Reproductive risk factors and breast cancer subtypes: a review of the literature

Metabolomics-enabled biomarker discovery in breast cancer research

Breast cancer (BC) remains the most prevalent malignancy among women worldwide. While genetic predisposition and reproductive history are key contributors to its development, modifiable risk factors are also important, particularly those linked to lifestyle behaviors, often influencing the endogenous metabolome. Over the past decade, mass spectrometry-based metabolomics has enabled agnostic investigations into correlations between the metabolome and BC risk. Here we review recent results from prospective nested case-control studies, which have led to the identification of significantly different metabolites between women who subsequently developed BC and those who did not. As replication of these findings remains limited, we emphasize the need for robust quantitative validation studies, cancer subtype-specific analyses in diverse populations, and expanded chemical space coverage of analytical assays.

c-Myc knockdown restores tamoxifen sensitivity in triple-negative breast cancer by reactivating the expression of ERα: the central role of miR-152 and miR-148a

BACKGROUND

Poor prognosis of triple-negative breast cancer (TNBC) is owing to its intrinsic heterogeneity and lack of targeted therapies. Emerging evidence has characterized that targeting c-Myc might be a promising way to treat TNBC.

METHODS

c-Myc knocked down TNBC cells were generated and the tamoxifen sensitivity was determined. Methylation-specific PCR analysis was used to detect the methylation status of ERα promoter, and c-Myc-mediated miRNA transcription was examined using chromatin immunoprecipitation and dual-luciferase reporter assays. The in vivo tamoxifen sensitivity was determined by mouse xenograft model.

RESULTS

c-Myc knockdown in TNBC cells leads to the reactivation of ERα and consequent acquisition its sensitivity to tamoxifen. c-Myc depletion decreased the methylation in the promoter of ERα and DNMT1 was identified as the main executor. c-Myc knockdown-induced tamoxifen sensitivity was reversed by DNMT1 overexpression. The expression of miR-152-3p and miR-148a-3p was largely induced in c-Myc knockdown TNBC cells, and both miR-152-3p and miR-148a-3p could target DNMT1 to regulate its expression. c-Myc binds to the promoter regions of miR-152-3p and miR-148a-3p to exert transcriptional suppression. By suppressing miR-152-3p or miR-148a-3p expression using inhibitors, enhanced sensitivity to tamoxifen induced by c-Myc knockdown was partially reversed. In vivo xenograft tumor model demonstrated that c-Myc knockdown mildly inhibits the growth of tumor, and a dramatic decline was observed when administrated with tamoxifen combined with c-Myc knockdown.

CONCLUSION

Our study first illustrated that c-Myc knockdown in TNBC cells reactivate ERα expression in a miR-152/miR-148a-DNMT1-dependent manner, and brought new sights into treating TNBC using hormonal therapies.

Contribution of Prediagnostic Host Factors to Shaping the Stromal Microenvironment of Breast Cancer among Sub-Saharan African Women

BACKGROUND

The stromal microenvironment (SME) is integral to breast cancer biology, impacting metastatic proclivity and treatment response. Emerging data indicate that host factors may impact the SME, but the relationship between prediagnostic host factors and SME phenotype remains poorly characterized, particularly among women of African ancestry.

METHODS

We conducted a case-only analysis involving 792 patients with breast cancer (17-84 years) from the Ghana Breast Health Study. High-accuracy machine-learning algorithms were applied to standard H&E-stained images to characterize SME phenotypes [including percent tumor-associated connective tissue stroma, Ta-CTS (%); tumor-associated stromal cellular density, Ta-SCD (%)]. Associations between prediagnostic host factors and SME phenotypes were assessed in multivariable linear regression models.

RESULTS

Decreasing Ta-CTS and increasing Ta-SCD were associated with aggressive, mostly high-grade tumors (P-value < 0.001). Several prediagnostic host factors were associated with Ta-SCD independently of tumor characteristics. Compared with nulliparous women, parous women had higher levels of Ta-SCD [mean (standard deviation, SD) = 31.3% (7.6%) vs. 28.9% (7.1%); P-value = 0.01]. Similarly, women with a positive family history of breast cancer had higher levels of Ta-SCD than those without family history [mean (SD) = 33.0% (7.5%)] vs. 30.9% (7.6%); P-value = 0.03]. Conversely, increasing body size was associated with decreasing Ta-SCD [mean (SD) = 31.6% (7.4%), 31.4% (7.3%), and 30.1% (8.0%) for slight, average, and large body sizes, respectively; P-value = 0.005].

CONCLUSIONS

Epidemiological risk factors were associated with varying degrees of stromal cellularity in tumors, independently of clinicopathological characteristics.

IMPACT

The findings raise the possibility that epidemiological risk factors may partly influence tumor biology via the stromal microenvironment. See related In the Spotlight, p. 459.

Alcohol Consumption Does not Modify the Polygenic Risk Score-Based Genetic Risk of Breast Cancer in Postmenopausal Women: Atherosclerosis Risk in Communities Study

High genetic risk and alcohol consumption ≥1 drink/day are associated with increased breast cancer risk. However, the interaction between alcohol and genetics on breast cancer risk is poorly understood, including in populations not enriched with daily drinkers. We prospectively studied 5,651 White and Black postmenopausal women in the Atherosclerosis Risk in Communities study. Alcohol intake was assessed by a food frequency questionnaire. The 313-SNP polygenic risk score (PRS) was calculated. Breast cancer cases were ascertained primarily by cancer registry linkage through 2015. Multivariable Cox regression was used to estimate HRs and 95% confidence intervals (CI) for the association of PRS and current ethanol intake with breast cancer, and their interaction. Of these individuals, 50.6% were current drinkers, and of them, 50.8% drank <1 drink/week and 12.8% drank >7 drinks/week. A higher PRS was associated with a higher breast cancer risk among White (HR1-SD, 1.48; 95% CI, 1.34-1.65) and Black (HR1-SD, 1.15; 95% CI, 0.96-1.38) women. Positive associations were not observed between current ethanol intake and breast cancer risk (White: HR13 g/week, 1.00; 95% CI, 0.98-1.03; Black: HR, 0.83; 95% CI, 0.69-1.00). Among both White and Black women, PRS generally seemed to be positively associated with risk in drinkers and nondrinkers. There was no evidence of a PRS-ethanol intake interaction among White or Black women. Patterns in Black women were similar when using an 89-SNP PRS developed among African ancestry women. In conclusion, in a prospective analysis of White and Black postmenopausal women in a study population not enriched with daily drinkers, our findings suggest that alcohol drinking does not modify the PRS-based genetic risk of breast cancer. Prevention Relevance: Although our findings suggest that alcohol drinking does not modify the PRS-based genetic risk of breast cancer among White and Black women with lower alcohol intake, nevertheless, women should consider limiting alcohol consumption as a general cancer prevention strategy, as indicated in dietary guidelines.

Material deprivation, racial inequalities and mortality from female breast, prostate, and cervical neoplasm in the Brazilian adult population: an ecological study

This article aims to identify the relationship between material deprivation and mortality from breast, cervical, and prostate neoplasms in the Brazilian adult population and the relationship between ethnicity/skin color and material deprivation. This cross-sectional ecological study calculated the mean mortality rate per 100,000 inhabitants, and deaths were standardized by age and gender and redistributed per to ill-defined causes, stratified by age group and ethnicity/skin color. We applied the Negative Binomial model, containing the interaction between ethnicity/skin color and the Brazilian Deprivation Index (IBP). We analyzed 85,903 deaths, and the most prevalent were those due to female breast neoplasms. The risk of death from cervical cancer was 8.5% higher for Black women than white women. In other places, mortality was higher among white people. For all causes, mortality increased with age. There was a significant interaction between ethnicity/skin color and IBP for all causes. Only deaths due to cervical neoplasms increased with higher IBP, while a decline was observed in other causes but was less significant among Black people. The IBP offers a multidimensional view of the socioeconomic conditions of the Brazilian population, allowing a better understanding of how social determinants operate on selected neoplasms.

Risk factors for breast cancer subtypes by race and ethnicity: a scoping review

BACKGROUND

Breast cancer consists of distinct molecular subtypes. Studies have reported differences in risk factor associations with breast cancer subtypes, especially by tumor estrogen receptor (ER) status, but their consistency across racial and ethnic populations has not been comprehensively evaluated.

METHODS

We conducted a qualitative, scoping literature review using the Preferred Reporting Items for Systematic Reviews and Meta-analysis, extension for Scoping Reviews to investigate consistencies in associations between 18 breast cancer risk factors (reproductive, anthropometric, lifestyle, and medical history) and risk of ER-defined subtypes in women who self-identify as Asian, Black or African American, Hispanic or Latina, or White. We reviewed publications between January 1, 1990 and July 1, 2022. Etiologic heterogeneity evidence (convincing, suggestive, none, or inconclusive) was determined by expert consensus.

RESULTS

Publications per risk factor ranged from 14 (benign breast disease history) to 66 (parity). Publications were most abundant for White women, followed by Asian, Black or African American, and Hispanic or Latina women. Etiologic heterogeneity evidence was strongest for parity, followed by age at first birth, postmenopausal body mass index, oral contraceptive use, and estrogen-only and combined menopausal hormone therapy. Evidence was limited for other risk factors. Findings were consistent across racial and ethnic groups, although the strength of evidence varied.

CONCLUSION

The literature supports etiologic heterogeneity by ER for some established risk factors that are consistent across race and ethnicity groups. However, in non-White populations evidence is limited. Larger, more comparable data in diverse populations are needed to better characterize breast cancer etiologic heterogeneity.

Polycystic ovary syndrome and risk of breast cancer in premenopausal and postmenopausal women: a nationwide population-based cohort study

PURPOSE

Although some reproductive and metabolic characteristics of polycystic ovary syndrome (PCOS) are known risk factors for breast cancer, the evidence regarding a potential association between PCOS and breast cancer is scarce. In this population-based cohort study including all 1,719,452 women born in Denmark between 1940 and 1993, we investigated the association between PCOS and breast cancer.

METHODS

PCOS diagnoses, cancer diagnoses, covariates, migrations, and vital status were all obtained from national population and health registers. Hazard ratios (HR) and 95% confidence intervals (CI) for breast cancer overall and for histological subtypes separately were calculated based on adjusted cox proportional hazards models.

RESULTS

During a median follow-up of 26 years, 63,078 women were diagnosed with breast cancer. We found an increased risk of breast cancer overall among women with PCOS compared with women without PCOS (HR: 1.21, 95% CI 1.02-1.44). In analyses stratified for menopausal status, the increased risk was restricted to postmenopausal women (HR: 1.63, 95% CI 1.23-2.15). The results for ductal and lobular histological subtypes analyses separately resembled those observed for breast cancer overall.

CONCLUSION

This is the first study to report an increased risk of breast cancer among women with a history of PCOS. The increased risk was seemingly confined to postmenopausal women. Our results therefore contribute to an increased knowledge of the etiology of breast cancer, but our findings should be further confirmed in other large cohort studies with an appropriately long follow-up period.

Advancements in breast cancer therapy: The promise of copper nanoparticles

BACKGROUND

Breast cancer (BC) is the most prevalent cancer among women worldwide and poses significant treatment challenges. Traditional therapies often lead to adverse side effects and resistance, necessitating innovative approaches for effective management.

OBJECTIVE

This review aims to explore the potential of copper nanoparticles (CuNPs) in enhancing breast cancer therapy through targeted drug delivery, improved imaging, and their antiangiogenic properties.

METHODS

The review synthesizes existing literature on the efficacy of CuNPs in breast cancer treatment, addressing common challenges in nanotechnology, such as nanoparticle toxicity, scalability, and regulatory hurdles. It proposes a novel hybrid method that combines CuNPs with existing therapeutic modalities to optimize treatment outcomes.

RESULTS

CuNPs demonstrate the ability to selectively target cancer cells while sparing healthy tissues, leading to improved therapeutic efficacy. Their unique physicochemical properties facilitate efficient biodistribution and enhanced imaging capabilities. Additionally, CuNPs exhibit antiangiogenic activity, which can inhibit tumor growth by preventing the formation of new blood vessels.

CONCLUSION

The findings suggest that CuNPs represent a promising avenue for advancing breast cancer treatment. By addressing the limitations of current therapies and proposing innovative solutions, this review contributes valuable insights into the future of nanotechnology in oncology.

Genetics of female and male reproductive traits and their relationship with health, longevity and consequences for offspring

Substantial shifts in reproductive behaviors have recently taken place in many high-income countries including earlier age at menarche, advanced age at childbearing, rising childlessness and a lower number of children. As reproduction shifts to later ages, genetic factors may become increasingly important. Although monogenic genetic effects are known, the genetics underlying human reproductive traits are complex, with both causal effects and statistical bias often confounded by socioeconomic factors. Here, we review genome-wide association studies (GWASs) of 44 reproductive traits of both female and male individuals from 2007 to early 2024, examining reproductive behavior, reproductive lifespan and aging, infertility and hormonal concentration. Using the GWAS Catalog as a basis, from 159 relevant studies, we isolate 37 genes that harbor association signals for four or more reproductive traits, more than half of which are linked to rare Mendelian disorders, including ten genes linked to reproductive-related disorders: FSHB, MCM8, DNAH2, WNT4, ESR1, IGSF1, THRB, BRWD1, CYP19A1 and PTPRF. We also review the relationship of reproductive genetics to related health and behavioral traits, aging and longevity and the effect of parental age on offspring outcomes as well as reflecting on limitations, open questions and challenges in this fast-moving field.

The shared genetic landscape of polycystic ovary syndrome and breast cancer: convergence on ER + breast cancer but not ER- breast cancer

BACKGROUND

The clinically high comorbidity between polycystic ovary syndrome (PCOS) and breast cancer (BC) has been extensively reported. However, limited knowledge exists regarding their shared genetic basis and underlying mechanisms.

METHOD

Leveraging summary statistics from the largest genome-wide association studies (GWASs) to date, we conducted a comprehensive genome-wide cross-trait analysis of PCOS and BC. A variety of genetic statistical methods were employed to uncover potential shared genetic causes.

RESULTS

Our analysis revealed genetic overlap between the three trait pairs. After partitioning the genome into 2,495 independent regions, we identified two loci, chr8: 75,011,700-76,295,483 and chr17: 6,305,079-7,264,458, with significant localized genetic correlations. Pleiotropic analysis under a composite null hypothesis identified 1,183 significant pleiotropic single nucleotide polymorphisms (SNPs) across three trait pairs. FUMA mapped 26 pleiotropic loci, with regions 16q12.2 and 6q25.1 duplicated across all three trait pairs, while COLOC detected three loci with colocalization evidence. Gene-based analysis identified 23 unique candidate pleiotropic genes, including the FTO shared by all trait pairs, as well as SER1, RALB, and others in two trait pairs. Pathway enrichment analysis further highlighted key biological pathways, primarily involving the significant biological pathways were the metabolism of regulation of autophagy, regulation of cellular catabolic process, and positive regulation of catabolic process. Latent Heritable Confounder Mendelian randomization (LHC-MR) supported a positive causal relationship between PCOS and both BCALL and ERPBC but not with ERNBC.

CONCLUSION

In conclusion, our genome-wide cross-trait analysis identified a shared genetic basis between PCOS and BC, specific identical genetic mechanisms and causality between PCOS and various BC subtypes, which could better explains the genetics of the co-morbidity of PCOS and ERPBC rather than PCOS and ERNBC. These findings provide new insights into the biological mechanisms underlying the co-morbidity of these two complex diseases, which have important implications for clinical disease intervention, treatment, and improved prognosis.

An umbrella review of socioeconomic status and cancer

Extensive evidence underscores the pivotal role of socioeconomic status (SES) in shaping cancer-related outcomes. However, synthesizing definitive and actionable insights from the expansive body of literature remains a significant challenge. To elucidate the associations between SES, cancer outcomes, and the overall cancer burden, we conducted a comprehensive burden estimation coupled with an umbrella review of relevant meta-analyses. Our findings reveal that robust or highly suggestive meta-analytic evidence supports only a limited number of these associations. Individuals with lower SES, compared to those with higher SES, are disproportionately disadvantaged by reduced access to immunotherapy, KRAS testing for colorectal cancer, targeted cancer therapies, and precision treatments for melanoma. Additionally, they exhibit lower rates of breast cancer screening and higher incidence rates of lung cancer. Furthermore, countries with a higher Human Development Index demonstrate a substantially greater burden related cancer incidence, with this disparity being more pronounced among men than women.

Trends in the incidence and survival of women with hormone receptor-positive breast cancer from 1990 to 2019: a large population-based analysis

Hormone receptor-positive breast cancer (BC) is the most prevalent subtype of BC and is generally correlated with a favorable prognosis. This study aimed to determine the incidence and survival trends among women diagnosed with hormone receptor-positive BC between 1990 and 2019. Female patients with hormone receptor-positive BC for calendar years 1990-2019 were obtained from the Surveillance, Epidemiology, and End Results (SEER) database and categorized into six diagnostic groups according to the year of diagnosis. Age-adjusted incidence rates (IRs) were calculated using joinpoint regression. We used the Kaplan-Meier method and multivariate Cox regression analyses to determine the association between diagnostic groups, and overall survival (OS) and BC-specific survival (BCSS). The final analysis included 370,729 women, among whom 37,943 (10.2%), 49,266 (13.3%), 55,652 (15.0%), 64,451 (17.4%), 77,127 (20.8%), and 86,290 (23.3%) were diagnosed between 1990 and 1994, 1995-1999, 2000-2004, 2005-2009, 2010-2014, and 2015-2019, respectively. Within the overall cohort, IRs gradually increased from 70 per 100,000 in 1990 to 113 per 100,000 in 2019 (average annual percent change, 1.59%; 95% CI, 1.18-1.99). Multivariate Cox regression analysis revealed that the survival outcomes gradually improved over nearly three decades among hormone receptor-positive BC patients, with a 0.8% and 1.3% decrease in risk for all-cause and BC-specific mortality each year, respectively. Compared to 1990-1994, hormone receptor-positive BC patients diagnosed in 2015-2019 had a 22% lower risk of all-cause death (hazard ratio [HR], 0.78; 95% CI, 0.76-0.81) and a 27% lower risk of BC-specific death (HR, 0.73; 95% CI, 0.70-0.76). The development of treatment strategies within the past three decades, especially endocrine therapy, may contribute to the continuous improvement of clinical outcomes in patients with hormone receptor-positive BC.

Is it really over when it is over? physical, mental and emotional health status of long-term breast cancer survivors compared to healthy matched controls

PURPOSE

This study aimed to assess pain, fitness condition, physical activity (PA) level, comorbidities, cancer-related fatigue (CRF), mood state and health-related quality of life (HRQoL) in long-term breast cancer survivors (LTBCS) compared to women without cancer history, matched by age, weight, height, and educational level.

METHODS

A cross-sectional study conducted in Granada between April 2018 and July 2023 involved 80 LTBCS and 80 matched controls. Pain, fitness condition, PA level, comorbidities, CRF, mood state, and HRQoL were evaluated ≥ 5 years post-diagnosis using validated instruments.

RESULTS

LTBCS, compared to the controls, reported significantly higher levels of "pain intensity and interference", CRF (in all domains and > 40% exhibited moderate-to-severe fatigue levels), "sadness-depression", "anxiety", "anger/hostility", and "symptom scales" (All: P = .000 to .027). Moreover, 66.25% of LTBCS not only did not reach recommended PA levels (P = .035), but also presented significantly lower levels of "general physical fitness", "muscular strength", "happiness", "functioning scales" (except "emotional functioning"), and "global health status" (All: P = .000 to .048).

CONCLUSION

LTBCS still suffer from physical (pain, fitness condition, and CRF), both mental and emotional (sadness-depression, anxiety and anger/hostility) long-term side effects as well as multiple HRQoL issues (including lower levels of physical functioning and higher levels of symptoms). These findings highlight the chronic nature of this disease and the importance of continuing long- term follow-up care for survivors many years after the diagnosis of breast cancer.

Risk perception regarding social determinants of health among women with breast cancer in Iran: a qualitative study

OBJECTIVES

Breast cancer is the most common cancer among women all around the world. Today, in addition to factors including hormones and genetics that are involved in the occurrence of breast cancer, special attention is paid to the role of social and non-medical determinants of health. This study aims to explore the perception of Social Determinants of Health (SDH) in women with breast cancer.

DESIGN

Qualitative study design with a conventional thematic analysis approach.

SETTING

The study was conducted in Tehran, Iran, between December 2021 and February 2023.

PARTICIPANTS

19 women with breast cancer were selected through purposeful and snowball sampling with maximum variation. Sampling continued until data saturation was reached.

PRIMARY AND SECONDARY OUTCOME MEASURES

The study categorised the extracted codes from interviews into three main categories and 12 subcategories related to SDH in women with breast cancer.

RESULTS

The study identified factors such as personal and family health records, health behaviours and lifestyles and medical screening and follow-up as key themes in the perception of SDH among women with breast cancer. The main categories were also categorised into 12 subcategories, 'including family history', 'environmental factors', 'hormonal and medicinal changes', 'metaphysical factors', 'traditional medicine-related factors', 'stress', 'body weight', 'physical activity', 'nutrition', 'smoking and tobacco use', 'screening', 'self-examination' and 'barriers to medical follow-up'. 'Near the telecommunications tower', 'Improper use of supplements', 'Being subjected to the evil eye regularly', 'Eating cold nature foods', 'Breast weight' and 'Being ashamed of the doctor' were some examples of the codes.

CONCLUSIONS

Participants identified a number of environmental, personal and cultural factors as contributing to the disease. Woman's screening behaviours were influenced by factors such as fear of disease and death, disbelief in getting sick and shame, depending on cultural context. The study suggests the need for further research to explore the impact of these factors on screening behaviours and outcomes in different cultural contexts.

Pregnancy-Related Factors and Breast Cancer Risk for Women Across a Range of Familial Risk

Importance

Few studies have investigated whether the associations between pregnancy-related factors and breast cancer (BC) risk differ by underlying BC susceptibility. Evidence regarding variation in BC risk is critical to understanding BC causes and for developing effective risk-based screening guidelines.

Objective

To examine the association between pregnancy-related factors and BC risk, including modification by a of BC where scores are based on age and BC family history.

Design, Setting, and Participants

This cohort study included participants from the prospective Family Study Cohort (ProF-SC), which includes the 6 sites of the Breast Cancer Family Registry (US, Canada, and Australia) and the Kathleen Cuningham Foundation Consortium (Australia). Analyses were performed in a cohort of women enrolled from 1992 to 2011 without any personal history of BC who were followed up through 2017 with a median (range) follow-up of 10 (1-23) years. Data were analyzed from March 1992 to March 2017.

Exposures

Parity, number of full-term pregnancies (FTP), age at first FTP, years since last FTP, and breastfeeding.

Main Outcomes and Measures

BC diagnoses were obtained through self-report or report by a first-degree relative and confirmed through pathology and data linkages. Cox proportional hazards regression models estimated hazard ratios (HR) and 95% CIs for each exposure, examining modification by PARS of BC. Differences were assessed by estrogen receptor (ER) subtype.

Results

The study included 17 274 women (mean [SD] age, 46.7 [15.1] years; 791 African American or Black participants [4.6%], 1399 Hispanic or Latinx participants [8.2%], and 13 790 White participants [80.7%]) with 943 prospectively ascertained BC cases. Compared with nulliparous women, BC risk was higher after a recent pregnancy for those women with higher PARS (last FTP 0-5 years HR for interaction, 1.53; 95% CI, 1.13-2.07; P for interaction < .001). Associations between other exposures were limited to ER-negative disease. ER-negative BC was positively associated with increasing PARS and increasing years since last FTP (P for interaction < .001) with higher risk for recent pregnancy vs nulliparous women (last FTP 0-5 years HR for interaction, 1.54; 95% CI, 1.03-2.31). ER-negative BC was positively associated with increasing PARS and being aged 20 years or older vs less than 20 years at first FTP (P for interaction = .002) and inversely associated with multiparity vs nulliparity (P for interaction = .01).

Conclusions and Relevance

In this cohort study of women with no prior BC diagnoses, associations between pregnancy-related factors and BC risk were modified by PARS, with greater associations observed for ER-negative BC.

Global untargeted and individual targeted plasma metabolomics of breast cancer recurrence modified by hormone receptors

BACKGROUND

Breast cancer is a heterogeneous and complex etiological disease. Understanding perturbations of circulating metabolites could improve prognosis.

METHODS

We recruited breast cancer patients from Kaohsiung Medical University (KMU) to perform untargeted (case-control design) and targeted (patient cohort) metabolomics analyses in the discovery and validation phases to evaluate interaction effects between clinical factors and plasma metabolites using multivariable Cox proportional hazards model.

RESULTS

In the discovery phase, partial least squares-discriminant analysis (PLS-DA) showed that plasma metabolites were significantly different between recurrent and non-recurrent breast cancer patients. Metabolite set enrichment analysis (MSEA) and metabolomic pathway analysis (MetPA) showed that valine, leucine, and isoleucine degradation was the significant pathway, and volcano plot showed significant ten upregulated and two downregulated metabolites between recurrent and non-recurrent cases. Combined with receiver operating characteristic (ROC) curve and biological significance, creatine, valine, methionine, and mannose were selected for the validation phase. In this patient cohort with 41 new-recurrent vs. 248 non-recurrent breast cancer cases, followed for 720.49 person-years, compared with low level of valine, high valine level was significantly negatively associated with recurrent breast cancer (aHR: 0.36, 95% CI: 0.18-0.72, P = 0.004), especially in ER-negative and PR-negative status. There were interaction effects between valine and ER (Pinteraction = 0.006) as well as PR (Pinteraction = 0.002) on recurrent breast cancer. After Bonferroni correction, stratification effects between valine and hormone receptors were still significant.

CONCLUSION

Our study revealed that plasma metabolites were significantly different between recurrent and non-recurrent patients, proposing therapeutic insights for breast cancer prognosis.

Relationship between educational level and survival of patients with cancer: A multicentre cohort study

BACKGROUND

Although socioeconomic factors are important determinants of population mortality, the effect of educational level on the survival of patients with cancer in China is unclear. This study aimed to assess whether educational level is associated with the prognosis of patients with cancer and to explore the mediators of this association.

METHODS

This multicentre cohort study included 18,251 patients diagnosed with cancer between May 2013 and December 2018. The main parameters measured were overall survival (OS) and all-cause mortality. The relationship between educational level and all-cause mortality was assessed using multifactor-corrected Cox survival analysis. Logistic regression was used to analyze the association between educational level and patient-generated subjective global assessment (PG-SGA).

RESULTS

The mean age of the 18,251 participants (men, 9939 [54.4%]) was 57.37 ± 11.66 years. Multifactorial survival analysis showed that patients survived longer with increasing education (university and above vs. elementary school and below; p = p = <0.001, HR = 0.84, 95% CI: 0.77-0.92), and the differences were statistically significant in different subgroups. The potential impact factors included sex, age, TNM stage, and PG-SGA score. Logistic regression showed a significant negative association between educational level and the modifiable factor PG-SGA (secondary vs. primary and below; p = 0.004, HR = 0.90, 95% CI: 0.83-0.97; university and above vs. primary and below; p < 0.001, HR = 0.79, 95% CI: 0.71-0.88).

CONCLUSIONS

Educational level was a significant prognostic factor for patients with cancer, independent of other known prognostic factors. This association was further improved by modifying the nutritional status.

[Association between reproductive history, breast cancer subtype, and survival in premenopausal women]

BACKGROUND AND OBJECTIVE

Reproductive history influences breast cancer risk. We analysed its association with tumour subtype and survival in premenopausal women.

PATIENTS AND METHODS

Retrospective, observational study of premenopausal women with stage I-III breast carcinoma in the last 20 years. Review of reproductive history, clinical data, and treatments in health records.

RESULTS

In 661 premenopausal women (32.40% of 1377 total cases), median age was 47 years (19-53), menarche 12 (7-17), first delivery 28 (16-41) and number of deliveries 2 (0-9). One hundred and eleven (18.20%) were nulliparous. Three hundred and fifty-nine (58.80%) used natural lactation, with a median duration of 6 months. Anovulatory drugs were used by 271 (44.40%), with a median duration of 36 months. Associations were found between menarche <10 years and lower risk of luminal subtype (OR: 0.52, 95% CI: 0.28-0.94; P=.03), between menarche >11 years and lower risk of HER2 subtype (OR: 0.50, 95% CI: 0.26-0.97; P=.04) and between first birth >30 years and lower risk of triple negative subtype (OR: 0.40, 95% CI: 0.17-0.93; P=.03). The 20-year overall and disease-free survival probabilities were 0.80 (95% CI: 0.71-0.90) and 0.72 (95% CI: 0.64-0.79) respectively. Patients with ≥1 delivery had better overall survival than nulliparous patients (HR: 0.51, 95% CI: 0.27-0.96, P=.04).

CONCLUSIONS

The findings suggest an association between age at menarche and age at first delivery and breast cancer subtype. Nulliparity is associated with worse survival.

Risk factors for breast cancer subtypes by race and ethnicity: A scoping review of the literature

Background

Breast cancer is comprised of distinct molecular subtypes. Studies have reported differences in risk factor associations with breast cancer subtypes, especially by tumor estrogen receptor (ER) status, but their consistency across racial and ethnic populations has not been comprehensively evaluated.

Methods

We conducted a qualitative, scoping literature review using the Preferred Reporting Items for Systematic Reviews and Meta-analysis, extension for Scoping Reviews to investigate consistencies in associations between 18 breast cancer risk factors (reproductive, anthropometric, lifestyle, and medical history) and risk of ER-defined subtypes in women who self-identify as Asian, Black or African American, Hispanic or Latina, or White. We reviewed publications between January 1, 1990 and July 1, 2022. Etiologic heterogeneity evidence (convincing, suggestive, none, or inconclusive) was determined by expert consensus.

Results

Publications per risk factor ranged from 14 (benign breast disease history) to 66 (parity). Publications were most abundant for White women, followed by Asian, Black or African American, and Hispanic or Latina women. Etiologic heterogeneity evidence was strongest for parity, followed by age at first birth, post-menopausal BMI, oral contraceptive use, and estrogen-only and combined menopausal hormone therapy. Evidence was limited for other risk factors. Findings were consistent across racial and ethnic groups, although the strength of evidence varied.

Conclusion

The literature supports etiologic heterogeneity by ER for some established risk factors that are consistent across race and ethnicity groups. However, in non-White populations evidence is limited. Larger, more comparable data in diverse populations is needed to better characterize breast cancer etiologic heterogeneity.

Sex differences in associated factors for age-related hearing loss

The prevalence and age of onset of hearing loss differ according to sex. This study aimed to identify associated factors for age-related hearing loss (ARHL) and determine whether there are differences between males and females regarding associated factors for ARHL. This cross-sectional study used data from adults who underwent medical examinations including hearing tests from 2011 to 2021. A total of 2,349 individuals were included. The study conducted sex-specific analyses using both univariate and multiple regression. Univariate analysis employed logistic regression, while multiple regression involved variable selection through the augmented backward elimination method. Separate multiple logistic regression analyses were conducted for each sex. In the univariate analysis, among males, age, underweight, alcohol consumption, weight, and height exhibited statistical significance. Among females, age, hypertension, diabetes, dyslipidemia, obesity, sarcopenia, weight, height, age at menarche, and duration of hormone exposure were found to be significant factors. However, in the multiple logistic regression model for males, underweight, and smoking emerged as significant, while in females, age, weight, obesity, and age at menarche retained their significance. We found that there are different associated factors for ARHL in each sex. Assessment and counseling for smoking, obstetric history, underweight, and obesity may be beneficial in managing patients with ARHL.

In-silico and in-vitro evidence suggest LINC01405 as a sponge for miR-29b and miR-497-5p, and a potential regulator of Wnt, PI3K, and TGFB signaling pathways in breast carcinoma

BACKGROUND

Carcinoma of the breast, a prevailing factor in female mortality worldwide, involves dysregulation of lncRNAs and microRNAs.

AIM

The main goal of this research was to predict and experimentally examine the LINC01405 expression status in breast cancer subtypes, along with investigation of its interaction with miR-29b and miR-497-5p that results in regulating PI3-Kinase, WNT, and TGF-beta signaling pathways.

METHODS AND RESULTS

We performed a meta-analysis of five GEO datasets, encompassing microarray and RNA-seq data, to identify differentially expressed genes. The Cancer Genome Atlas transcriptome dataset was also analyzed to determine essential gene modules, associated with different stages of breast cancer by weighted gene co-expression networks. In addition, networks of drug-gene interactions were constructed to explore potential treatment options. LINC01405 as a microRNA sponge was chosen and examined. furthermore, downstream target genes were discovered. Experimental validation consisted of plasmid constructs used in cell culture experiments, RT-qPCR for expression analysis, and cell cycle assays. Our bioinformatics findings showed higher LINC01405 expression in Basal-like triple-negative breast carcinoma. In contrast, lower expression in Luminal samples was observed compared with normal samples, which was consistently observed in both breast cancer tissues and cell lines. LINC01405 expression level was correlated with miR-29b and miR-497 levels. The MDA-MB-231 cell line demonstrated higher LINC01405 expression and lower miR-29b and miR-497 expression levels. However, SKBR3 and MCF7 cells had lower LINC01405 expression and higher miR-29b and miR-497 levels, suggesting a regulatory role for LINC01405 as a competing endogenous RNA. This was experimentally confirmed when LINC01405 was overexpressed in SKBR3 cells, and the common target genes of miR-29b and miR-497 were upregulated. Additionally, LINC01405 upregulation led to the increased cell populations, proliferation, and upregulation of critical cancer-related genes, including AKT1, AKT3, mTOR, WNT3A, SMAD3, CYCLIN D1, CYCLIN D2, BCL2, and GSK3B.

CONCLUSION

We revealed the differential expression of LINC01405 in several types of breast cancer and its role in regulating signaling pathways, potentially via scavenging miRNAs. These findings clarified the role of LINC01405 in breast cancer development and identified potential therapeutic targets.

Risk of breast cancer in daughters of agricultural workers in Denmark

OBJECTIVES

Agricultural workers face unique occupational hazards such as pesticide exposure, which has been associated with breast cancer. However, research considering the association between parental agricultural work and breast cancer in female offspring is lacking. Therefore, the aim of the present nested case-control study was to explore this association.

METHODS

The Danish Cancer Registry was utilized to identify women diagnosed with primary breast cancer. A total of 5587 cases were included in the study, and for each case, 20 cancer-free female controls were selected, matched on year of birth. It was a requisition that both cases and controls were born in Denmark and that either maternal or paternal employment history was available.

RESULTS

Adverse associations were consistently noted for different time windows of maternal employment in "Horticulture" and breast cancer. Inverse associations were observed for paternal employment in most of the examined agricultural industries, although a small increased risk was indicated for perinatal employment in "Horticulture". Furthermore, maternal preconceptional employment in "Horticulture" was observed to increase the risk of ER positive tumors (odds ratio [OR] = 1.79, 95% confidence interval [CI]: 1.13-2.85, whereas parental perinatal employment was linked to an elevated risk of ER negative tumors (maternal employment: OR = 2.48, 95% CI: 1.18-5.21; paternal employment: OR = 1.62, 95% CI: 0.70-3.77).

CONCLUSIONS

The present study indicates that maternal horticultural employment in different potential susceptible time windows may elevate the risk of breast cancer subtypes in daughters. These findings need to be reproduced in future prospective cohort studies, including information on e.g., pesticide exposure withing agricultural job categories and lifestyle factors.

Application of Metabolomics to Epidemiologic Studies of Breast Cancer: New Perspectives for Etiology and Prevention

PURPOSE

To provide an overview on how the application of metabolomics (high-throughput characterization of metabolites from cells, organs, tissues, or biofluids) to population-based studies may inform our understanding of breast cancer etiology.

METHODS

We evaluated studies that applied metabolomic analyses to prediagnostic blood samples from prospective epidemiologic studies to identify circulating metabolites associated with breast cancer risk, overall and by breast cancer subtype and menopausal status. We provide some important considerations for the application and interpretation of metabolomics approaches in this context.

RESULTS

Overall, specific lipids and amino acids were indicated as the most common metabolite classes associated with breast cancer development. However, comparison of results across studies is challenging because of heterogeneity in laboratory techniques, analytical methods, sample size, and applied statistical methods.

CONCLUSION

Metabolomics is being increasingly applied to population-based studies for the identification of new etiologic hypotheses and/or mechanisms related to breast cancer development. Despite its success in applications to epidemiology, studies of larger sample size with detailed information on menopausal status, breast cancer subtypes, and repeated biologic samples collected over time are needed to improve comparison of results between studies and enhance validation of results, allowing potential clinical translation of findings.

Breast cancer: Epidemiology, risk factors and screening

Breast cancer is a global health concern with a significant impact on the well-being of women. Worldwide, the past several decades have witnessed changes in the incidence and mortality of breast cancer. Additionally, epidemiological data reveal distinct geographic and demographic disparities globally. A range of modifiable and non-modifiable risk factors are established as being associated with an increased risk of developing breast cancer. This review discusses genetic, hormonal, behavioral, environmental, and breast-related risk factors. Screening plays a critical role in the effective management of breast cancer. Various screening modalities, including mammography, ultrasound, magnetic resonance imaging (MRI), and physical examination, have different applications, and a combination of these modalities is applied in practice. Current screening recommendations are based on factors including age and risk, with a significant emphasis on minimizing potential harms to achieve an optimal benefits-to-harms ratio. This review provides a comprehensive insight into the epidemiology, risk factors, and screening of breast cancer. Understanding these elements is crucial for improving breast cancer management and reducing its burden on affected individuals and healthcare systems.

Exposure to Organochlorine Pesticides and Female Breast Cancer Risk According to Molecular Receptors Expression: a Systematic Review and Meta-analysis of Epidemiological Evidence

PURPOSE OF REVIEW

Organochlorine pesticides (OCP) have been proposed as potential mammary carcinogens since they interact with steroid signaling pathways. However, the epidemiological results are not conclusive. Most studies have evaluated breast cancer (BC) as a single entity without considering the different molecular expressions, including estrogen receptor (ER), progesterone receptor (PR), and HER2, that could differ in their association with these contaminants. Hence, we assessed the association between biological concentration of OCP and BC, according to its molecular receptor expression, based on a systematic review and meta-analysis.

RECENT FINDINGS

Of the 141 articles eligible for full-text review, nine met the inclusion criteria. The way in which molecular expression was reported was heterogeneous; therefore, the inclusion of studies in the meta-analysis was limited to eight articles. A negative association was identified for β-hexachlorocyclohexane and trans-nonachlor with ER + tumors and between hexachlorobenzene and ER - tumors. No associations were observed for p,p'-dichlorodiphenyldichloroethylene, cis-nonachlor, and dieldrin, and it was not possible to evaluate the associations between OCP with HER2 expression or triple-negative tumors due to lack of data. The results suggest that some OCP might be associated with BC depending on the expression of ER. However, the evidence is not conclusive due to the scarce data. We identified several methodological aspects to fill the gaps in knowledge and increase the comparability among studies.

Protooncogenic Role of ARHGAP11A and ARHGAP11B in Invasive Ductal Carcinoma: Two Promising Breast Cancer Biomarkers

Invasive duct carcinoma (IDC) is one of the most common types of breast cancer (BC) in women worldwide, with a high risk of malignancy, metastasis, recurrence, and death. So far, molecular patterns among IDC cases have not been fully defined. However, extensive evidence has shown that dysregulated Rho family small GTPases (Rho GTPases) including Rho GTPase activating proteins (RhoGAPs) have important roles in the invasive features of IDCs. In the current study, we analyzed the expression levels of two RhoGAP genes, ARHGAP11A and ARHGAP11B, in The Cancer Genome Atlas (TCGA) breast cancer (BRCA) and also our 51 IDC tumors compared to their matched normal tissues using quantitative polymerase chain reaction (qPCR). Our TCGA data analysis revealed higher expression of ARHGAP11A and ARHGAP11B in various cancers comprising BCs. Also, we found correlations between these genes and other genes in TCGA-BRCA. Moreover, our methylation analysis showed that their promotor methylation had a negative correlation with their overexpression. QPCR revealed their significant upregulation in our tumor samples. Furthermore, we found that the expression level of ARHGAP11A was considerably lower in women who were breastfeeding. Moreover, it had overexpression in cases who had regular menstrual cycles and early age (younger than 14) at menarche. However, ARHGAP11B had a higher expression in HER2-positive tumors versus HER2-positive and ER-positive tumors. Our study found possible protooncogenic roles for these genes and their involvement in IDC pathogenesis and malignancy. Therefore, they can be considered novel prognostic and diagnostic biomarkers for IDC.

Cumulative environmental quality is associated with breast cancer incidence differentially by summary stage and urbanicity

Individual environmental contaminants have been associated with breast cancer; however, evaluations of multiple exposures simultaneously are limited. Herein, we evaluated associations between breast cancer summary stages and the Environmental Quality Index (EQI), which includes a range of environmental factors across five domains. The EQI (2000-2005) was linked to county-level age-standardized incidence rates (SIRs) obtained from the North Carolina Central Cancer Registry (2010-2014). Incidence rates and SIRs of total, in situ, localized, regional, and distant breast cancers were evaluated stratified by rural-urban status. In counties with poor environmental quality compared to those with good environmental quality, total breast cancer incidence was higher by 10.82 cases per 100,000 persons (95% CI 2.04, 19.60, p = 0.02). This association was most pronounced for localized breast cancer (β = 5.59, 95% CI 0.59, 10.58, p = 0.03). Higher incidence of early-stage disease (carcinoma in situ β = 5.25, 95% CI 2.34, 8.16, p = 0.00 and localized breast cancer β = 6.98, 95% CI 2.24, 11.73, p = 0.00) and total breast cancer (β = 11.44, 95% CI 3.01, 19.87, p = 0.01) occurred in counties with poor land quality, especially urban counties. Our analyses indicate significant associations between environmental quality and breast cancer incidence, which differ by breast cancer stage and urbanicity, identifying a critical need to assess cumulative environmental exposures in the context of cancer stage.

Potential diagnostic and prognostic biomarkers for breast cancer: A compiled review

Breast cancer is one of the major reason for death of women worldwide. As per the International Agency for Research on Cancer (IARC) statistics, the number of cases of breast cancer is increasing year by year in many parts of the world. As per the recent global cancer burden figures, in 2020, there were 2.26 million incidences of breast cancer cases and it is one of the main causes of mortality due to cancer in women in the world. Biomarkers of breast cancer would prove to be very beneficial to screen women who are at higher risk and for detection of disease recurrence. Here, studies carried out on biomarkers of breast cancer and susceptibility to the disease have been reviewed. Various databases like Google Scholar, ScienceDirect and PubMed have been used for searching and majorly literature from the last 10 years have been considered. Potential biomarkers of breast cancer including blood based angiogenic factors, glycoprotein-based biomarkers, hormone receptor biomarkers and other biomarkers that were identified from various studies have been summarized.

Gut microbiome influences incidence and outcomes of breast cancer by regulating levels and activity of steroid hormones in women

BACKGROUND

Breast cancer, the leading cancer type in women worldwide, is affected by reproductive and nonreproductive factors. Estrogen and progesterone influence the incidence and progression of breast cancer. The microbiome of the gut, a complex organ that plays a vital role in digestion and homeostasis, enhances availability of estrogen and progesterone in the host. Thus, an altered gut microbiome may influence the hormone-induced breast cancer incidence. This review describes the current understanding of the roles of gut microbiome in influencing the incidence and progression of breast cancer, with an emphasis on the microbiome-induced metabolism of estrogen and progesterone.

RECENT FINDINGS

Microbiome has been recognized as a promising hallmark of cancer. Next-generation sequencing technologies have aided in rapid identification of components of the gut microbiome that are capable of metabolizing estrogen and progesterone. Moreover, studies have indicated a wider role of the gut microbiome in metabolizing chemotherapeutic and hormonal therapy agents and reducing their efficacy in patients with breast cancer, with a predominant effect in postmenopausal women.

CONCLUSION

The gut microbiome and variations in its composition significantly alter the incidence and therapy outcomes of patients with breast cancer. Thus, a healthy and diverse microbiome is required for better response to anticancer therapies. Finally, the review emphasizes the requirement of studies to elucidate mechanisms that may aid in improving the gut microbiome composition, and hence, survival outcomes of patients with breast cancer.

Androgens Modulate Bcl-2 Agonist of Cell Death (BAD) Expression and Function in Breast Cancer Cells

Androgen receptor (AR) expression in estrogen receptor-positive (ER+) breast cancer (BC) correlates with lower tumor grade and a better clinical outcome. Additionally, in normal mammary epithelium or ER+ BC preclinical models, androgens counteract basal/ER-dependent proliferation. Here, we report an additional mechanism, underlining the protective role exerted by AR. Specifically, the activation of intracellular AR upregulates the Bcl-2-family protein BAD, and TCGA database analyses show that in ER+ BC, BAD expression is associated with better disease-free survival. Ligand-activated AR influences its own and BAD cellular compartmentalization by enhancing levels in the nucleus, as well as in mitochondrial fractions. In both compartments, BAD exerts unconventional functions. In the nucleus, BAD and AR physically interact and, upon androgen stimulation, are recruited at the AP-1 and ARE sites within the cyclin D1 promoter region, contributing to explaining the anti-proliferative effect of androgens in BC cells. Androgens cause an enrichment in BAD and AR content in the mitochondria, correlated with a decrease in mitochondrial function. Thus, we have defined a novel mechanism by which androgens modulate BAD expression, its mitochondria localization, and nuclear content to force its ability to act as a cell cycle inhibitor, strengthening the protective role of androgen signaling in estrogen-responsive BCs.

Risk factors for breast cancer among women in Ekurhuleni Metropolitan Municipality, Gauteng province of South Africa, 2017‒2020: a case-control study

Introduction

Breast cancer (BC) is the most common cancer among women in South Africa (SA), with an age-standardised incidence rate of 52.6 and an age-standardised mortality rate of 16.0 per 100,000 population. There is a paucity of evidence on the risk factors for BC among women of all races in SA. Given the rising prevalence of BC in SA, literature-based evidence is critical for the appropriate dissemination of preventative measures. This study aimed to identify the risk factors associated with the development of BC among women in Ekhuruleni Metropolitan Municipality.

Methods

An unmatched case-control study was conducted from 1 January 2017 to 31 December 2020 using secondary data extracted from the Ekurhuleni Population-Based Cancer Registry. Unconditional multivariable logistic regression analysis was carried out using the adjusted odds ratio (aOR). The variables race, employment, human immunodeficiency virus (HIV), smoking and alcohol status were included in the multivariable logistic regression model while the model was adjusted for age.

Results

A total of 2,217 cases and 851 controls were enrolled in the study. The mean age (±SD) in years was 55.7 (±15.2). The White population group, being self-employed and being HIV positive was significantly associated with reduced odds of BC development. HIV-positive women were 61% less likely to have BC than women who were HIV-negative (aOR 0.39; 95% confidence interval (CI): 0.27‒0.57). White women were 65% less likely to have BC than women of other races (aOR 0.35; 95% CI: 0.29‒0.43). Self-employed women were 59% less likely to have BC than women who were formally employed (aOR 0.41; 95% CI: 0.18‒0.97). No evidence of association was observed between tobacco smoking and BC as well as alcohol consumption and BC.

Conclusion

There was a 65% reduction in BC risk among White women compared to other races. HIV-positive women demonstrated a 61% lower likelihood of BC while self-employed women showed a 59% reduced risk of developing BC. These findings suggest that being White, self-employed or HIV-positive may provide some protection against BC. However, additional research is needed to validate these results and establish the underlying reasons behind these associations.

Cancer Epidemiology in the Northeastern United States (2013-2017)

We tested the hypotheses that adult cancer incidence and mortality in the Northeast region and in Northern New England (NNE) were different than the rest of the United States, and described other related cancer metrics and risk factor prevalence. Using national, publicly available cancer registry data, we compared cancer incidence and mortality in the Northeast region with the United States and NNE with the United States overall and by race/ethnicity, using age-standardized cancer incidence and rate ratios (RR). Compared with the United States, age-adjusted cancer incidence in adults of all races combined was higher in the Northeast (RR, 1.07; 95% confidence interval [CI] 1.07-1.08) and in NNE (RR 1.06; CI 1.05-1.07). However compared with the United States, mortality was lower in the Northeast (RR, 0.98; CI 0.98-0.98) but higher in NNE (RR, 1.05; CI 1.03-1.06). Mortality in NNE was higher than the United States for cancers of the brain (RR, 1.16; CI 1.07-1.26), uterus (RR, 1.32; CI 1.14-1.52), esophagus (RR, 1.36; CI 1.26-1.47), lung (RR, 1.12; CI 1.09-1.15), bladder (RR, 1.23; CI 1.14-1.33), and melanoma (RR, 1.13; CI 1.01-1.27). Significantly higher overall cancer incidence was seen in the Northeast than the United States in all race/ethnicity subgroups except Native American/Alaska Natives (RR, 0.68; CI 0.64-0.72). In conclusion, NNE has higher cancer incidence and mortality than the United States, a pattern that contrasts with the Northeast region, which has lower cancer mortality overall than the United States despite higher incidence.

Significance

These findings highlight the need to identify the causes of higher cancer incidence in the Northeast and the excess cancer mortality in NNE.

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.

Stromal Tumor-Infiltrating Lymphocytes Associated with Immunohistopathology and Molecular Subtypes of Breast Cancer in Vietnam

OBJECTIVE

Breast cancer is a heterogeneous disease with varied symptoms and pathogenesis, as well as variable prognosis and therapeutic outcomes. Stromal tumor-infiltrating lymphocytes, one of the tumor microenvironment factors, has been recognized as an important immunological biomarker that reflected the antitumor immune response in breast cancer.

METHODS

We analyzed 207 invasive breast cancer patients who had lumpectomy or mastectomy and have not received any pre-operative treatment. Clinicopathological characteristics, immunohistochemistry characteristics, molecular subtypes classification and stromal TILs evaluation were investigated.

RESULT

Stromal TILs correlated with well-established prognostic markers. Tumor grade showed significantly higher sTILs percentages in high-grade tumors than in low-grade tumors (p<0.001). There was a statistically significant association between intermediate and high levels of sTILs and a high Ki-67 index (p< 0.001). ER/PR negative was significantly related to high sTILs. Mean sTILs score was significantly higher in TNBC (40.1±31.6%) compared to others, statistically significant (p<0.001). In HER2-negative breast cancer, sTILs were significantly associated with histologic grade, ER status, PR status, and Ki67 index.

CONCLUSION

sTILs played an important role, associated with unfavorable factors in breast cancer. Our findings support the use of stromal sTILs to identify a more aggressive phenotype of tumors.

Hesperetin effect on MLH1 and MSH2 expression on breast cancer cells BT-549

Due to its genetic and phenotypic heterogeneity, breast cancer is very difficult to eliminate. The harmful consequences of conventional therapies like radiation and chemotherapy have prompted the search for organic-based alternatives. Hesperetin (HSP), a flavonoid, has been discovered to possess the ability to hinder the proliferation of cell associated with breast cancer by acting as an epigenetic agent and modifying gene expression. In this investigation, breast cancer cells (BT-549) and normal cells (MCF-10a) were subjected to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test and three different doses (200, 400, and 600 μM/mL) of HSP for real-time polymerase chain reaction and flow cytometry to examine its cytotoxic and anti-malignant potential. HSP was shown to be cytotoxic to both normal and breast cancer cells, but had a more pronounced effect on the cancer cell lines. After 48 h of treatment, the half-maximal inhibitory concentration (IC50) for BT-549 was 279.2 μM/mL, whereas the IC50 for MCF-10a was 855.4 μM/mL. At high HSP concentrations, upregulation of the MLH1 and MSH2 genes was observed in both cell lines. The influence of HSP on MLH1 gene expression was concentration dependent. Moreover, HSP had a concentration-dependent effect on MSH2 gene expression in the BT-549 cell line but not in the MCF-10a cell line. Cell death and early apoptosis were shown to be concentration dependent upon the application of HSP, as determined by flow cytometric analysis. HSP's capacity to cause apoptosis and its stronger impact on the malignant cell line when analyzed with the normal cell line imply that it might be useful as an effective therapeutic approach for combating breast cancer.

Spatial pattern and environmental drivers of breast cancer incidence in Chinese women

Breast cancer (BC) had the highest incidence of all cancers in Chinese women. However, studies on spatial pattern and environmental drivers of BC were still lacked as they were either limited in a small area or few considered the comprehensive impact of multiple risk factors. In this study, we firstly performed spatial visualization and the spatial autocorrelation analysis based on Chinese women breast cancer incidence (BCI) data of 2012-2016. Then, we explored the environmental drivers related to BC by applying univariate correlation analysis and geographical detector model. We found that the BC high-high clusters were mainly distributed in the eastern and central regions, such as Liaoning, Hebei, Shandong, Henan, and Anhui Provinces. The BCI in Shenzhen was significantly higher than other prefectures. Urbanization rate (UR), per capita GDP (PGDP), average years of school attainment (AYSA), and average annual wind speed (WIND) had higher explanatory power on spatial variability of the BCI. PM10, NO2, and PGDP had significant nonlinear enhanced effect on other factors. Besides, normalized difference vegetation index (NDVI) was negatively associated with BCI. Therefore, high socioeconomic status, serious air pollution, high wind speed, and low vegetation cover were the risk factors for BC. Our study may able to provide evidence for BC etiology research and precise identification of areas requiring focused screening.

Structural immunoinformatics approach for rational design of a multi-epitope vaccine against triple negative breast cancer

TNBC is a highly malignant breast cancer known for its aggressive behavior affecting young female adults. The standard treatment for TNBC includes surgery, chemotherapy, and radiotherapy, which often have significant side effects. Therefore, novel preventive methods are required to combat TNBC effectively. In this study, we utilized immunoinformatics to construct an in-silico vaccine against TNBC using the TRIM25 molecule via the reverse vaccinology method. Four vaccines were designed by generating T and B-cell epitopes linked with four different linkers. The modeled vaccine was docked and the results showed that vaccine-3 exhibited the highest affinity with the immune receptors. The molecular dynamics results revealed that the binding affinity and stability of Vaccine-3 were greater than those of Vaccine 2 complexes. This study has great potential preventive measures for TNBC, and further research is warranted to evaluate its efficacy in preclinical settings. This study presents an innovative preventive strategy for triple-negative breast cancer (TNBC) through immunoinformatics and reverse vaccinology to develop an in-silico vaccine. Leveraging these innovative techniques offers a novel avenue for combating the complex challenges associated with TNBC. This approach demonstrates considerable potential as a significant breakthrough in preventive measures for this particularly aggressive and malignant form of breast cancer.

Reproductive history and breast cancer survival: Findings from the African breast cancer-Disparities in outcomes cohort and implications of Africa's fertility transition on breast cancer prognosis

Reproductive characteristics are known risk factors for breast cancer but, other than recent birth, their role as prognostic factors is less clear, and has not been studied in Sub-Saharan Africa (SSA). In this setting, we examined whether reproductive factors independently influence breast cancer survival in a subset of the African Breast Cancer-Disparities in Outcomes cohort study. In 1485 women with incident breast cancer recruited between 2014 and 2017, we examined birth cohort changes in reproductive factors, and used Cox models to examine whether reproductive characteristics were associated with all-cause mortality after adjusting for confounders (age, stage, treatment, HIV, and social factors). Four years after diagnosis, 822 (56%) women had died. Median parity was 4 (IQR = 2, 6) and 209 (28%) of premenopausal women had had a recent birth (<3 years prior to cancer diagnosis). Each pregnancy was associated with a 5% increase (95% CI: 2%, 8%) in mortality rates, which held among postmenopausal women (5%, [1%-9%]). Pre-menopausal women with a recent birth had 52% (20%, 92%) higher mortality rates. Fertility trends by birth cohort showed declining parity, increasing age at first birth and declining age at last birth, however the impact of these population-level changes on future average survival was predicted to be very small (<3% absolute gain).

Linking Physical Activity to Breast Cancer via Inflammation, Part 2: The Effect of Inflammation on Breast Cancer Risk

This review synthesized and appraised the evidence for an effect of inflammation on breast cancer risk. Systematic searches identified prospective cohort and Mendelian randomization studies relevant to this review. Meta-analysis of 13 biomarkers of inflammation were conducted to appraise the evidence for an effect breast cancer risk; we examined the dose-response of these associations. Risk of bias was evaluated using the ROBINS-E tool and the quality of evidence was appraised with Grading of Recommendations Assessment, Development, and Evaluation. Thirty-four observational studies and three Mendelian randomization studies were included. Meta-analysis suggested that women with the highest levels of C-reactive protein (CRP) had a higher risk of developing breast cancer [risk ratio (RR) = 1.13; 95% confidence interval (CI), 1.01-1.26] compared with women with the lowest levels. Women with highest levels of adipokines, particularly adiponectin (RR = 0.76; 95% CI, 0.61-0.91) had a reduced breast cancer risk, although this finding was not supported by Mendelian randomization analysis. There was little evidence of an effect of cytokines, including TNFα and IL6, on breast cancer risk. The quality of evidence for each biomarker ranged from very low to moderate. Beyond CRP, the published data do not clearly support the role of inflammation in the development of breast cancer.

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.

Menopause hormone treatment after cancer

Regular improvement in survival of women after treatment for cancer has been reached in these last years. Menopause hormone therapy (MHT) remains the most efficient treatment to alleviate climacteric symptoms and improve quality of life in symptomatic women. The long-term effects of estrogen deficiency can be, at least partially, prevented by MHT. However, using MHT in an oncologic context can be associated with contraindications. Patients who have experienced breast cancer frequently face severe climacteric symptoms, but results from randomized trials are not in favor of using MHT in these women. Three randomized trials are available in women treated by MHT after ovarian cancer, and report better survival rates in the active group of treatment, suggesting that, at least in serous high-grade ovarian carcinoma, MHT could be allowed. No robust data are available for MHT after endometrial carcinoma. According to various guidelines, MHT could be possible in low grades with good prognosis. Progestogen, however, is not contraindicated and can help to alleviate climacteric symptoms. Squamous cell cervical carcinoma is not hormone-dependent and therefore patients can be treated with MHT without restrictions, whereas cervical adenocarcinoma is likely to be estrogen-dependent, despite lack of robust data, and thus only progesterone or progestin might be potentially used. It is possible that, in future, better molecular characterization of genomic profiles of various cancers may allow MHT to be used with some patients.

Association of education level with the risk of female breast cancer: a prospective cohort study

BACKGROUND

Breast cancer is a serious threat to female health, and its incidence varies with education level (EL). In the present study, the association between EL and the risk of developing female breast cancer was investigated.

METHODS

From May 2006 to December 2007, 20,400 observation subjects in Kailuan Cohort received questionnaires and were subjected to clinical examinations for data collection on baseline population characteristics, height, weight, lifestyle and past disease history. Then, these participants were followed up with from the date of recruitment to December 31, 2019. Cox proportional risk regression models were used to analyse the association between EL and the risk of developing female breast cancer.

RESULTS

The cumulative follow-up period of 20,129 observation subjects that meet the inclusion criteria of this study was 254,386.72 person-years, and the median follow-up time was 12.96 years. During the follow-up period, 279 cases of breast cancer were diagnosed. In comparison with the low EL group, the risk of developing breast cancer was significantly higher in the medium (hazard ratio [HR] (95% confidence interval [CI]) = 2.23 (1.12-4.64)] and high [HRs (95% CI) = 2.52 (1.12-5.70)] EL group.

CONCLUSION

An increased risk of breast cancer was associated with a higher EL, and some certain factors, such as alcohol use and hormone therapy, may play a mediating role.

Characterizing breast cancer incidence and trends among Asian American, Native Hawaiian, and non-Hispanic White women in Hawai'i, 1990-2014

PURPOSE

To characterize breast cancer (BC) incidence by age at diagnosis and BC subtype among disaggregated Asian American, Native Hawaiian, and Pacific Islander (AANHPI) women and non-Hispanic White (NHW) women in Hawai'i.

METHODS

Using 1990-2014 data from the Hawai'i tumor registry, we estimated age-adjusted incidence rates (AAIR) of BC and the annual percent change in BC incidence by age (<50 and ≥50 years) and BC subtype (hormone receptor [HR]+/human epidermal growth factor receptor 2 [HER2]-, HR+/HER2+, HR-/HER2+, triple negative BC) for Filipino American (FA), Japanese American (JA), Native Hawaiian (NH), and NHW women.

RESULTS

Among young (<50 years) women, annual BC incidence increased 2.9% (1994-2014) among JA and 1.0% (1990-2014) among NHW women. Incidence was highest among young JA women (2010-2014 AAIR 52.0 per 100,000; 95% confidence interval [CI] 45.6, 58.9). HR+/HER2- BC, the major BC subtype, was similarly highest among young JA women (AAIR 39.5; 95% CI 33.9, 45.4). Among older (≥50 years) women, annual BC incidence increased 1.6% (1990-2014) among FA and 4.2% (2006-2014) for JA women. BC incidence was highest among older NH women (AAIR 137.6, 95% CI 128.2, 147.4), who also displayed highest incidence of two subtypes: HR+/HER2- (AAIR 106.9; 95% CI 98.6, 115.5) and HR+/HER2+ (AAIR 12.1; 95% CI 9.4, 15.1).

CONCLUSION

We observed high and increasing BC incidence among JA women ages <50 years and high incidence among NH women ages ≥50 years. These results highlight racial and ethnic differences in BC incidence among disaggregated AANHPI populations in Hawai'i by age and BC subtype.

Misconceptions About Female Cancers Contributing to Late Presentation to Health Facilities in Ethiopia: A Qualitative Study

Introduction

Morbidity and mortality from female cancers is a major public health problem in low- and middle-income countries, including Ethiopia. More than three quarters of women visiting health facilities are diagnosed with late-stage cervical and breast cancer. Evidence reveals that misconception affects timely health seeking behavior which could have averted expensive treatment and poor survival. This study aimed to explore misconceptions about female cancers that may have contributed to late presentation of the problem to health facilities in Sidama region, Ethiopia.

Methods

A descriptive qualitative study was carried out in June 2021. Nine focus group discussions (six with women and three with men) and 14 key informants were conducted. Data were collected using interview guide until all information get saturated. Data were inductively coded and qualitative content analysis was applied.

Results

A total of 63 (24 men and 39 women) people participated in this study. Nearly all (12) key informant interviewees have awareness about cervical and breast cancer, yet reported that their community members clearly lack awareness and they are working to improve misconceptions regarding cervical and breast cancer. The focus group discussion participants (15 men and 36 women) reported lack of detailed information related to cervical and breast cancer. Women believe that cervical and breast cancer mainly resulted from poor hygiene, trauma, having multiple sexual partners, early marriage, breast exposure to heat, not breast feeding, birth complication, urinating in the sun, hereditary, devil's intrusion and God's punishment.

Conclusion

There were misconceptions among the community on what cervical and breast cancer mean, how they could happen, what the symptoms are, why and when to screen, when to seek health care and how to use modern treatment options. Therefore, we recommended the design of social and behavioral change strategies to address the misconceptions among different population groups.

Multi-Morbidity and Risk of Breast Cancer among Women in the UK Biobank Cohort

(Multi-)Morbidity shares common biological mechanisms or risk factors with breast cancer. This study aimed to investigate the association between the number of morbidities and patterns of morbidity and the risk of female breast cancer. Among 239,436 women (40-69 years) enrolled in the UK Biobank cohort who had no cancer history at baseline, we identified 35 self-reported chronic diseases at baseline. We assigned individuals into morbidity patterns using agglomerative hierarchical clustering analysis. We fitted Cox models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for breast cancer risk. In total, 58.4% of women had at least one morbidity, and the prevalence of multi-morbidity was 25.8%. During a median 7-year follow-up, there was no association between breast cancer risk (5326 cases) and either the number of morbidities or the identified clinically relevant morbidity patterns: no-predominant morbidity (reference), psychiatric morbidities (HR = 1.04, 95%CI 0.94-1.16), respiratory/immunological morbidities (HR = 0.98, 95%CI 0.90-1.07), cardiovascular/metabolic morbidities (HR = 0.93, 95%CI 0.81-1.06), and unspecific morbidities (HR = 0.98, 95%CI 0.89-1.07), overall. Among women younger than 50 years of age only, however, there was a significant association with psychiatric morbidity patterns compared to the no-predominant morbidity pattern (HR = 1.25, 95%CI 1.02-1.52). The other associations did not vary when stratifying by age at baseline and adherence to mammography recommendations. In conclusion, multi-morbidity was not a key factor to help identify patients at an increased risk of breast cancer.

Long term trends of breast cancer incidence according to proliferation status

BACKGROUND

Long-term breast cancer incidence trends according to proliferation status are poorly described. We studied time-trends in breast cancer incidence, using mitotic count and Ki-67 as markers of proliferation.

METHODS

Among 83,298 Norwegian women followed for breast cancer occurrence 1961-2012, 2995 incident breast cancers were diagnosed. Ki-67 was assessed using immunohistochemistry on tissue microarrays and mitoses were counted on whole sections. We compared incidence rates according to proliferation status among women born 1886-1928 and 1929-1977, estimating age-specific incidence rate ratios. We performed multiple imputations to account for unknown proliferation status. Mean values of Ki-67 and mitotic counts were calculated, according to age and birth year. We performed separate incidence analyses for HER2⁺ and triple negative breast cancers.

RESULTS

Among women aged 40-69 years, incidence rates of tumours with low-proliferative activity were higher among those born in 1929 or later, compared to before 1929, according to Ki-67 and mitotic count. Incidence rates of tumours with high-proliferative activity were also higher in women born in 1929 or later compared to before 1929 according to Ki-67, but not according to mitotic count. Mean values of Ki-67 and mitotic count varied according to age and birth year. In subtype-specific analyses we found an increase of high-proliferative HER2⁺ tumours according to Ki-67 in women born in 1929 or later, compared to before 1929.

CONCLUSIONS

There has been a temporal increase in both low- and high-proliferative breast cancers.

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.

Impact of modifiable reproductive factors on cancer incidence and mortality in Korea: a systematic review protocol

INTRODUCTION

Cancer is a leading cause of death worldwide. In Korea, it is also a major public health problem. Cancer burden may increase significantly due to ageing population and changes in lifestyle. The features of reproductive factors have changed, which include increased age at first childbirth and decreased breastfeeding duration. This study aims to systematically summarise the association between modifiable reproductive factors and cancer incidence and mortality to provide evidence for planning strategies aimed at reducing cancer incidence and mortality in women.

METHODS AND ANALYSIS

A literature search was performed using the EMBASE, MEDLINE, Cochrane Library and Korean databases such as the Korean Studies Information Service System, Research Information Sharing Service, KoreaMED, Korean Medical Database, National Assembly Library and Korea Institute from their inception to 24 August 2022. We will include cohort studies addressing the associations between at least one of the reproductive factors and the incidence and mortality of all or specific cancers among Korean women. Two reviewers will screen the references, extract the data, and assess the risk of bias independently and in duplicates. Discrepancies will be resolved through discussion or consultation with a third-party reviewer. We will use the Grading of Recommendations, Assessment, Development and Evaluation approach to evaluate the certainty of evidence. We will summarise the findings of the included systematic reviews through quantitative or narrative syntheses and present the summarised findings in tables.

ETHICS AND DISSEMINATION

Ethical approval is not required, since we will use only the published data. We will disseminate the study findings in peer-reviewed publications.

PROSPERO REGISTRATION NUMBER

CRD42022356085.