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2025
J Clin Oncol
A large California study of over 58,000 racially and ethnically diverse women found that long-term exposure to fine particulate matter (PM2.5) air pollution was associated with a statistically significant 28% increased risk of breast cancer for each 10 μg/m³ increase in PM2.5 concentration, with the association consistent across African American, Latino, and other ethnic groups. When combined with data from 10 other studies in a meta-analysis, PM2.5 exposure showed a borderline significant 5% increased breast cancer risk, providing strong evidence that air pollution is an important breast cancer risk factor. These findings emphasize that breast cancer prevention strategies should extend beyond individual lifestyle changes to include population-level policies aimed at reducing air pollution, particularly as traditional risk factors explain only half of breast cancer cases and incidence continues to rise globally.
2025
Int J Environ Health Res
In this case-control study of African American women in Memphis, 355 participants aged 20–88 were enrolled, and the final analysis included 50 breast cancer cases and 157 controls whose home addresses were linked to detailed environmental and socioeconomic data. Using logistic regression, the researchers found that women living closer to heavy traffic had higher odds of breast cancer (OR 1.64, 95% CI: 1.05–2.56), and those living nearer to Superfund hazardous waste sites had markedly higher odds (OR 12.26, 95% CI: 1.81–82.86) compared with women living farther away. Spatial mapping showed that cases clustered in Southwest Memphis, an area with higher environmental burden and disadvantage. These findings suggest that environmental inequities in the built and industrial environment may substantially contribute to breast cancer disparities among African American women in this region.
2024
Int J Hyg Environ Health
A study of 48,665 California women in the Multiethnic Cohort found that exposure to specific ambient air toxics at residential addresses was associated with increased breast cancer risk over a 10-year follow-up period. Industrial chemicals showed the strongest associations, with 1,1,2,2-tetrachloroethane linked to a 322% increased risk, ethylene dichloride to a 181% increased risk, and vinyl chloride to a 127% increased risk. Gasoline-related pollutants also showed elevated risks, including benzene (32% increase), acrolein (126% increase), and toluene (29% increase), with generally stronger associations observed among African American and White women. These findings suggest that toxic air pollutants, particularly from industrial sources and vehicle emissions, may contribute to breast cancer development, which is especially concerning for populations living in high-pollution areas like Los Angeles.
2024
Environ Health Perspect
A nationwide study using CDC biomonitoring data found that California’s Proposition 65, which requires warnings about chemicals that cause cancer or reproductive harm, led to reduced exposures to listed chemicals across the entire United States, not just California. While blood and urine concentrations of 37 monitored chemicals generally declined over time, the researchers found evidence of problematic chemical substitution—for example, after bisphenol A (BPA) was listed, its concentrations dropped 15% but levels of the unlisted substitute bisphenol S (BPS) increased 20%. Californians generally had lower levels of harmful chemicals in their bodies compared to residents of other states, suggesting the law had additional protective effects. The findings indicate that transparency laws like Prop 65 can drive manufacturers to reformulate products nationwide, but regulations need to address entire chemical classes rather than individual substances to prevent companies from simply switching to similar but unlisted toxic chemicals.
2022
Environ Res
This case-only study included 2,998 women with breast cancer from the Women’s Circle of Health Study and examined how characteristics of hair dye and hair relaxer use were related to tumor features. Compared with women who only used salon-applied permanent hair dye, those using home dye kits or both salon and home dye had higher odds of having poorly differentiated (more aggressive) tumors, especially among Black women (for Black women: home kits OR 2.22, 95% CI: 1.21–5.00; combination use OR 2.46, 95% CI: 1.21–5.00) and among women with ER-positive tumors (combination use OR 2.98, 95% CI: 1.62–5.49). Combination use of hair relaxers was also associated with larger tumors (>2.0 cm vs <1.0 cm; OR 1.82, 95% CI: 1.23–2.69). Although some associations did not remain statistically significant after strict multiple-comparison correction, the overall pattern suggests that frequent, mixed use of hair dyes and relaxers may be linked to more aggressive breast tumor characteristics.
2022
Ann Surg
A genomic study of 308 women with stage I-IV breast cancer (non-Hispanic White, Hispanic White, Hispanic Black, and non-Hispanic Black) using peripheral blood analysis found that increasing West African (WA) ancestry was associated with 6% higher odds of triple-negative breast cancer per percentage increase (OR = 1.06; 95% CI: 1.001-1.126) and higher neighborhood socioeconomic status (nSES) showed a protective effect (OR = 0.343; 95% CI: 0.151-0.781), though WA ancestry’s association with TNBC was attenuated when adjusting for nSES. Local ancestry analysis revealed nSES-independent enriched WA ancestral segments at specific chromosomal loci (χ²=42004914, p=3.70×10⁻⁵) associated with TNBC, while multinomial logistic regression demonstrated that women from low nSES neighborhoods remained more likely to have TNBC independent of genetic ancestry. These findings reveal the complex interplay between genetic ancestry and socioeconomic environment in TNBC etiology: while specific genetic variants linked to West African ancestry contribute to TNBC risk through biological mechanisms, neighborhood socioeconomic disadvantage exerts independent effects, highlighting that both genetic susceptibility and environmental/social determinants contribute to the disproportionate TNBC burden in Black women and underscoring the critical importance of studying gene-environment interactions as drivers of aggressive breast cancer disparities.
2021
Environ Pollut
A pilot study of 250 predominantly postmenopausal women in Hawaii found that higher levels of AMPA (the primary breakdown product of the herbicide Glyphosate) in urine were associated with significantly increased breast cancer risk, with women in the highest exposure group having 4.5 times the risk compared to those with the lowest exposure. AMPA was detected in the urine of 90% of breast cancer cases and 84% of healthy controls, with cases showing 38% higher average AMPA levels. This is the first study to prospectively examine the link between AMPA exposure and breast cancer, and while the findings suggest a concerning association, the authors emphasize that larger studies are needed to confirm these preliminary results and explore potential differences across racial and ethnic groups.
2021
Cancer Epi
This study of nearly 48,000 women found that frequent use of chemical hair straighteners and perms during adolescence (ages 10-13) was associated with more than double the risk of premenopausal breast cancer, though no increased risk was seen for postmenopausal breast cancer. Black women who used permanent hair dye during adolescence had a 77% increased breast cancer risk, though permanent dye use was uncommon overall in the study population. The findings are particularly concerning because adolescence is a critical developmental window when breast tissue may be more vulnerable to chemical exposures, and these hair products contain hormonally active and potentially carcinogenic compounds that may have long-lasting effects on breast cancer risk decades later.
2021
Epidemiol
A study of 1,407 North Carolina women examined the relationship between blood levels of polychlorinated biphenyls (PCBs)—banned industrial chemicals that persist in the environment—and breast cancer risk. The researchers found that exposure to mixtures of PCBs was associated with increased breast cancer risk, with stronger associations observed among Black women (50% increased risk) compared to White women (10% increased risk) at higher exposure levels. Several individual PCB compounds showed elevated breast cancer risk when comparing highest to lowest exposure groups, with risk increases ranging from 20-40%. These findings support the hypothesis that PCB exposure may increase breast cancer risk, though additional studies in other populations are needed to confirm the results.
2021
Int J Cancer
In a nested case-control study of over 1,000 breast cancer cases and matched controls from the Multiethnic Cohort, pre-diagnostic urinary concentrations of bisphenol A (BPA), triclosan, and parabens were evaluated in relation to breast cancer risk. BPA was not significantly associated with risk; the highest tertile of total parabens had OR ≈ 0.77 (95% CI: 0.62–0.97) relative to the lowest tertile, indicating a modest inverse association. These results suggest that the relationships between common endocrine-disrupting chemicals and breast cancer may be more complex than anticipated and vary by exposure type.
2019
Environ Int
This 20-year study of 748 women diagnosed with breast cancer in North Carolina found that those with the highest levels of DDE (a breakdown product of the banned pesticide DDT) in their blood had nearly twice the risk of death compared to those with the lowest levels. The association between DDE exposure and breast cancer death was particularly strong among Black women and women with estrogen receptor-negative tumors, with Black women showing more than double the mortality risk. Since DDT was banned in the U.S. in 1972 but DDE persists in the environment and body fat for decades, these findings suggest that legacy pesticide exposure may contribute to worse breast cancer outcomes and racial disparities in breast cancer survival.
2018
Discov Oncol
This systematic review examined the relation of 4 neighborhood factors on breast cancer incidence and prognosis among African-American women: neighborhood socioeconomic status (nSES), residential segregation, spatial access to mammography, and residential pollution. The authors found that nSES, residential segregation and access to mammography were all related to stage at diagnosis, and nSES and living in more segregated areas were both associated with mortality. Residential pollution was not associated with increased risk of breast cancer in the studies reviewed.
2025
JAMA Netw Open
A cross-sectional study of 121 Black and White women with breast cancer found that chronic stressors—including perceived stress, inadequate social support, discrimination, and neighborhood deprivation—were associated with harmful immune and tumor changes, with particularly pronounced effects in Black women who also lived in significantly more socioeconomically deprived neighborhoods. Higher stress, discrimination, and neighborhood deprivation were linked to increased systemic inflammation, immune-suppressive tumor environments (including tumor-promoting M2 macrophages), and elevated tumor mutational burden, while greater social support was associated with beneficial immune-stimulatory changes including increased natural killer cells in breast tissue. Black women showed distinct stress-related immunologic signatures including enhanced chemotaxis, immune suppression at the systemic level, and increased tumor-associated myeloid cells, suggesting that chronic psychosocial and environmental stressors may biologically contribute to breast cancer disparities by creating a pro-tumorigenic immune environment—findings that underscore the urgent need for interventions addressing social determinants of health as cancer prevention strategies.
2024
Environ Sci Technol
A study of 751 reproductive-aged Black women found that the relationship between personal care product (PCP) use and exposure to endocrine-disrupting chemicals (EDCs) varied significantly by socioeconomic status (SES), with different patterns of chemical exposure from the same products depending on women’s education, income, and employment. For example, vaginal powder use was associated with higher phenol exposure (a class of EDCs) among lower SES women but showed no such association in higher SES women, suggesting that product formulations, brands, or usage patterns may differ across SES groups. These findings highlight that Black women face inequitable EDC exposures that are influenced by both race and socioeconomic factors, underscoring the need for targeted public health interventions that address these intersecting disparities in chemical exposures from everyday products
2024
Maturitas
A comprehensive review of breast cancer disparities highlights that Non-Hispanic Black women experience markedly elevated breast cancer mortality due to multifactorial causes, including unique risk profiles such as higher prevalence of early-onset triple-negative breast cancer, specific reproductive risk factors, obesity patterns traced to infant feeding practices, and barriers to genetic risk assessment and high-risk referrals. The authors propose risk- and race-based screening strategies given the prevalence of aggressive early-onset disease in young Black women, emphasize the importance of early hereditary/familial risk identification while addressing challenges in interpreting uncertain genetic results, and stress the need for culturally sensitive approaches to healthy lifestyle promotion and clinical trial participation. Addressing breast cancer disparities requires tackling social determinants of health, educating patients and clinicians about factors driving outcome inequities, building trust to foster adherence and follow-up, and encouraging participation in targeted research to better serve all communities and reduce the disproportionate burden of breast cancer mortality in Black women.
2024
Cancer Causes Control
A population-based study using Kentucky cancer registry data (77,637 breast cancer and 56,598 colorectal cancer cases) found that higher ambient air concentrations of carcinogenic metals—cadmium, arsenic, nickel, and chromium(VI)—were associated with increased odds of residing in breast and colorectal cancer hotspots, independent of individual risk factors including age, race, smoking, and neighborhood socioeconomic characteristics. Cancer hotspot populations were disproportionately Black and exhibited markers of lower socioeconomic status, and importantly, the metal-cancer associations persisted even after adjusting for these factors, suggesting environmental metal exposure is an independent contributor to geographic cancer clustering. These findings provide evidence that historically marginalized communities face disproportionate exposure to carcinogenic metals through environmental pollution, likely contributing to cancer disparities, and underscore the urgent need for environmental justice interventions including stricter air quality regulations, cleanup of contaminated sites, and individual-level exposure assessments to fully understand how metal exposures drive cancer inequities in vulnerable populations.
2024
CA Cancer J Clin
Every two years, the ACS releases a report of updates on statistics on breast cancer among women. One in eight U.S. women will be diagnosed with invasive breast cancer, a 13% lifetime risk. From 2012 to 2021, diagnoses rose by 1% annually, with a 1.4% increase for women under 50. Asian American and Pacific Islander (AAPI) women saw the fastest rise in diagnoses. Despite a 44% drop in mortality since 1989, disparities persist—mortality rates remain highest among Black women, and there’s been no improvement for American Indian/Alaska Native women. These findings highlight the urgent need for equitable breast cancer diagnosis and treatment.
2024
Int J Mol Sci
This comprehensive review covers breast cancer biology from classification and risk factors through diagnosis and treatment, highlighting how the disease varies by subtype and between racial groups. The review examines both traditional factors like staging systems and molecular subtypes (Luminal A/B, Triple Negative, HER2-enriched) as well as emerging research on genetic mutations, epigenetic changes, and microbiome imbalances that may contribute to breast cancer development and progression. Recent evidence suggests that disruptions in the body’s microbial communities may play a role in breast cancer, with patterns potentially differing across populations, adding a new dimension to understanding racial disparities in breast cancer outcomes.
2024
BMC
A 2021 survey of over 5,000 U.S. women found that only about one-quarter were aware that alcohol consumption increases breast cancer risk, while 40% were unsure and over one-third believed there was no connection. Awareness was higher among younger women (18-25), college graduates, and those with alcohol use disorder symptoms, but lower among Black women compared to white women. These findings reveal a significant knowledge gap about an established and modifiable breast cancer risk factor, highlighting the need for targeted education campaigns to increase awareness across different demographic groups.
2024
Healthcare
This article highlights the disparities in the treatment of breast cancer based on various demographic factors. In terms of prevention and screening, people of minority groups such as African American and Hispanic women face challenges in accessing preventative measures like mammograms, mostly because of inequitable access to healthcare, financial constraints, and inadequate insurance coverage. These disparities also lead to delayed diagnoses and therefore worse outcomes in the treatment of these cancers. Additionally, provider bias, patient mistrust in the healthcare system, and systemic inequalities in the healthcare infrastructure cause inefficient treatment of breast cancer in these minority groups as well.
2024
Environ Int
A study of 1,031 pregnant women from the socioeconomically diverse CANDLE cohort in the urban South found that ultra-processed foods constituted 38.6% of participants’ diets on average, with each 10% higher dietary proportion of ultra-processed foods associated with 13.1% higher urinary concentrations of DEHP phthalate metabolites, while specific foods like hamburgers, French fries, soda, and cake showed 6-10.5% higher DEHP per standard deviation increase in consumption. Causal mediation analyses revealed that lower income and education levels were associated with 1.9% and 1.4% higher DEHP exposure respectively, mediated through increased ultra-processed food consumption, indicating that ultra-processed foods contribute to socioeconomic disparities in phthalate exposure during pregnancy. The findings demonstrate that consuming ultra-processed foods increases exposure to endocrine-disrupting phthalates from food contact materials, and because socioeconomic barriers can prevent dietary modifications, policies to reduce phthalates in food packaging and processing are needed rather than relying solely on individual dietary recommendations to reduce prenatal phthalate exposures.
2023
JAMA Oncol
A retrospective analysis of 60,137 women with early-stage, ER-positive, node-negative breast cancer found that Black women had an 82% increased risk of breast cancer death compared to White women, with social determinants of health (neighborhood disadvantage and insurance status) mediating 19% of this disparity and tumor biological characteristics (including genomic recurrence scores) mediating 20%. When all factors were combined in a fully adjusted model, 44% of the racial survival disparity was explained, suggesting that social determinants and aggressive tumor biology contribute roughly equally to worse outcomes in Black women, though over half of the disparity remains unexplained. Notably, neighborhood disadvantage itself mediated 8% of racial differences in high-risk recurrence scores, indicating that social factors may influence tumor biology, and highlighting that addressing breast cancer disparities requires dual approaches targeting both structural barriers to healthcare access and quality while investigating the biological mechanisms—including ancestry-related genetic variants and molecular pathways—that may drive more aggressive disease in Black women.
2023
Breast Cancer Res Treat
A study of 1,398 Black women (567 breast cancer cases, 831 controls) found preliminary evidence of gene-environment interactions between genetic variants in the mTOR signaling pathway and vigorous physical activity affecting breast cancer risk, though results did not survive correction for multiple testing. Specific variants in AKT1 were associated with 49-85% reduced ER-positive breast cancer risk only among physically active women, while an MTOR variant showed a 124% increased ER-positive cancer risk and an EIF4E variant showed dramatically elevated ER-negative cancer risk (over 20-fold), but only in the context of vigorous physical activity. These exploratory findings suggest that the relationship between physical activity and breast cancer may vary by genetic background in Black women, potentially explaining some of the heterogeneity in physical activity-breast cancer associations, though larger studies with multiple testing correction are needed to confirm whether these gene-exercise interactions truly modify breast cancer risk.
2023
Cancer Causes Control
A review examining how low socioeconomic status (SES) contributes to early chronic disease onset and reduced life expectancy found that neighborhood-level factors—including environmental pollutants, deprivation, social isolation, structural racism, and discrimination—create chronic life stress that affects molecular processes like DNA methylation, inflammation, and immune response, contributing to more aggressive tumor biology, particularly in Black Americans. Despite decades of research showing associations between neighborhood factors and cancer outcomes in marginalized communities, the biological mechanisms linking SES to cancer disparities remain poorly understood, though emerging evidence suggests chronic stress pathways may play a central role. The authors summarize current methods for measuring neighborhood-level deprivation, discrimination, and structural racism in cancer disparities research and recommend adopting a multi-faceted intersectional approach to reduce cancer health inequities and develop effective interventions promoting health equity.
2023
Endocrinol Metab Clin North Am
Multiple social and structural determinants of health undoubtedly contribute to the marked racial/ethnic-, gender-, and socioeconomic-based disparities in endocrine health; however, the contribution of environmental injustice is vastly underappreciated. Indeed, those groups disproportionately burdened by endocrine disorders are often exposed to higher levels of various EDCs, including PCBs, phthalates, bisphenols, OC pesticides, air pollutants, PFASs, toxic metals/metalloids, and BFRs. These chemicals threaten our reproductive and metabolic health, contributing to diabetes prevalences, obesity, and disorders related to hormonal regulation. This review increases awareness of these disparities and encouraged equitable healthcare for those who are disadvantaged.
2023
Frontiers
A meta-analysis of 21 studies including 734,372 participants worldwide found that light at night (LAN) exposure was associated with a 12% increased breast cancer risk overall, with case-control studies showing 16% increased risk and cohort studies showing 8% increased risk. The association was particularly pronounced in Asian populations (24% increased risk) and for ER-positive breast cancers (10% increased risk), while outdoor LAN specifically showed a 7% increased risk. These findings support the hypothesis that artificial light exposure at night disrupts circadian rhythms and suppresses melatonin production—a hormone with anti-cancer properties—though the authors caution against taking melatonin supplements for prevention without medical advice until mechanisms are better understood, and emphasize the need for high-quality research accounting for environmental confounding factors to clarify the role of light pollution in breast cancer development.
2023
Environ Health Perspect
A case-cohort study within the prospective Cancer Prevention Study II (CPS-II) LifeLink cohort examined associations between serum per- and polyfluoroalkyl substances (PFAS) concentrations and cancer risk by analyzing blood samples collected 1998-2001 from 999 randomly selected participants and 3,762 cancer cases (breast, bladder, kidney, pancreas, prostate, and hematologic cancers), with particular attention to histologic subtypes. The study found that higher serum PFOA concentrations were positively associated with renal cell carcinoma in women (HR per PFOA doubling: 1.54; 95% CI: 1.05-2.26) but not men, while higher PFHxS concentrations were associated with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) in men (HR per PFHxS doubling: 1.34; 95% CI: 1.02-1.75), with some variation in associations observed across histologic subtypes within cancer sites. These findings in a general population cohort support previous observations linking PFOA to kidney cancer in women and identify a new association between PFHxS and CLL/SLL in men, highlighting the importance of considering both sex differences and specific histologic cancer subtypes when evaluating PFAS-cancer relationships. The study demonstrates that PFAS exposure at levels found in the general U.S. population may be associated with increased risk of certain cancers, extending concerns beyond highly exposed occupational or community populations.
2023
Front Oncol
A study of 80 Black and White women with breast cancer at Emory University Hospitals (2008-2017) examined associations between contemporary neighborhood redlining—a structural racism measure derived from Home Mortgage Disclosure Act data—and DNA methylation patterns in breast tumor tissue. Contemporary redlining was significantly associated with aberrant methylation at 5 CpG sites (FDR<0.10) in genes implicated in breast carcinogenesis, inflammation, immune function, and stress response (ANGPT1, PRG4), with additional top sites showing interaction by ER status and association with mortality; redlining was also associated with epigenetic age acceleration (β=5.35; 95% CI: 0.30-10.4 by Hannum metric). These novel findings suggest that structural racism—manifested through discriminatory housing policies leading to inequitable social and environmental exposures—may biologically embed in the breast tumor epigenome through altered DNA methylation patterns, potentially contributing to documented racial disparities in breast cancer outcomes and highlighting the need for further research on epigenetic mechanisms linking neighborhood-level structural racism to cancer prognosis.
2022
Endocrinology
A review examining PFAS (found in nonstick cookware, food packaging, and stain-resistant fabrics) and parabens (used in personal care products) found that exposure to these endocrine-disrupting chemicals is linked to breast cancer development, with marginalized and socially disadvantaged communities facing disproportionately higher exposures due to structural racism and inequitable environmental conditions. These disparities in chemical exposure may contribute to poorer breast cancer outcomes in these populations, yet breast cancer research continues to underrepresent these communities, limiting our ability to address treatment disparities and improve survival rates. The authors emphasize the urgent need to both reduce EDC exposures in vulnerable communities and increase research inclusion of diverse populations to understand how environmental injustices intersect with breast cancer risk and develop interventions that address these health inequities.
2022
Environ Sci Pollut Res
The following study explores the presence of endocrine disruptors such as phthalates (specifically mono-2-ethyl phthalate and mono-n-butyl phthalate), bisphenol A (BPA), and 1-hydroxypyrene in the urine samples of marginalized Indigenous populations. The study found that 100% of the women sampled showed exposure to these harmful chemicals, with higher concentrations than observed in similar studies from other communities. This increased exposure is linked to environmental and cultural factors, such as the common use of plastic containers and practices such as burning garbage. The women sampled were found to have especially high levels of mono-2-ethyl phthalate, which suggests significant exposure to di(2-ethylhexyl) phthalate. These findings highlight the vulnerability of indigenous communities to pollution due to a lack of awareness, limited healthcare access, and inadequate regulatory measures.
2022
Environ Res
A case-control study of 499 breast cancer patients and 499 controls in Northern Mexico found that women with breast cancer had distinct patterns of urinary metal exposure, with higher concentrations of tin and lower concentrations of vanadium, cobalt, and molybdenum compared to controls. Using principal component analysis to identify metal mixtures, researchers discovered two distinct exposure patterns with opposite breast cancer associations: a mixture containing chromium, nickel, antimony, aluminum, lead, and tin showed a 15% increased risk, while a mixture of molybdenum and cobalt showed a 44% reduced risk. This is the first study to identify specific urinary metal mixture profiles associated with breast cancer, highlighting that metals may interact synergistically or antagonistically rather than acting independently, and underscoring the critical need for mixture-based approaches in environmental health research—since real-world exposures involve multiple simultaneous contaminants whose combined effects may differ substantially from predictions based on individual metals alone—along with mechanistic studies to understand how metal interactions influence breast carcinogenesis.
2020
Eur J Clinic Nutr
A prospective cohort study in the Multiethnic Cohort found no direct associations between four widely-used diet quality indexes—including the Healthy Eating Index 2015, Alternate Healthy Eating Index 2010, alternate Mediterranean diet score, and DASH diet—and breast cancer risk when comparing highest versus lowest quintiles of adherence. However, overweight and obesity were significantly associated with breast cancer incidence, suggesting that diet quality may influence breast cancer risk indirectly through its effects on body weight rather than through direct mechanisms. These findings indicate that the breast cancer prevention benefits of healthy dietary patterns may operate primarily through weight management pathways, highlighting that maintaining healthy body weight through diet—rather than specific dietary patterns per se—may be the critical factor for breast cancer prevention, and underscoring the importance of comprehensive lifestyle interventions that address both diet quality and weight control rather than focusing on dietary patterns alone.
2020
Breast Cancer Res Treat
A pilot study of 37 breast cancer patients found that women with HER2-positive breast cancer (an aggressive subtype) had 12-23% lower gut bacterial diversity and different bacterial compositions compared to HER2-negative patients, with less Firmicutes and more Bacteroidetes bacteria. The research also revealed that women who started menstruating early (age 11 or younger) and those with higher body fat had lower gut bacterial diversity, suggesting links between gut microbiome composition and known breast cancer risk factors. While the study was small, these findings indicate that gut bacteria composition may be connected to both breast cancer characteristics and established risk factors, warranting larger studies to better understand these relationships and their potential implications for prevention and treatment.
2018
Breast Cancer Res Treat
A meta-analysis of 25 epidemiological studies (23 cohort studies and 2 randomized trials) found that hormone replacement therapy (HRT) was associated with a 33% increased breast cancer risk overall, with combined estrogen-progestin therapy (EPT) showing stronger associations than estrogen-only therapy (ET). EPT was associated with both ductal (51% increased risk) and lobular breast cancer (38% increased risk), and all HRT types were linked to ER-positive but not ER-negative breast cancers, consistent with hormone-driven carcinogenesis. Notably, Asian women using HRT showed higher breast cancer risk than Western women, possibly due to differences in baseline hormone levels, genetic susceptibility, body composition, or HRT formulations used—a finding highlighting the importance of considering racial and ethnic differences when counseling women about menopausal hormone therapy risks and benefits.
2018
Breast Cancer Res
A pooled analysis of three population-based case-control studies including 6,320 women (3,934 cases, 2,386 controls) aged 35-64 years examined whether the associations between body mass index (BMI) and breast cancer risk differ by tumor subtype defined by estrogen receptor (ER), progesterone receptor (PR), and HER2 status. Higher BMI at age 18 was inversely associated with premenopausal breast cancer risk across all ER/PR/HER2 subtypes (≥25 vs. <20 kg/m²: OR=0.72), with the strongest protection seen in premenopausal women who had high BMI both at age 18 and currently (46% reduced risk; OR=0.54; 95% CI: 0.38-0.78), while no significant associations were found for postmenopausal breast cancer. The findings indicate that high BMI during late adolescence provides similar protective effects against all molecular subtypes of premenopausal breast cancer regardless of hormone receptor or HER2 status, and this protection appears to be maximized when women maintain higher BMI consistently throughout their premenopausal years. These results suggest that the mechanisms by which adiposity protects against premenopausal breast cancer operate broadly across different tumor subtypes rather than being specific to hormone receptor-positive disease.
2017
Molec Cell Endocrinol
This study examines the role of environmental estrogen-like endocrine-disrupting chemicals (EEDs) in breast cancer development. EEDs are synthetic compounds that mimic estrogen, and the ones being studied in this paper include polychlorinated biphenyls (PCBs), bisphenol A (BPA), and phthalates. The results of the study show that of the EEDs tested, only one type of PCB, PCB138, had a strong association with the formation of breast cancer, where as phthalates (and it metabolites) but and BPA showed no strong correlation. Additionaly, the researchers identify that these EEDs promote the proliferation of breast cancer cells, induce epigenetic changes that may increase susceptibility to cancer, as well as alter developmental pathways during critical windows of breast development.
2016
Cancer Med
A review examining breast cancer disparities in African American women—who now have similar incidence rates to non-Hispanic White women but significantly higher mortality—found growing evidence linking hair product use to breast cancer risk through exposure to estrogen-like chemicals and endocrine-disrupting chemicals (EDCs). The review identified three converging lines of evidence: environmental estrogen and EDC exposures increase breast cancer risk, these chemicals are present in personal care products including hair products, and certain hair products used disproportionately by African American women may contribute to elevated breast cancer risk in this population. The findings highlight an understudied environmental justice issue and call for additional research using community-collaborative approaches to better understand how culturally specific beauty practices may contribute to health disparities, representing what researchers term the potential “cost of beauty.”
2015
PLOS One
A recent study investigated the potential carcinogen 4-methylimidazole (4-MEI) in popular beverages colored with caramel, revealing potential cancer risks. Using data from California, where Proposition 65 enforces warning labels on drinks exceeding safe 4-MEI levels, researchers found that 4-MEI concentrations varied by brand and region. For example, Malta Goya had the highest 4-MEI levels, while Coca-Cola had the lowest. Regular consumption of certain sodas could result in daily 4-MEI exposure above safe limits.