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2024
Nutrients
This study of 989 women with BRCA1 mutations in Poland examined whether blood lead levels affect cancer risk in this high-risk population. Women with elevated blood lead levels (above 13.6 μg/L) showed 3.33 times higher risk of developing ovarian cancer (95% CI: 1.23-9.00, p=0.02) compared to those with lower levels, though this association lost significance after adjusting for other factors (HR=2.10, 95% CI: 0.73-6.01), while no significant association was found with breast cancer risk. These findings suggest that lead exposure may be an additional risk factor for ovarian cancer in BRCA1 mutation carriers and could inform the timing of preventive surgery (removal of ovaries and fallopian tubes) in this population. The authors recommend validation of these findings in other populations and investigation of whether reducing lead exposure through detoxification could lower ovarian cancer risk in BRCA1 carriers.
2023
Asian Pac J Cancer Prev
A study of 360 participants found that agricultural workers exposed to pesticides who carry genetic variations that impair their body’s ability to detoxify chemicals (null mutations in GSTT1 and GSTM1 genes) had substantially increased cancer risk, with 4-7 times higher odds of developing lymphoma or breast cancer compared to those with normal detoxification genes. The study also found elevated markers of oxidative stress (cellular damage) in farm workers with these genetic variants who developed leukemia, suggesting that pesticide exposure combined with impaired detoxification capacity triggers cancer development. These findings indicate that certain genetic profiles make agricultural workers particularly vulnerable to pesticide-related cancers, highlighting the importance of protective measures for farm workers and potential genetic screening to identify high-risk individuals.
2022
Cancers
This meta-analysis of nine studies involving over 33,000 women with BRCA1 or BRCA2 gene mutations. One significant finding was that women who first started using oral contraceptives at age 20 or older had a 21% increased risk of breast cancer compared to those who never used them. These findings suggest that the timing of oral contraceptive use may be important for women with BRCA mutations, though more research is needed to fully understand the relationship between hormonal contraception and cancer risk in genetic mutation carriers.
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.
2022
Cancer Epiemiol
The first Indian case-control study examining phthalates (chemicals widely used in plastics, cosmetics, and food packaging) and breast cancer found that women with higher urinary levels of di-butyl phthalate (DBP) had 1.5 times increased breast cancer risk, while those with higher DEHP levels had nearly 3 times increased risk. Analysis of breast tumor tissue revealed mutations in several genes known to respond to phthalate exposure, affecting pathways involved in hormones, metabolism, and cancer development. These findings suggest that exposure to certain phthalates may increase breast cancer risk through genetic changes, though larger studies are needed to confirm these results and understand how early-life exposures might contribute to cancer development later in life.
2022
Am J Prev Med
A systematic review of five studies examining physical activity during adolescence and young adulthood in women with BRCA1/BRCA2 gene mutations found that higher activity levels may reduce or delay breast cancer risk later in life. Four of the five studies showed protective effects, with one specifically finding a 38% reduction in premenopausal breast cancer risk and another showing that active young women developed breast cancer at older ages. However, the limited number of studies and reliance on self-reported activity data suggest that while the findings are promising, more research is needed to confirm whether early-life physical activity can help protect BRCA mutation carriers from breast cancer.
2019
Occ Environ Med
This Canadian study of over 2,200 women found that occupational exposure to polycyclic aromatic hydrocarbons (PAHs)—chemicals released from burning materials like coal, oil, and gasoline—increased breast cancer risk by 32%, with higher risks seen in women exposed to high levels for more than 7 years. The association was particularly strong among women with a family history of breast cancer, where prolonged high exposure nearly tripled the risk. These findings suggest that workplace PAH exposure may be an important and preventable breast cancer risk factor, especially for women with genetic susceptibility to the disease.
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
Front Glob Women’s Health
A systematic review of 51 studies (2 RCTs and 49 observational studies) examined the association between modern contraceptive use and the risk of breast and reproductive cancers in women of reproductive age. The review found that hormonal contraceptive use significantly reduced the risk of ovarian cancer by 36% and endometrial cancer, while cervical cancer rates were lower among contraceptive users compared to non-users; notably, no increased breast cancer risk was found among healthy women (RR 1.00), but BRCA1/2 mutation carriers using oral contraceptives showed a 39% increased risk of breast cancer. These findings highlight the complex cancer-related effects of hormonal contraceptives: while they offer protective benefits against ovarian and endometrial cancers for most women, BRCA mutation carriers face elevated breast cancer risk, emphasizing the need for personalized contraceptive counseling that accounts for individual genetic risk factors. The study underscores the importance of healthcare providers considering family history and genetic profiles when discussing contraceptive options with women, particularly those with hereditary cancer susceptibility.
2023
J Epidemiol
A comprehensive systematic review and meta-analysis of 169 observational studies published through January 2020 examined the association between cigarette smoking and breast cancer risk using random-effects models and dose-response analyses. The pooled analysis found that current smokers had 7% increased breast cancer risk, former smokers 8% increased risk, and ever smokers 9% increased risk compared to never smokers, with results consistent across both case-control and cohort studies and across most covariates including genetic mutations (BRCA) and relevant polymorphisms. Importantly, breast cancer risk increased in a linear dose-response manner with both smoking intensity (12% increased risk for 20 cigarettes/day, 26% for 40 cigarettes/day) and duration (5% increased risk for 20 years, 11% for 40 years), demonstrating clear dose-response relationships. This large and comprehensive meta-analysis, which employed innovative search methods, provides strong evidence supporting a causal role of tobacco smoking in breast cancer development, resolving previous controversy on this association and establishing smoking as a modifiable risk factor for breast cancer with risks increasing proportionally to the amount and duration of smoking exposure.
2023
Nutrients
A case-control study of 42 newly diagnosed, treatment-naïve breast cancer patients and 44 age-matched cancer-free controls at Oregon Health & Science University (2020-2021) found reduced gut microbial diversity in breast cancer patients and enrichment of three specific bacterial genera—Acidaminococcus, Tyzzerella, and Hungatella—in fecal samples from cases, with these genera associated with distinct dietary patterns including vegetables and dairy (Hungatella) and whole fruits (Acidaminococcus). Breast cancer patients also had significantly higher BMI and lower physical activity levels, and microbiome analysis revealed significant differences in composition between cases and controls using 16S rRNA sequencing. These findings highlight complex interactions between the gut microbiome, dietary habits (assessed via National Cancer Institute Diet History Questionnaire), lifestyle factors like weight management and physical activity, and breast cancer risk, suggesting the gut microbiome may serve as a source of biomarkers for breast cancer risk assessment, though larger studies are needed to establish causal relationships and validate these microbial signatures.
2022
Carcinogen
A meta-analysis of 12 breast cancer studies and 8 ovarian cancer studies in women with BRCA1 or BRCA2 mutations found that oral contraceptive (OC) use was associated with a 24% increased breast cancer risk but a 47% decreased ovarian cancer risk. The increased breast cancer risk was observed only with long-term OC use (>5 years), while the ovarian cancer protection occurred regardless of duration, and these patterns were consistent when BRCA1 and BRCA2 carriers were analyzed separately. These findings present a complex risk-benefit trade-off for BRCA mutation carriers considering oral contraceptives, suggesting that while OCs provide substantial protection against ovarian cancer—a particularly deadly cancer in this high-risk population—they also modestly increase breast cancer risk with prolonged use, requiring careful individualized counseling about contraceptive choices and cancer prevention strategies.
2022
Front Endocrinol
A meta-analysis of 8 studies (5 cohort and 3 case-control studies) examined whether fertility treatments increase breast cancer risk in genetically susceptible women, including those with a family history of breast cancer or BRCA mutations. The analysis found no significant increase in breast cancer risk associated with fertility treatments in genetically susceptible women overall (OR 1.18), women with a family history of breast cancer (OR 1.35), or BRCA mutation carriers (OR 1.02), with similarly reassuring results across subgroups including BRCA1 carriers, BRCA2 carriers, and women treated with specific fertility medications like in vitro fertilization, clomiphene citrate, or gonadotropins. This first meta-analysis on this topic provides reassuring evidence that fertility treatments do not significantly increase breast cancer risk even in women with hereditary susceptibility, though the authors note that larger prospective studies with more detailed information are needed to fully understand potential risks. Future research should examine whether risks vary by breast cancer subtype, explore the genetic mechanisms underlying hormone-related breast cancer, and investigate the relationship between BRCA mutations and hormone receptor-positive breast cancer specifically.
2020
J Natl Cancer Inst
A prospective study of 146,326 women in the UK Biobank found that maintaining a healthy lifestyle—combining favorable diet, physical activity, healthy weight, limited alcohol, and no smoking—was associated with 22% and 31% reduced breast cancer risk in premenopausal and postmenopausal women respectively, even among women with high genetic risk (top third of polygenic risk score). Importantly, women with high genetic risk who maintained favorable lifestyles still achieved 27-32% risk reductions across menopausal groups, and while high genetic risk doubled breast cancer risk overall, lifestyle factors provided consistent protective benefits regardless of genetic predisposition. These findings demonstrate that genetic risk is not destiny: even women with the highest genetic susceptibility to breast cancer can substantially reduce their risk through modifiable lifestyle factors, supporting the critical importance of population-wide lifestyle interventions for breast cancer prevention and providing hope that women at elevated genetic risk can take meaningful action to lower their cancer risk through behavioral changes.
2020
Cancer Epidemiol Biomark Prev
A large international study of BRCA1 and BRCA2 mutation carriers conducted both retrospective (9,232 carriers) and prospective (3,886 carriers) analyses to examine whether tobacco smoking and alcohol consumption affect breast cancer risk in this high-risk population. The study found that smoking for more than 5 years before a first full-term pregnancy (FFTP) was associated with increased breast cancer risk in both BRCA1 carriers (19-36% increased risk) and BRCA2 carriers (25-30% increased risk) compared to women who never smoked, while other smoking variables and alcohol consumption showed no significant associations. These findings suggest that smoking specifically during the prereproductive years may increase breast cancer risk for BRCA mutation carriers, a finding that requires further investigation given its potential public health importance for this high-risk population. This represents the largest prospective study to date examining these lifestyle risk factors in women with BRCA mutations, who already face substantially elevated lifetime breast cancer risk.