First pregnancy characteristics and subsequent breast cancer risk among young women

Status of breast cancer detection in young women and potential of liquid biopsy

Young onset breast cancer (YOBC) is an increasing demographic with unique biology, limited screening, and poor outcomes. Further, women with postpartum breast cancers (PPBCs), cancers occurring up to 10 years after childbirth, have worse outcomes than other young breast cancer patients matched for tumor stage and subtype. Early-stage detection of YOBC is critical for improving outcomes. However, most young women (under 45) do not meet current age guidelines for routine mammographic screening and are thus an underserved population. Other challenges to early detection in this population include reduced performance of standard of care mammography and reduced awareness. Women often face significant barriers in accessing health care during the postpartum period and disadvantaged communities face compounding barriers due to systemic health care inequities. Blood tests and liquid biopsies targeting early detection may provide an attractive option to help address these challenges. Test development in this area includes understanding of the unique biology involved in YOBC and in particular PPBCs that tend to be more aggressive and deadly. In this review, we will present the status of breast cancer screening and detection in young women, provide a summary of some unique biological features of YOBC, and discuss the potential for blood tests and liquid biopsy platforms to address current shortcomings in timely, equitable detection.

Hypertensive conditions of pregnancy, preterm birth, and premenopausal breast cancer risk: a premenopausal breast cancer collaborative group analysis

PURPOSE

Women with preeclampsia are more likely to deliver preterm. Reports of inverse associations between preeclampsia and breast cancer risk, and positive associations between preterm birth and breast cancer risk are difficult to reconcile. We investigated the co-occurrence of preeclampsia/gestational hypertension with preterm birth and breast cancer risk using data from the Premenopausal Breast Cancer Collaborative Group.

METHODS

Across 6 cohorts, 3096 premenopausal breast cancers were diagnosed among 184,866 parous women. We estimated multivariable hazard ratios (HR) and 95% confidence intervals (CI) for premenopausal breast cancer risk using Cox proportional hazards regression.

RESULTS

Overall, preterm birth was not associated (HR 1.02, 95% CI 0.92, 1.14), and preeclampsia was inversely associated (HR 0.86, 95% CI 0.76, 0.99), with premenopausal breast cancer risk. In stratified analyses using data from 3 cohorts, preterm birth associations with breast cancer risk were modified by hypertensive conditions in first pregnancies (P-interaction = 0.09). Preterm birth was positively associated with premenopausal breast cancer in strata of women with preeclampsia or gestational hypertension (HR 1.52, 95% CI: 1.06, 2.18), but not among women with normotensive pregnancy (HR = 1.09, 95% CI: 0.93, 1.28). When stratified by preterm birth, the inverse association with preeclampsia was more apparent, but not statistically different (P-interaction = 0.2), among women who did not deliver preterm (HR = 0.82, 95% CI 0.68, 1.00) than those who did (HR = 1.07, 95% CI 0.73, 1.56).

CONCLUSION

Findings support an overall inverse association of preeclampsia history with premenopausal breast cancer risk. Estimates for preterm birth and breast cancer may vary according to other conditions of pregnancy.

Mammary Glands of Women, Female Dogs and Female Rats: Similarities and Differences to Be Considered in Breast Cancer Research

Breast cancer is one of the most common and well-known types of cancer among women worldwide and is the most frequent neoplasm in intact female dogs. Female dogs are considered attractive models or studying spontaneous breast cancer, whereas female rats are currently the most widely used animal models for breast cancer research in the laboratory context. Both female dogs and female rats have contributed to the advancement of scientific knowledge in this field, and, in a "One Health" approach, they have allowed broad understanding of specific biopathological pathways, influence of environmental factors and screening/discovery of candidate therapies. This review aims to clearly showcase the similarities and differences among woman, female dog and female rat concerning to anatomical, physiological and histological features of the mammary gland and breast/mammary cancer epidemiology, in order to better portray breast tumorigenesis, and to ensure appropriate conclusions and extrapolation of results among species. We also discuss the major aspects that stand out in these species. The mammary glands of female dogs and women share structural similarities, especially with respect to the lactiferous ducts and lymphatic drainage. In contrast, female rats have only one lactiferous duct per nipple. A comprehensive comparison between humans and dogs is given a special focus, as these species share several aspects in terms of breast/mammary cancer epidemiology, such as age of onset, hormonal etiology, risk factors, and the clinical course of the disease. Holistically, it is clear that each species has advantages and limitations that researchers must consider during the development of experimental designs and data analysis.

The association between the multiple birth and breast cancer incidence: an update of a systematic review and meta-analysis from 1983 to 2022

BACKGROUND

It has been assumed that perinatal factors such as multiple pregnancies may affect subsequent breast cancer risk in the mother. Considering the inconsistencies in the results of case-control and cohort studies published in the world, this meta-analysis was conducted in order to determine the exact association between multiple pregnancies (twins or more) and the breast cancer incidence.

METHODS

This study was performed as a meta-analysis based on PRISMA guidelines by searching the international databases of PubMed (Medline), Scopus, and Web of Science as well as by screening selected articles based on their subject, abstract and full text. The search time was from January 1983 to November 2022. Then the NOS checklist was used to evaluate the quality of the final selected articles. The indicators considered for the meta-analysis included the odds ratio (OR) and the risk ratio (RR) along with the confidence interval reported in the selected primary studies. The desired analyzes were performed with STATA software version 17 to be reported.

RESULTS

In this meta-analysis, 19 studies were finally selected for analysis, which fully met the inclusion criteria. Of these, 11 were case-control studies and 8 were cohort ones. Their sample size was 263,956 women (48,696 with breast cancer and 215,260 healthy) and 1,658,378 (63,328 twin or multiple pregnancies and 1,595,050 singleton pregnancies), respectively. After combining the results of cohort and case-control studies, the effect of multiple pregnancies on the breast cancer incidence was equal to 1.01 (95% CI: 0.89-1.14; I2: 44.88%, P: 0.06) and 0.89 (95% CI: 0.83-0.95; I2: 41.73%, P: 0.07), respectively.

CONCLUSION

The present meta-analysis results showed, in general, multiple pregnancies were one of the preventive factors of breast cancer.

Gestational Hypertensive Disorders and Maternal Breast Cancer Risk in a Nationwide Cohort of 40,720 Parous Women

BACKGROUND

Preeclampsia and gestational hypertension are hypothesized to be associated with reduced maternal breast cancer risk, but the epidemiologic evidence is inconclusive. Our objective was to examine associations between gestational hypertensive disorders and breast cancer in a nationwide cohort of women with a family history of breast cancer.

METHODS

Women ages 35-74 years who had a sister previously diagnosed with breast cancer, but had never had breast cancer themselves, were enrolled in the Sister Study from 2003 to 2009 (N = 50,884). At enrollment, participants reported diagnoses of eclampsia, preeclampsia, or gestational hypertension in each pregnancy. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between history of a gestational hypertensive disorder and incident invasive breast cancer or ductal carcinoma in situ among 40,720 parous women. We used age as the time scale and adjusted for birth cohort, race-ethnicity, and reproductive, socioeconomic, and behavioral factors. We examined effect measure modification by risk factors for gestational hypertensive disease and breast cancer and assessed possible etiologic heterogeneity across tumor characteristics.

RESULTS

The prevalence of gestational hypertensive disease was 12%. During follow-up (mean = 10.9 years), 3,198 eligible women self-reported a breast cancer diagnosis. History of a gestational hypertensive disorder was not associated with breast cancer risk (HR = 1.0; 95% CI = 0.90, 1.1). We did not observe clear evidence of effect measure modification or etiologic heterogeneity.

CONCLUSIONS

History of a gestational hypertensive disorder was not associated with breast cancer risk in a cohort of women with a first-degree family history of breast cancer.

Hypertensive diseases of pregnancy and risk of breast cancer in the Black Women's Health Study

PURPOSE

Compared to white women, Black women have increased risk of developing hypertensive diseases of pregnancy (HDOP) and have a higher incidence of aggressive breast cancer subtypes. Few studies of HDOP and breast cancer risk have included large numbers of Black women. This study examined the relation of HDOP to incidence of breast cancer overall and by estrogen receptor (ER) status in Black women.

METHODS

We followed 42,982 parous women in the Black Women's Health Study, a nationwide prospective study of Black women. Multivariable Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) to assess associations of self-reported HDOP, including preeclampsia and gestational hypertension, with breast cancer incidence overall and by ER subtype, adjusted for age and established breast cancer risk factors.

RESULTS

Over 20 years of follow-up, we identified 2376 incident breast cancer cases. History of HDOP (11.7%) was not associated with breast cancer risk overall (HR 0.98; 95% CI 0.87, 1.11). HRs for invasive ER+ and ER- breast cancer were 1.11 (95% CI 0.93, 1.34) and 0.81 (95% CI 0.61, 1.07), respectively.

CONCLUSIONS

HDOP was not associated with risk of overall breast cancer in Black women. A suggestive inverse association with ER- breast cancer may reflect an anti-tumorigenic hormone profile in HDOP, but those results require confirmation in other studies.

Gestational diabetes and risk of breast cancer before age 55 years

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Transiently increased risk of breast cancer after childbirth: implications for fertility treatments and surrogacy

Whereas longstanding dogma has purported that pregnancies protect women from breast cancer, a recent meta-analysis now mandates reconsideration since it reported an actual higher breast cancer risk for more than two decades after childbirth before the relative risk turns negative. Moreover, the risk of breast cancer appears higher for women having their first birth at an older age and with a family history and it is not reduced by breastfeeding. The process of obtaining informed consent for all fertility treatments, therefore, must make patients aware of the facts that every pregnancy, to a small degree, will increase the short-term breast cancer risk. This observation may be even more relevant in cases of surrogacy where women agree to conceive without deriving benefits of offspring from assuming the risk, thus creating a substantially different risk-benefit ratio. Consequently, it appears prudent for professional societies in the field to update recommendations regarding consent information for all fertility treatments but especially for treatments involving surrogacy.

Hypertensive Disorders of Pregnancy (HDP) and the Risk of Common Cancers in Women: Evidence from the European Prospective Investigation into Cancer (EPIC)-Norfolk Prospective Population-Based Study

Simple Summary

One in ten pregnancies is complicated with high blood pressure. Whilst the association between high blood pressure during pregnancy and cardiovascular disease in later life is well-established, its association with cancer is less so. We aimed to determine the association between hypertensive disorders of pregnancy (HDP) and common cancers in a UK population-based longitudinal study. No statistically significant association was found between HDP and the odds of future cancer, and independent site-specific cancers of breast, colorectal, lung, ovarian and endometrial cancers in a UK-based general practice-derived population. Current research underlining HDP and cancer risk is limited to specific populations only. Future work in different populations is required, focusing on complex genetic and hormonal factors involved in these conditions.

Abstract

Purpose: The purpose was to determine the association between HDP and cancer in a UK cohort. Methods: Between 1993 and 1997, participants from the EPIC-Norfolk cohort attended baseline health-checks and completed questionnaires, where a history of HDP was collected. Incident cancer cases were identified through NHS record linkage until March 2016. Univariable and multivariable logistic regression analyses were employed to determine the association between HDP and odds of cancer, with adjustment for potential confounders including co-morbidities, sociodemographic, lifestyle and reproductive factors. Results: 13,562 women were included after excluding prevalent cancer cases and women with no pregnancies. 2919 (21.5%) reported HDP and 2615 incident cancers occurred during mean follow up of 19 years. Median age (IQR) at baseline for incident cancer was 60.8 (±14.8) years. Among incident cancer cases, 578 (22.1%) had HDP. In multivariable analyses, HDP had odds ratio (OR) 1.06; 95% CI 0.95–1.18 for incident cancer. The ORs (95% CIs) for common site-specific cancers including breast, colorectal, lung, ovarian and endometrial cancers were 1.06 (0.88–1.28), 1.15 (0.92–1.45), 0.96 (0.68–1.35), 1.30 (0.93–1.83) and 1.16 (0.80–1.67). Conclusion: We found no association between HDP and cancer risk. Further studies are required to confirm and account for any underlying genetic factors involved in pregnancy-related exposures and cancer risk.

Subsequent risk of cancer among women with a history of placental abruption

BACKGROUND

Placentation is characterized by extensive cell proliferation and neovascularization, which is similar to the processes observed in the development of cancer. Nonetheless, little is known about the relation between abnormal placentation, such as placental abruption, and cancer.

MATERIAL AND METHODS

Data on women with placental abruption in a singleton pregnancy between 1971 and 2005 (n = 7804) were collected from the Finnish Hospital Discharge Registry and the Finnish Medical Birth Registry. The cohort was then linked with the Finnish Cancer Registry records until the end of 2013. Standardized incidence ratios (SIRs) were calculated for different cancers by dividing the observed numbers of cancers by those expected. The expected numbers were based on national cancer incidence rates.

RESULTS

During follow-up, 597 cancers were found among women with a history of placental abruption. The overall risk of cancer was not increased (SIR 0.95, 95% CI 0.88-1.02). However, the history of placental abruption was associated with an increased risk of lung cancer (SIR 1.51, 95% CI 1.05-2.10) and thyroid cancer (SIR 1.47, 95% CI 1.04-2.02). A decreased risk was found for breast cancer (SIR 0.85, 95% CI 0.75-0.96). The risk of rectal cancer was also decreased, although these numbers were small (SIR 0.49, 95% CI 0.20-1.01).

CONCLUSIONS

Overall, the risk of lung cancer was increased, and the risk of breast cancer decreased, in women with a history of placental abruption. These observations can be explained to some extent by risk factors or risk markers for placental abruption. The increased risk of thyroid cancer may be explained by surveillance bias.

Breast Cancer Risk After Recent Childbirth: A Pooled Analysis of 15 Prospective Studies

Background

Parity is widely recognized as protective for breast cancer, but breast cancer risk may be increased shortly after childbirth. Whether this risk varies with breastfeeding, family history of breast cancer, or specific tumor subtype has rarely been evaluated.

Objective

To characterize breast cancer risk in relation to recent childbirth.

Design

Pooled analysis of individual-level data from 15 prospective cohort studies.

Setting

The international Premenopausal Breast Cancer Collaborative Group.

Participants

Women younger than 55 years.

Measurements

During 9.6 million person-years of follow-up, 18 826 incident cases of breast cancer were diagnosed. Hazard ratios (HRs) and 95% CIs for breast cancer were calculated using Cox proportional hazards regression.

Results

Compared with nulliparous women, parous women had an HR for breast cancer that peaked about 5 years after birth (HR, 1.80 [95% CI, 1.63 to 1.99]) before decreasing to 0.77 (CI, 0.67 to 0.88) after 34 years. The association crossed over from positive to negative about 24 years after birth. The overall pattern was driven by estrogen receptor (ER)-positive breast cancer; no crossover was seen for ER-negative cancer. Increases in breast cancer risk after childbirth were pronounced when combined with a family history of breast cancer and were greater for women who were older at first birth or who had more births. Breastfeeding did not modify overall risk patterns.

Limitations

Breast cancer diagnoses during pregnancy were not uniformly distinguishable from early postpartum diagnoses. Data on human epidermal growth factor receptor 2 (HER2) oncogene overexpression were limited.

Conclusion

Compared with nulliparous women, parous women have an increased risk for breast cancer for more than 20 years after childbirth. Health care providers should consider recent childbirth a risk factor for breast cancer in young women.

Primary Funding Source

The Avon Foundation, the National Institute of Environmental Health Sciences, Breast Cancer Now and the UK National Health Service, and the Institute of Cancer Research.

Maternal breast cancer risk in relation to birthweight and gestation of her offspring

BACKGROUND

Parity and age at first pregnancy are well-established risk factors for breast cancer, but the effects of other characteristics of pregnancies are uncertain and the literature is inconsistent.

METHODS

In a cohort of 83,451 parous women from the general population of the UK, which collected detailed information on each pregnancy and a wide range of potential confounders, we investigated the associations of length of gestation and birthweight of offspring in a woman's pregnancies with her breast cancer risk, adjusting for a full range of non-reproductive as well as reproductive risk factors unlike in previous large studies.

RESULTS

Gestation of the first-born offspring was significantly inversely related to the risk of pre-menopausal breast cancer (p trend = 0.03; hazard ratio (HR) for 26-31 compared with 40-41 weeks, the baseline group, = 2.38, 95% confidence interval (CI) 1.26-4.49), and was borderline significantly related to risk of breast cancer overall (p trend = 0.05). Risk was significantly raised in mothers of high birthweight first-born (HR for breast cancer overall = 1.53, 95% CI 1.06-2.21 for ≥ 4500 g compared with 3000-3499 g, the baseline group). For gestation and birthweight of most recent birth, there were no clear effects. Analyses without adjustment for confounders (other than age) gave similar results.

CONCLUSIONS

Our data add to evidence that short gestation pregnancies may increase the risk of breast cancer, at least pre-menopausally, perhaps by hormonal stimulation and breast proliferation early in pregnancy without the opportunity for the differentiation that occurs in late pregnancy. High birthweight first pregnancies may increase breast cancer risk, possibly through the association of birthweight with oestrogen and insulin-like growth factor 1 levels.

Impact of parental cancer on IQ, stress resilience, and physical fitness in young men

Background

A parental cancer diagnosis is a stressful life event, potentially leading to increased risks of mental and physical problems among children. This study aimed to investigate the associations of parental cancer with IQ, stress resilience, and physical fitness of the affected men during early adulthood.

Materials and methods

In this Swedish population-based study, we included 465,249 men born during 1973–1983 who underwent the military conscription examination around the age of 18 years. We identified cancer diagnoses among the parents of these men from the Cancer Register. IQ, stress resilience, and physical fitness of the men were assessed at the time of conscription and categorized into three levels: low, moderate, and high (reference category). We used multinomial logistic regression to assess the studied associations.

Results

Overall, parental cancer was associated with higher risks of low stress resilience (relative risk ratio [RRR]: 1.09 [95% confidence interval (CI) 1.04–1.15]) and low physical fitness (RRR: 1.12 [95% CI 1.05–1.19]). Stronger associations were observed for parental cancer with a poor expected prognosis (low stress resilience: RRR: 1.59 [95% CI 1.31–1.94]; low physical fitness: RRR: 1.45 [95% CI 1.14–1.85]) and for parental death after cancer diagnosis (low stress resilience: RRR: 1.29 [95% CI 1.16–1.43]; low physical fitness: RRR: 1.40 [95% CI 1.23–1.59]). Although there was no overall association between parental cancer and IQ, parental death after cancer diagnosis was associated with a higher risk of low IQ (RRR: 1.11 [95% CI 1.01–1.24]).

Conclusion

Parental cancer, particularly severe and fatal type, is associated with higher risks of low stress resilience and low physical fitness among men during early adulthood. Men who experienced parental death after cancer diagnosis also have a higher risk of low IQ.

Stromal immunoglobulin κC expression is associated with initiation of breast cancer in TA2 mice and human breast cancer

The initiation of spontaneous breast cancer (SBC) in Tientsin Albino 2 (TA2) mice is related to mouse mammary tumor virus (MMTV) infection, and MMTV amplification is hormonally regulated. To explore the insertion site of MMTVLTR in TA2 mouse genome, reverse PCR and nested PCR were used to amplify the unknown sequence on both sides of the MMTV‐LTRSAG gene in SBC and normal breast tissue of TA2 mice. Furthermore, the clinicopathological significance of the insertion site was evaluated in 43 samples of normal breast tissue, 46 samples of breast cystic hyperplasia, 54 samples of ductal carcinoma in situ, 142 samples of primary breast cancer and 47 samples of lymph node metastatic breast cancer by RNA in situ hybridization. We confirmed that the insertion site of the MMTV‐LTRSAG gene was located between Igκv2‐112 and Igκv14‐111 in chromosome 6 of TA2 mouse. IGκC was localized in the stromal cells of TA2 mouse with SBC and in human breast cancer tissues. Tumor cells were negative for IGκC in RNA in situ hybridization. The positive staining index of IGκC in stromal cells was the highest in lymph node metastatic breast cancer, followed by primary breast cancer, ductal carcinoma in situ, and breast cystic hyperplasia. Furthermore, the positive staining index of IGκC was related to the expression of ER, PR, HER2 and Ki‐67. Our findings showed that stromal IGκC expression was associated with the initiation of SBC in TA2 mice. IGκC may be a high‐risk factor for the initiation and progression of human breast cancer.

Psychiatric disorders among children of parents with cancer: A Swedish register-based matched cohort study

OBJECTIVE

To investigate the risk of psychiatric disorders among children of parents with cancer in a nationwide population-based setting.

METHODS

Based on Swedish national registers, the study included 101 339 children with parental cancer diagnosed either during pregnancy (N = 1047) or after birth (N = 100 292) that were born during 1983 to 2000. For each exposed child, we randomly selected 10 unexposed children from the general population after individual matching by year of birth and sex. The matched cohort was followed during 2001 to 2010. Clinical diagnoses of psychiatric disorders and use of prescribed psychiatric medications were identified for all children. Cox regression and logistic regression were used to evaluate the associations of parental cancer with psychiatric disorder diagnosis and psychiatric medication use, respectively.

RESULTS

Parental cancer during pregnancy was not associated with the risk of psychiatric disorders overall, although paternal cancer during pregnancy was associated with a higher risk of psychiatric medication use among females. Parental cancer after birth was associated with higher risks of psychiatric disorder diagnoses, particularly stress reaction and adjustment disorders (males: hazard ratio [HR]: 1.24, 95% confidence interval [CI], 1.08-1.43; females: HR: 1.27, 95% CI, 1.14-1.41), and use of psychiatric medication (males: odds ratio [OR]: 1.09, 95% CI, 1.04-1.13; females: OR: 1.14, 95% CI, 1.10-1.18). The positive associations were stronger for parental cancer with poor expected survival and for parental death after cancer diagnosis.

CONCLUSIONS

Parental cancer, primarily the life-threatening cancer, might confer a higher risk of psychiatric disorders among children. These findings have potential implications for health care professionals in providing targeted support to children living with a parent with cancer.

The Premenopausal Breast Cancer Collaboration: A Pooling Project of Studies Participating in the National Cancer Institute Cohort Consortium

Breast cancer is a leading cancer diagnosis among premenopausal women around the world. Unlike rates in postmenopausal women, incidence rates of advanced breast cancer have increased in recent decades for premenopausal women. Progress in identifying contributors to breast cancer risk among premenopausal women has been constrained by the limited numbers of premenopausal breast cancer cases in individual studies and resulting low statistical power to subcategorize exposures or to study specific subtypes. The Premenopausal Breast Cancer Collaborative Group was established to facilitate cohort-based analyses of risk factors for premenopausal breast cancer by pooling individual-level data from studies participating in the United States National Cancer Institute Cohort Consortium. This article describes the Group, including the rationale for its initial aims related to pregnancy, obesity, and physical activity. We also describe the 20 cohort studies with data submitted to the Group by June 2016. The infrastructure developed for this work can be leveraged to support additional investigations. Cancer Epidemiol Biomarkers Prev; 26(9); 1360-9. ©2017 AACR.

Mortality and causes of death among women with a history of placental abruption

INTRODUCTION

Women with a history of placental abruption have an increased later morbidity, but not much is known of the later mortality.

MATERIAL AND METHODS

Data on women with placental abruption (index cohort) between 1969 and 2005 (n = 7805) were collected from the Finnish Hospital Discharge Register and the Finnish Medical Birth Register. A matched reference cohort consisted of women without placental abruption (n = 23 523). The causes of death were retrieved from the Cause-of-Death Register. Cause-specific mortality was compared by hazard ratios (HR). Standardized mortality ratios were calculated to compare both cohorts with the general female population. The main outcome measure was subsequent mortality.

RESULTS

By the end of 2013 there were 395 deaths in the index cohort and 863 deaths in the reference cohort. The overall mortality was increased in the index cohort compared with the reference cohort [HR 1.39, 95% confidence interval (CI) 1.24-1.57]. The index cohort had an increased risk of death from respiratory tract malignancies (HR 1.72, 95% CI 1.05-2.82), alcohol-related causes (HR 1.84, 95% CI 1.25-2.72), and external causes (HR 1.63, 95% CI 1.19-2.22), especially suicide (HR 1.71, 95% CI 1.07-2.74). The mortality from cardiovascular diseases did not differ. The standardized mortality ratio was increased in the index cohort compared with the general Finnish female population (HR 1.13, 95% CI 1.02-1.24), especially for respiratory tract malignancies (HR 1.79, 95% CI 1.16-2.64). The index cohort women tended to die younger than referent women (p < 0.001).

CONCLUSIONS

Overall mortality among women with a history of placental abruption is increased. These women tend to die younger than referent women do.

Functional IGF1R variant predicts breast cancer risk in women with preeclampsia in California Teachers Study

Purpose

Hypertension in pregnancy has been associated with decreased future risk of breast cancer in many but not all studies. In the Marin Women’s Study, pregnancy-induced hypertension was shown to interact with the T allele of a functional IGF1R gene variant, rs2016347, to result in lower breast density, as well as decreased breast cancer risk. Our objective was to explore these findings in a larger sample of women from the California Teachers Study (CTS).

Methods

The CTS cohort consists of over 130,000 female educators. DNA was available from a nested case–control study, which included 2,030 non-Hispanic white women who developed breast cancer and 1,552 controls. The current study included all participants from the case–control group with a self-reported history of preeclampsia (80 cases/57 controls).

Results

Comparing TT to GG genotypes revealed adjusted odds ratios of 0.38 (CI 0.13, 1.14) for all invasive breast cancers, 0.26 (CI 0.07, 0.89) for hormone receptor-positive (HR+) breast cancers, 0.15 (CI 0.04, 0.56) for those with age at first birth (AFB) < 30, and 0.10 (CI 0.02, 0.49) for those with AFB < 30 and HR+ breast cancers. Trend analysis yielded p values of 0.09, 0.03, 0.005, and 0.004 respectively, suggesting a biological effect for each T allele.

Conclusion

Study findings indicate that the T allele of IGF1R variant rs2016347 is associated with a significant reduction in breast cancer risk in women with a history of preeclampsia, most marked for HR+ breast cancer and in women with AFB < 30.

Preeclampsia and maternal risk of breast cancer: a meta-analysis of cohort studies

BACKGROUND

Pregnancy-related hypertensive disorders, including preeclampsia (PE) and pregnancy-induced hypertension (PIH), may influence the maternal risk of breast cancer. However, results of the cohort studies were inconsistent.

METHODS

An updated meta-analysis of cohort studies was performed to evaluate the association between PE, PIH and maternal breast cancer incidence. Relevant studies were identified via searching of PubMed and Embase databases. A random effect model was applied to synthesize the results. Stratified analyses were performed to evaluate the potential influence of parity, gender of offspring, and study design on the association between PE and maternal breast cancer incidence.

RESULTS

Ten cohort studies with 2,417,899 pregnant women were included. Maternal risk of breast cancer was not significantly affected by PE (risk ration [RR] = 0.93, 95% confidence interval [CI]: 0.82-1.06, p = .27), or PIH (RR = 0.95, 95% CI: 0.81-1.12, p = .54). Interestingly, PE was associated with significantly lowered maternal incidence of breast cancer in women who give birth to male offspring (RR = 0.79, p < .01), and in those of prospective cohort studies (RR = 0.87, p < .01). However, no significant association between PE and maternal breast cancer was detected in primiparous women, those who gave birth to female offspring, or those of retrospective cohorts.

CONCLUSIONS

Current evidence did not support a conclusive association between PE, PIH and the maternal risk of breast cancer. Gender of the offspring may influence the association between PE and maternal breast cancer incidence.

Do racial differences exist in the association between pregnancy-induced hypertension and breast cancer risk?

BACKGROUND

Previous studies investigating the relationship between pregnancy-induced hypertension (PIH) and breast cancer risk have yielded inconsistent results. Unlike numerous Western studies, studies have reported that PIH may be a risk factor for breast cancer in Western Asian women. To confirm these results, we designed a retrospective population-based cohort study to assess the relationship between PIH and subsequent risk for breast cancer in Taiwan.

METHODS

Patients with newly diagnosed PIH were selected from the Taiwan National Health Insurance Research Database (NHIRD), and a 1:4 matched cohort of women without PIH based on age and the year of delivery was randomly selected from the same database as the comparison group. The incidence of new-onset breast cancer was assessed in both cohorts.

RESULTS

Among the 23.3 million individuals registered in the NHIRD, 26,638 patients with PIH and 106,552 matched controls were identified. The incidence rate of breast cancer was higher in patients with PIH than in the matched controls (incidence rate ratio = 1.09, 95% confidence interval [CI] = 1.09-1.10, p < 0.0001). However, the Kaplan-Meier analysis revealed a similar cumulative incidence rate of breast cancer between the PIH and comparison cohorts (log-rank p = 0.4303). Moreover, results from a multivariate analysis indicated that PIH was not a statistically significant independent risk factor for breast cancer (adjusted hazard ratio = 1.10, 95% CI = 0.87-1.39, p = 0.4247).

CONCLUSIONS

The present study demonstrated no significant temporal relationship between PIH and risk for subsequent breast cancer in Eastern Asian women.

Potential Mechanisms underlying the Protective Effect of Pregnancy against Breast Cancer: A Focus on the IGF Pathway

A first full-term birth at an early age protects women against breast cancer by reducing lifetime risk by up to 50%. The underlying mechanism resulting in this protective effect remains unclear, but many avenues have been investigated, including lobular differentiation, cell fate, and stromal composition. A single pregnancy at an early age protects women for 30-40 years, and this long-term protection is likely regulated by a relatively stable yet still modifiable method, such as epigenetic reprograming. Long-lasting epigenetic modifications have been shown to be induced by pregnancy and to target the IGF pathway. Understanding how an early first full-term pregnancy protects against breast cancer and the role of epigenetic reprograming of the IGF system may aid in developing new preventative strategies for young healthy women in the future.

Eating Disorders and Breast Cancer

BACKGROUND

Eating disorders such as anorexia nervosa and bulimia nervosa affect overall and reproductive health and may also affect breast cancer risk. We studied the association between self-reported eating disorders and breast cancer risk in a prospective cohort study.

METHODS

In 2003-2009, the Sister Study enrolled women ages 35-74 years who had a sister with breast cancer but had never had it themselves. Using data from 47,813 women, we estimated adjusted HRs and 95% confidence intervals (CI) for the association between eating disorders and invasive breast cancer over a median of 5.4 years of follow-up.

RESULTS

Three percent (n = 1,569) of participants reported a history of an eating disorder. Compared with women who never had an eating disorder, women who reported eating disorders in the past had reduced breast cancer risk (HR = 0.62; 95% CI, 0.42-0.92).

CONCLUSIONS

In this large prospective, observational cohort study, we observed an inverse association between having a history of an eating disorder and invasive breast cancer.

IMPACT

Historical eating disorders may be associated with a long-term reduction in breast cancer risk. Cancer Epidemiol Biomarkers Prev; 26(2); 206-11. ©2016 AACR.

Gestational Age and the Risk of Maternal Breast Cancer: A Population-Based Case-Control Study

There is limited evidence that the gestational age at delivery may influence the risk of maternal breast cancer. While extreme prematurity has been suggested to increase the risk, there seems to be no study available so far that investigates the due effects of a late delivery. This research aimed to identify the impact of both preterm and late deliveries on the risk of maternal breast cancer within a period of 5 years after birth. Our dataset was created by linking data from the Nevada Cancer Registry database (1995-2008) and the birth certificates issued by the Nevada State Health Division (1994-2003). The study cohort consisted of 213,250 women who gave birth from January 1, 1994 to December 31, 2003. We performed a nested population-based case-control study on 126 Nevada mothers with a first lifetime breast cancer diagnosed from January 1, 1995 through December 31, 2003, and 504 Nevada cancer-free mothers. Women with pregnancies who progressed beyond 40 weeks of gestation were at a significantly lower risk of developing breast cancer for the 5-year period following a delivery, when compared to women who delivered at 37-40 weeks of gestation (OR: 0.33, 95% CI: 0.11-0.92) in a multivariate model. Additional pregnancy characteristics did not significantly predict the risk of maternal breast cancer. Pregnancies that extended beyond 40 weeks of gestation were strongly associated with a lower likelihood of premenopausal breast cancer. Biological plausibility for this association may correspond to the fact that as pregnancy develops into more advanced stages, mammary cells have more time to attain complete differentiation and maturation; a process that starts early in the third trimester.

Long-term impact of preeclampsia on maternal endometrial cancer risk

BACKGROUND

Endometrial cancer is mainly dependent on oestrogen exposure. Preeclampsia has shown to reduce oestrogen levels hence preeclampsia may affect later endometrial cancer risk.

METHODS

We conducted a case-control study of 523 Danish women with endometrial cancer and 52 299controls during 1978-2010. The association between preeclampsia and later endometrial cancer was evaluated overall and according to preeclampsia onset and type of endometrial cancer in conditional logistic regression models.

RESULTS

We observed no overall association between preeclampsia and endometrial cancer risk (OR=1.11 (95% CI 0.68-1.81)). This was true for all endometrial cancer subtypes. In an analysis of preeclampsia onset, however, we report a markedly increased risk of endometrial cancer following early-onset preeclampsia (OR=2.64 (95% CI 1.29-5.38)).

CONCLUSIONS

Although we report no obvious association between preeclampsia and endometrial cancer, studying the subset of early-onset preeclampsia may prove fruitful in further understanding the aetiology of endometrial cancer.

The controversial role of human chorionic gonadotropin in the development of breast cancer and other types of tumors

INTRODUCTION

Breast cancer is the most often diagnosed tumor of women and one of the leading cause of cancer related death. Due to different known risk factors there are epidemiological differences. Beside genetic disorders and patient's age it is especially the age of the first full-term pregnancy and in this context the pregnancy hormone human chorionic gonadotropin that seems to play an important role.

METHODS

This review is based on a PubMed research in publications of the last 20 years. Only articles in English language were considered.

RESULTS

The effect of human chorionic gonadotropin on development of cancer is controversial. In fact, for breast cancer there is evidence that this hormone has a protective effect against tumorigenesis due the differentiation of the mammary tissue after a full term pregnancy through the downregulation of estrogen receptors.

CONCLUSION

Human chorionic gonadotropin has among promoting pregnancy important controversial functions especially in tumor development. The mechanisms that explain the pro- and anti-carcinogenic effects are not fully understood yet. It seems to have a protective effect on breast cancer through increasing differentiation and hereby decreasing susceptibility of the mammary tissue for toxicants. This knowledge might help developing a preventive agent in the next future that uses the anti-carcinogenic effect of human chorionic gonadotropin and thereby decrease the mortality out of breast cancer.

Pregnancy history and risk of premenopausal breast cancer-a nested case-control study

BACKGROUND

Reproductive factors are well-known risk factors for premenopausal breast cancer (PBC). It is unknown whether these associations are modified by familial factors, including genetic and early environment factors.

METHODS

Using Swedish health registries, we performed a nested case-control study with two control groups: sister controls and population controls. The study population included women with live singleton births between 1973 and 2010, who also had a full sister who gave birth during this period. All women subsequently diagnosed with PBC were selected as cases (n = 8327). Sisters with the least age difference and without PBC at the time of her sister's diagnosis were selected as sister controls. For each incident case, one population control without previous PBC was selected.The population controls were individually matched with the sister controls on year of birth. Conditional logistic regression was used to estimate associations between reproductive factors and PBC.

RESULTS

Increasing parity was inversely associated with PBC using population controls, and multiparity was a risk factor using sister controls. Very preterm delivery (≤ 31 weeks) was associated with a slightly higher PBC risk using sister controls. Preeclampsia was associated with a slightly protective effect using population controls. With respect to other factors, there were no substantial differences in risks of PBC by choice of control group.

CONCLUSIONS

The divergent results with regard to parity and PBC risk when using sister and population controls suggest that the influence of childbearing may be modified by genotype. Selection bias when using different control groups must also be considered.

Childhood injury after a parental cancer diagnosis

A parental cancer diagnosis is psychologically straining for the whole family. We investigated whether a parental cancer diagnosis is associated with a higher-than-expected risk of injury among children by using a Swedish nationwide register-based cohort study. Compared to children without parental cancer, children with parental cancer had a higher rate of hospital contact for injury during the first year after parental cancer diagnosis (hazard ratio [HR] = 1.27, 95% confidence interval [CI] = 1.22-1.33), especially when the parent had a comorbid psychiatric disorder after cancer diagnosis (HR = 1.41, 95% CI = 1.08-1.85). The rate increment declined during the second and third year after parental cancer diagnosis (HR = 1.10, 95% CI = 1.07-1.14) and became null afterwards (HR = 1.01, 95% CI = 0.99-1.03). Children with parental cancer also had a higher rate of repeated injuries than the other children (HR = 1.13, 95% CI = 1.12-1.15). Given the high rate of injury among children in the general population, our findings may have important public health implications.

DOI:http://dx.doi.org/10.7554/eLife.08500.001

A diagnosis of cancer can be devastating for both a person and his or her family. Over the past 40 years, the number of individuals in Sweden diagnosed with cancer has more than doubled leaving growing numbers of families coping with the aftermath. Many individuals diagnosed with cancer have young children. Parents with cancer and their spouses often struggle to cope with disease and the demands of parenting simultaneously. In fact, previous research has shown children with a parent who has cancer have a greater risk of behavioral problems or distress than children with two healthy parents.

Whether the stress of having a parent with cancer also affects the children’s physical wellbeing hasn’t been studied much. One concern in particular is whether these children may be at increased risk of injury. Injuries are the most common reason for a child to visit a hospital and in some cases lead to deaths. Children who are not well supervised or whose parents have poor mental health are at increased risk of injury. Coping with cancer and the mental anguish it causes may distract parents and possibly place their children at increased risk of injury.

Based on data from nationwide population and health registers in Sweden, Chen, Regodón Wallin et al. now provide evidence that a child with a parent who has cancer is at a greater risk of injury than a child with two parents who are free of cancer. The analysis also revealed that the risk is particularly great if the parent with cancer also develops mental illness after the cancer diagnosis. The risk of injury is greatest in the first year after the parent’s diagnosis. Fortunately, the elevated risk of injury decreases overtime and is almost non-existing after the third year. The analyses suggest that providing extra support for parents with cancer might help to reduce the risk of injury in their children.

DOI:http://dx.doi.org/10.7554/eLife.08500.002

Fetal growth and subsequent maternal risk of thyroid cancer

Thyroid cancer has peak incidence among women of reproductive age, and growth factors, which have procarcinogenic properties, may play an important etiologic role. However, the association between fetal growth rate during a woman's pregnancy and her subsequent risk of thyroid cancer has not been previously examined. We conducted a national cohort study of 1,837,634 mothers who had a total of 3,588,497 live-births in Sweden in 1973-2008, followed up for thyroid cancer incidence through 2009. There were 2,202 mothers subsequently diagnosed with thyroid cancer in 36.8 million person-years of follow-up. After adjusting for maternal age, height, weight, smoking, and sociodemographic factors, high fetal growth (birth weight standardized for gestational age and sex) was associated with a subsequent increased risk of thyroid cancer in the mother (incidence rate ratio [IRR] per additional 1 standard deviation, 1.05; 95% CI, 1.01-1.09; p = 0.02). Each 1,000 g increase in the infant's birth weight was associated with a 13% increase in the mother's subsequent risk of thyroid cancer (IRR, 1.13; 95% CI, 1.05-1.22; p = 0.001). These findings appeared to involve both papillary and follicular subtypes, and did not vary significantly by the mother's height, weight or smoking status. In this large national cohort study, high fetal growth during a woman's pregnancy was independently associated with a subsequent increased risk of her developing thyroid cancer. If confirmed, these findings suggest an important role of maternal growth factors in the development of thyroid cancer, and potentially may help facilitate the identification of high-risk subgroups of women.

Preeclampsia and breast cancer: The influence of birth characteristics

BACKGROUND

In parous women preeclampsia has been associated with reduced risk of developing breast cancer. Characteristics of births following preeclamptic pregnancies may help understand mechanisms involved in the breast cancer risk reduction inferred by preeclampsia.

METHODS

We conducted a register-based cohort study of all Danish women giving birth during 1978-2010 (n = 778,701). The association between preeclampsia and breast cancer was evaluated overall and according to birth characteristics by means of incidence rate ratios (IRR) estimated in Poisson regression models.

RESULTS

Compared with women with non-preeclamptic pregnancies only, women with one or more preeclamptic pregnancies were 19% significantly less likely to develop breast cancer (IRR = 0.81 [95% CI 0.72-0.93]). We found some indication of greater risk reduction in women with term births, one or more previous births, and in women giving birth to boys. These findings, however, did not reach statistical significance. Finally, risk reduction was slightly greater following milder forms of preeclampsia.

CONCLUSION

Our data is compatible with an approximately 20% reduction in risk of developing breast cancer following preeclampsia. Although we find some variability according to birth characteristics, the risk reduction inferred by preeclampsia seems applicable to most preeclamptic pregnancies.

Fetal growth and subsequent maternal risk of colorectal cancer

BACKGROUND

High birth weight has been associated with subsequent increased risk of breast cancer in the infant's mother, possibly related to maternal estrogen and growth factor pathways. However, its association with maternal risk of colorectal cancer, the third most common cancer among women, is unknown.

METHODS

We conducted a national cohort study of 1,838,509 mothers who delivered 3,590,523 babies in Sweden in 1973-2008, followed up for colorectal cancer incidence through 2009.

RESULTS

There were 7,318 mothers diagnosed with colorectal cancer in 36.8 million person-years of follow-up. After adjusting for maternal age, body mass index, diabetes, and other potential confounders, high fetal growth was associated with a subsequent increased risk of colorectal cancer in the mother [incidence rate ratio (IRR) per additional 1 SD relative to mean birth weight for gestational age and sex, 1.05; 95% confidence intervals (CI), 1.03-1.07; P < 0.0001]. Each 1,000 g increase in the infant's birth weight was associated with a 12% increase in the mother's subsequent risk of colorectal cancer (IRR, 1.12; 95% CI, 1.07-1.17; P < 0.0001). Multiple gestation was also independently associated with increased maternal risk of colorectal cancer (IRR for twin or higher order vs. singleton, 1.22; 95% CI, 1.04-1.44; P = 0.02).

CONCLUSION

In this large cohort study, high fetal growth and multiple gestation were independently associated with subsequent higher maternal risk of colorectal cancer. These findings warrant further investigation of maternal growth factor and estrogen pathways in the etiology of colorectal cancer.

IMPACT

If confirmed, our findings may help identify subgroups of women at high risk of colorectal cancer.

First Pregnancy Characteristics, Postmenopausal Breast Density, and Salivary Sex Hormone Levels in a Population at High Risk for Breast Cancer

BACKGROUND

It remains unknown if later life breast cancer risk as determined by reproductive history is mediated by postmenopausal breast density and/or sex steroid levels.

METHODS

Increased breast density is a strong surrogate for future breast cancer risk. A cross-sectional study with a longitudinal follow up for breast health outcomes evaluated women without breast cancer (n = 1,023; 682 = parous), drawn from a high risk postmenopausal population, with questionnaire reported reproductive histories. The questionnaire was linked to prospective screening mammogram breast density measurements, and saliva biospecimens that were used to assess sex steroid hormone levels.

RESULTS

Expected age and postmenopause related declines in salivary estradiol (E), progesterone (P), dehydroepiandrosterone (DHEA) and testosterone (T) levels were observed. This was most pronounced for DHEA and T, which were also the only postmenopausal hormone levels significantly associated with any reproductive characteristics: parity and breast feeding for DHEA, age-at-first birth for T. Postmenopausal breast density was borderline significantly lower with parity and higher body mass index (BMI). After multivariate analysis, T was the only hormone level to retain any association (negative, p<0.05) with breast density.

CONCLUSIONS AND GENERAL SIGNIFICANCE

While reproductive characteristics, in particular parity, generally demonstrated independent associations with postmenopausal breast density and E, P and DHEA levels, T levels showed concordant inverse associations with age-at-first birth and breast density. These findings suggest that reproductive effects and later life salivary sex steroid hormone levels may have independent effects on later life breast density and cancer risk.

Association between gestational diabetes mellitus and subsequent risk of cancer: a systematic review of epidemiological studies

PURPOSE

This study aimed at summarizing epidemiological evidence of the association between gestational diabetes mellitus (GDM) and subsequent risk of cancer.

MATERIALS AND METHODS

We searched Medline, Embase, Cancer Lit and CINAHL for epidemiological studies published by February 1, 2014 examining the risk of cancer in patients with history of GDM using highly inclusive algorithms. Information about first author, year of publication, country of study, study design, cancer sites, sample sizes, attained age of subjects and methods used for determining GDM status were extracted by two researchers and Stata version 11.0 was used to perform the meta-analysis and estimate the pooled effects.

RESULTS

A total of 9 articles documented 5 cohort and 4 case- control studies containing 10,630 cancer cases and 14,608 women with a history of GDM were included in this review. Taken together, the pooled odds ratio (OR) between GDM and breast cancer risk was 1.01 (0.87-1.17); yet the same pooled ORs of case-control and cohort studies were 0.87 (0.71-1.06) and 1.25 (1.00-1.56) respectively. There are indications that GDM is strongly associated with higher risk of pancreatic cancer (HR=8.68) and hematologic malignancies (HR=4.53), but no relationships were detected between GDM and other types of cancer.

CONCLUSIONS

Although GDM increases the risk of certain types of cancer, these results should be interpreted with caution becuase of some methodological flaws. The issue merits added investigation and coordinated efforts between researchers, antenatal clinics and cancer treatment and registration agencies to help attain better understanding.

Reproduction and breast cancer risk

Reproduction is doubtlessly one of the main biological meanings of life. It is therefore not surprising that various aspects of reproduction impact on breast cancer risk. Various developmental levels may become targets of breast tumorigenesis. This review follows the chronologic sequence of events in the life of a female at risk, starting with the intrauterine development. Furthermore, the influence of both contraceptive measures and fertility treatment on breast cancer development is dealt with, as well as various pregnancy-associated factors, events, and perinatal outcomes. Finally, the contribution of breast feeding to a reduced breast cancer risk is discussed.

Efferocytosis produces a prometastatic landscape during postpartum mammary gland involution

Breast cancers that occur in women 2-5 years postpartum are more frequently diagnosed at metastatic stages and correlate with poorer outcomes compared with breast cancers diagnosed in young, premenopausal women. The molecular mechanisms underlying the malignant severity associated with postpartum breast cancers (ppBCs) are unclear but relate to stromal wound-healing events during postpartum involution, a dynamic process characterized by widespread cell death in milk-producing mammary epithelial cells (MECs). Using both spontaneous and allografted mammary tumors in fully immune-competent mice, we discovered that postpartum involution increases mammary tumor metastasis. Cell death was widespread, not only occurring in MECs but also in tumor epithelium. Dying tumor cells were cleared through receptor tyrosine kinase MerTK-dependent efferocytosis, which robustly induced the transcription of genes encoding wound-healing cytokines, including IL-4, IL-10, IL-13, and TGF-β. Animals lacking MerTK and animals treated with a MerTK inhibitor exhibited impaired efferocytosis in postpartum tumors, a reduction of M2-like macrophages but no change in total macrophage levels, decreased TGF-β expression, and a reduction of postpartum tumor metastasis that was similar to the metastasis frequencies observed in nulliparous mice. Moreover, TGF-β blockade reduced postpartum tumor metastasis. These data suggest that widespread cell death during postpartum involution triggers efferocytosis-induced wound-healing cytokines in the tumor microenvironment that promote metastatic tumor progression.

First pregnancy events and future breast density: modification by age at first pregnancy and specific VEGF and IGF1R gene variants

Purpose

Pregnancy characteristics have been associated with breast cancer risk, but information is limited on their relationship with breast density. Our objective was to examine the relationship between first pregnancy characteristics and later life breast density, and whether the association is modified by genotype.

Methods

The Marin Women’s Study was initiated to examine breast cancer in a high-incidence mammography population (Marin County, CA). Reproductive characteristics and pregnancy information including pregnancy-induced hypertension (PIH) were self-reported at the time of mammography. Forty-seven candidate single nucleotide polymorphisms were obtained from saliva samples; seven were assessed in relation to PIH and percent fibroglandular volume (%FGV). Breast density assessed as %FGV was measured on full-field digital mammograms by the San Francisco Mammography Registry.

Results

A multivariable regression model including 2,440 parous women showed that PIH during first pregnancy was associated with a statistically significant decrease in %FGV (b = −0.31, 95 % CI −0.52, −0.11), while each month of breast-feeding after first birth was associated with a statistically significant increase in %FGV (b = 0.01, 95 % CI 0.003, 0.02). PIH and breast-feeding associations with %FGV were modified by age at first birth. In a subsample of 1,240 women, there was evidence of modification in the association between PIH and %FGV by specific vascular endothelial growth factor (VEGF) (rs3025039) and insulin growth factor receptor-1 (IGFR1) (rs2016347) gene variants.

Conclusion

These findings suggest that first pregnancy characteristics may exert an influence on extent of breast density later in life and that this influence may vary depending on inherited IGFR1 and VEGF genotypes.

Electronic supplementary material

The online version of this article (doi:10.1007/s10552-014-0386-2) contains supplementary material, which is available to authorized users.

Birth size in the most recent pregnancy and maternal mortality in premenopausal breast cancer by tumor characteristics

The main aim of this study was to investigate possible associations between measures of offspring size at birth in the most recent pregnancy before premenopausal breast cancer diagnosis and the risks of maternal breast cancer mortality, taking tumor characteristics into account. We also aimed to investigate if these associations are modified by age at childbirth, time since childbirth, parity, and age at diagnosis. We followed 6,019 women from their date of premenopausal breast cancer (diagnosed from 1992 to 2008) until emigration, death or December 31st, 2009, whichever occurred first. We used Cox proportional hazard regression models, adjusted for parity, age at diagnosis, and education level, to estimate associations between women pregnancy, cancer characteristics and offspring birth characteristics, and mothers' mortality risk. In stratified analyses, mortality risks were estimated by tumor stage, ER or PR status. There was no association between offspring birth weight (HR = 1.00, 95 % CI 0.99-1.01, when used as a continuous variable), birth weight for gestational age or ponderal index, and premenopausal breast cancer mortality. Similarly, in analyses stratified by tumor stage, receptor status, and time difference between last pregnancy and date of diagnosis, we found no associations between birth size and breast cancer mortality. Our findings suggest that the hypothesis that "premenopausal breast cancer mortality is associated with offspring birth characteristics in the most recent pregnancy before the diagnosis" may not be valid. In addition, these associations are not modified by tumor characteristics.

The relationship between preeclampsia, pregnancy-induced hypertension and maternal risk of breast cancer: a meta-analysis

BACKGROUND

It has long been recognized that some human breast cancers are hormone dependent. Preeclampsia is a syndrome of pregnancy defined by the onset of hypertension and proteinuria and characterized by dysfunction of the maternal endothelium. Many hormonal changes occur with preeclampsia, and we hypothesize that these changes may influence the risk of maternal breast cancer. We also analyzed the relation between pregnancy-induced hypertension (PIH) and maternal risk of breast cancer.

METHODS

Among 13 relevant publications about preeclampsia and six relevant publications about PIH, some studies find preeclampsia associated with a lower risk of breast cancer, but others did not. Therefore, these results are inconclusive. We conducted meta-analysis to evaluate more precisely the relationship between preeclampsia, PIH and maternal risk of breast cancer.

RESULTS

The pooled estimate of the hazard ratio (HR) associated with preeclampsia was 0.86 (95% CI 0.73-1.01), and that associated with PIH was 0.83 (0.66-1.06), both based on the random effects model.

CONCLUSION

Some suggestive but not entirely consistent nor conclusive evidence was found on the association between the history of preeclampsia or PIH with the subsequent risk of breast cancer.

Pregnancy-related characteristics and breast cancer risk

Breast tissues undergo extensive physiologic changes during pregnancy, which may affect breast carcinogenesis. Gestational hypertension, preeclampsia/eclampsia, gestational diabetes, pregnancy weight gain, and nausea and vomiting (N&V) during pregnancy may be indicative of altered hormonal and metabolic profiles and could impact breast cancer risk. Here, we examined associations between these characteristics of a woman's pregnancy and her subsequent breast cancer risk. Participants were parous women that were recruited to a population-based case-control study (Western New York Exposures and Breast Cancer Study). Cases (n = 960), aged 35-79 years, had incident, primary, histologically confirmed breast cancer. Controls (n = 1,852) were randomly selected from motor vehicle records (< 65 years) or Medicare rolls (≥ 65 years). Women were queried on their lifetime pregnancy experiences. Multivariable-adjusted logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). N&V during pregnancy was inversely associated with breast cancer risk. Relative to those who never experienced N&V, ever experiencing N&V was associated with decreased risk (OR 0.69, 95% CI 0.56-0.84) as were increased N&V severity (p trend < 0.001), longer duration (p trend < 0.01), and larger proportion of affected pregnancies (p trend < 0.0001) among women with ≥ 3 pregnancies. Associations were stronger for more recent pregnancies (< 5 years). Findings did not differ by menopausal status or breast cancer subtype including estrogen receptor and HER2 expression status. Other pregnancy characteristics examined were not associated with risk. We observed strong inverse associations between pregnancy N&V and breast cancer risk. Replication of these findings and exploration of underlying mechanisms could provide important insight into breast cancer etiology and prevention.

High Bab Birth Weight Andof Hormone-Associated Cancer in Mothers: The Cancer–Cardiovascular Disease Dichotomy and its Possible Causes

The idea of intrauterine or fetal factors being the cause of several prevalent noninfectious diseases in adults has recently gained the status of an axiom. One of the most thoroughly studied predictors is birth weight (BW). Although many published studies point at relations between BW and later adult morbidity or mortality, much less attention is paid to associations between baby BW and maternal morbidity. Available data suggest a sort of dichotomy in these relationships. Thus, cardiovascular risk is higher in mothers of babies with a reduced BW, while cancer risk, mainly of the breast and some other hormone-dependent cancers, is often higher among mothers of babies with a large BW (newborn macrosomia). This review addresses possible causes and endocrine mechanisms of this topic and suggests a ‘particular’ and ‘general’ solution for arising controversy. Emphasis is placed on a probable competition between chronic diseases (mainly, between female hormone-related cancer and cardiovascular pathology) within the concept of multiple causes of death. These associations should be remembered while studying the relation between offspring BW and maternal predisposition to hormone-associated cancers and other noncommunicable diseases.

Postpartum remodeling, lactation, and breast cancer risk: summary of a National Cancer Institute-sponsored workshop

The pregnancy-lactation cycle (PLC) is a period in which the breast is transformed from a less-developed, nonfunctional organ into a mature, milk-producing gland that has evolved to meet the nutritional, developmental, and immune protection needs of the newborn. Cessation of lactation initiates a process whereby the breast reverts to a resting state until the next pregnancy. Changes during this period permanently alter the morphology and molecular characteristics of the breast (molecular histology) and produce important, yet poorly understood, effects on breast cancer risk. To provide a state-of-the-science summary of this topic, the National Cancer Institute invited a multidisciplinary group of experts to participate in a workshop in Rockville, Maryland, on March 2, 2012. Topics discussed included: 1) the epidemiology of the PLC in relation to breast cancer risk, 2) breast milk as a biospecimen for molecular epidemiological and translational research, and 3) use of animal models to gain mechanistic insights into the effects of the PLC on breast carcinogenesis. This report summarizes conclusions of the workshop, proposes avenues for future research on the PLC and its relationship with breast cancer risk, and identifies opportunities to translate this knowledge to improve breast cancer outcomes.

The milk protein α-casein functions as a tumor suppressor via activation of STAT1 signaling, effectively preventing breast cancer tumor growth and metastasis

Here, we identified the milk protein α-casein as a novel suppressor of tumor growth and metastasis. Briefly, Met-1 mammary tumor cells expressing α-casein showed a ~5-fold reduction in tumor growth and a near 10-fold decrease in experimental metastasis. To identify the molecular mechanism(s), we performed genome-wide transcriptional profiling. Interestingly, our results show that α-casein upregulates gene transcripts associated with interferon/STAT1 signaling and downregulates genes associated with "stemness." These findings were validated by immunoblot and FACS analysis, which showed the upregulation and hyperactivation of STAT1 and a decrease in the number of CD44(+) "cancer stem cells." These gene signatures were also able to predict clinical outcome in human breast cancer patients. Thus, we conclude that a lactation-based therapeutic strategy using recombinant α-casein would provide a more natural and non-toxic approach to the development of novel anticancer therapies.

Hypertensive diseases in pregnancy and breast cancer risk

Background:

Hypertensive diseases in pregnancy may be associated with a reduced risk of breast cancer. Most previous studies are small and have shown conflicting results.

Methods:

In a cohort of 919 712 women who gave their first birth between 1967 and 2008, with linkage of information from two national registries, we assessed whether women with pregnancy hypertensive diseases are at reduced breast cancer risk. We used Cox regression to estimate hazard ratios (HRs) with 95% confidence intervals (CI).

Results:

Compared with women with a normotensive first pregnancy, women with hypertension or preeclampsia in their first pregnancy had a reduced breast cancer risk (HR 0.83, 95% CI 0.77, 0.90). A reduced risk was consistently observed for hypertensive disease in any pregnancy, for recurrent hypertensive disease in pregnancy, and before and after 50 years of age at breast cancer diagnosis. The association was strongest for women with hypertension in pregnancy, who delivered at term/post-term (HR 0.81, 95% CI 0.75, 0.88) or had a child of average birth weight (HR 0.77, 95% CI 0.69, 0.85).

Conclusion:

Women with pregnancy hypertensive diseases are at reduced breast cancer risk. Whether this association can be attributed to pregnancy-specific events or to underlying biological traits remains unclear.

Benefits and risks of ovarian function and reproduction for cancer development and prevention

Ovarian function and menstrual cycle disturbances, pregnancy, and reproductive medicine procedures can either increase gynecological cancer risk or prevent cancer development. For ovarian cancer development, there are two hypotheses, which are connected with ovulation and gonadotropin secretion. Most of the ovarian cancers seem to be derived from displaced ovarian surfice epithelial cells. One year of ovulatory cycles increases the ovarian cancer risk by 6%. Ovulation between 22 and 29 years of age causes the highest risk increase per year. In contrast, progesterone or progestins appear to create protection. Lifestyle can affect or modify ovarian cancer risk. Breast cancer risk is very much related to age of menarche and menopause, pregnancy, and breast feeding. All of which are related to ovarian function and progestogenic impact that translates either into breast cancer risk increase or decrease. This is modified by body mass index, physical activity, and lifestyle in general. The risk of endometrial cancer is most closely related to endogenous progesterone during the menstrual cycle and pregnancy or by exogenous progestogens as in oral contraceptives. These effects are progestogen dose and time dependent. Endometrial cancer risk can also be increased by estrogen-producing tumors or long-term estrogen treatment.