Role of birthweight in the etiology of breast cancer

Association between birth weight and risk of nonneurological childhood cancers: a systematic review and meta-analysis

OBJECTIVES

This systematic review aims to synthesize the available literature to determine the association between birthweight and the risk of nonneurological childhood cancers.

METHODS

We conducted a systematic search of PubMed, Web of Science, and Scopus databases up to May 2023 to identify observational studies. Heterogeneity between studies was evaluated using the I2 statistics. Publication bias was assessed using Begg and Egger tests. We calculated the odds ratio (OR) or risk ratio (RR) with a 95% confidence interval (CI) using a random-effects model.

RESULTS

Of 11 034 studies retrieved from the search, 56 studies (including 10 568 091 participants) were eligible. The ORs (95% CI) of low (<2500 g) versus normal birthweight (2500-4000 g) and childhood cancers were as follows: leukemia, 0.92 (0.77-1.11); acute lymphoblastic leukemia, 0.82 (0.72-0.94); acute myeloid leukemia, 0.98 (0.77-1.24); lymphoma, 0.99 (0.47-2.10); Hodgkin, 0.79 (0.61-1.03); non-Hodgkin, 0.85 (0.60-1.20); neuroblastoma, 1.34 (1.14-1.58); retinoblastoma, 0.95 (0.68-1.32); rhabdomyosarcoma, 0.86 (0.61-1.20); embryonal, 0.97 (0.66-1.43); alveolar, 1.92 (0.43-8.51); and Wilms tumor, 1.01 (0.83-1.24). The ORs (95% CI) of high (>4000 g) versus normal birthweight and childhood cancers were as follows: leukemia, 1.30 (1.18-1.42); acute lymphoblastic leukemia, 1.27 (1.16-1.39); acute myeloid leukemia, 1.13 (0.98-1.30); lymphoma, 1.69 (0.72-3.94); Hodgkin, 1.22 (1.02-1.46); non-Hodgkin, 1.22 (0.80-1.86); neuroblastoma, 1.20 (1.02-1.41); retinoblastoma, 1.17 (0.93-1.48); rhabdomyosarcoma, 1.07 (0.90-1.27); embryonal, 1.22 (1.00-1.49); alveolar, 1.02 (0.46-2.27); and Wilms tumor, 1.49 (1.34-1.67).

CONCLUSION

This meta-analysis identified high birth weight as a potential risk factor for some childhood cancers, while low birth weight might be protective against a few.

Maternal obesity and resistance to breast cancer treatments among offspring: Link to gut dysbiosis

BACKGROUND

About 50 000 new cases of cancer in the United States are attributed to obesity. The adverse effects of obesity on breast cancer may be most profound when affecting the early development; that is, in the womb of a pregnant obese mother. Maternal obesity has several long-lasting adverse health effects on the offspring, including increasing offspring's breast cancer risk and mortality. Gut microbiota is a player in obesity as well as may impact breast carcinogenesis. Gut microbiota is established early in life and the microbial composition of an infant's gut becomes permanently dysregulated because of maternal obesity. Metabolites from the microbiota, especially short chain fatty acids (SCFAs), play a critical role in mediating the effect of gut bacteria on multiple biological functions, such as immune system, including tumor immune responses.

RECENT FINDINGS

Maternal obesity can pre-program daughter's breast cancer to be more aggressive, less responsive to treatments and consequently more likely to cause breast cancer related death. Maternal obesity may also induce poor response to immune checkpoint inhibitor (ICB) therapy through increased abundance of inflammation associated microbiome and decreased abundance of bacteria that are linked to production of SCFAs. Dietary interventions that increase the abundance of bacteria producing SCFAs potentially reverses offspring's resistance to breast cancer therapy.

CONCLUSION

Since immunotherapies have emerged as highly effective treatments for many cancers, albeit there is an urgent need to enlarge the patient population who will be responsive to these treatments. One of the factors which may cause ICB refractoriness could be maternal obesity, based on its effects on the microbiota markers of ICB therapy response among the offspring. Since about 40% of children are born to obese mothers in the Western societies, it is important to determine if maternal obesity impairs offspring's response to cancer immunotherapies.

Association of birth weight with cancer risk: a dose-response meta-analysis and Mendelian randomization study

BACKGROUND

Several articles have shown that birth weight is associated with the risk of many types of cancers. However, the results are inconsistent, and whether the relationship has a causal effect remains unknown.

METHODS

We searched the PubMed and Embase libraries up to March 2021 and selected observational studies reporting the relationship between birth weight and adult-onset cancer risk. Dose-response meta-analysis and two-sample Mendelian randomization (MR) analysis were used to estimate the effect.

RESULT

In our dose-response meta-analysis, six cancers from 46 studies were found to have significant associations with birth weight. (Ovarian cancer: RR: 1.21, 95% CI 1.01-1.44; breast cancer: RR: 1.12, 95% CI 1.08-1.16; colorectal cancer: RR: 1.20, 95% CI 1.01-1.43; endometrial cancer: RR: 0.85, 95% CI 0.78-0.93; prostate cancer: RR: 1.27, 95% CI 1.01-1.61; testicular cancer: RR: 1.21, 95% CI 1.03-1.43). As birth weight increased, the slope of the dose-response curve of breast cancer increased continuously, and the curve of testicular cancer was U-shaped. In the MR study, seven cancers were included. Only invasive mucinous ovarian cancer was found to have a causal effect on birth weight (OR: 0.62; 95% CI 0.39-0.97), while other cancers did not.

CONCLUSIONS

Our findings suggest that birth weight are unlikely to have a casual effect on risk of cancers via the MR analysis, although the dose-response meta-analysis shows that there is a nonlinear relationship between birth weight and breast cancer and testicular cancer. More relevant researches are needed to further investigate their effect.

Birth weight and the risk of overall breast cancer, premenopausal and postmenopausal breast cancer in adulthood: a dose-response meta-analysis of observational studies

IMPORTANCE

The effect of birth weight on breast cancer across different menopausal states remains unknown.

OBJECTIVE

The aim of this study was to systematically evaluate the association of birth weight with the risk of overall breast cancer (OBC) and premenopausal and postmenopausal breast cancer during adulthood. In parallel, the dose-response analyses were performed.

EVIDENCE REVIEW

Relevant studies were systematically searched from the PubMed, Embase, and the Cochrane Library databases from the inception to May 25, 2021, without language restrictions. All the results were pooled according to risk ratios (RRs).

FINDINGS

In total, 21 cohort studies comprising 1,139,032 participants were included. An increase in the birth weight was not associated with the risk of OBC and premenopausal and postmenopausal breast cancer. Compared with women having normal weight at birth, those with a high birth weight are likely to have an increased risk of invasive breast cancer (RR: 1.19, 95% confidence intervals: 1.03-1.38; I2: 28.6%). The dose-response analyses showed that the risk of premenopausal breast cancer increased significantly in unknown singleton status with birth weight over 2850 g (RR: 1.14 [1.02-1.30]). Similarly, postmenopausal breast cancer risk was increased in singleton births with birth weight over 3750 g (RR: 1.21 [1.00-1.47]).

CONCLUSIONS AND RELEVANCE

High weight at birth might be not significantly associated with the risk of OBC, premenopausal and postmenopausal breast cancer and ER+ and ER- breast cancer but is positively associated with the risk of invasive breast cancer, regardless of parity. Furthermore, with an increase in birth weight, the risk of postmenopausal breast cancer is likely to increase in the singleton births, whereas the risk of premenopausal breast cancer is likely to increase in unknown singleton status.

Prenatal and Perinatal Factors and Risk of Cancer in Middle and Older Adulthood among Men

BACKGROUND

Prenatal factors have been associated with risk of cancers later in life, although studies in men have largely been case-control and focused on birth size only.

METHODS

We used data from 5,845 men in the Health Professionals Follow-up Study (HPFS) to prospectively examine associations between several prenatal and perinatal factors and incident adult cancer risk. In 1994, mothers of participants reported information on characteristics and behaviors related to their pregnancy with their sons. We used multivariable Cox proportional hazards models to calculate HRs and 95% confidence intervals (CI) of associations between prenatal and perinatal risk factors and cancer risk.

RESULTS

During 20 years of follow-up, 1,228 incident cases of overall cancer were documented. Men with a birth weight of ≥4 kg had a 21% increased risk of overall cancer (HR, 1.21; 95% CI, 1.02-1.43) compared with those with a birth weight of 2.5 to 3.9 kg. Greater weight gain during pregnancy (>13.6 kg vs. 6.8-8.6 kg) was also associated with a higher risk of overall cancer (HR, 1.22; 95% CI, 1.02-1.46), and was stronger for men whose mothers had a prepregnancy BMI<21 kg/m² (HR, 1.30; 95% CI, 1.00-1.67) compared with body mass index (BMI) ≥21 kg/m² (HR, 1.14; 95% CI, 0.85-1.51). There was no association between maternal age and overall cancer risk.

CONCLUSIONS

Higher birth weight and maternal weight gain are associated with increased cancer risk in adult men.

IMPACT

Our findings support the hypothesis that the in utero environment plays a role in the etiology of cancer in middle and older adulthood.

Birth Characteristics and Risk of Pediatric Thyroid Cancer: A Population-Based Record-Linkage Study in California

Background: Incidence rates of thyroid cancer in children and young adults (age 0-19 years) have nearly doubled over a recent 15-year period in the United States. Children with thyroid cancer may require long-term therapy and surveillance and are at greater risk for second primary malignancies. High-dose exposure to ionizing radiation is the only known nongenetic risk factor; the vast majority of cases have an unknown etiology. Methods: We conducted a population-based nested case-control study to evaluate the relationship between a range of birth characteristics and the risk of pediatric thyroid cancer. Using linked birth records and cancer registry data from California, we included 1012 cases who were diagnosed with first primary thyroid cancer at the age of 0-19 years from 1988 to 2015 and 50,600 birth-year matched controls (1:50 case to control ratio). We estimated adjusted odds ratios (OR) and 95% confidence intervals (CI) by using multivariable logistic regression models applied to the full population and stratified by thyroid cancer subtypes (papillary and follicular), race/ethnicity (white and Hispanic), and age at diagnosis (0-14 and 15-19 years). Results: Hispanic ethnicity (OR: 1.20 [CI 1.01-1.42]), higher birth weight (OR: 1.11 [CI 1.04-1.18] per 500g), and higher maternal education (13-15 years OR: 1.35 [CI 1.09-1.68], 16+ years OR: 1.35 [CI 1.07-1.71]) were associated with an increased risk of pediatric thyroid cancer, while male sex (OR: 0.21 [CI 0.18-0.25]) and higher birth order (third or higher OR: 0.81 [CI 0.68-0.98]) were associated with a decreased risk. Some heterogeneity was observed across subtype, most notably an elevated OR with higher birth order for follicular thyroid cancer, in contrast to the reduced risk for this category among papillary thyroid cancer cases (p-value for interaction = 0.01). Hispanic ethnicity was a risk factor for papillary, but not follicular thyroid cancer (p-value for interaction = 0.07). Conclusions: In this population-based study of birth characteristics and pediatric thyroid cancer, we identified several important risk factors for pediatric thyroid cancer, including female sex, Hispanic ethnicity, higher birth weight, higher maternal educational attainment, and lower birth order. Our data provide new areas for replication and investigation of biological mechanisms for this poorly understood malignancy.

Maternal DNA Methylation During Pregnancy: a Review

Multiple environmental, behavioral, and hereditary factors affect pregnancy. Recent studies suggest that epigenetic modifications, such as DNA methylation (DNAm), affect both maternal and fetal health during the period of gestation. Some of the pregnancy-related risk factors can influence maternal DNAm, thus predisposing both the mother and the neonate to clinical adversities with long-lasting consequences. DNAm alterations in the promoter and enhancer regions modulate gene expression changes which play vital physiological role. In this review, we have discussed the recent advances in our understanding of maternal DNA methylation changes during pregnancy and its associated complications such as gestational diabetes and anemia, adverse pregnancy outcomes like preterm birth, and preeclampsia. We have also highlighted some major gaps and limitations in the area which if addressed might improve our understanding of pregnancy and its associated adverse clinical conditions, ultimately leading to healthy pregnancies and reduction of public health burden.

Genistein Reduces the Risk of Local Mammary Cancer Recurrence and Ameliorates Alterations in the Gut Microbiota in the Offspring of Obese Dams

The risk of recurrence of estrogen receptor-positive breast cancer remains constant, even 20 years after diagnosis. Recurrence may be more likely in patients pre-programmed for it already in the womb, such as in the daughters born to obese mothers. Maternal obesity persistently alters offspring’s gut microbiota and impairs tumor immune responses. To investigate if the gut dysbiosis is linked to increased risk of mammary cancer recurrence in the offspring of obese rat dams, we fed adult offspring genistein which is known to have beneficial effects on the gut bacteria. However, the effects of genistein on breast cancer remain controversial. We found that genistein intake after tamoxifen response prevented the increased risk of local recurrence in the offspring of obese dams but had no effect on the control offspring. A significant increase in the abundance of inflammatory Prevotellaceae and Enterobacteriaceae, and a reduction in short-chain fatty acid producing Clostridiaceae was observed in the offspring of obese dams. Genistein supplementation reversed these changes as well as reversed increased gut metabolite N-acetylvaline levels which are linked to increased all-cause mortality. Genistein supplementation also reduced genotoxic tyramine levels, increased metabolites improving pro-resolving phase of inflammation, and reversed the elevated tumor mRNA expression of multiple immunosuppressive genes in the offspring of obese dams. If translatable to breast cancer patients, attempts to prevent breast cancer recurrences might need to focus on dietary modifications which beneficially modify the gut microbiota.

The Association Between High Birth Weight and Long-Term Outcomes-Implications for Assisted Reproductive Technologies: A Systematic Review and Meta-Analysis

Background: Studies have shown that the prevalence of children born with high birth weight or large for gestational age (LGA) is increasing. This is true for spontaneous pregnancies; however, children born after frozen embryo transfer (FET) as part of assisted reproductive technology (ART) also have an elevated risk. In recent years, the practice of FET has increased rapidly and while the perinatal and obstetric risks are well-studied, less is known about the long-term health consequences. Objective: The aim of this systematic review was to describe the association between high birth weight and LGA on long-term child outcomes. Data Sources: PubMed, Scopus, and Web of Science were searched up to January 2021. Exposure included high birth weight and LGA. Long-term outcome variables included malignancies, psychiatric disorders, cardiovascular disease, and diabetes. Study Selection: Original studies published in English or Scandinavian languages were included. Studies with a control group were included while studies published as abstracts and case reports were excluded. Data Extraction: The methodological quality, in terms of risk of bias, was assessed by pairs of reviewers. Robins-I (www.methods.cochrane.org) was used for risk of bias assessment in original articles. For systematic reviews, AMSTAR (www.amstar.ca) was used. For certainty of evidence, we used the GRADE system. The systematic review followed PRISMA guidelines. When possible, meta-analyses were performed. Results: The search included 11,767 articles out of which 173 met the inclusion criteria and were included in the qualitative analysis, while 63 were included in quantitative synthesis (meta-analyses). High birth weight and/or LGA was associated with low to moderately elevated risks for certain malignancies in childhood, breast cancer, several psychiatric disorders, hypertension in childhood, and type 1 and 2 diabetes. Conclusions: Although the increased risks for adverse outcome in offspring associated with high birth weight and LGA represent serious health effects in childhood and in adulthood, the size of these effects seems moderate. The identified risk association should, however, be taken into account in decisions concerning fresh and frozen ART cycles and is of general importance in view of the increasing prevalence in high birthweight babies.

Birth Weight and Subsequent Risk of Total Leukemia and Acute Leukemia: A Systematic Review and Meta-Analysis

Objective: Birth weight, an important indicator of fetal nutrition and degree of development, may affect the risk of subsequent leukemia. At present, little is known about the effect of birth weight on acute myeloid leukemia (AML) and whether there is a dose-dependent relationship of birth weight with acute lymphoid leukemia (ALL) and AML. To address these questions, the present work aimed to systematically investigate the relationship between birth weight and the risk of subsequent leukemia based on the current epidemiological studies Methods: Relevant studies were systematically retrieved from electronic databases PubMed, Embase, and Cochrane Library, from inception to May 15th, 2021. Finally, 28 studies (including 21 case-control studies and 7 cohort studies) were included for the final meta-analysis. Results in cohort studies were performed by risk ratios (RRs), while those in case-control studies by odds ratios (ORs), and all results were assessed by adopting the random-effect model. Besides, a dose-dependent analysis was conducted based on the cohort studies. Results: Compared with the population with normal birth weight (NBW), the population with high birth weight (HBW) might have an increased risk of leukemia (OR 1.33, 95%CI 1.20-1.49; I ² 0%). Meanwhile, low birth weight (LBW) was associated with a decreased risk of ALL, as evidenced from the pooled analysis of case-control studies (OR 0.83, 95% CI 0.75-0.92; I ² 23.3%). However, relative to NBW population, the HBW population might have an increased risk of ALL (OR 1.28, 95% CI 1.20-1.35; I ² 7%). There was no obvious evidence supporting the relationship between LBW and the risk of AML from the pooled analysis of case-control studies (OR, 1.11 95% CI 0.87-1.42; I ² 31.7%). Conclusions: Overall, in children and young adults, HBW population may be associated with the risks of subsequent leukemia and AML relative to NBW population, but the supporting dose-dependent evidence is lacking. In addition, compared with NBW population, there is stronger evidence supporting a significantly increased risk of subsequent ALL in HBW population, and a decreased risk in LBW population in a dose-dependent manner. More prospective studies with large samples are warranted in the future to validate and complement these findings.

Perinatal and postnatal exposures and risk of young-onset breast cancer

Background

Perinatal factors have been associated with some adult health outcomes, but have not been well studied in young-onset breast cancer. We aimed to evaluate the association between young-onset breast cancer and perinatal exposures and to explore etiologic heterogeneity in the relationship between associated perinatal factors and estrogen receptor status of the tumor.

Methods

We addressed this in a sister-matched case-control study. Cases were women who had been diagnosed with ductal carcinoma in situ or invasive breast cancer before the age of 50. Each case had a sister control who was free of breast cancer up to the same age at which her case sister developed the disease. The factors considered were self-reported and included the mother’s preeclampsia in that pregnancy, mother’s smoking in that pregnancy, gestational hypertension, prenatal diethylstilbestrol use, and gestational diabetes, as well as low birth weight (less than 5.5 pounds), high birth weight (greater than 8.8 pounds), short gestational length (less than 38 completed weeks), and being breastfed or being fed soy formula.

Results

In conditional logistic regression analyses, high birth weight (odds ratio [OR] = 1.59, 95% confidence interval [CI] 1.07–2.36) and preeclampsia (adjusted OR = 1.92, CI 0.824–4.5162) were positively associated with risk. The association with preeclampsia was stronger when the analysis was restricted to invasive breast cancer (OR = 2.87, CI 1.08–7.59). We also used case-only analyses to assess etiologic heterogeneity for estrogen receptor (ER)-positive versus estrogen receptor-negative cancer. Women who were born to a preeclamptic pregnancy and later developed young-onset breast cancer were at increased odds for the ER-negative type (OR = 2.27; CI 1.05–4.92).

Conclusion

These results suggest that being born to a preeclamptic pregnancy may increase risk for young-onset breast cancer, especially for the ER-negative subtype.

Effects of Maternal Grape Juice Intake on Unfolded Protein Response in the Mammary Glands of Offspring of High Fat Diet Fed Rat Dams

Maternal high fat diet (HFD) and obesity during pregnancy increase female offspring′s mammary cancer risk in animal studies. We aimed to observe whether the consumption of grape juice during pregnancy can reverse this risk. During pregnancy and lactation, female Wistar rats were fed either a control or HFD and also received grape juice or tap water. At the age of 50 days, female offspring were euthanized, and mammary glands were collected to assess changes in biomarkers of increased mammary cancer risk. Maternal HFD increased the number of terminal end buds in offspring’s mammary glands and promoted cell proliferation (ki67). Maternal grape consumption blocked these effects. Apoptosis marker caspase 7, but not caspase 3, was reduced in the HFD offspring. HFD offspring also exhibited a reduction in the indicators of cell cycle regulation (p27, p21) and an ability to maintain DNA integrity (reduced p53). Maternal grape juice did not have any effect on these endpoints in the HFD offspring but reduced caspase 7 and p53 levels in the control offspring, perhaps reflecting reduced cellular stress. Maternal HFD increased oxidative stress marker GPx1 mRNA expression, and grape juice increased the levels of GPx2 in both the control and HFD offspring. HFD increased XBP1/Xbp1s, Atf4 and Atf6 mRNA expression and reduced ATF6 and CHOP protein levels. Maternal grape juice reversed the increase in XBP1/Xbp1s, Atf4 and Atf6 in the HFD offspring. PPARγ was downregulated in the HFD group, and grape juice reversed this effect. Grape juice also reduced the levels of HER2 and IRS, both in the control and HFD offspring. In conclusion, maternal grape juice supplementation reversed some of the biomarkers that are indicative of increased breast cancer risk in the HFD offspring.

Birth Weight and Incidence of Breast Cancer: Dose-Response Meta-analysis of Prospective Studies

BACKGROUND

Many studies have shown the association between birth weight and breast cancer (BC), but the evidence remains limited and inconsistent, especially in different menopause status. We sought to clarify the relationship and shape of the dose-response relation between birth weight and BC.

METHODS

The Web of Science, PubMed, and Embase databases were searched for prospective studies involving the relationship between birth weight and risk of BC published to November 2019. Random effects of generalized least squares regression models were used to estimate the quantitative dose-response association, and restricted cubic splines were used to model the association.

RESULTS

We included reports of 16 prospective studies describing 16,000 incident cases among 553,644 participants. We identified a modest-in-magnitude, but significant, association between birth weight and BC risk: risk increased by 2% (risk ratio, 1.02, 95% confidence interval, 1.01-1.03) and 9% (risk ratio, 1.09, 95% confidence interval, 1.04-1.15) with a per-500 g birth weight increment in all ages and premenopausal women, respectively. Our results showed a linear dose-response relationship between birth weight and BC risk (P_nonlinearity = .311) in premenopausal women, with statistical significance when birth weight was above about 3.5 kg. No significant association was found in postmenopausal women.

CONCLUSION

Higher birth weight has a relationship with increased risk of BC in premenopausal women, particularly when birth weight is above 3.5 kg.

Maternal and Infant Anthropometric Characteristics and Breast Cancer Incidence in the Daughter

The intrauterine and early life environments have been linked to the etiology of breast cancer in prior studies. We prospectively examined whether maternal and newborn anthropometric factors as reported by the mother are related to an increased incidence of adult breast cancer in the daughter. We used data from 35,133 mother-daughter dyads of the Nurses’ Health Study (NHS) II and the Nurses’ Mothers’ Cohort Study. In 2001, living mothers of NHS II participants who were free of cancer completed a questionnaire on their pregnancy with the nurse and their nurse daughter’s early life experience. During 403,786 years of follow-up, 865 daughters developed incident cases of invasive breast cancer. Nurses with a birthweight of ≥4000 g had a 32% greater risk for breast cancer (multivariable-adjusted hazard ratio (HR) = 1.32, 95% confidence interval (CI) = 1.02–1.71, p-trend = 0.09) compared with those with birthweights of 3000–3499 g. Higher birth length tended to increase risk of premenopausal breast cancer (p for trend = 0.05). We further noted a modest U-shaped relation between maternal weight gain during pregnancy and premenopausal breast cancer incidence in the daughter. Fetal growth may contribute to shaping later life risk for breast cancer, especially prior to menopause.

Reversal of increased mammary tumorigenesis by valproic acid and hydralazine in offspring of dams fed high fat diet during pregnancy

Maternal or paternal high fat (HF) diet can modify the epigenome in germ cells and fetal somatic cells leading to an increased susceptibility among female offspring of multiple generations to develop breast cancer. We determined if combined treatment with broad spectrum DNA methyltransferase (DNMT) inhibitor hydralazine and histone deacetylase (HDAC) inhibitor valproic acid (VPA) will reverse this increased risk. C57BL/6 mouse dams were fed either a corn oil-based HF or control diet during pregnancy. Starting at age 7 weeks, female offspring were administered 3 doses of 7,12-dimethylbenz[a]anthracene (DMBA) to initiate mammary cancer. After last dose, offspring started receiving VPA/hydralazine administered via drinking water: no adverse health effects were detected. VPA/hydralazine reduced mammary tumor multiplicity and lengthened tumor latency in HF offspring when compared with non-treated HF offspring. The drug combination inhibited DNMT3a protein levels and increased expression of the tumor suppressor gene Cdkn2a/p16 in mammary tumors of HF offspring. In control mice not exposed to HF diet in utero, VPA/hydralazine increased mammary tumor incidence and burden, and elevated expression of the unfolded protein response and autophagy genes, including HIF-1α, NFkB, PERK, and SQSTM1/p62. Expression of these genes was already upregulated in HF offspring prior to VPA/hydralazine treatment. These findings suggest that breast cancer prevention strategies with HDAC/DNMT inhibitors need to be individually tailored.

Early-Life Growth and Benign Breast Disease

Using prospective data from the Early Determinants of Mammographic Density study (United States, 1959-2008, n = 1121), we examined the associations between maternal body size, birth size, and infant and early childhood growth during 3 time periods (0-4 months, 4-12 months, and 1-4 years) and benign breast disease (BBD) using multivariable logistic regression with generalized estimating equations. A total of 197 women (17.6%) reported receiving a diagnosis of BBD by a physician. Higher body mass index at age 7 years was inversely associated with BBD risk. Rapid weight gain from age 1 year to 4 years, defined as an increase of least 2 major percentiles (e.g., 5th, 10th, 25th, 50th, 75th, and 95th) relative to stable growth, defined as remaining within 2 percentiles, was also inversely associated with BBD (odds ratio (OR) = 0.51, 95% confidence interval (CI): 0.23, 1.15). In contrast, rapid weight gain in infancy was positively associated with BBD relative to stable growth (from 0 to 4 months, OR = 1.65, 95% CI: 1.04, 2.62; from 4 to 12 months, 1.85, 95% CI: 0.89, 3.85), independent of birth weight, which was not associated with BBD. Our results suggest that patterns of early-life weight gain are important to BBD risk. Thus, susceptibility to BBD, like susceptibility to breast cancer, might start in early life.

Current opportunities to catalyze research in nutrition and cancer prevention - an interdisciplinary perspective

Cancer Research UK and Ludwig Cancer Research convened an inaugural international Cancer Prevention and Nutrition Conference in London on December 3-4, 2018. Much of the discussion focused on the need for systematic, interdisciplinary approaches to better understand the relationships of nutrition, exercise, obesity and metabolic dysfunction with cancer development. Scientists at the meeting underscored the importance of studying the temporal natural history of exposures that may cumulatively impact cancer risk later in life.A robust dialogue identified obesity as a major risk for cancer, and the food environment, especially high energy and low nutrient processed foods, as strong and prevalent risk factors for obesity. Further engagement highlighted challenges in the post-diagnostic setting, where similar opportunities to understand the complex interplay of nutrition, physical activity, and weight will inform better health outcomes.Going forward, holistic research approaches, encompassing insights from multiple disciplines and perspectives, will catalyze progress urgently needed to prevent cancer and improve public health.

Childhood growth and risk of inflammatory bowel disease: a population-based study of 317,030 children

Background: Growth in childhood is associated with later development of autoimmune diseases and cancer, but the impact of growth on risk of inflammatory bowel disease (IBD) remains unknown. We conducted a population-based cohort study to examine whether birth weight, childhood height, or changes in height associated with later risk of IBD. Methods: Our cohort consisted of 317,030 children from the Copenhagen School Health Records Register (born 1930-1989) with height repeatedly measured from age 7 to 13 and with data on birth weight on a subset. Through linkage to the Danish National Patients Register, cases of IBD were identified. Cox proportional hazard regression was used to examine associations between measures of childhood growth and risk of IBD. Results: During more than 9 million years of follow-up, 1612 individuals were diagnosed with Crohn's disease (CD) and 2,640 with ulcerative colitis (UC). Birth weight and childhood heights were not associated with subsequent risk of CD or UC (HRs close to 1.00). Childhood growth from 7 to 10 years (CD: HR, 1.00; 95% CI, 0.85-1.18; UC: HR, 0.92; 95% CI, 0.81-1.05) and 10 to 13 years (CD: HR, 1.02; 95% CI, 0.89-1.17; UC: HR, 0.95; 0.85-1.05) did not associate with risk of IBD either. Conclusion: In this large population-based cohort study, birth weight and childhood growth did not influence risk of IBD, which contrasts with observations in other chronic diseases. Thereby, the study also suggests that pre-clinical effects of adult IBD are not measurable in childhood and that childhood risk factors for IBD do not influence growth.

The association between weight at birth and breast cancer risk revisited using Mendelian randomisation

Observational studies suggest that higher birth weight (BW) is associated with increased risk of breast cancer in adult life. We conducted a two-sample Mendelian randomisation (MR) study to assess whether this association is causal. Sixty independent single nucleotide polymorphisms (SNPs) known to be associated at P < 5 × 10-8 with BW were used to construct (1) a 41-SNP instrumental variable (IV) for univariable MR after removing SNPs with pleiotropic associations with other breast cancer risk factors and (2) a 49-SNP IV for multivariable MR after filtering SNPs for data availability. BW predicted by the 41-SNP IV was not associated with overall breast cancer risk in inverse-variance weighted (IVW) univariable MR analysis of genetic association data from 122,977 breast cancer cases and 105,974 controls (odds ratio = 0.86 per 500 g higher BW; 95% confidence interval 0.73-1.01). Sensitivity analyses using four alternative methods and three alternative IVs, including an IV with 59 of the 60 BW-associated SNPs, yielded similar results. Multivariable MR adjusting for the effects of the 49-SNP IV on birth length, adult height, adult body mass index, age at menarche, and age at menopause using IVW and MR-Egger methods provided estimates consistent with univariable analyses. Results were also similar when all analyses were repeated after restricting to estrogen receptor-positive or -negative breast cancer cases. Point estimates of the odds ratios from most analyses performed indicated an inverse relationship between genetically-predicted BW and breast cancer, but we are unable to rule out an association between the non-genetically-determined component of BW and breast cancer. Thus, genetically-predicted higher BW was not associated with an increased risk of breast cancer in adult life in our MR study.

Do Birth Weight and Weight Gain During Infancy and Early Childhood Explain Variation in Mammographic Density in Women in Midlife? Results From Cohort and Sibling Analyses

High birth weight is associated with increased breast cancer risk and, less consistently, with higher mammographic density. In contrast, adolescent body size has been consistently, negatively associated with both MD and breast cancer risk. It is unclear when the direction of these associations changes and whether weight gain in infancy is associated with MD. We evaluated the associations of birth weight and postnatal weight (measured at 4 months, 1 year, and 4 years) by absolute and velocity measures (relative within-cohort percentile changes) with adult mammographic density, assessed using a computer-assisted thresholding program (Cumulus), using linear regression models with generalized estimating equations to account for correlation between siblings in the Early Determinants of Mammographic Density study (1959-2008; n = 700 women with 116 sibling sets; mean age = 44.1 years). Birth weight was positively associated with dense area (per 1-kg increase, β = 3.36, 95% confidence interval (CI): 0.06, 6.66). Weight gains from 0 months to 4 months and 1 year to 4 years were negatively associated with dense area (for 10-unit increase in weight percentile, β = -0.65, 95% CI: -1.23, -0.07, and β = -1.07, 95% CI: -1.98, -0.16, respectively). Findings were similar in the sibling subset. These results support the hypothesis that high birth weight is positively associated with increased breast density and suggest that growth spurts starting in early infancy reduce mammographic dense area in adulthood.

Associations of Maternal Exposure to Dichlorodiphenyltrichloroethane and Pyrethroids With Birth Outcomes Among Participants in the Venda Health Examination of Mothers, Babies and Their Environment Residing in an Area Sprayed for Malaria Control

Although effective in controlling malaria, indoor residual spraying results in elevated exposure to insecticides such as dichlorodiphenyltrichloroethane (DDT) and pyrethroids. These chemicals cross the placenta, but no studies have examined their associations with birth outcomes in populations residing in indoor residual spraying areas. We investigated this question in the Venda Health Examination of Mothers, Babies and Their Environment (VHEMBE), a birth cohort study of 751 South African children born between 2012 and 2013. We measured maternal peripartum serum DDT and urine pyrethroid metabolite concentrations and collected data on birth weight, length, head circumference, and duration of gestation. We analyzed the data using marginal structural models with inverse-probability-of-treatment weights, generalized propensity scores, and standard conditional linear regression. Using all 3 analytical methods, p,p'-DDT, o,p'-DDT, and to a lesser extent p,p'-dichlorodiphenyldichloroethylene were related to elevated birth weight, birth length, and head circumference among girls. Changes in gestational duration did not mediate this relationship, suggesting that these exposures accelerate fetal growth, which is consistent with the known estrogenic properties of o,p'-DDT and p,p'-DDT. No associations with pyrethroid metabolites were found. Results suggest that prenatal exposure to DDT is related to elevated birth size. Further studies are needed to elucidate the implications of these findings.

Body fatness at a young age, body fatness gain and risk of breast cancer: systematic review and meta-analysis of cohort studies

Higher body fatness in adulthood has been consistently associated with an increased risk of postmenopausal breast cancer, as well as a tendency towards a lower risk of premenopausal breast cancer. However, the association between body fatness at a young age (≤30 years), body fatness gain and the risk of breast cancer is less defined. PubMed and Web of Science databases were searched to identify relevant publications. Risk estimates with 95% confidence intervals from each study were transformed into a continuous variable for each 5 kg m^-2 increase in body mass index (BMI) and were pooled under a random-effects model. Each 5 kg m^-2 increase in BMI was significantly associated with a 14%, 12% and 17% lower risk of breast cancer later in life among all women, premenopausal women and postmenopausal women, respectively. Significant heterogeneity and publication bias were observed. The results remained unchanged after the trim and fill method was applied to correct the bias. Each 5 kg m^-2 increase in BMI from a young age until cohort entry was significantly associated with a 13% and 14% higher risk of breast cancer in all women and postmenopausal women, respectively. In summary, higher body fatness at a young age may have a protective role in the later development of breast cancer in both premenopausal and postmenopausal women. However, this potential benefit should not be overemphasized, as our findings suggest that increased body fatness gain from a young age is positively associated with postmenopausal breast cancer risk. These findings further justify the need to maintain a steady weight throughout life.

Incidence of breast cancer in Chinese women exposed to the 1959-1961 great Chinese famine

BACKGROUND

The association of malnutrition in early life with breast cancer risk has been studied in Europe by investigating survivors of the Dutch Hunger Winter Famine, but not in China. We evaluated the effect of exposure to the 1959-1961 Great Leap Forward famine on subsequent breast cancer risk in Chinese women.

METHODS

A total of 59,060 women born in 1955~1966 were recruited from Minhang district, Shanghai, China, during the period 2008 to 2012. A baseline survey was conducted to collect demographic characteristics and known risk factors for breast cancer. Incident breast cancers were identified by conducting record linkage with the Shanghai Cancer Registry up to June 30, 2015, and confirmed through medical records. Cumulative probabilities of cancer incidence were evaluated after adjusting for age, educational level and other confounders. Cox regression models were applied to estimate the hazard ratios (HR) and 95% confidence intervals (CI) of breast cancer.

RESULTS

The overall crude incidence of in situ and invasive breast cancer were 19.2 and 115.0 per 100,000, respectively, in women conceived or born during the famine (1959-1962), slightly higher than those in women born before (1955-1958) (13.2 and 109.8/100,000) and after (1963-1966) (10.4 and 101.5/100,000). Particularly, at age group of 50-52 years when all participants contributed person-year of observations, the age-specific incidence of invasive breast cancer was higher in pre-natal exposed women (123.7/100,000, 95%CI: 94.5-161.9/100,000) than in post-natal exposed (109.6/100,000, 95%CI: 69.1-174.0/100,000) and unexposed women (82.7/100,000, 95%CI: 46.9-145.7/100,000). However, the incidence of cancer in situ was slightly lower in pre-natal exposed women at the age group. Adjusted cumulative probabilities of breast cancer incidence, both in-situ and invasive, were also observed to be higher in women exposed to the famine, however, the difference was not statistically significant.

CONCLUSION

Our results suggest a possible adverse, but limited, impact of exposure to the Great famine on the risk of breast cancer in Chinese women.

Impact of folic acid intake during pregnancy on genomic imprinting of IGF2/H19 and 1-carbon metabolism

Folic acid is an essential component of 1-carbon metabolism, which generates methyl groups for DNA methylation. Disruption of genomic imprinting leads to biallelic expression which may affect disease susceptibility possibly reflected in high levels of S-adenosyl-homocysteine (SAH) and low levels of S-adenosyl-methionine (SAM). We investigated the association between folic acid supplementation during pregnancy and loss of imprinting (LOI) of IGF2 and H19 genes in placentas and cord blood of 90 mother-child dyads in association with the methylenetetrahydrofolate reductase (MTHFR) genotype. Pyrosequencing was used to evaluate deviation from monoallelic expression among 47 placentas heterozygous for H19 and 37 placentas and cord blood tissues heterozygous for IGF2 and H19 methylation levels of 48 placentas. We detected relaxation of imprinting (ROI) and LOI of H19 in placentas not associated with differences in methylation levels of the H19ICR. Placentas retained monoallelic allele-specific gene expression of IGF2, but 32.4% of cord blood samples displayed LOI of IGF2 and 10.8% showed ROI. High SAH levels were significantly associated with low H19 methylation. An interesting positive association between SAM/SAH ratio and high H19 methylation levels was detected among infants with low B₁₂ levels. Our data suggest profound differences in regulation of imprinting in placenta and cord blood; a lack of correlation of the methylome, transcriptome, and proteome; and a complex regulatory feedback network between free methyl groups and genomic imprinting at birth.-Tserga, A., Binder, A. M., Michels, K. B. Impact of folic acid intake during pregnancy on genomic imprinting of IGF2/H19 and 1-carbon metabolism.

Role of Growth Hormone in Breast Cancer

Breast cancer is one of the most common cancers diagnosed in women. Approximately two-thirds of all breast cancers diagnosed are classified as hormone dependent, which indicates that hormones are the key factors that drive the growth of these breast cancers. Ovarian and pituitary hormones play a major role in the growth and development of normal mammary glands and breast cancer. In particular, the effect of the ovarian hormone estrogen has received much attention in regard to breast cancer. Pituitary hormones prolactin and growth hormone have also been associated with breast cancer. Although the role of these pituitary hormones in breast cancers has been studied, it has not been investigated extensively. In this review, we attempt to compile basic information from most of the currently available literature to understand and demonstrate the significance of growth hormone in breast cancer. Based on the available literature, it is clear that growth hormone plays a significant role in the development, progression, and metastasis of breast cancer by influencing tumor angiogenesis, stemness, and chemoresistance.

Social and anthropometric factors explaining racial/ethnical differences in birth weight in the United States

Though disparities in birth weight by race/ethnicity have been extensively reported in the United States, few studies have systematically investigated factors attributing to its variability. For 10,638,415 singleton infants born during 2009-2012 in the United States, we examined birth weight differences among 14 races and ethnicities (non-Hispanic white, non-Hispanic Black, American Indian, Asian Indian, Chinese, Filipino, Japanese, Korean, Vietnamese, Hawaiian, Guamanian, Mexican, Puerto Rican and Cuban), after sequentially adjusting for maternal, socio-economic and behavioral factors. Average birthweight of non-Hispanic white infants was 3381 g, while for other races/ethnicities birth weight ranged from being 289 g smaller in Japanese to 126 g larger in Samoan infants. Factors explaining differences of more than 50 grams in birth weight compared to white infants were: gestational age for black infants, height and body mass index for all Asian and Samoan mothers, and gestational weight gain for Japanese mothers. Difference in maternal age, parity, socioeconomic and behavioral characteristics did not account for significant portion of birthweight variations for any race. Our findings suggest that differences in maternal anthropometrics, gestational weight gain, and preterm birth rate, but not in maternal age, parity, socioeconomic or behavioral characteristics contribute to racial/ethnic differences in birthweight.

Maternal height and breast cancer risk: results from a study nested within the EPIC-Greece cohort

The positive association of adult height with breast cancer (BC) risk has been hypothesized to be partly accounted for by an association of this risk with maternal height (operating in utero to modify hormone effects). In a case-control study (271 BC patients and 791 controls) nested within the EPIC-Greece cohort, we applied mediation analysis to calculate the direct and indirect (through the woman's own height) effect of maternal height on BC risk. Per 5 cm increase in maternal height and depending on its reference value: the indirect effect odds ratio ranges from 1.02 to 1.07; the direct effect odds ratio from 1.06 to 1.11; and the total (direct and indirect effects) from 1.08 to 1.19. The effect sizes consistently increased for higher reference categories of maternal height, but did not generally reach statistical significance, possibly due to the limited sample size.

Body size from birth through adolescence in relation to risk of benign breast disease in young women

PURPOSE

Body size, from birth throughout adulthood, is associated with breast cancer risk, but few studies have investigated early-life body size and benign breast disease (BBD), a well-established breast cancer risk factor. We consider whether prenatal factors and size at birth, 10, 18 year, and intervening growth, are related to BBD risk.

METHODS

The Growing Up Today Study includes 9032 females who completed questionnaires annually from 1996 to 2001, then 2003, 2005, 2007, 2010, and 2013. In 1996, their mothers provided pregnancy-related data. From 2005 to 2013, participants (18 year+) reported whether they had ever been diagnosed with biopsy-confirmed BBD (N = 142 cases).

RESULTS

Girls had greater adiposity (BMI; kg/m2) at 10 year if they were larger at birth, if mother's pre-pregnancy BMI was higher, or if gestational weight gain was greater (all p < .01). Maternal height was (positively) associated (p < .05) with adolescent peak height growth velocity (PHV; in./year). Greater 10 year adiposity was associated with lower PHV and less height growth 10-18 year (both p < .01). Adiposity at 10 year was inversely associated with BBD (OR 0.83/(kg/m2), p < .01) as was increasing adiposity 10-18 year (OR 0.85/(kg/m2), p = .01). In a separate model, 10 year height (OR 1.13/in., p = .02) and height growth 10-18 year (OR 1.19/in.; p < .01) were positively associated. PHV was similarly positively associated (OR 2.58, p = .01, fastest versus slowest growth quartiles). In a multivariable model of BBD risk, gestational weight gain (daughters at highest risk if <20 lb gained), PHV (slowest growing girls at lowest risk), age 10 year height (positive), and BMI (inverse) were the most critical childhood risk factors (each p < .05).

CONCLUSIONS

Body size factors from pregnancy through adolescence were independently associated with BBD risk in young women.

Previous GWAS hits in relation to young-onset breast cancer

PURPOSE

Genome-wide association studies (GWAS) have identified dozens of single-nucleotide polymorphisms (SNPs) associated with breast cancer. Few studies focused on young-onset breast cancer, which exhibits etiologic and tumor-type differences from older-onset disease. Possible confounding by prenatal effects of the maternal genome has also not been considered.

METHODS

Using a family-based design for breast cancer before age 50, we assessed the relationship between breast cancer and 77 GWAS-identified breast cancer risk SNPs. We estimated relative risks (RR) for inherited and maternally mediated genetic effects. We also used published RR estimates to calculate genetic risk scores and model joint effects.

RESULTS

Seventeen of the candidate SNPs were nominally associated with young-onset breast cancer in our 1296 non-Hispanic white affected families (uncorrected p value <0.05). Top-ranked SNPs included rs3803662-A (TOX3, RR = 1.39; p = 7.0 × 10-6), rs12662670-G (ESR1, RR = 1.56; p = 5.7 × 10-4), rs2981579-A (FGFR2, RR = 1.24; p = 0.002), and rs999737-G (RAD51B, RR = 1.37; p = 0.003). No maternally mediated effects were found. A risk score based on all 77 SNPs indicated that their overall relationship to young-onset breast cancer risk was more than additive (additive-fit p = 2.2 × 10-7) and consistent with a multiplicative joint effect (multiplicative-fit p = 0.27). With the multiplicative formulation, the case sister's genetic risk score exceeded that of her unaffected sister in 59% of families.

CONCLUSIONS

The results of this family-based study indicate that no effects of previously identified risk SNPs were explained by prenatal effects of maternal variants. Many of the known breast cancer risk variants were associated with young-onset breast cancer, with evidence that TOX3, ESR1, FGFR2, and RAD51B are important for young-onset disease.

Maternal Anthropometry and Mammographic Density in Adult Daughters

OBJECTIVE

We examined the relation between maternal anthropometry and mammographic density in the adult daughter using prospectively collected data.

METHODS

Our study included a total of 700 mother-daughter dyads participating in an adult follow-up of women born in 2 US birth cohorts: the Child Health and Development Study and the Boston, Massachusetts, and Providence, Rhode Island sites of the National Collaborative Perinatal Project.

RESULTS

We observed an increased percent breast density at a mean age of 43.1 years in the daughters of mothers who gained 5 kg or less during pregnancy compared with mother-daughter pairs in which the mother gained 5 to 10 kg (β = 4.8, 95% confidence interval: 1.0 to 8.6). The daughters of mothers who were overweight at the time of conception (prepregnancy BMI ≥25) and who gained >5 kg during pregnancy had a lower percent density (β = -3.2, 95% confidence interval: -6.2 to -0.2) compared with mothers with a BMI <25 at conception who gained >5 kg.

CONCLUSIONS

We did not find any strong and consistent patterns between maternal anthropometry and the daughter's breast density, a strong predictor of breast cancer risk. A modest association between low gestational weight gain and increased breast density 40 years later in the daughter was observed, even after accounting for adult body size, and if confirmed, possible mechanisms need to be further elucidated.

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.

Pre-natal exposures and breast tissue composition: findings from a British pre-birth cohort of young women and a systematic review

BACKGROUND

Breast density, the amount of fibroglandular tissue in the adult breast for a women's age and body mass index, is a strong biomarker of susceptibility to breast cancer, which may, like breast cancer risk itself, be influenced by events early in life. In the present study, we investigated the association between pre-natal exposures and breast tissue composition.

METHODS

A sample of 500 young, nulliparous women (aged approximately 21 years) from a U.K. pre-birth cohort underwent a magnetic resonance imaging examination of their breasts to estimate percent water, a measure of the relative amount of fibroglandular tissue equivalent to mammographic percent density. Information on pre-natal exposures was collected throughout the mothers' pregnancy and shortly after delivery. Regression models were used to investigate associations between percent water and pre-natal exposures. Mediation analysis, and a systematic review and meta-analysis of the published literature, were also conducted.

RESULTS

Adjusted percent water in young women was positively associated with maternal height (p for linear trend [p t] = 0.005), maternal mammographic density in middle age (p t = 0.018) and the participant's birth size (p t < 0.001 for birthweight). A 1-SD increment in weight (473 g), length (2.3 cm), head circumference (1.2 cm) and Ponderal Index (4.1 g/cm3) at birth were associated with 3 % (95 % CI 2-5 %), 2 % (95 % CI 0-3 %), 3 % (95 % CI 1-4 %) and 1 % (95 % CI 0-3 %), respectively, increases in mean adjusted percent water. The effect of maternal height on the participants' percent water was partly mediated through birth size, but there was little evidence that the effect of birthweight was primarily mediated via adult body size. The meta-analysis supported the study findings, with breast density being positively associated with birth size.

CONCLUSIONS

These findings provide strong evidence of pre-natal influences on breast tissue composition. The positive association between birth size and relative amount of fibroglandular tissue indicates that breast density and breast cancer risk may share a common pre-natal origin.

The Theory of the Sick Breast Lobe and the Possible Consequences

We hypothesize that carcinoma in situ, and consequently breast carcinoma in general, is a lobar disease because the simultaneously or asynchronously appearing, often multiple tumor foci develop within a single lobe. The sick lobe carries some kind of genetic instability already from its initialization during the early embryonic life and is more sensitive to noxious influences than the other lobes within the same breast. Decades of postnatal life with accumulation of additional genetic alterations are needed for malignant transformation of the cells within the sick lobe. The transformation is often multifocal (involving separate distant lobules of this lobe) or diffuse (involving the larger ducts). This hypothesis offers new perspectives in cancer prevention, because selective visualization, excision, or destruction of the sick lobe before development of malignant lesions would substantially reduce the incidence of breast carcinoma.

Body fatness throughout the life course and the incidence of premenopausal breast cancer

BACKGROUND

The role of body fatness in the aetiology of breast cancer is complex. We evaluated the independent and synergistic effects of body fatness, at different stages throughout a woman's life course, on premenopausal breast cancer risk.

METHODS

Premenopausal participants of the Nurses' Health Study II (NHSII) were followed from 1991 up to 2009. Body fatness factors including birthweight, somatotype (a 9-level pictogram with level 1 being the leanest) at ages 5 and 10 years and body mass index (BMI) at age 18 were collected at baseline. Current BMI was updated biennially. Multivariate Cox regression models were used to evaluate the association between each body fatness factor as well as cross-classification of all factors and the incidence of breast cancer.

RESULTS

Based on 1574 incident premenopausal breast cancer cases and 1 133 893 person-years of follow-up, a lower incidence was associated with lower birthweight: hazard ratio (HR) [95% confidence interval (CI)] = 0.74 (0.58-0.95) for <2.5kg vs 3.9+kg, P for trend < 0.001; higher somatotype at age 5: HR=0.57 (95% CI 0.44-0.73) for 5-9 vs 1, P fortrend < 0.0001]; and at age 10: HR=0.61 (95% CI 0.49-0.75) for 5-9 vs 1, P for trend < 0.0001]; and BMI at age 18: HR=0.67 (95% 0.47-0.95) for ≥ 27.5 kg/m² vs < 18.5 kg/m², P for trend = 0.009], after adjusting for age and body fatness measures earlier in life and other risk factors, respectively. No significant interaction between body fatness measures was found. Women with the lowest birthweight, the highest somatotype at ages 5 and 10 and the highest BMI at age 18 and currently had a 72% (95% CI 54%-83%) lower incidence of invasive premenopausal breast cancer than women with the opposite extreme of each body fatness indicator.

CONCLUSION

The lowest incidence of premenopausal breast cancer was associated with the lowest birthweight and the highest childhood, adolescent and early adult body fatness.

A family-based, genome-wide association study of young-onset breast cancer: inherited variants and maternally mediated effects

Young-onset breast cancer shows certain phenotypic and etiologic differences from older-onset breast cancer and may be influenced by some distinct genetic variants. Few genetic studies of breast cancer have targeted young women and no studies have examined whether maternal variants influence disease in their adult daughters through prenatal effects. We conducted a family-based, genome-wide association study of young-onset breast cancer (age at diagnosis <50 years). A total of 602 188 single-nucleotide polymorphisms (SNPs) were genotyped for 1279 non-Hispanic white cases and their parents or sisters. We used likelihood-based log-linear models to test for transmission asymmetry within families and for maternally mediated genetic effects. Three autosomal SNPs (rs28373882, P=2.8 × 10(-7); rs879162, P=9.2 × 10(-7); rs12606061, P=9.1 × 10(-7)) were associated with risk of young-onset breast cancer at a false-discovery rate below 0.20. None of these loci has been previously linked with young-onset or overall breast cancer risk, and their functional roles are unknown. There was no evidence of maternally mediated, X-linked, or mitochondrial genetic effects, and no notable findings within cancer subcategories defined by menopausal status, estrogen receptor status, or by tumor invasiveness. Further investigations are needed to explore other potential genetic, epigenetic, or epistatic mechanisms and to confirm the association between these three novel loci and young-onset breast cancer.

Prenatal factors and infant feeding in relation to risk of benign breast disease in young women

Benign breast disease (BBD) is a well-established risk factor for breast cancer, but little work has considered a girl's early life and her risk for BBD in adulthood. We investigated factors, from pre-conception through infant feeding practices, in relation to subsequent BBD risk in young women. The Growing Up Today Study (GUTS) includes 9032 females, born 1980-1987, who completed questionnaires annually from 1996 through 2001, then 2003, 2005, 2007, 2010, and 2013. In 1996, their mothers provided each participant's birth weight and length, gestational age, biological father's height, and infant feeding factors (e.g., breast-fed, type of formula). In 1999, their mothers reported maternal pre-pregnancy weight and weight gain during index pregnancy. Beginning in 2005, daughters (18 years+) reported whether they had ever been diagnosed with biopsy-confirmed BBD (n = 142 cases, through 2013). Logistic regression estimated associations between early life factors and biopsy-confirmed BBD. Girls whose mother's BMI prior to pregnancy was 20-25 kg/m(2) were at lower risk of BBD as young women (OR = 0.66, p = 0.04, vs. maternal pre-pregnancy BMI < 20). Girls whose mothers gained 20 + pounds (vs. <20 pounds) during pregnancy were at lower risk (among full-term singleton births: OR = 0.48, p = 0.007, if mother gained 20-35 pounds). However, neither birth weight nor BMI at birth were associated with subsequent BBD risk. We found no evidence that infant feeding practices were linked to BBD. A healthy maternal BMI before pregnancy and sufficient weight gain during pregnancy may produce daughters at lower risk for BBD as young women. Further examination of these findings is needed.

High Birth Weight Increases the Risk for Bone Tumor: A Systematic Review and Meta-Analysis

There have been several epidemiologic studies on the relationship between high birth weight and the risk for bone tumor in the past decades. However, due to the rarity of bone tumors, the sample size of individual studies was generally too small for reliable conclusions. Therefore, we have performed a meta-analysis to pool all published data on electronic databases with the purpose to clarify the potential relationship. According to the inclusion and exclusion criteria, 18 independent studies with more than 2796 cases were included. As a result, high birth weight was found to increase the risk for bone tumor with an Odds Ratio (OR) of 1.13, with the 95% confidence interval (95% CI) ranging from 1.01 to 1.27. The OR of bone tumor for an increase of 500 gram of birth weight was 1.01 (95% CI 1.00–1.02; p = 0.048 for linear trend). Interestingly, individuals with high birth weight had a greater risk for osteosarcoma (OR = 1.22, 95% CI 1.06–1.40, p = 0.006) than those with normal birth weight. In addition, in the subgroup analysis by geographical region, elevated risk was detected among Europeans (OR = 1.14, 95% CI 1.00–1.29, p = 0.049). The present meta-analysis supported a positive association between high birth weight and bone tumor risk.

Size at birth and risk of breast cancer: update from a prospective population-based study

Birth size variables (birth weight, birth length and head circumference) have been reported to be positively associated with adult breast cancer risk, whereas a possible association of placental weight has not been adequately studied. It has also been suggested that maternal height may modify the association of birth size with adult breast cancer risk, but this has not been studied in detail. We updated a long-term follow-up of 22,931 Norwegian women (average of 51 years of follow up during which 870 women were diagnosed with breast cancer) and assessed placental weight in relation to breast cancer risk, in addition to providing updated analyses on breast cancer risk in relation to birth weight, birth length and head circumference. Placental weight was not associated with risk for breast cancer in adulthood, but there was a positive association of breast cancer risk with birth length (HR 1.13, 95% CI 1.05-1.21, per 2 cm increment), though not with birth weight (HR 1.02, 95% CI 0.95-1.10 per 0.5 kg increment). For birth length, the graded increase in risk was particularly strong among women whose mothers were relatively tall (p for trend, 0.001), compared to the trend among women whose mothers were relatively short (p for trend, 0.221). The results showed a robust and positive association of birth length with breast cancer risk, and may be especially strong in women whose mothers were relatively tall. We found no association of placental weight with risk for breast cancer.

Birthweight, early life body size and adult mammographic density: a review of epidemiologic studies

PURPOSE

To evaluate the association between birth weight and early life body size with adult mammographic density in the peer-reviewed literature.

METHODS

A comprehensive literature search was conducted through January, 2014. English language articles that assessed adult mammographic density (MD) in relation to early life body size (≤18 years old), or birthweight were included.

RESULTS

Nine studies reported results for early life body size and %MD. Both exposure and outcome were assessed at different ages using multiple methods. In premenopausal women, findings were inconsistent; two studies reported significant, inverse associations, one reported a non-significant, inverse association, and two observed no association. Reasons for these inconsistencies were not obvious. In postmenopausal women, four of five studies supported an inverse association. Two of three studies that adjusted for menopausal status found significant, inverse associations. Birthweight and %MD was evaluated in nine studies. No association was seen in premenopausal women and two of three studies reported positive associations in postmenopausal women. Three of four studies that adjusted for menopausal status found no association.

DISCUSSION

Early life body size and birthweight appear unrelated to %MD in premenopausal women while an inverse association in postmenopausal women is more likely. Although based on limited data, birthweight and %MD appear positively associated in postmenopausal women. Given the small number of studies, the multiple methods of data collection and analysis, other methodologic issues, and lack of consistency in results, additional research is needed to clarify this complex association and develop a better understanding of the underlying biologic mechanisms.

Birth weight, childhood body mass index, and height in relation to mammographic density and breast cancer: a register-based cohort study

Introduction

High breast density, a strong predictor of breast cancer may be determined early in life. Childhood anthropometric factors have been related to breast cancer and breast density, but rarely simultaneously. We examined whether mammographic density (MD) mediates an association of birth weight, childhood body mass index (BMI), and height with the risk of breast cancer.

Methods

13,572 women (50 to 69 years) in the Copenhagen mammography screening program (1991 through 2001) with childhood anthropometric measurements in the Copenhagen School Health Records Register were followed for breast cancer until 2010. With logistic and Cox regression models, we investigated associations among birth weight, height, and BMI at ages 7 to 13 years with MD (mixed/dense or fatty) and breast cancer, respectively.

Results

8,194 (60.4%) women had mixed/dense breasts, and 716 (5.3%) developed breast cancer. Childhood BMI was significantly inversely related to having mixed/dense breasts at all ages, with odds ratios (95% confidence intervals) ranging from 0.69 (0.66 to 0.72) at age 7 to 0.56 (0.53 to 0.58) at age 13, per one-unit increase in z-score. No statistically significant associations were detected between birth weight and MD, height and MD, or birth weight and breast cancer risk. BMI was inversely associated with breast cancer, with hazard ratios of 0.91 (0.83 to 0.99) at age 7 and 0.92 (0.84 to 1.00) at age 13, whereas height was positively associated with breast cancer risk (age 7, 1.06 (0.98 to 1.14) and age 13, 1.08 (1.00 to 1.16)). After additional adjustment for MD, associations of BMI with breast cancer diminished (age 7, 0.97 (0.88 to 1.06) and age 13, 1.01 (0.93 to 1.11)), but remained with height (age 7, 1.06 (0.99 to 1.15) and age 13, 1.09 (1.01 to 1.17)).

Conclusions

Among women 50 years and older, childhood body fatness was inversely associated with the breast cancer risk, possibly via a mechanism mediated by MD, at least partially. Childhood tallness was positively associated with breast cancer risk, seemingly via a pathway independent of MD. Birth weight was not associated with MD or breast cancer in this age group.

Breast cancer and the importance of early life nutrition

Epigenetic processes play a central role in regulating the tissue-specific expression of genes. Alterations in these processes can lead to profound changes in phenotype and have been implicated in the pathogenesis of many human diseases including human cancer. There is growing evidence that the environment, particularly variations in diet, during specific developmental periods can induce changes in the epigenome, which are then stably maintained throughout life influencing susceptibility to cancer in later life. This chapter will review the evidence that alterations in early life nutritional exposure can affect breast cancer risk through the altered epigenetic regulation of genes and discuss how detection of such altered epigenetic marks in early life may provide biomarkers to detect individuals at increased risk of disease.