A case-control study of reproductive factors associated with subtypes of breast cancer in Northeast China

The role of breastfeeding in breast cancer prevention: a literature review

Breast cancer stands as the most prevalent malignancy globally. Despite the array of treatment options, its mortality rate continues to rise annually. Thus, reevaluation of factors directly linked to breast cancer emergence is imperative, alongside the development of more effective preventive measures. Estrogen levels, profoundly tied to reproduction, play a pivotal role in breast cancer development. Speculation centers on the potential of breastfeeding to mitigate cancer risk in women. However, the precise mechanism remains elusive. Breastfeeding is a modifiable reproductive factor extensively studied. Studies highlight a direct connection between lack of breastfeeding and breast cancer emergence, potentially linked to DNA methyltransferase expression alteration, aberrant methylation levels, pregnancy-associated plasma protein-A, cellular microenvironment, and oncogenes. This study reviews recent mechanisms underlying breastfeeding's role in reducing breast cancer incidence.

A Narrative Review of Breastfeeding and Its Correlation With Breast Cancer: Current Understanding and Outcomes

Breastfeeding has been extensively studied in relation to breast cancer risk. The results of the reviewed studies consistently show a decreased risk of breast cancer associated with breastfeeding, especially for 12 months or longer. This protective effect is attributed to hormonal, immunological, and physiological changes during lactation. Breastfeeding also appears to have a greater impact on reducing breast cancer risk in premenopausal women and specific breast cancer subtypes. Encouraging breastfeeding has dual benefits: benefiting infants and reducing breast cancer risk long-term. Healthcare professionals should provide evidence-based guidance on breastfeeding initiation, duration, and exclusivity, while public health policies should support breastfeeding by creating enabling environments. This review examines the existing literature and analyzes the correlation between breastfeeding and breast cancer risk.

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.

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).

Breast cancer subtype and clinical characteristics in women from Peru

Introduction

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

Methods

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

Results

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

Discussion

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

Plg-RKT Expression in Human Breast Cancer Tissues

The plasminogen activation system regulates the activity of the serine protease, plasmin. The role of plasminogen receptors in cancer progression is being increasingly appreciated as key players in modulation of the tumor microenvironment. The interaction of plasminogen with cells to promote plasminogen activation requires the presence of proteins exposing C-terminal lysines on the cell surface. Plg-R_KT is a structurally unique plasminogen receptor because it is an integral membrane protein that is synthesized with and binds plasminogen via a C-terminal lysine exposed on the cell surface. Here, we have investigated the expression of Plg-R_KT in human breast tumors and human breast cancer cell lines. Breast cancer progression tissue microarrays were probed with anti-Plg-R_KT mAB and we found that Plg-R_KT is widely expressed in human breast tumors, that its expression is increased in tumors that have spread to draining lymph nodes and distant organs, and that Plg-R_KT expression is most pronounced in hormone receptor (HR)-positive tumors. Plg-R_KT was detected by Western blotting in human breast cancer cell lines. By flow cytometry, Plg-R_KT cell surface expression was highest on the most aggressive tumor cell line. Future studies are warranted to address the functions of Plg-R_KT in breast cancer.

Association of EGFR mutations in second primary lung cancer and HER2 expression in breast cancer survivors

Background

The incidence of second primary lung cancer (SPLC) is increasing with longer survival rates from breast cancer. Despite of studies to suggest the mutual exclusivity of epidermal growth factor receptor (EGFR) and human epidermal growth receptor 2 (HER2) in several cancers, the effect of HER2 expression in breast cancer on EGFR mutations in SPLC is unclear. Therefore, this study aimed to determine the association between HER2 expression and EGFR mutations.

Methods

We conducted a retrospective cohort study of breast cancer survivors diagnosed with SPLC after breast cancer treatment between 1997 and 2018. We investigated the association between HER2 expression in breast cancer and EGFR mutations in SPLC, specifically focusing on negative correlations by using logistic regression analysis.

Results

EGFR mutations in SPLC were detected in 19 of 38 patients. Analysis for HER2 revealed a statistically significant difference in the proportion of EGFR mutations between patients with SPLC and previous HER2 positive breast cancer (43.5%) and those with SPLC and previous HER2 negative breast cancer (90.0%; P=0.021). The ratio of EGFR mutations decreased with the degree of HER2 expression in patients with previous breast cancer (90.0%: for no HER2 expression, 62.5% for HER2 1+, 0.0% for HER2 2+, and 41.7% for HER2 3+; P=0.018). Multivariate logistic analyses revealed that EGFR mutations in SPLC were significantly associated with age [odds ratio (OR): 1.11, 95% confidence interval (CI): 1.01-0.23, P=0.039] and HER2 positive status (OR: 0.04, 95% CI: 0.01-0.56, P=0.017).

Conclusions

This study suggests that the frequency of EGFR mutations in SPLC may be associated with low HER2 expression in previous breast cancer.

Breastfeeding and Reduced Risk of Breast Cancer: A Systematic Review and Meta-Analysis

BACKGROUND

Evidences which prove relation between breastfeeding women and risk of breast cancer have been limited.

OBJECTIVE

A meta-analysis was carried out on the basis of published literature from clinical trials and studies among different parts of the world.

METHODS

Studies were analyzed and extracted using PRISMA flowchart. RevMan 5.4.1 was used for analyzing the extracted data. Included studies were fully cited texts with complete information about studies, trails conducted for risk of breast cancer, and breastfeeding correlations.

RESULTS

Menarche age, family history, lactation duration, and menopausal status have a strong effect on the risks of breast cancer. Family history studies concluded that for 95% CI, the risk ratio was 2.66 (2.00, 3.52).

CONCLUSION

Findings have suggested that family history and lactation duration affect the risks of breast cancer.

Menstrual and Reproductive Factors in Association With Breast Cancer Risk in Vietnamese Women: A Case-Control Study

OBJECTIVES

Though menstrual and reproductive factors have been associated with the risk of breast cancer in many populations, very few studies have been conducted among Vietnamese women. This study aimed to assess the association between menstrual and reproductive factors and the risk of breast cancer in Vietnamese women.

METHODS

A retrospective case-control study of 490 breast cancer cases and 468 controls was conducted in Northern Vietnam. Unconditional logistic regression models adjusting for confounders were used to estimate odds ratios (ORs) and their 95% confidence intervals (CIs) for the associations of menstrual and reproductive factors with the risk of breast cancer; overall and by cancer subtype.

RESULTS

Among breast cancer patients, the luminal B subtype was the most frequent (48.6%), followed by HER2-overexpressing (24.5%), luminal A (16.7%), and triple-negative breast cancer (TNBC; 10.2%). Among menopausal women, menopausal age at 50 years or older (OR = 1.71, 95% CI: 1.15-2.57 vs. <50 y) was associated with an increased risk of breast cancer. Earlier age at menarche (<13 y) was associated with a significantly increased risk of breast cancer (OR = 2.66, 95% CI: 1.08-7.51) among premenopausal women only and the luminal A subtype of breast cancer (OR = 3.06, 95% CI: 1.04-8.16). Having more than two children was associated with a reduced risk of premenopausal (OR = .42, 95%CI: .21-.83), luminal B (OR = .43, 95% CI: .24-.79), and TNBC (OR = .34, 95% CI: .14-.89). Later menopause was positively associated with the risk of breast cancer with HER2 overexpression (OR = 2.19, 95% CI: 1.14-4.23).

CONCLUSION

Associations of menstrual and reproductive factors with breast cancer among Vietnamese women, particularly for among premenopausal women and for the luminal A subtype, are generally consistent with those reported from other countries. These findings suggest that changes in menstrual and reproductive patterns among young Vietnamese women may contribute to the recent rising incidence of breast cancer in Vietnam.

OUP accepted manuscript

Background

Methods

Results

Conclusion

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Expression and clinicopathological significance of AOC4P, PRNCR1, and PCAT1 lncRNAs in breast cancer

Long none coding RNAs (lncRNAs) AOC4P, PRNCR1, and PCAT-1 are dysregulated in various types of malignancies. However, their expression and clinicopathological significances are uncertain in breast cancer (BC). Quantitative real-time polymerase chain reaction (RT- qPCR) was used to measure the expression levels of the selected lncRNAs in tumor tissues obtained from 50 BC patients compared to the normal adjacent tissues (NATs) and 50 clinically healthy normal tissues. Our results revealed a significant downregulation of AOC4P, however, upregulated PRNCR1 and PCAT1 were found in tumor tissues compared to NATs and clinically healthy normal tissues (P < 0.05). Interestingly, remarkable decreased expression of AOC4P was observed in NATs than clinically healthy normal tissues. Dysregulation of the lncRNAs was correlated with worse outcomes of patients. Furthermore, our data showed that the altered expression levels of lncRNAs AOC4P, PRNCR1, and PCAT1 might be occurred through the function of demographic and reproductive variables. Taken together, the altered regulation of AOC4P, PRNCR1, and PCAT1 may highlight their crucial roles in BC development and pathogenesis. Our findings also proposed demographic and reproductive variables as risk factors in BC through the possible influence on the expression of the studied lncRNAs. Nevertheless, further explorations are required to elucidate the more detailed functions of these lncRNAs in BC.

Heterogeneous Associations Between Obesity and Reproductive-Related Factors and Specific Breast Cancer Subtypes Among Hong Kong Chinese Women

Previous studies reported heterogeneous associations between obesity and reproductive-related breast cancer risk factors and breast cancer intrinsic subtypes; however, few studies have been conducted in Asian populations. Here, we aimed to examine whether risks associated with established breast cancer risk factors varied by breast cancer subtypes in Chinese women. We conducted a hospital-based case-control study in Hong Kong, including a total of 2169 Chinese women. Unconditional polytomous logistic regression models were used to calculate adjusted odds ratios (AORs) and 95% confidence intervals(95%CIs) to estimate relative risks associated with examined risk factors in case-control analyses and to test for heterogeneity across breast cancer subtypes in case-case analyses. In case-case analyses, compared with luminal A patients, luminal B (AOR = 1.76, 95% CI = 1.07-2.88), HER2 overexpressing (AOR = 3.40, 95% CI = 1.56-7.39), and triple negative (TNBC, AOR = 2.39, 95% CI = 1.18-4.82) patients were more likely to be postmenopausal. In case-control analyses, reduced risks associated with parity and younger age at first birth were only seen for luminal A and B cases especially among postmenopausal women, whereas having ≥ 3 children was associated with increased risk for HER2 overexpressing and TNBC among premenopausal women. Obesity was associated with increased risk for all subtypes. We found heterogeneous associations between parity-related risk factors by menopausal status and breast cancer subtypes among Chinese patients, which is similar to those observed in Western populations. Interestingly, obesity was associated with increased breast cancer risk regardless of menopausal status or subtypes, except for premenopausal luminal patients, which appears to be unique in Asian populations.

Metabolomics and lipidomics study unveils the impact of polybrominated diphenyl ether-47 on breast cancer mice

Polybrominated diphenyl ether-47 (BDE-47) is a congener of polybrominated diphenyl ethers (PBDEs) and relates to different health risks. However, in vivo study of the association between BDE-47 and breast cancer was scarce. In this study, we performed in vivo exposure of BDE-47 to breast cancer nude mice and conducted mass spectrometry-based metabolomics and lipidomics analysis to investigate the metabolic changes in mice. Results showed that the tumor sizes were positively associated with the dosage of BDE-47. Metabolomics and lipidomics profiling analysis indicated that BDE-47 induced significant alterations of metabolic pathways in livers, including glutathione metabolism, ascorbate and aldarate metabolism, and lipids metabolism, etc. The upregulations of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) suggested the membrane remodeling, and the downregulations of Lyso-PCs and Lyso-PEs might be associated with the tumor growth. Targeted metabolomics analysis revealed that BDE-47 inhibited fatty acid β-oxidation (FAO) and induced incomplete FAO. The inhibition of FAO and downregulation of PPARγ would contribute to inflammation, which could promote tumor growth. In addition, BDE-47 elevated the expression of the cytokines TNFRSF12A, TNF-α, IL-1β and IL-6, and lowered the cytokines SOCS3 and the nuclear receptor PPARα. The changes of cytokines and receptor may contribute to the tumor growth of mice.

Reproductive Risk Factors Associated with Breast Cancer Molecular Subtypes among Young Women in Northern China

Purpose

Accumulated evidence suggests that reproductive factors are related to different breast cancer subtypes, but most studies on these relationships are mainly focused on middle-aged and older patients, and it remains unclear how reproductive factors impact different subtypes of breast cancer in young women.

Methods

We assessed the relationships between fertility factors and luminal A, luminal B, human epidermal growth factor receptor 2 (HER2)-enriched, and triple-negative breast cancer (TNBC) subtypes in 3792 patients and 4182 controls aged 20–70 years. Data on the reproductive history of the study participants were acquired through face-to-face interviews and questionnaires. We conducted case-control comparisons among tumor subtypes based on estrogen receptor (ER), progesterone receptor (PR), and HER2 statuses using unconditional polychotomous multivariate logistic regression models to compute odds ratios (ORs) and 95% confidence intervals (CIs).

Results

Parity was inversely related to both luminal A and luminal B subtypes in young women and older women (all P_trend < 0.05). Later age at first full-term birth was inversely related to the luminal A subtype (P_trend < 0.05) in young women but correlated with an increased risk of the luminal A subtype (P_trend < 0.05) in older women. Parous Chinese women 40 years old or younger who breastfed for 12 months or longer had a lower risk of luminal B and TNBC subtypes than women who never breastfed (OR = 0.55, 95% CI 0.36-0.84 and OR = 0.52, 95% CI 0.28-0.99, respectively).

Conclusions

Our results implied that parity exerted a strong protective effect against luminal A and luminal B subtype breast cancer in young Chinese women, and long-term breastfeeding obviously decreased the risk of luminal B and TNBC subtypes in this population.

A cumulative index of exposure to endogenous estrogens and breast cancer by molecular subtypes in northern Mexican women

PURPOSE

To evaluate breast cancer (BC) molecular subtypes association with reproductive characteristics and an index of cumulative exposure to endogenous estrogens (EEI) in Mexican women.

METHODS

We performed a study of incident cases and population controls in northern Mexico. We included BC cases with tumor molecular classification in their medical records (n = 509), and classified them as HR+/HER2- (ER+ and/or PR+ and HER2-) (n = 289), HER2+ (HR+ or HR-) (n = 117) or triple negative (TN) (n = 103). We matched controls (n = 1030) by age and place of residence with index cases. Women were interviewed about their reproductive history, from which the EEI was developed. We used logistic regression models to estimate BC molecular subtypes associations with reproductive characteristics and EEI.

RESULTS

The EEI was higher in all subtypes compared to controls (Median HR+/HER2- 27.25, HER2+ 26.8, TN 24.2 vs. controls 22.8 years, p < 0.05), and was associated with HR+/HER2- (OR_T3 vs. T1 = 2.58, 95% CI 1.77-3.55, p-trend < 0.001) and HER2+ (OR_T3 vs. T1 = 4.17, 95% CI 2.15-8.08, p-trend < 0.001) BC. Additionally, HR+/HER2- tumors were positively associated with age at first pregnancy and age at menopause, and negatively with age at menarche, parity and breastfeeding. The HER2+ subtype was associated in the same direction as HR+/HER2- tumors with all the reproductive characteristics except for age at menarche. TN tumors were negatively associated with parity and breastfeeding.

CONCLUSION

Endogenous estrogens exposure throughout Mexican women reproductive life may contribute to the development of all but TN BC, however, these findings should be confirmed in other Hispanic populations.

Risk of breast cancer and adipose tissue concentrations of polychlorinated biphenyls and organochlorine pesticides: a hospital-based case-control study in Chinese women

Polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), and dichlorodiphenyldichloroethylene (DDE) are suspected to be associated with breast cancer risk, but the results are controversial. This study was performed to evaluate the associations between adipose tissue PCB, DDT, and DDE concentrations and breast cancer risk. Two hundred and nine pathologically diagnosed breast cancer cases and 165 controls were recruited from three local hospitals in Shantou city, China, from 2014 to 2016. Concentrations of 7 PCB congeners, p,p'-DDT, and p,p'-DDE were measured in adipose tissues obtained from the breast for cases and the breast/abdomen for controls during surgery. Clinicopathologic information and demographic characteristics were collected from medical records. PCBs, p,p'-DDT, and p,p'-DDE concentrations in adipose tissues were compared between cases and controls. Multivariate logistic regression model was used to analyze the risk of breast cancer by PCBs, p,p'-DDT, and p,p'-DDE concentrations in adipose tissues. Breast cancer cases have relatively higher menarche age, higher breastfeeding and postmenopausal proportion than controls. Levels of PCB-52, PCB-101, PCB-118, PCB-138, PCB-153, PCB-180, total PCBs (∑PCBs), and p,p'-DDE were relatively higher in breast cancer cases than controls. Breast cancer risk was increased in the third tertile of PCB-101, PCB-118, PCB-138, PCB-153, PCB-180, ∑PCBs, and p,p'-DDE as compared with the first tertile in both adjusted and unadjusted logistic regression models (odds ratios [ORs] were from 1.58 to 7.88); and increased linearly across categories of PCB-118 and p,p'-DDE in unadjusted model, and PCB-118 and PCB-153 in the adjusted model with trend (all P < 0.01). While breast cancer risk was declined in the second tertile of PCB-28, PCB-52, and PCB-101 in both unadjusted and adjusted models, also second tertile of p,p'-DDT and third tertile of PCB-28 in the adjusted models. This study suggests associations between the exposure of PCBs, p,p'-DDT, and p,p'-DDE and breast cancer risk. Based on adjusted models, PCB-118, PCB-138, PCB-153, PCB-180, ∑PCBs, and p,p'-DDE exposures increase breast cancer risk at current exposure levels, despite existing inconsistent even inverse results in PCB-28, PCB-52, PCB-101, and p,p'-DDT. More epidemiological studies are still needed to verify these findings in different populations.

Clinical and epidemiologic factors associated with breast cancer and its subtypes among Northeast Chinese women

The incidence of breast cancer has increased dramatically in China. We evaluated the clinical and epidemiologic factors associated with breast cancer, and its stage in a case‐control study of Northeast Chinese women. We also examined whether these factors were differentially distributed among molecular subtypes of breast cancer in a case‐only analysis. We identified 1118 breast cancer patients and 2284 healthy women from Cancer Hospital of Medical University between January 2014 and December 2017. Logistic regression models were used to calculate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs). We found that postmenopausal women had a decreased risk of breast cancer (multivariate‐adjusted OR = 0.33, 95% CI:0.25‐0.43), and tended to have breast cancer of human epidermal growth factor receptor 2 (HER2)‐overexpressing (multivariate‐adjusted OR = 2.99, 95% CI: 1.49‐5.97) and triple‐negative (multivariate‐adjusted OR = 2.16, 95% CI: 1.02‐4.56) subtypes, compared with the luminal B subtype. Women with history of abortion had an increased risk of breast cancer (multivariate‐adjusted OR = 4.70, 95% CI: 3.60‐6.14). Women with high breast density and high Breast Imaging Reporting and Data System (BIRADS) scores of lesions tended to have breast cancer of advanced stage, but were not differentially distributed among its molecular subtypes. In conclusion, postmenopausal women had decreased risk of breast cancer, and tended to have nonluminal subtype, while women with history of abortion had increased risk of breast cancer. Women with high breast density and BIRADS scores of lesions tended to have advanced stage breast cancer. We provide evidence on the epidemiologic factors for breast cancer and its subtypes, which may help with breast cancer risk stratification.

Biological, Behavioral and Physiological Consequences of Drug-Induced Pregnancy Termination at First-Trimester Human Equivalent in an Animal Model

Given the significant physiological changes that take place during and resulting from pregnancy, as well as the relative absence of such information in relation to pregnancy termination, this study investigated the potential for developing a valid animal model to objectively assess the biological, physiological and behavioral consequences of drug-induced pregnancy termination. Female Long-Evans rats were divided into four groups (n = 19-21/group), controlling for drug [mifepristone (50 mg/kg/3 ml, i.g.)/misoprostol (0.3 mg/kg/ml, i.g.) or vehicle (1% Carboxymethylcellulose Sodium/0.2% Tween® 80 suspension, i.g.)] and pregnancy. Drug administration took place on days 12-14 of gestation (days 28-40 human gestational equivalent). Vehicle was administered to the controls on the same days. Parameters measured included rat body weight, food intake, vaginal impedance, sucrose consumption/preference, locomotor activity, forced swim test, and home-cage activity. At the termination of the study, rats were deeply anesthetized using urethane, and blood, brain, and liver were collected for biochemical analysis. Following drug/vehicle administration, only the pregnancy termination group (pregnant, drug) displayed a significant decrease in body weight, food intake, locomotor activity-related behaviors and home-cage activity relative to the control group (non-pregnant, vehicle). Additionally, the pregnancy termination group was the only group that displayed a significant reduction in sucrose consumption/preference during Treatment Week relative to Pre-Treatment Week. Vaginal impedance did not significantly decrease over time in parous rats in contrast to all other groups, including the rats in the pregnancy termination group. Biochemical analysis indicated putative drug- and pregnancy-specific influences on oxidative balance. Regression analysis indicated that pregnancy termination was a predictor variable for body weight, food intake and all locomotor activity parameters measured. Moreover, pertaining to body weight and food intake, the pregnancy termination group displayed significant changes, which were not present in a group of naturally miscarrying rats following pregnancy loss. Overall, our results appear to suggest negative biological and behavioral effects following pregnancy termination, that appear to also be distinct from natural miscarriage, and potential benefits of parity pertaining to fecundity. Thus, our findings indicate the importance for further objective investigation of the physiological and behavioral consequences of medical abortion, in order to provide further insight into the potential implications in humans.

[Influence of hormonal factors on triple-negative breast cancer prognosis]

OBJECTIVES

Triples negative breast cancer defined by the absence of expression of the hormone receptors and HER2 protein, are considered as aggressive tumours with bad outcome in comparison to the hormone sensitive tumours. The aim of the study was to evaluate the link between hormone factors and prognostic factors of triple-negative tumours.

METHODS

All patients managed for a triple-negative breast cancer between January, 2009 and December, 2013 were included. For every patient, collected data were the clinical, histological, adjuvant or neoadjuvant treatments, as well as survival data.

RESULTS AND CONCLUSION

During the study period, 1682 patients were operated for a breast cancer, among which 1444 presented at least an invasive tumour. One hundred and fifty-five women (10.7%) had a negative triple tumour. The average age of diagnosis was 56.4years, is significantly younger than for patients with other types of tumours, P=0.0001. For women with a triple-negative tumour, the parity was the only hormonal factor identified as an independent factor for axillary lymph node involvement (OR=1.53; 95% CI [1.10-2.25] P=0.02) and previous hormone replacement therapy as an independent factor of locoregional recurrence (OR=0.13 [0.005-0.64] P=0.001). We did not find any hormonal factor predictive of distant metastasis. We did not find any difference in overall survival according to the parity (P=0.72), the Body mass index (P=0.62) or the use of HRT (P=0.49).

CONCLUSION

Hormone factors seem to have a prognostic implication for triple-negative despite the absence of hormone receptors expression.

Adipose tissue levels of polybrominated diphenyl ethers and breast cancer risk in Chinese women: A case-control study

Polybrominated diphenyl ethers (PBDEs) are suspected to be associated with breast cancer risk because of their estrogenic potencies. Epidemiological studies of PBDEs and breast cancer are scarce. Our study aimed to estimate the association between adipose-tissue PBDE concentrations and breast cancer risk. A total of 209 breast cancer cases and 165 controls were recruited from hospitals between January 2014 and May 2016 in Shantou, Chaoshan area, China. Concentrations of 14 PBDE congeners were measured in adipose tissues obtained from the breast for cases and the abdomen/breast for controls during surgery. Demographic and clinicopathologic characteristics were obtained from medical records. Breast cancer risk as well as clinicopathologic characteristics were evaluated by adipose-tissue PBDE level. Odds ratios (ORs) and 95% confidence intervals (95% CIs) for breast cancer risk associated with levels of PBDE congeners were estimated from logistic regression models for all cases and stratified by estrogen receptor (ER) status. Level of total PBDEs (∑PBDE) and most individual PBDE congeners were higher in breast cancer cases than controls (median ∑PBDE, 94.99 vs 73.72 ng/g lipid). In the adjusted univariate model for all cases, breast cancer risk was increased with both 2nd and 3rd tertiles versus the 1st tertile of BDE-47 level (OR 2.05 [95% CI 1.08-3.92]; 5.47 [2.96-10.11]) and BDE-209 level (2.48 [1.30-4.73]; 4.72 [2.52-8.83]) with trend (both P < 0.001) and with the 3rd tertile of BDE-28 level (2.83 [1.63-4.92]), BDE-99 (3.22 [1.85-5.60]), BDE-100 (5.45 [2.90-10.23]), BDE-138 (2.40 [1.37-4.20]), BDE-153 (1.74 [1.02-2.97]), BDE-154 (1.84 [1.05-3.22]), and ∑PBDE levels (1.83 [1.07-3.14]) but decreased with the 3rd tertile of BDE-71 level (0.38 [0.22-0.65]) with trend (all P < 0.01). After stratifying by ER-positive or -negative status, the adjusted results were similar for ER-positive patients except for BDE-153 and BDE-154, with no statistical significance. In the multivariate model for all cases, age, menarche age, BDE-47, 71, 99, 100, 183 and 209 were independent factors associated with breast-cancer risk. ∑PBDE and most individual PBDE congeners investigated were positively associated with breast cancer risk in women from the Chaoshan area, China. PBDE may play a role in the occurrence and development of breast cancer.

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

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

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

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

Induced abortion and breast cancer: An updated meta-analysis

Different epidemiological studies have indicated conflicting information about the association of induced abortion (IA) with breast cancer risk. A recent meta-analysis with prospective evidences did not support the positive association between IA and breast cancer risk. Thus, we in our meta-analysis study have tried to analyze this specific association.We searched all relevant articles from an English-language literature using Pubmed, Embase, and Cochrane databases, until December 10, 2016. All the statistical analyses were performed on case-control studies, using Review Manager Software 5.3 (Cochrane Collaboration, Oxford, UK).Our meta-analysis results based on 25 studies, including 5 studies with Chinese patients, indicated that there was no association of IA with breast cancer (OR = 1.08, 95% CI 0.98-1.19, P = .1). However, significant heterogeneity was observed, and thus further subgroup analyses were conducted. The combined OR of subjects with only 1-time IA was 1.03, 95% CI 0.90 to 1.18, P = .63, while for subjects with 2 or more IAs, it was 1.06, 95% CI 0.86 to 1.30, P = .58. In addition, the ORs of subjects, with 1st IA age either less than 30 or older than 30, were 1.05, 95% CI 0.88 to 1.26, P = .59, and 1.18, 95% CI 0.93 to 1.49, P = .17, respectively. These observations indicated that number of IAs and the age of 1st IA were not associated with breast cancer risk. Due to lack of dose-response relationships, it is difficult to say if number of IAs contributed into statistical heterogeneity. But after subgroup analysis, the age at the 1st IA appeared to impact the statistical heterogeneity. The different reproductive history appears to account for the high heterogeneity among individual studies. Also analysis of nulliparous women showed no significant difference in the association of IA and breast cancer (OR = 1.02, 95% CI 0.86-1.21, P = .85). However, parous women had higher IA rate in case group than control group (OR = 1.11, 95% CI 1.02-1.20, P = .01). Ethnicities might also result in high heterogeneity; thus, we conducted subgroup analyses on Chinese subjects, importantly, with 5 studies having Chinese patients, and did not observe any difference in the incidence of IA and its association with breast cancer between case and control groups (OR = 1.05, 95% CI 0.97-1.13, P = .21).After subgroup analysis, our study showed that IA might increase the risk of breast cancer in parous women, but in the nulliparous, IA was not significantly associated with an increased risk of breast cancer.

Triple negative breast cancer in Asia: An insider's view

While tremendous improvement has been made for the treatment of breast cancers, the treatment of triple negative breast cancer (TNBC) still remains a challenge due to its aggressive characteristics and limited treatment options. Most of the studies on TNBC were conducted in Western population and TNBC is reported to be more frequent in the African women. This review encapsulates the studies conducted on TNBC patients in Asian population and elucidates the similarities and differences between these two regions. The current treatment of TNBC includes surgery, radiotherapy and chemotherapy. In addition to the current chemotherapies, which mainly include cytotoxic agents, such as taxanes and anthracyclines, many clinical trials are investigating the potential use of other chemotherapy drugs, targeted therapeutics and combinational therapies to treat TNBC. Moreover, this review also integrates the studies involving novel markers, which will help us to dissect the pathologic process of TNBC and in turn facilitate the development of better treatment strategies to combat TNBC.

A case-control study on risk factors of breast cancer in Han Chinese women

This study aimed to investigate risk factors associated with breast cancer among Han Chinese women in northern and eastern China. A matched case-control study involving 1489 patients with breast cancer and 1489 controls was conducted across 21 hospitals in 11 provinces in China, from April 2012 to April 2013. We developed a structured questionnaire to record information from face-to-face interviews with participants. Student's t-tests, Pearson's chi-square tests, and univariate and multivariate conditional logistic regression analyses were used to identify variables with significant differences between the case and control groups. Ten variables were identified (P<0.05): location, economic status, waist-to-hip ratio, menopause, family history of breast cancer, present life satisfaction, sleep satisfaction, milk products, behavior prevention scores, and awareness of breast cancer. We identified a comprehensive range of factors related to breast cancer, among which several manageable factors may contribute to breast cancer prevention. Further prospective studies concerning psychological interventions, sleep regulation, health guidance, and physical exercise are required. A screening model for high-risk populations should be put on the agenda.

Differential Association of the Lifestyle-Related Risk Factors Smoking and Obesity with Triple Negative Breast Cancer in a Brazilian Population

Background: A longer lifespan and changing lifestyle-related and reproductive risk factors have led to an increased incidence of breast cancer in Brazil. There have been few studies about associations of specific risk factors with molecular subtypes of the disease. The aim of the present study was to identify factors that modulate the risk of triple negative breast cancer. Materials and Methods: A case-case analysis was performed. Data for 236 breast cancer patients from two reference centres in North-eastern Brazil were applied to assess the association of risk factors with triple negative breast cancer relative to the luminal A subtype. Molecular subtypes were defined by expression status of hormone receptors and amplification of HER2. Nominal logistic regression was used to estimate odds ratios and to generate a model of independent variables. Results: Smoking and body mass index were differentially associated with likelihood of triple negative breast cancer compared to the Luminal A subtype (p= 0.013; p= 0.004): Women who ever smoked some time in their lives were 4.016 (OR= 0.249; CI 95%: 0.09- 0.71) times less likely to have triple negative breast cancer. Obese and overweight patients, respectively, were 4.489 (CI 95%: 1.32- 15.28) and 1.340 (CI 95%: 0.38- 4.69) times more likely to have triple negative breast cancer. Conclusions: Case-case analysis with the Luminal A subtype as the reference group indicated that smoking and body mass index are differentially associated with risk of triple negative breast cancer.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Parity, hormones and breast cancer subtypes - results from a large nested case-control study in a national screening program

Background

Breast cancer comprises several molecular subtypes with different prognoses and possibly different etiology. Reproductive and hormonal factors are associated with breast cancer overall, and with luminal subtypes, but the associations with other subtypes are unclear. We used data from a national screening program to conduct a large nested case-control study.

Methods

We conducted a nested case-control study on participants in the Norwegian Breast Cancer Screening Program in 2006 − 2014. There was information on estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) for 4748 cases of breast cancer. Breast cancer subtypes were defined as luminal A-like (ER+ PR+ HER2-), luminal B-like (ER+ PR- HER2- or ER+ PR+/PR-HER2+), HER2-positive (ER- PR- HER2+) and triple-negative (ER- PR- HER2-). Conditional logistic regression was used to estimate odds ratios (ORs) of breast cancer associated with age at first birth, number of pregnancies, oral contraceptive use, intrauterine devices and menopausal hormone therapy. Analyses were adjusted for age, body mass index, education, age at menarche, number of pregnancies and menopausal status.

Results

Number of pregnancies was inversely associated with relative risk of luminal-like breast cancers (p-trend ≤0.02), and although not statistically significant, with HER2-positive (OR = 0.60, 95% CI 0.31–1.19) and triple-negative cancer (OR = 0.70, 95% CI 0.41–1.21). Women who had ≥4 pregnancies were at >40% lower risk of luminal-like and HER2-positive cancers than women who had never been pregnant. However, there was a larger discrepancy between tumor subtypes with menopausal hormone use. Women who used estrogen and progesterone therapy (EPT) had almost threefold increased risk of luminal A-like cancer (OR = 2.92, 95% CI 2.36–3.62) compared to never-users, but were not at elevated risk of HER2-positive (OR = 0.88, 95% CI 0.33–2.30) or triple-negative (OR = 0.92, 95% CI 0.43 − 1.98) subtypes.

Conclusions

Reproductive factors were to some extent associated with all subtypes; the strongest trends were with luminal-like subtypes. Hormone therapy use was strongly associated with risk of luminal-like breast cancer, and less so with risk of HER2-positive or triple-negative cancer. There are clearly some, but possibly limited, etiologic differences between subtypes, with the greatest contrast between luminal A-like and triple-negative subtypes.

Trial registration

Not applicable.

Reproductive factors and the risk of triple-negative breast cancer in white women and African-American women: a pooled analysis

BACKGROUND

Early age at menarche, nulliparity, late age at first completed pregnancy, and never having breastfed, are established breast cancer risk factors. However, among breast cancer subtypes, it remains unclear whether all of these are risk factors for triple-negative breast cancer (TNBC).

METHODS

We evaluated the associations of these reproductive factors with TNBC, in 2658 patients with breast cancer (including 554 with TNBC) and 2448 controls aged 20-64 years, who participated in one of the three population-based case-control studies: the Women's Contraceptive and Reproductive Experiences Study, the Women's Breast Carcinoma in situ Study, or the Women's Learning the Influence of Family and Environment Study. We used multivariable polychotomous unconditional logistic regression methods to conduct case-control comparisons among breast cancer subtypes defined by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 expression status.

RESULTS

TNBC risk decreased with increasing duration of breastfeeding (P trend = 0.006), but age at menarche, age at first completed pregnancy, and nulliparity were not associated with risk of TNBC. Parous women who breastfed for at least one year had a 31% lower risk of TNBC than parous women who had never breastfed (odds ratio, OR = 0.69; 95% confidence interval, CI = 0.50-0.96). The association between breastfeeding and risk of TNBC was modified by age and race. Parous African-American women aged 20-44 years who breastfed for 6 months or longer had an 82% lower risk of TNBC than their counterparts who had never breastfed (OR = 0.18, 95% CI = 0.07-0.46).

CONCLUSIONS

Our data indicate that breastfeeding decreases the risk of TNBC, especially for younger African-American women.

BMI, reproductive factors, and breast cancer molecular subtypes: A case-control study and meta-analysis

Background

The effects of body mass index (BMI) and reproductive factors may vary among breast cancer molecular subtypes, evidence of which is lacking in East Asia.

Methods

From 2002 to 2010, 1256 breast cancer patients and 1416 healthy women were recruited. Anthropometric and reproductive factors were collected from medical charts. Breast cancer subtype was defined by ER, PR, and HER2 status. Polytomous logistic regression was used to evaluate associations between risk factors and breast cancer subtypes, with subgroup analysis by menopausal status. A meta-analysis of relevant published studies in East Asia was also performed.

Results

In our case-control study, late menarche was negatively associated with luminal tumor risk (P_trend = 0.03). Higher BMI was associated with risk of both luminal and triple-negative tumors (P_trend<0.001). Late age at first live birth was associated with a 1.41- to 2.08-fold increased risk of all subtypes, while late menopause increased risk by 2.62–5.56 times. Heterogeneity of these associations was not detected for different menopausal statuses. The meta-analysis revealed a positive dose-response relationship between BMI and risk of both luminal and ER-PR- subtypes (P_trend<0.05). Early menarche and nulliparity increased luminal tumor risk by 1.39 and 1.26 times, respectively. Non-breastfeeding also increased the risk of all subtypes.

Conclusions

For East Asian women, overweight, late menopause, and lack of breastfeeding appear to increase risk of both luminal and ER−PR− tumors. Early menarche and nulliparity mainly impacted luminal tumor risk. These associations were not impacted by menopausal status.

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For East Asian women, overweight increases risk of both luminal and ER-PR- tumors.

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For East Asian women, early menarche increases luminal tumor risk.

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For East Asian women, nulliparity increases luminal tumor risk.

Reproductive behaviors and risk of developing breast cancer according to tumor subtype: A systematic review and meta-analysis of epidemiological studies

BACKGROUND

Breast cancer is composed of distinct subtypes defined mainly based on the expression of hormone receptors (HR) and HER2. For years, reproductive factors were shown to impact breast cancer risk but it is unclear whether this differs according to tumor subtype. In this meta-analysis we evaluated the association between parity, age at first birth, breastfeeding and the risk of developing breast cancer according to tumor subtype.

METHODS

PubMed and Embase were searched to identify epidemiological studies that evaluated the impact of parity and/or age at first birth and/or breastfeeding on breast cancer risk with available information on HR and HER2. Tumor subtypes were defined as: luminal (HR-positive, HER2-negative or HER2-positive), HER2 (HR-negative, HER2-positive) and triple-negative (HR-negative, HER2-negative). Summary risk estimates (pooled OR [pOR]) and 95% confidence intervals (CI) were calculated using random effects models. The MOOSE guidelines were applied.

RESULTS

This meta-analysis evaluated 15 studies, including 21,941 breast cancer patients and 864,177 controls. Parity was associated with a 25% reduced risk of developing luminal subtype (pOR 0.75; 95% CI, 0.70-0.81; p<0.0001). Advanced age at first birth was associated with an increased risk of developing luminal subtype (pOR 1.15; 95% CI, 1.00-1.32; p=0.05). Ever breastfeeding was associated with a reduced risk of developing both luminal (pOR 0.77; 95% CI, 0.66-0.88; p=0.003) and triple-negative (pOR 0.79, 95% CI, 0.66-0.94; p=0.01) subtypes.

CONCLUSIONS

The reproductive behaviors impact the risk of developing breast cancer but this varies according to subtype.

Correlational study on mitochondrial DNA mutations as potential risk factors in breast cancer

The presented study performed an mtDNA genome-wide association analysis to screen the peripheral blood of breast cancer patients for high-risk germline mutations. Unlike previous studies, which have used breast tissue in analyzing somatic mutations, we looked for germline mutations in our study, since they are better predictors of breast cancer in high-risk groups, facilitate early, non-invasive diagnoses of breast cancer and may provide a broader spectrum of therapeutic options. The data comprised 22 samples of healthy group and 83 samples from breast cancer patients. The sequencing data showed 170 mtDNA mutations in the healthy group and 393 mtDNA mutations in the disease group. Of these, 283 mtDNA mutations (88 in the healthy group and 232 in the disease group) had never been reported in the literature. Moreover, correlation analysis indicated there was a significant difference in 32 mtDNA mutations. According to our relative risk analysis of these 32 mtDNA mutations, 27 of the total had odds ratio values (ORs) of less than 1, meaning that these mutations have a potentially protective role to play in breast cancer. The remaining 5 mtDNA mutations, RNR2-2463 indelA, COX1-6296 C>A, COX1-6298 indelT, ATP6-8860 A>G, and ND5-13327 indelA, whose ORs were 8.050, 4.464, 4.464, 5.254 and 4.853, respectively, were regarded as risk factors of increased breast cancer. The five mutations identified here may serve as novel indicators of breast cancer and may have future therapeutic applications. In addition, the use of peripheral blood samples was procedurally simple and could be applied as a non-invasive diagnostic technique.

Breastfeeding and maternal health outcomes: a systematic review and meta-analysis

AIM

To evaluate the effect of breastfeeding on long-term (breast carcinoma, ovarian carcinoma, osteoporosis and type 2 diabetes mellitus) and short-term (lactational amenorrhoea, postpartum depression, postpartum weight change) maternal health outcomes.

METHODS

A systematic literature search was conducted in PubMed, Cochrane Library and CABI databases. Outcome estimates of odds ratios or relative risks or standardised mean differences were pooled. In cases of heterogeneity, subgroup analysis and meta-regression were explored.

RESULTS

Breastfeeding >12 months was associated with reduced risk of breast and ovarian carcinoma by 26% and 37%, respectively. No conclusive evidence of an association between breastfeeding and bone mineral density was found. Breastfeeding was associated with 32% lower risk of type 2 diabetes. Exclusive breastfeeding and predominant breastfeeding were associated with longer duration of amenorrhoea. Shorter duration of breastfeeding was associated with higher risk of postpartum depression. Evidence suggesting an association of breastfeeding with postpartum weight change was lacking.

CONCLUSION

This review supports the hypothesis that breastfeeding is protective against breast and ovarian carcinoma, and exclusive breastfeeding and predominant breastfeeding increase the duration of lactational amenorrhoea. There is evidence that breastfeeding reduces the risk of type 2 diabetes. However, an association between breastfeeding and bone mineral density or maternal depression or postpartum weight change was not evident.

Breastfeeding and breast cancer risk by receptor status--a systematic review and meta-analysis

BACKGROUND

Breastfeeding is inversely associated with overall risk of breast cancer. This association may differ in breast cancer subtypes defined by receptor status, as they may reflect different mechanisms of carcinogenesis. We conducted a systematic review and meta-analysis of case-control and prospective cohort studies to investigate the association between breastfeeding and breast cancer by estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status.

DESIGN

We searched the PubMed and Scopus databases and bibliographies of pertinent articles to identify relevant articles and used random-effects models to calculate summary odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

This meta-analysis represents 27 distinct studies (8 cohort and 19 case-control), with a total of 36 881 breast cancer cases. Among parous women, the risk estimates for the association between ever (versus never) breastfeeding and the breast cancers negative for both ER and PR were similar in three cohort and three case-control studies when results were adjusted for several factors, including the number of full-term pregnancies (combined OR 0.90; 95% CI 0.82-0.99), with little heterogeneity and no indication of publication bias. In a subset of three adjusted studies that included ER, PR, and HER2 status, ever breastfeeding showed a stronger inverse association with triple-negative breast cancer (OR 0.78; 95% CI 0.66-0.91) among parous women. Overall, cohort studies showed no significant association between breastfeeding and ER+/PR+ or ER+ and/or PR+ breast cancers, although one and two studies (out of four and seven studies, respectively) showed an inverse association.

CONCLUSIONS

This meta-analysis showed a protective effect of ever breastfeeding against hormone receptor-negative breast cancers, which are more common in younger women and generally have a poorer prognosis than other subtypes of breast cancer. The association between breastfeeding and receptor-positive breast cancers needs more investigation.

The characteristics of breast cancer subtypes: implications for treatment guidelines and individualized treatment strategies in China

This study aimed at investigating the characteristics of invasive breast cancer among molecular subtypes. Patients with invasive breast cancer, with complete information on the expressions of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 (HER2), were recruited. χ tests and an unconditional logistic regression model were used for statistical analysis. The percentages of luminal A, luminal B, HER2/neu, and triple-negative subtypes were 54.2% (1639/3021), 14.0% (422/3021), 8.9% (269/3021), and 22.9% (691/3021), respectively. Differences among molecular subtypes (P<0.05) in tumor size, stage, pathologic type, and lymph node status were observed. The HER2/neu, luminal B, and triple-negative subtypes were more aggressive compared with the luminal A subtype in tumor stage, lymph node status, or pathologic type (P<0.05), when the findings were adjusted for age. Molecular subtypes were distributed differently between both age groups and regional groups on the basis of the socioeconomic status (P<0.05). In conclusion, luminal A and triple-negative subtypes were the 2 main subtypes of invasive breast cancer in China. The variations of molecular subtypes in pathology, age, and regional distribution may give some suggestions for updating treatment guidelines and individualized treatment strategies in China.

Prevalence of papillomaviruses, polyomaviruses, and herpesviruses in triple-negative and inflammatory breast tumors from algeria compared with other types of breast cancer tumors

BACKGROUND

The possible role of viruses in breast cancer etiology remains an unresolved question. We hypothesized that if some viruses are involved, it may be in a subgroup of breast cancers only. Epidemiological arguments drove our interest in breast cancer subgroups that are more frequent in Africa, namely inflammatory breast cancer (IBC) and triple-negative breast cancer. We tested whether viral prevalence was significantly higher in these subgroups.

MATERIALS AND METHODS

One hundred fifty-five paraffin-embedded malignant breast tumors were randomly selected at the pathology laboratory of the University Hospital of Annaba (Algeria) to include one third of IBC and two thirds of non-IBC. They were tested for the presence of DNA from 61 viral agents (46 human papillomaviruses, 10 polyomaviruses, and 5 herpesviruses) using type-specific multiplex genotyping assays, which combine multiplex PCR and bead-based Luminex technology.

RESULTS

Viral DNA was found in 22 (17.9%) of 123 tumors. The most prevalent viruses were EBV1 and HPV16. IBC tumors carried significantly more viruses (any type) than non-IBC tumors (30% vs. 13%, p<0.04). Similarly, triple-negative tumors displayed higher virus-positivity than non-triple-negative tumors (44% vs. 14%, p<0.009).

CONCLUSIONS

Our results suggest an association between the presence of viral DNA and aggressive breast cancer phenotypes (IBC, triple-negative). While preliminary, they underline the importance of focusing on subgroups when studying viral etiology in breast cancer. Further studies on viruses in breast cancer should be conducted in much larger samples to confirm these initial findings.

Modern reproductive patterns associated with estrogen receptor positive but not negative breast cancer susceptibility

It has long been accepted that modern reproductive patterns are likely contributors to breast cancer susceptibility because of their influence on hormones such as estrogen and the importance of these hormones in breast cancer. We conducted a meta-analysis to assess whether this ‘evolutionary mismatch hypothesis’ can explain susceptibility to both estrogen receptor positive (ER-positive) and estrogen receptor negative (ER-negative) cancer. Our meta-analysis includes a total of 33 studies and examines parity, age of first birth and age of menarche broken down by estrogen receptor status. We found that modern reproductive patterns are more closely linked to ER-positive than ER-negative breast cancer. Thus, the evolutionary mismatch hypothesis for breast cancer can account for ER-positive breast cancer susceptibility but not ER-negative breast cancer.

Effects of interval between age at first pregnancy and age at diagnosis on breast cancer survival according to menopausal status: a register-based study in Korea

Background

The influence of parity and time interval between age at first pregnancy (AFP) and age at diagnosis on breast cancer survival is not established in the same way as their influence on breast cancer risk. We aimed to investigate the association of time interval or parity with prognosis in pre- and postmenopausal women in Korea.

Methods

We conducted a retrospective study of 29,167 women with breast cancer through the Korean Breast Cancer Registry from 1993–2009. Information on reproductive factors, including breastfeeding, AFP, and parity were collected from a routine questionnaire. Conditional logistic regression was used to estimate the associations between menopausal status and overall mortality (OM) and breast-cancer-specific mortality (BCSM), adjusting for treatment and stage.

Results

High parity (≥5) increased the hazard ratios (HR) of BCSM (HR = 1.33, 95% confidence interval (CI): 0.83–2.11, p < 0.001) and OM (HR = 1.20, 95% CI: 0.85–1.68.73, p < 0.001) in premenopausal and postmenopausal women (BCSM, HR: 1.62, 95% CI: 0.93–2.82, p < 0.001; OM, HR = 1.58, 95% CI: 1.14–2.21, p <0.001). A longer time interval between age at breast cancer diagnosis and AFP reduced the HRs of BCSM (HR = 0.97, 95% CI: 0.96–0.98, p = 0.001) and OM (HR = 0.98, 95% CI: 0.97–0.98, p < 0.001) in premenopausal women, but had an adverse effect on the HR of OM (HR = 1.03, 95% CI: 1.02–1.03, p < 0.001) in postmenopausal women.

Conclusions

High parity (≥5) was associated with poor breast cancer prognosis in both pre- and postmenopausal women. The time intervals between reproductive events had different effects on breast cancer outcomes depending on menopausal status.

Electronic supplementary material

The online version of this article (doi:10.1186/1472-6874-14-113) contains supplementary material, which is available to authorized users.

The breast cancer epidemic: 10 facts

Breast cancer, affecting one in eight American women, is a modern epidemic. The increasing frequency of breast cancer is widely recognized. However, the wealth of compelling epidemiological data on its prevention is generally not available, and as a consequence, is largely unknown to the public. The purpose of this report is to review the epidemiological evidence of preventable causes of breast cancer. [Table: see text].

Features of breast cancer in developing countries, examples from North-Africa

Epidemiological features of breast cancer appear to be different in developing countries compared to Western countries, with notably large proportions of young patients, male patients and aggressive forms of the disease. Using North-Africa (Morocco, Algeria, Tunisia, Libya and Egypt) as an example, we document the magnitude and explore possible explanations for such patterns. Articles and reports published since the seventies were reviewed. Results show that breast cancer incidence in females is 2-4 times lower in North-Africa than in Western countries while incidence in males is similar. Consequently, the relative proportion of male breast cancer is high (≈2% of all breast cancers). Similarly, the incidence of aggressive forms of the disease, like inflammatory or triple negative breast cancer (in females), is not higher in North Africa than in Western countries, but their relative proportion in case series (up to 10% for inflammatory and 15-25% for triple negative) is significantly higher because of low incidence of other forms of the disease. In North Africa, the incidence among women aged 15-49 is lower than in Western countries, but the very low incidence among women aged more than 50, combined to the young age pyramid of North-Africa, makes the relative proportions of young patients substantially higher (50-60% versus 20% in France). Such epidemiological features result mainly from peculiar risk factor profiles, which are typical for many developing countries and include notably rapid changes in reproductive behaviours. These features have important implications for breast cancer control and treatment.

Reproductive risk factors and oestrogen/progesterone receptor-negative breast cancer in the Breast Cancer Family Registry

BACKGROUND

Oestrogen receptor (ER)- and progesterone receptor (PR)-negative (ER-PR-) breast cancer is associated with poorer prognosis compared with other breast cancer subtypes. High parity has been associated with an increased risk of ER-PR- cancer, but emerging evidence suggests that breastfeeding may reduce this risk. Whether this potential breastfeeding benefit extends to women at high risk of breast cancer remains critical to understand for prevention.

METHODS

Using population-based ascertained cases (n=4011) and controls (2997) from the Breast Cancer Family Registry, we examined reproductive risk factors in relation to ER and PR status.

RESULTS

High parity (≥3 live births) without breastfeeding was positively associated only with ER-PR- tumours (odds ratio (OR)=1.57, 95% confidence interval (CI), 1.10-2.24); there was no association with parity in women who breastfed (OR=0.93, 95% CI 0.71-1.22). Across all race/ethnicities, associations for ER-PR- cancer were higher among women who did not breastfeed than among women who did. Oral contraceptive (OC) use before 1975 was associated with an increased risk of ER-PR- cancer only (OR=1.32, 95% CI 1.04-1.67). For women who began OC use in 1975 or later there was no increased risk.

CONCLUSIONS

Our findings support that there are modifiable factors for ER-PR- breast cancer and that breastfeeding in particular may mitigate the increased risk of ER-PR- cancers seen from multiparity.

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

Aside from age, sex, and family history, risk of developing breast cancer is largely linked to reproductive factors, which characterize exposure to sex hormones. Given that, molecular testing at the tumor level is currently possible, clinical characterization of tumor subtypes is routinely conducted to guide treatment decisions. However, despite the vast amount of published data from observational studies on reproductive factor associations and breast cancer risk, relatively fewer reports have been published on associations specific to breast tumor subtypes. We conducted a review of the literature and summarized the results of associations between reproductive factors and risk or odds of three distinct tumor subtypes: estrogen receptor/progesterone receptor positive (hormone receptor positive, HR+ tumors), tumors overexpressing the human epidermal receptor 2 protein (HER2+), and triple negative breast cancer (TNBC), which lacks the three markers. Results show that the most consistent evidence for associations with reproductive risk factors exists for HR+ breast cancers, with nulliparity, current use of menopausal hormone therapy, and prolonged interval between menarche and age at first birth being the strongest risk factors; increased age at first birth and decreased age at menarche were fairly consistently associated with HR+ cancers; and though less consistent, older age at menopause was also positively associated, while lactation was inversely associated with HR+ tumors. Fewer consistent associations have been reported for TNBC. The single protective factor most consistently associated with TNBC was longer duration of breastfeeding. Increased parity, younger age at first birth, older age at menarche, and oral contraceptive use were less consistently shown to be associated with TNBC. No remarkable associations for HER2+ breast cancers were evident, although this was based on relatively scarce data. Findings suggest heterogeneity in reproductive risk factors for the distinct subtypes of breast tumors, which may have implications for recommended prevention strategies.