of subtypes was 52% HR+HER2-, 19% HR+HER2+, 16% HR-HER2-, and 13% HR-HER2+. Indigenous American (IA) genetic ancestry was higher, and height was lower among individuals with the HR-HER2+ subtype (80% IA vs. 76% overall, p=0.007; 152 cm vs. 153 cm overall, p=0.032, respectively). In multivariate models, IA ancestry was associated with HR-HER2+ subtype (OR=1.38,95%CI=1.06-1.79, p=0.017) and parous women showed increased risk for HR-HER2+ (OR=2.7,95%CI=1.5-4.8, p<0.001) and HR-HER2- tumors (OR=2.4,95%CI=1.5-4.0, p<0.001) compared to nulliparous women. Multiple patient and tumor characteristics differed by age at diagnosis (<50 vs. >=50), including ancestry, region of residence, family history, height, BMI, breastfeeding, parity, and stage at diagnosis (p<0.02 for all variables).

Discussion

The characteristics of the PEGEN-BC study participants do not suggest heterogeneity by tumor subtype except for IA genetic ancestry proportion, which has been previously reported. Differences by age at diagnosis were apparent and concordant with what is known about pre- and post-menopausal-specific disease risk factors. Additional studies in Peru should be developed to further understand the main contributors to the specific age of onset and molecular disease subtypes in this population and develop population-appropriate predictive models for prevention.

Long-term impact of hypothyroidism during gestation and lactation on the mammary gland

The functional differentiation of the mammary gland (MG) is fundamental for the prevention of mammary pathologies. This process occurs throughout pregnancy and lactation, making these stages key events for the study of pathologies associated with development and differentiation. Many studies have investigated the link between mammary pathologies and thyroid diseases, but most have ignored the role of thyroid hormone (TH) in the functional differentiation of the MG. In this work, we show the long-term impact of hypothyroidism in an animal model whose lactogenic differentiation occurred at low TH levels. We evaluated the ability of the MG to respond to hormonal control and regulate cell cycle progression. We found that a deficit in TH throughout pregnancy and lactation induces a long-term decrease in Rb phosphorylation, increases p53, p21, Cyclin D1 and Ki67 expression, reduces progesterone receptor expression, and induces nonmalignant lesions in mammary tissue. This paper shows the importance of TH level control during mammary differentiation and its long-term impact on mammary function.

Annual report to the nation on the status of cancer, part 1: National cancer statistics

BACKGROUND

The American Cancer Society, the Centers for Disease Control and Prevention, the National Cancer Institute, and the North American Association of Central Cancer Registries collaborate to provide annual updates on cancer occurrence and trends in the United States.

METHODS

Data on new cancer diagnoses during 2001-2018 were obtained from the North American Association of Central Cancer Registries' Cancer in North America Incidence file, which is comprised of data from Centers for Disease Control and Prevention-funded and National Cancer Institute-funded, population-based cancer registry programs. Data on cancer deaths during 2001-2019 were obtained from the National Center for Health Statistics' National Vital Statistics System. Five-year average incidence and death rates along with trends for all cancers combined and for the leading cancer types are reported by sex, racial/ethnic group, and age.

RESULTS

Overall cancer incidence rates were 497 per 100,000 among males (ranging from 306 among Asian/Pacific Islander males to 544 among Black males) and 431 per 100,000 among females (ranging from 309 among Asian/Pacific Islander females to 473 among American Indian/Alaska Native females) during 2014-2018. The trend during the corresponding period was stable among males and increased 0.2% on average per year among females, with differing trends by sex, racial/ethnic group, and cancer type. Among males, incidence rates increased for three cancers (including pancreas and kidney), were stable for seven cancers (including prostate), and decreased for eight (including lung and larynx) of the 18 most common cancers considered in this analysis. Among females, incidence rates increased for seven cancers (including melanoma, liver, and breast), were stable for four cancers (including uterus), and decreased for seven (including thyroid and ovary) of the 18 most common cancers. Overall cancer death rates decreased by 2.3% per year among males and by 1.9% per year among females during 2015-2019, with the sex-specific declining trend reflected in every major racial/ethnic group. During 2015-2019, death rates decreased for 11 of the 19 most common cancers among males and for 14 of the 20 most common cancers among females, with the steepest declines (>4% per year) reported for lung cancer and melanoma. Five-year survival for adenocarcinoma and neuroendocrine pancreatic cancer improved between 2001 and 2018; however, overall incidence (2001-2018) and mortality (2001-2019) continued to increase for this site. Among children (younger than 15 years), recent trends were stable for incidence and decreased for mortality; and among, adolescents and young adults (aged 15-39 years), recent trends increased for incidence and declined for mortality.

CONCLUSIONS

Cancer death rates continued to decline overall, for children, and for adolescents and young adults, and treatment advances have led to accelerated declines in death rates for several sites, such as lung and melanoma. The increases in incidence rates for several common cancers in part reflect changes in risk factors, screening test use, and diagnostic practice. Racial/ethnic differences exist in cancer incidence and mortality, highlighting the need to understand and address inequities. Population-based incidence and mortality data inform prevention, early detection, and treatment efforts to help reduce the cancer burden in the United States.

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.

Associations between quantitative measures of TDLU involution and breast tumor molecular subtypes among breast cancer cases in the Black Women's Health Study: a case-case analysis

BACKGROUND

Terminal duct lobular units (TDLUs) are the structures in the breast that give rise to most breast cancers. Previous work has shown that TDLU involution is inversely associated with TDLU metrics, such as TDLU count/100mm2, TDLU span (µm), and number of acini/TDLU, and that these metrics may be elevated in the normal breast tissue of women diagnosed with triple-negative (TN) compared with luminal A breast tumors. It is unknown whether this relationship exists in Black women, who have the highest incidence of TN breast cancer and the highest overall breast cancer mortality rate. We examined relationships between TDLU metrics and breast cancer molecular subtype among breast cancer cases in the Black Women's Health Study (BWHS).

METHODS

We assessed quantitative TDLU metrics (TDLU count/100mm2, TDLU span (µm), and number of acini/TDLU) in digitized 247 hematoxylin and eosin-stained adjacent normal tissue sections from 223 BWHS breast cancer cases, including 65 triple negative (TN) cancers (estrogen receptor (ER) negative, progesterone receptor (PR) negative, human epidermal growth factor-2 (HER2) negative) and 158 luminal A cancers (ER positive, HER2 negative). We evaluated associations of least square mean TDLU metrics adjusted for age and body mass index (BMI) with patient and clinical characteristics. In logistic regression models, we evaluated associations between TDLU metrics and breast cancer subtype, adjusting for age, BMI, and tumor size.

RESULTS

Older age and higher BMI were associated with lower TDLU metrics and larger tumor size and lymph node invasion with higher TDLU metrics. The odds of TN compared with luminal A breast cancer increased with increasing tertiles of TDLU metrics, with odds ratios (95% confidence intervals) for tertile 3 versus tertile 1 of 2.18 (0.99, 4.79), 2.77 (1.07, 7.16), and 1.77 (0.79, 3.98) for TDLU count, TDLU span, and acini count/TDLU, respectively.

CONCLUSION

Associations of TDLU metrics with breast cancer subtypes in the BWHS are consistent with previous studies of White and Asian women, demonstrating reduced TDLU involution in TN compared with luminal A breast cancers. Further investigation is needed to understand the factors that influence TDLU involution and the mechanisms that mediate TDLU involution and breast cancer subtype.

Young-Onset Breast Cancer Outcomes by Time Since Recent Childbirth in Utah

IMPORTANCE

Breast cancer diagnosed within 5 to 10 years after childbirth, called postpartum breast cancer (PPBC), is associated with increased risk for metastasis and death. Whether a postpartum diagnosis is an independent risk factor or a surrogate marker of cancer features associated with poor outcomes remains understudied.

OBJECTIVE

To determine whether diagnostic temporal proximity to childbirth is associated with features of breast cancer associated with poor outcomes, including tumor stage, estrogen receptor (ER) status, and risk for distant metastasis and breast cancer-specific mortality, using a population database from the state of Utah.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study using the Utah Population Database (UPDB) included individuals with stage I to III breast cancer diagnosed at age 45 years or younger between 1996 and 2017, followed-up until February 2020. Participant data were analyzed from November 2019 to August 2022.

EXPOSURE

The primary exposures were no prior childbirth or time between most recent childbirth and breast cancer diagnosis. Patients were grouped by diagnoses within less than 5 years, 5 to less than 10 years, or 10 years or more since recent childbirth.

MAIN OUTCOMES AND MEASURES

The 2 primary outcomes were distant metastasis-free survival and breast cancer-specific death. Cox proportional hazard models were used to investigate associations between exposures and outcomes adjusting for diagnosis year, patient age, tumor stage, and estrogen receptor (ER) status.

RESULTS

Of 2970 individuals with breast cancer diagnosed at age 45 years or younger (mean [SD] age, 39.3 [5.0] years; 12 Black individuals [0.4%], 2679 White individuals [90.2%]), breast cancer diagnosis within 5 years of recent childbirth was independently associated with approximately 1.5-fold elevated risk for metastasis (hazard ratio [HR], 1.5; 95% CI, 1.2-2.0) and breast cancer-specific death (HR, 1.5; 95% CI, 1.1-2.1) compared with nulliparous individuals. For cancers classically considered to have tumor features associated with good outcomes (ie, stage I or II and ER-positive), a postpartum diagnosis was a dominant feature associated with increased risk for metastasis and death (eg, for individuals with ER-positive disease diagnosed within <5 years of childbirth: age-adjusted metastasis HR, 1.5; 95% CI, 1.1-2.1; P = .01; age-adjusted death HR, 1.5; 95% CI, 1.0-2.1; P = .04) compared with nulliparous individuals. Furthermore, liver metastases were specifically increased in the group with diagnosis within 5 years postpartum and with positive ER expression (38 of 83 patients [45.8%]) compared with the nulliparous (28 of 77 patients [36.4%]), although the difference was not statistically significant. Overall, these data implicate parity-associated breast and liver biology in the observed poor outcomes of PPBC.

CONCLUSIONS AND RELEVANCE

In this cohort study of individuals with breast cancer diagnosed at age 45 years or younger, a postpartum breast cancer diagnosis was a risk factor associated with poor outcomes. Irrespective of ER status, clinical consideration of time between most recent childbirth and breast cancer diagnosis could increase accuracy of prognosis in patients with young-onset breast cancer.

Latent Class Models of Early-life Trauma and Incident Breast Cancer

BACKGROUND

Psychosocial trauma has been hypothesized to influence breast cancer risk, but little is known about how co-occurring traumas-particularly during early life-may impact incidence. We examine the relationship between multiple measures of early-life trauma and incident breast cancer.

METHODS

The Sister Study is a prospective cohort study of US women (n = 50,884; enrollment 2003-2009; ages 35-74). Of 45,961 eligible participants, 3,070 developed invasive breast cancer or ductal carcinoma in situ through 2017. We assessed trauma before age 18 using previously studied measures (cumulative score, individual trauma type, and substantive domain) and a six-class latent variable to evaluate co-occurring traumas. We accounted for missing data using multiple imputation and estimated hazard ratios (HRs) and 95% confidence intervals (CIs) using Cox proportional-hazards models.

RESULTS

Approximately 49% of participants reported early-life trauma. Using the latent class variable approach, breast cancer hazard was higher among participants who had sexual trauma or household dysfunction (HR = 1.1; CI = 0.93, 1.3) or moderate (HR = 1.2; CI = 0.99, 1.4) but not high trauma (HR = 0.66; CI = 0.44, 0.99) compared to low trauma. Breast cancer HRs associated with sexual early-life trauma or household dysfunction were elevated for pre- and postmenopausal breast cancer and by estrogen receptor status. We found no effect modification by race-ethnicity. Estimated effects were attenuated with report of constant childhood social support.

CONCLUSIONS

Breast cancer incidence varied by latent patterns of co-occurring early-life trauma. Models capturing childhood social support and trauma patterning, rather than cumulative or discrete indicators, may be more meaningful in breast cancer risk assessment.

Towards defining morphologic parameters of normal parous and nulliparous breast tissues by artificial intelligence

BACKGROUND

Breast terminal duct lobular units (TDLUs), the source of most breast cancer (BC) precursors, are shaped by age-related involution, a gradual process, and postpartum involution (PPI), a dramatic inflammatory process that restores baseline microanatomy after weaning. Dysregulated PPI is implicated in the pathogenesis of postpartum BCs. We propose that assessment of TDLUs in the postpartum period may have value in risk estimation, but characteristics of these tissues in relation to epidemiological factors are incompletely described.

METHODS

Using validated Artificial Intelligence and morphometric methods, we analyzed digitized images of tissue sections of normal breast tissues stained with hematoxylin and eosin from donors ≤ 45 years from the Komen Tissue Bank (180 parous and 545 nulliparous). Metrics assessed by AI, included: TDLU count; adipose tissue fraction; mean acini count/TDLU; mean dilated acini; mean average acini area; mean "capillary" area; mean epithelial area; mean ratio of epithelial area versus intralobular stroma; mean mononuclear cell count (surrogate of immune cells); mean fat area proximate to TDLUs and TDLU area. We compared epidemiologic characteristics collected via questionnaire by parity status and race, using a Wilcoxon rank sum test or Fisher's exact test. Histologic features were compared between nulliparous and parous women (overall and by time between last birth and donation [recent birth: ≤ 5 years versus remote birth: > 5 years]) using multivariable regression models.

RESULTS

Normal breast tissues of parous women contained significantly higher TDLU counts and acini counts, more frequent dilated acini, higher mononuclear cell counts in TDLUs and smaller acini area per TDLU than nulliparas (all multivariable analyses p < 0.001). Differences in TDLU counts and average acini size persisted for > 5 years postpartum, whereas increases in immune cells were most marked ≤ 5 years of a birth. Relationships were suggestively modified by several other factors, including demographic and reproductive characteristics, ethanol consumption and breastfeeding duration.

CONCLUSIONS

Our study identified sustained expansion of TDLU numbers and reduced average acini area among parous versus nulliparous women and notable increases in immune responses within five years following childbirth. Further, we show that quantitative characteristics of normal breast samples vary with demographic features and BC risk factors.

Newly identified breast luminal progenitor and gestational stem cell populations likely give rise to HER2-overexpressing and basal-like breast cancers

Breast Cancer (BrC) is a common malignancy with genetically diverse subtypes. There is evidence that specific BrC subtypes originate from particular normal mammary cell populations. However, the cell populations that give rise to most BrC subtypes are unidentified. Several human breast scRNAseq datasets are available. In this research, we utilized a robust human scRNAseq dataset to identify population-specific marker genes and then identified the expression of these marker genes in specific BrC subtypes. In humans, several BrC subtypes, HER2-enriched, basal-like, and triple-negative (TN), are more common in women who have had children. This observation suggests that cell populations that originate during pregnancy give rise to these BrCs. The current human datasets have few normal parous samples, so we supplemented this research with mouse datasets, which contain mammary cells from various developmental stages. This research identified two novel normal breast cell populations that may be the origin of the basal-like and HER2-overexpressing subtypes, respectively. A stem cell-like population, SC, that expresses gestation-specific genes has similar gene expression patterns to basal-like BrCs. A novel luminal progenitor cell population and HER2-overexpressing BrCs are marked by S100A7, S100A8, and S100A9 expression. We bolstered our findings by examining SC gene expression in TN BrC scRNAseq datasets and S100A7-A9 gene expression in BrC cell lines. We discovered that several potential cancer stem cell populations highly express most of the SC genes in TN BrCs and confirmed S100A8 and A9 overexpression in a HER2-overexpressing BrC cell line. In summary, normal SC and the novel luminal progenitor cell population likely give rise to basal-like and HER2-overexpressing BrCs, respectively. Characterizing these normal cell populations may facilitate a better understanding of specific BrCs subtypes.

Cancer Epidemiology in Hispanic Populations: What Have We Learned and Where Do We Need to Make Progress?

The Hispanic/Latino(x) population (H/L) in the United States of America is heterogeneous and fast growing. Cancer is the number one cause of death among H/Ls, accounting for 21% of deaths. Whereas for the most common cancers, incidence rates are lower in H/Ls compared with non-H/L White (NHW) individuals, H/Ls have a higher incidence of liver, stomach, cervical, penile, and gallbladder cancers. H/L patients tend to be diagnosed at more advanced stages for breast, colorectal, prostate, and lung cancers, and melanoma compared with NHW individuals. Etiologic and cancer outcomes research among H/Ls lags other populations. In this review, we provide a summary of challenges, opportunities, and research priorities related to cancer etiology, cancer outcomes, and survivorship to make progress in addressing scientific gaps. Briefly, we prioritize the need for more research on determinants of obesity, nonalcoholic fatty liver disease and its progression to liver cancer, stomach and gallbladder cancers, and pediatric acute lymphoblastic leukemia. We emphasize the need to improve cancer screening, early detection of cancer, and survivorship care. We highlight critical resources needed to make progress in cancer epidemiologic studies among H/L populations, including the importance of training the next generation of cancer epidemiologists conducting research in H/Ls.

Aberrant RET expression impacts on normal mammary gland post-lactation transition enhancing cancer potential

RET is a receptor tyrosine kinase with oncogenic potential in the mammary epithelium. Several receptors with oncogenic activity in the breast are known to participate in specific developmental stages. We found that RET is differentially expressed during mouse mammary gland development: RET is present in lactation and its expression dramatically decreases in involution, the period during which the lactating gland returns to a quiescent state after weaning. Based on epidemiological and pre-clinical findings, involution has been described as tumor promoting. Using the Ret/MTB doxycycline-inducible mouse transgenic system, we show that sustained expression of RET in the mammary epithelium during the post-lactation transition to involution is accompanied by alterations in tissue remodeling and an enhancement of cancer potential. Following constitutive Ret expression, we observed a significant increase in neoplastic lesions in the post-involuting versus the virgin mammary gland. Furthermore, we show that abnormal RET overexpression during lactation promotes factors that prime involution, including premature activation of Stat3 signaling and, using RNA sequencing, an acute-phase inflammatory signature. Our results demonstrate that RET overexpression negatively affects the normal post-lactation transition.

Summary: We show that RET activation stimulates Stat3 signaling in mammary epithelial cell culture and in vivo during post-lactation transition, demonstrating that the RET receptor participates in the post-lactation transition priming tumorigenesis.

Racial/ethnic differences in postmenopausal breast cancer risk by hormone receptor status: The multiethnic cohort study

There are racial/ethnic differences in the incidence of hormone receptor positive and negative breast cancer. To understand why these differences exist, we investigated associations between hormone-related factors and breast cancer risk by race/ethnicity in the Multiethnic Cohort (MEC) Study. Among 81 511 MEC participants (Native Hawaiian, Japanese American, Latina, African American and White women), 3806 estrogen receptor positive (ER+) and 828 ER- incident invasive breast cancers were diagnosed during a median of 21 years of follow-up. We used Cox proportional hazards regression models to calculate associations between race/ethnicity and breast cancer risk, and associations between hormone-related factors and breast cancer risk by race/ethnicity. Relative to White women, ER+ breast cancer risk was higher in Native Hawaiians and lower in Latinas and African Americans; ER- disease risk was higher in African Americans. We observed interaction with race/ethnicity in associations between oral contraceptive use (OC; Pint .03) and body mass index (BMI; Pint .05) with ER+ disease risk; ever versus never OC use increased risk only in Latinas and positive associations for obese versus lean BMI were strongest in Japanese Americans. For ER- disease risk, associations for OC use, particularly duration of use, were strongest for African Americans (Pint .04). Our study shows that associations of OC use and obesity with ER+ and ER- breast cancer risk differ by race/ethnicity, but established risk factors do not fully explain racial/ethnic differences in risk. Further studies are needed to identify factors to explain observed racial/ethnic differences in breast cancer incidence.

Gestational diabetes and risk of breast cancer before age 55 years

BACKGROUND

The history of gestational diabetes mellitus (GDM) has been associated with breast cancer risk in some studies, particularly in young women, but results of cohort studies are conflicting.

METHODS

We pooled data from 257 290 young (age <55 years) women from five cohorts. We used multivariable Cox proportional-hazards regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between GDM history and risk of breast cancer, overall and by oestrogen receptor (ER) status, before age 55 years, adjusted for established breast cancer risk factors.

RESULTS

Five percent of women reported a history of GDM and 6842 women reported an incident breast-cancer diagnosis (median follow-up = 16 years; maximum = 24 years). Compared with parous women without GDM, women with a history of GDM were not at increased risk of young-onset breast cancer overall (HR = 0.90; 95% CI: 0.78, 1.03) or by ER status (HR = 0.96; 95% CI: 0.79, 1.16 for ER-positive; HR = 1.07; 95% CI: 0.78, 1.47 for ER-negative). Compared with nulliparous women, parous women with a history of GDM had a lower risk of breast cancer overall (HR = 0.79; 95% CI: 0.68, 0.91) and of ER-positive (HR = 0.82; 95% CI: 0.66, 1.02) but not ER-negative (HR = 1.09; 95% CI: 0.76, 1.54) invasive breast cancer. These results were consistent with the HRs comparing parous women without GDM to nulliparous women.

CONCLUSIONS

Results of this analysis do not support the hypothesis that GDM is a risk factor for breast cancer in young women. Our findings suggest that the well-established protective effect of parity on risk of ER-positive breast cancer persists even for pregnancies complicated by GDM.

Mycotoxin-mixture assessment in mother-infant pairs in Nigeria: From mothers' meal to infants' urine

Exposure to food and environmental contaminants is a global environmental health issue. In this study, innovative LC-MS/MS approaches were applied to investigate mycotoxin co-exposure in mother-infant pairs (n = 23) by analyzing matched plate-ready food, breast milk and urine samples of mothers and their exclusively breastfed infants. The study revealed frequent co-occurrence of two to five mycotoxins. Regulated (e.g. aflatoxins, deoxynivalenol and ochratoxin A) and emerging mycotoxins (e.g. alternariol monomethyl ether and beauvericin) were frequently detected (3 %-89 % and 45 %-100 %), in at least one specimen. In addition, a moderate association of ochratoxin A in milk to urine of mothers (r = 0.47; p = 0.003) and infants (r = 0.52; p = 0.019) but no other significant correlations were found. Average concentration levels in food mostly did not exceed European maximum residue limits, and intake estimates demonstrated exposure below tolerable daily intake values. Infants were exposed to significantly lower toxin levels compared to their mothers, indicating the protective effect of breastfeeding. However, the transfer into milk and urine and the resulting chronic low-dose exposure warrant further monitoring. In the future, occurrence of mycotoxin-mixtures, and their combined toxicological effects need to be comprehensively considered and implemented in risk management strategies. These should aim to minimize early-life exposure in critical developmental stages.

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.

Trace analysis of emerging and regulated mycotoxins in infant stool by LC-MS/MS

Infants are sensitive to negative effects caused by food contaminants such as mycotoxins. To date, analytical methods assessing mycotoxin mixture exposure in infant stool are absent. Herein, we present a novel multi-mycotoxin LC-MS/MS assay capable of detecting 30+ analytes including the regulated mycotoxin classes (aflatoxins, trichothecenes, ochratoxins, zearalenone, citrinin), emerging Alternaria and Fusarium toxins, and several key metabolites. Sample preparation consisted of a ‘dilute, filter, and shoot’ approach. The method was in-house validated and demonstrated that 25 analytes fulfilled all required criteria despite the high diversity of chemical structures included. Extraction recoveries for most of the analytes were in the range of 65–114% with standard deviations below 30% and limits of detection between 0.03 and 11.3 ng/g dry weight. To prove the methods’ applicability, 22 human stool samples from premature Austrian infants (n = 12) and 12-month-old Nigerian infants (n = 10) were analyzed. The majority of the Nigerian samples were contaminated with alternariol monomethyl ether (8/10) and fumonisin B₁ (8/10), while fumonisin B₂ and citrinin were quantified in some samples. No mycotoxins were detected in any of the Austrian samples. The method can be used for sensitive human biomonitoring (HBM) purposes and to support exposure and, potentially, risk assessment of mycotoxins. Moreover, it allows for investigating potential associations between toxicant exposure and the infants’ developing gut microbiome.

Options for Endocrine-Refractory, Hormone Receptor-Positive Breast Cancer: Which Target and When?

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in Journal of Clinical Oncology, to patients seen in their own clinical practice.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Parity and risk of developing breast cancer according to tumor subtype: A systematic review and meta-analysis

BACKGROUND

Clinical breast cancer subtypes are categorized basing on the expression of hormone receptors and overexpression of the human epidermal growth factor receptor 2 (HER2). It is still unclear whether parity impact the risk of different breast cancer subtypes.

METHODS

We searched eight mainstream databases for published epidemiologic studies that assessed the relationship between parity and risk of breast cancer subtypes up to January 12, 2021. Parity number were unified into nulliparity and ever parity. The random-effects or fixed-effect models were used to calculate the pooled odds ratios (ORs) and 95% confidence intervals (CIs) among different subtypes. Restricted cubic spline analysis with four knots was applied to determine the relationship of parity number and risk of breast cancer subtypes.

RESULTS

We pooled sixteen case-control and four cohort studies, and performed an analysis including 7795 luminal A, 3576 luminal B, 1794 HER2-overexpressing, and 5192 triple-negative breast cancer cases among 1135131 participants. The combined ORs for ever parity versus nulliparity indicated a 34% reduction in luminal A risk (OR=0.66, 95% CI: 0.56-0.78), and a 29% reduction in luminal B risk (OR=0.71, 95% CI: 0.63-0.81), there was no significant association in HER2-overexpressing or TNBC risk. In the dose-response analysis, we observed a potentially non-linear and gradually increasing protective relationship between the number of parity and luminal breast cancer risk.

CONCLUSIONS

The effect of parity on breast cancer seems to vary among breast tumor subtypes, and it plays a protective role in luminal breast cancer.

Premenopausal Breast Cancer Risk Factors and Associations with Molecular Subtypes: A Case-Control Study

Background

Breast cancer (BC) is the most prevalent cancer in women and the leading cause of women's cancer-related deaths and morbidity worldwide. In Rwanda, BC incidence is increasing with an unacceptably high mortality rate in premenopausal women.

Objectives

The purpose was to identify modifiable BC risk factors and assess associations between common breast cancer risks factors and molecular subtypes in premenopausal women in Rwanda.

Methods

This was a case-control study. Premenopausal women with histological confirmation of BC and frequency-matched for age controls were recruited. A preestablished questionnaire was administered to both cases and controls for sociodemographics, BC probable risk factors, and clinical and pathological characteristics. BC was classified into luminal A, luminal B, HER2-type, basal-like (triple negative), and unclassified molecular subtypes by immunohistochemistry (IHC). Odds ratio (OR) and 95% confidence interval (CI) were estimated using multivariate logistic regression analysis.

Results

340 participants were recruited into the study (170 cases vs. 170 controls). The median age was 39 years. The majority of cases presented at advanced stages of the disease (51.2% in stages III and IV) and had invasive ductal carcinoma (98.2%). 60.6% had subtypes of poor prognosis (HER2 enriched 14.7%, triple negative 12.9%, and unclassified 32.9%). Alcohol intake (AOR = 3.73, 95%CI 2.19 - 6.32, p < 0.001), obesity/overweight in adolescence or early adulthood (AOR = 10.86, 95%CI 4.82 - 24.4, p < 0.001), history of primary infertility (AOR = 33.8, 95%CI 3.5 - 321.5, p = 0.002), nulliparity (AOR = 3.75, 95%CI 1.61 - 8.75, p = 0.002), and a history of benign breast disease (AOR = 6.06, 95%CI 1.19 - 30.73, p = 0.03) were associated with the occurrence of premenopausal breast cancer. There was no significant difference between risk factor stratification per molecular subtype.

Conclusion

Several reproductive, environmental, and lifestyle risk factors have been identified to be associated with premenopausal BC. Among them, alcohol intake and obesity/overweight during adolescence/early adulthood can be modified. Interventions targeting alcohol consumption and obesity/overweight in adolescents and young adults may decrease the incidence of premenopausal breast cancer.

Risk factors for breast cancer subtypes among Black women undergoing screening mammography

PURPOSE

Black women are more likely than non-Hispanic White women to be diagnosed with triple negative breast cancer (TNBC), an aggressive subtype with limited treatment options. The study objective was to evaluate the associations of known breast cancer risk factors, including breast density, with TNBC among Black women.

METHODS

This study included Black women who underwent screening mammography between the ages of 40-84 years at a University of Pennsylvania Health System between 2010 and 2015. Cox proportional hazard models using multiple imputation with chained equations were used to estimate hazard ratios and 95% confidence intervals for risk factors for ER/PR+/HER2- and TNBC.

RESULTS

Among 25,013 Black women, there were 330 incident breast cancers (1.3%) during a mean follow-up of 5.8 years; 218 (66.1%) ER/PR+ HER- and 61 (18.1%) TNBC. Having dense breasts (heterogeneously dense or extremely dense) vs. non-dense breasts (almost entirely fatty or scattered areas of fibroglandular density) increased risk of ER/PR+/HER2- breast cancer almost 80% (HR 1.79, 95% CI 1.32-2.43) and TNBC more than twofold (HR 2.53, 1.45-4.44). Older age was associated with an increased risk for ER/PR+/HER2- (HR 1.04, 1.03-1.06) and TNBC (HR 1.03, 1.00-1.05). Having a BMI of > 30 kg/m² was associated with an increased risk (HR 2.77, 1.05-7.30) for TNBC and an increased risk of ERPR+/HER2- breast cancer in postmenopausal but not pre-menopausal women (p-interaction = 0.016).

CONCLUSION

Our results suggest that breast density and obesity are strong risk factors for TNBC among Black women. Understanding breast cancer subtype specific risk factors among Black women can help improve risk assessment.

Decreasing Incidence of Estrogen Receptor-Negative Breast Cancer in the United States: Trends by Race and Region

Background

Incidence of estrogen receptor (ER)-negative breast cancer, an aggressive subtype, is highest in US African American women and in Southern residents but has decreased overall since 1992. We assessed whether ER-negative breast cancer is decreasing in all age groups and cancer registries among non-Hispanic White (NHW), non-Hispanic Black (NHB), and Hispanic White (HW) women.

Methods

We analyzed 17 Surveillance, Epidemiology, and End-Results (SEER) Program registries (12 for 1992-2016; 5 for 2000-2016) to assess NHW, NHB, and HW trends by ER status and age group (30-39 years, 40-49 years, 50-69 years, 70-84 years). We used hierarchical age-period-cohort models that account for sparse data, which improve estimates to quantify between-registry heterogeneity in mean incidence rates and age-adjusted trends vs SEER overall.

Results

Overall, ER-negative incidence was highest in NHB, then NHW and HW women, and decreased from 1992-2016 in each age group and racial or ethnic group. The greatest decrease was for HW women aged 40-49 years, with an annual percent change of –3.5%/y (95% credible interval = −4.4%, −2.7%) averaged over registries. The trend heterogeneity was statistically significant in every race or ethnic and age group. Furthermore, the incidence relative risks by race or ethnicity compared with the race-specific SEER average were also statistically significantly heterogeneous across the majority of registries and age groups (62 of 68 strata). The greatest heterogeneity was seen in HW women, followed by NHB women, and the least in NHW women.

Conclusions

Decreasing ER-negative breast cancer incidence differs meaningfully by US region and age among NHB and HW women. Analytical studies including minority women from higher and lower incidence areas may provide insights into breast cancer racial disparities.

Dietary Vitamin A and Breast Cancer Risk in Black Women: The African American Breast Cancer Epidemiology and Risk (AMBER) Consortium

BACKGROUND

Studies in women of European descent showed an inverse association of dietary vitamin A (retinol and carotenoids) intake with breast cancer risks, mainly in premenopausal women.

OBJECTIVES

We examined whether higher compared with lower levels of dietary vitamin A are associated with reduced breast cancer risks among Black women by estrogen receptor (ER) and menopausal statuses.

METHODS

In this pooled analysis, data were from 3564 breast cancer cases and 11,843 controls (mean ages = 56.4 and 56.3 years, respectively) in the African American Breast Cancer Epidemiology and Risk (AMBER) Consortium. Dietary intake was assessed by FFQs. Multivariable logistic regressions were performed to estimate ORs and 95% CIs for study-specific quintiles of total vitamin A equivalents and individual carotenoids, and a pooled OR was estimated by a random-effect model.

RESULTS

We observed an inverse association of total vitamin A equivalents with ER-positive breast cancer (quintiles 5 compared with 1: pooled OR: 0.82; 95% CI: 0.67-1.00; P-trend = 0.045). The association was seen among premenopausal women (pooled OR: 0.60; 95% CI: 0.43-0.83; P-trend = 0.004), but not among postmenopausal women (pooled OR: 0.99; 95% CI: 0.77-1.28; P-trend = 0.78). Additionally, there were inverse associations of dietary β-carotene (quintiles 5 compared with 1: pooled OR: 0.70; 95% CI: 0.51-0.95; P-trend = 0.08) and lutein (pooled OR: 0.63; 95% CI: 0.45-0.87; P-trend = 0.020) with ER-positive breast cancer among premenopausal women. There was no evidence for an association of total vitamin A equivalents or individual carotenoids with ER-negative breast cancer, regardless of menopausal status.

CONCLUSIONS

Our findings on dietary vitamin A and breast cancer risks in Black women are consistent with observations in women of European descent and advance the literature showing an inverse association for ER-positive disease.

Relationship of established risk factors with breast cancer subtypes

Background

Breast cancer is a heterogeneous disease, divided into subtypes based on the expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2). Subtypes have different biology and prognosis, with accumulating evidence of different risk factors. The purpose of this study was to compare breast cancer risk factors across tumor subtypes in a large, diverse mammography population.

Methods

Women aged 40–84 without a history of breast cancer with a screening mammogram at three United States health systems from 2006 to 2015 were included. Risk factor questionnaires were completed at mammogram visit, supplemented by electronic health records. Invasive tumor subtype was defined by immunohistochemistry as ER/PR+HER2−, ER/PR+HER2+, ER, and PR−HER2+, or triple‐negative breast cancer (TNBC). Cox proportional hazards models were run for each subtype. Associations of race, reproductive history, prior breast problems, family history, breast density, and body mass index (BMI) were assessed. The association of tumor subtypes with screen detection and interval cancer was assessed using logistic regression among invasive cases.

Results

The study population included 198,278 women with a median of 6.5 years of follow‐up (IQR 4.2–9.0 years). There were 4002 invasive cancers, including 3077 (77%) ER/PR+HER2−, 300 (8%) TNBC, 342 (9%) ER/PR+HER2+, and 126 (3%) ER/PR−HER2+ subtype. In multivariate models, Black women had 2.7 times higher risk of TNBC than white women (HR = 2.67, 95% CI 1.99–3.58). Breast density was associated with increased risk of all subtypes. BMI was more strongly associated with ER/PR+HER2− and HER2+ subtypes among postmenopausal women than premenopausal women. Breast density was more strongly associated with ER/PR+HER2− and TNBC among premenopausal than postmenopausal women. TNBC was more likely to be interval cancer than other subtypes.

Conclusions

These results have implications for risk assessment and understanding of the etiology of breast cancer subtypes. More research is needed to determine what factors explain the higher risk of TNBC for Black women.

Cumulative menstrual months and breast cancer risk by hormone receptor status and ethnicity: The Breast Cancer Etiology in Minorities Study

Reproductive and hormonal factors may influence breast cancer risk via endogenous estrogen exposure. Cumulative menstrual months (CMM) can be used as a surrogate measure of this exposure. Using harmonized data from four population-based breast cancer studies (7284 cases and 7242 controls), we examined ethnicity-specific associations between CMM and breast cancer risk using logistic regression, adjusting for menopausal status and other risk factors. Higher CMM was associated with increased breast cancer risk in non-Hispanic Whites, Hispanics and Asian Americans regardless of menopausal status (all FDR adjusted P trends = .0004), but not in African Americans. In premenopausal African Americans, there was a suggestive trend of lower risk with higher CMM. Stratification by body mass index (BMI) among premenopausal African American women showed a nonsignificant positive association with CMM in nonobese (BMI <30 kg/m² ) women and a significant inverse association in obese women (OR per 50 CMM = 0.56, 95% CI 0.37-0.87, P_trend  = .03). Risk patterns were similar for hormone receptor positive (HR+; ER+ or PR+) breast cancer; a positive association was found in all premenopausal and postmenopausal ethnic groups except in African Americans. HR- (ER- and PR-) breast cancer was not associated with CMM in all groups combined, except for a suggestive positive association among premenopausal Asian Americans (OR per 50 CMM = 1.33, P = .07). In summary, these results add to the accumulating evidence that established reproductive and hormonal factors impact breast cancer risk differently in African American women compared to other ethnic groups, and also differently for HR- breast cancer than HR+ breast cancer.

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.

Cancer stem cells in TNBC

Triple-negative breast cancer (TNBC) is a broad collection of breast cancer that tests negative for estrogen receptors (ER), progesterone receptors (PR), and excess human epidermal growth factor receptor 2 (HER2) protein. TNBC is considered to have poorer prognosis than other types of breast cancer because of a lack of effective therapeutic targets. The success of precision cancer therapies relies on the clarification of key molecular mechanisms that drive tumor growth and metastasis; however, TNBC is highly heterogeneous in terms of their cellular lineage composition and the molecular nature within each individual case. In particular, the rare and sometimes slow cycling cancer stem cells (CSCs) can provide effective means for TNBC to resist various treatments. Single cell analysis technologies, including single-cell RNA-seq (scRNA-seq) and proteomics, provide an avenue to unravel patient-level intratumoral heterogeneity by identifying CSCs populations, CSC biomarkers and the range of tumor microenvironment cellular constituents that contribute to tumor growth. This review discusses the emerging evidence for the role of CSCs in driving TNBC incidence and the therapeutic implications in manipulating molecular signaling against this rare cell population for the control of this deadly disease.

Deletion of Foxa1 in the mouse mammary gland results in abnormal accumulation of luminal progenitor cells: a link between reproductive factors and ER-/TNBC breast cancer?

In humans, parity without breastfeeding increases risk of estrogen receptor-negative (ER-) breast cancer and is associated with hypermethylation of FOXA1, a pioneer factor regulating lineage commitment of mammary gland luminal progenitor cells. We postulate that pregnancy-associated repression of FOXA1 results in the accumulation of aberrant, differentiation-arrested luminal progenitor cells which, following additional genetic and epigenetic insults, may give rise to ER- tumors. Consistent with this hypothesis, we show that deletion of Foxa1 in the mouse mammary gland results in a two-fold increase in the proportion of luminal progenitor cells and a reduction in mammary gland epithelial cells that stain positive for ER. These results provide compelling support for the notion that reduced Foxa1 expression is sufficient to alter mammary gland luminal cell fate determination in vivo, which could be a mechanism linking parity with ER- breast cancer.

Are There Regional Differences in Triple Negative Breast Cancer among Non-Hispanic Black Women?

BACKGROUND

Non-Hispanic black women (NHB) are diagnosed with triple negative breast cancer (TNBC) more often than other ethnic or racial groups in the United States (US). This study describes regional differences in TNBC incidence among NHB women in the US from 2011 to 2015.

METHODS

We analyzed data from the United States Cancer Statistics (USCS) that includes incidence data from the Centers for Disease Control and Prevention's National Program of Cancer Registries (NPCR) and the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) programs.

RESULTS

Compared to the incidence rate for NHB women in the South, rates were significantly lower in the Northeast (22.6 per 100,000), higher in the Midwest (25.5 per 100,000) and similar in the West. These regional differences might be explained by genetic admixture among people with different geographic ancestral origins.

CONCLUSIONS

Results from this study highlight the need to extend etiological research and evidence-based cancer prevention and control efforts to women at high risk of this disease in order to decrease cancer disparities.

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.

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.

Social Determinants of Racial Disparities in Breast Cancer Mortality Among Black and White Women

INTRODUCTION

Mortality from breast cancer among Black women is 60% greater than that of White women in South Carolina (SC). The aim of this study was to assess racial differences in mortality among Black and White breast cancer patients based on variations in social determinants and access to state-based early detection programs.

METHODS

We obtained a retrospective record for breast cancer patients diagnosed between 2002 and 2010 from the SC Central Cancer Registry. Mortality was the main outcome while race-stratified Cox proportional hazard models were performed to assess disparities in mortality. We assessed effect modification, and we used an automated backward elimination process to obtain the best fitting models.

RESULTS

There were 3286 patients of which the majority were White women (2186, 66.52%). Compared with married White women, the adjusted hazard ratio (aHR) for mortality was greatest among Black unmarried women (aHR 2.31, CI 1.83, 2.91). Compared with White women who lived in the Low Country region mortality was greatest among Black women who lived in the Midland (aHR 2.17 CI 1.47, 3.21) and Upstate (aHR 2.96 CI 1.96, 2.49). Mortality was higher among Black women that were not receiving services in the Best Chance Network (BCN) program (aHR 1.70, CI 1.40, 2.04) compared with White women.

CONCLUSIONS

To reduce the racial disparity gap in survival in SC, Black breast cancer patients who live in the Upstate, are unmarried, and those that are not enrolled in the BCN program may benefit from more intense navigation efforts directed at early detection and linkage to breast cancer treatments.

Breast Cancer During Pregnancy: A Marked Propensity to Triple-Negative Phenotype

Breast and cervical cancers comprise 50% of all cancers during pregnancy. In particular, gestational breast cancer is considered one of the most aggressive types of cancers, which is a rare but fatal disease. However, the incidence of this type of cancer is increasing over the years and its prevalence is expected to rise further as more women delay childbearing. Breast cancer occurring after pregnancy is generally triple negative with specific characterizations of a poorer prognosis and outcome. On the other hand, it has been pointed out that this cancer is associated with a specific group of genes which can be used as precise targets to manage this deadly disease. Indeed, combination therapies consisting of gene-based agents with other cancer therapeutics is presently under consideration. We herein review recent progress in understanding the development of breast cancer during pregnancy and their unique subtype of triple negative which is the hallmark of this type of breast cancer.

Cancer health disparities in racial/ethnic minorities in the United States

There are well-established disparities in cancer incidence and outcomes by race/ethnicity that result from the interplay between structural, socioeconomic, socio-environmental, behavioural and biological factors. However, large research studies designed to investigate factors contributing to cancer aetiology and progression have mainly focused on populations of European origin. The limitations in clinicopathological and genetic data, as well as the reduced availability of biospecimens from diverse populations, contribute to the knowledge gap and have the potential to widen cancer health disparities. In this review, we summarise reported disparities and associated factors in the United States of America (USA) for the most common cancers (breast, prostate, lung and colon), and for a subset of other cancers that highlight the complexity of disparities (gastric, liver, pancreas and leukaemia). We focus on populations commonly identified and referred to as racial/ethnic minorities in the USA-African Americans/Blacks, American Indians and Alaska Natives, Asians, Native Hawaiians/other Pacific Islanders and Hispanics/Latinos. We conclude that even though substantial progress has been made in understanding the factors underlying cancer health disparities, marked inequities persist. Additional efforts are needed to include participants from diverse populations in the research of cancer aetiology, biology and treatment. Furthermore, to eliminate cancer health disparities, it will be necessary to facilitate access to, and utilisation of, health services to all individuals, and to address structural inequities, including racism, that disproportionally affect racial/ethnic minorities in the USA.

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.

Mucosal Immunity and Liver Metabolism in the Complex Condition of Lactation Insufficiency

Lactation insufficiency is variously defined and includes the inability to produce milk, not producing enough milk to exclusively meet infant growth requirements, and pathological interruption of lactation (e.g., mastitis). Of women with intent-to-breastfeed, lactation insufficiency has been estimated to affect 38%-44% of newly postpartum women, likely contributing to the nearly 60% of infants that are not breastfed according to the World Health Organization's guidelines. To date, research and clinical practice aimed at improving feeding outcomes have focused on hospital lactation support and education, with laudable results. However, researchers' reports of recent rodent studies concerning fundamental lactation biology have suggested that the underlying pathologies of lactation insufficiency may be more nuanced than is currently appreciated. In this article, we identify mucosal biology of the breast and lactation-specific liver biology as two under-researched aspects of lactation physiology. Specifically, we argue that further scientific inquiry into reproductive state-dependent regulation of immunity in the human breast will reveal insights into novel immune based requirements for healthy lactation. Additionally, our synthesis of the literature supports the hypothesis that the liver is an essential player in lactation-highlighting the potential that pathologies of the liver may also be associated with lactation insufficiency. More research into these biologic underpinnings of lactation is anticipated to provide new avenues to understand and treat lactation insufficiency.

Workplace programmes for supporting breast-feeding: a systematic review and meta-analysis

OBJECTIVE

To critically review the literature regarding workplace breast-feeding interventions and to assess their impact on breast-feeding indicators.

DESIGN

A systematic review and meta-analysis was conducted. Electronic searches for workplace intervention studies to support breast-feeding, without restriction on language or study design, were performed in PubMed, CENTRAL, CINAHL, Embase, Web of Science, Business Source Complete, ProQuest-Sociology and ProQuest-Social Science to 13 April 2020. A meta-analysis of the pooled effect of the programmes on breast-feeding indicators was conducted.

RESULTS

The search identified 10 215 articles; fourteen studies across eighteen publications met eligibility criteria. Programmes were delivered in the USA (n 10), Turkey (n 2), Thailand (n 1) or Taiwan (n 1). There were no randomised controlled trials. The pooled OR for exclusive breast-feeding at 3 or 6 months for participants v. non-participants of three non-randomised controlled studies was 3·21 (95 % CI 1·70, 6·06, I2 = 22 %). Despite high heterogeneity, other pooled outcomes were consistently in a positive direction with acceptable CI. Pooled mean duration of breast-feeding for five single-arm studies was 9·16 months (95 % CI 8·25, 10·07). Pooled proportion of breast-feeding at 6 months for six single-arm studies was 0·76 (95 % CI 0·66, 0·84) and breast-feeding at 12 months for three single-arm studies was 0·41 (95 % CI 0·22, 0·62). Most programmes were targeted at mothers; two were targeted at expectant fathers.

CONCLUSIONS

Workplace programmes may be effective in promoting breast-feeding among employed mothers and partners of employed fathers. However, no randomised controlled trials were identified, and better-quality research on workplace interventions to improve breast-feeding is needed.

Concordance of Immunohistochemistry-Based and Gene Expression-Based Subtyping in Breast Cancer

Background

Use of immunohistochemistry-based surrogates of molecular breast cancer subtypes is common in research and clinical practice, but information on their comparative validity and prognostic capacity is scarce.

Methods

Data from 2 PAM50-subtyped Swedish breast cancer cohorts were used: Stockholm tamoxifen trial–3 with 561 patients diagnosed 1976-1990 and Clinseq with 237 patients diagnosed 2005-2012. We evaluated 3 surrogate classifications; the immunohistochemistry-3 surrogate classifier based on estrogen receptor, progesterone receptor, and HER2 and the St. Gallen and Prolif surrogate classifiers also including Ki-67. Accuracy, kappa, sensitivity, and specificity were computed as compared with PAM50. Alluvial diagrams of misclassification patterns were plotted. Distant recurrence-free survival was assessed using Kaplan-Meier plots, and tamoxifen treatment benefit for luminal subtypes was modeled using flexible parametric survival models.

Results

The concordance with PAM50 ranged from poor to moderate (kappa = 0.36-0.57, accuracy = 0.54-0.75), with best performance for the Prolif surrogate classification in both cohorts. Good concordance was only achieved when luminal subgroups were collapsed (kappa = 0.71-0.69, accuracy = 0.90-0.91). The St. Gallen surrogate classification misclassified luminal A into luminal B; the reverse pattern was seen with the others. In distant recurrence-free survival, surrogates were more similar to each other than PAM50. The difference in tamoxifen treatment benefit between luminal A and B for PAM50 was not replicated with any surrogate classifier.

Conclusions

All surrogate classifiers had limited ability to distinguish between PAM50 luminal A and B, but patterns of misclassifications differed. PAM50 subtyping appeared to yield larger separation of survival between luminal subtypes than any of the surrogate classifications.

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.