Insulin-like growth factor-I, IGF-binding protein-3, and mammographic breast density.

Some studies have suggested that insulin-like growth factor (IGF) pathway is related to premenopausal breast density, one of the strongest known breast cancer risk factors. This study was designed specifically to test the hypothesis that higher levels of IGF-I and lower levels of IGF-binding protein (IGFBP)-3 are associated with high mammographic breast density among premenopausal but not among postmenopausal women. A total of 783 premenopausal and 791 postmenopausal healthy women were recruited during screening mammography examinations. Blood samples were collected at the time of mammography, and plasma IGF-I and IGFBP-3 levels were measured by ELISA. Mammographic breast density was estimated using a computer-assisted method. Spearman's partial correlation coefficients (r(s)) were used to evaluate the associations. Adjusted mean breast density was assessed by joint levels of IGF-I and IGFBP-3 using generalized linear models. Among premenopausal women, high levels of IGF-I and low levels of IGFBP-3 were independently correlated with high breast density (r(s) = 0.083; P = 0.021 and r(s) = -0.124; P = 0.0005, respectively). Correlation of IGF-I with breast density was stronger among women in the lowest tertile of IGFBP-3 than among those in the highest tertile of IGFBP-3 (r(s) = 0.138; P = 0.027 and r(s) = -0.039; P = 0.530, respectively). In contrast, the correlation of IGFBP-3 with breast density was stronger among women in the highest tertile of IGF-I than among those in the lowest tertile of IGF-I (r(s) = -0.150; P = 0.016 and r(s) = -0.008; P = 0.904, respectively). Women in the combined top tertile of IGF-I and bottom tertile of IGFBP-3 had higher mean breast density than those in the combined bottom tertile of IGF-I and top tertile of IGFBP-3 (53.8% versus 40.9%; P = 0.014). No significant association was observed among postmenopausal women. Our findings confirm that IGF-I and IGFBP-3 are associated with breast density among premenopausal women. They provide additional support for the idea that, among premenopausal women, these growth factors may affect breast cancer risk, at least in part, through their influence on breast tissue morphology as reflected on mammogram.     

Plasma insulin-like growth factor (IGF) I, IGF-binding protein 3, and mammographic density

Insulin-like growth factors (IGFs) and insulin-like growth factor-binding proteins (IGFBPs) play a role in the normal development of breast tissue and possibly in the etiology of breast cancer. Breast density is one of the strongest predictors of breast cancer. In a cross-sectional analysis within the Nurses' Health Study, we compared the associations of plasma levels of endogenous IGF-I and IGFBP-3 with breast density in 65 premenopausal and 192 postmenopausal women. The digitized film screen mammograms were evaluated by the computer-assisted Toronto method, in which visually selected gray-scale cut points are used to assess breast density. Generalized linear models and Spearman's partial correlation coefficients described the associations between breast density and IGF-I, IGFBP-3, and the IGF-I:IGFBP-3 ratio. Premenopausal breast density was positively correlated with IGF-I and inversely correlated with IGFBP-3; the association was strongest for the IGF-I:IGFBP-3 ratio and breast density (r = 0.39; P = 0.004). In contrast, the correlation between breast density and the IGF-I:IGFBP-3 ratio among postmenopausal women was -0.02 (P = 0.83). The associations of IGF-I:IGFBP-3 ratio with breast density differed significantly between premenopausal and postmenopausal women (P = 0.01). Mammographic density is positively associated with plasma IGF-I levels and inversely associated with plasma IGFBP-3 levels among premenopausal women, but not among postmenopausal women. These results are consistent with previous studies that showed a positive association between a higher IGF-I:IGFBP-3 ratio and subsequent risk of breast cancer only among premenopausal women. The findings raise the possibility that premenopausal levels of IGF-I and IGFBP-3 could be in the etiological pathway that relates higher breast density with increased breast cancer risk.     

Free insulin-like growth factor-I and breast cancer risk

Insulin-like growth factor-I (IGF-I) has mitogenic and anti-apoptotic effects on breast cancer cells. Epidemiologic studies have shown that high plasma levels of IGF-I and low levels of IGF binding protein (BP)-3 are associated with increased risk of breast cancer in premenopausal women. The actions of IGF-I are mediated through the IGF-I receptor (IGF-IR) and are regulated by IGFBPs. In circulation, most of the IGF-I binds to IGFBP-3, and binding of IGF-I to IGFBP-3 inhibits the actions of IGF-I. Since free IGF-I, which does not bind to IGFBPs, can readily cross the endothelial barrier to interact with IGF-IR, circulating free IGF-I is thought to be more relevant to the biologic activity of IGF-I. To examine the association of free IGF-I with breast cancer, we compared free IGF-I levels between 40 newly diagnosed breast cancer patients and 40 age- and race-matched healthy controls. Plasma levels of free IGF-I, total IGF-I and IGF-II, as well as total, intact and fragment IGFBP-3, were measured using commercial immunoassay kits. The association between IGF-I and breast cancer was examined using the conditional logistic regression analysis. Analysis of correlation (Spearman) showed that free IGF-I was correlated with total IGF-I and IGFBP-3 but not with IGF-II. The odds ratios for breast cancer patients having high plasma IGF-I (> or = median) after adjusting for menopausal status and IGFBP-3 were 2.00 (p < o r = 0.376) for total IGF-I and 6.31 (p < or = 0.047) for free IGF-I. A high ratio of IGF-I to IGFBP-3 was also associated with breast cancer (p < 0.05). No association was found for IGF-II, nor for total, intact and fragment IGFBP-3. The findings of this study suggest that measuring free IGF-I in circulation is more useful than measuring total IGF-I with respect to evaluation of an association between IGF-I and breast cancer risk.     

Endogenous sex steroids in premenopausal women and risk of breast cancer: the ORDET cohort

Introduction

Previous studies showed that higher testosterone levels are associated with greater risk of breast cancer in premenopausal women, but the literature is scant and inconsistent.

Methods

In a prospective nested case-control study of 104 premenopausal women with incident breast cancer and 225 matched controls, all characterized by regular menstrual cycles throughout their lifetime, we measured the concentration of estradiol, total and free testosterone (FT), progesterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in blood samples collected on days 20 through 24 of their cycles.

Results

In logistic regression models, the multivariate odds ratios (ORs) of invasive breast cancer for women in the highest tertile of circulating FT compared with the lowest was 2.43 (95% confidence interval (95% CI), 1.15 to 5.10; P_trend = 0.03), whereas for total testosterone, the association had the same direction but was not statistically significant (OR, 1.27; 95% CI, 0.62 to 2.61; P_trend = 0.51). Endogenous progesterone was not statistically associated with breast cancer (OR, 1.16; 95% CI, 0.60 to 2.27; P_trend = 0.75), nor were the other considered hormones.

Conclusions

Consistent with previous prospective studies in premenopausal women and our own earlier investigation, we observed that higher levels of FT are positively associated with breast cancer risk in women with regular menstrual cycles throughout their lifetimes. No evidence of risk was found associated with the other endogenous sex steroids.     

Fruit and vegetable intake and breast cancer risk defined by estrogen and progesterone receptor status: the Japan Public Health Center-based Prospective Study

Background

Epidemiological evidence for the impact of fruit and vegetable intake on breast cancer risk among the Japanese populations is scarce.

Objective

The purpose of this study was to evaluate the association between fruit and vegetable intake and breast cancer risk among 47,289 Japanese women.

Design

The study was conducted under a population-based prospective cohort design. Dietary assessment was performed using a validated food frequency questionnaire. A Cox proportional hazards regression model was used to calculate relative risks (RRs) and their corresponding 95 % confidence intervals (CIs).

Results

During an average of 10.2 years of follow-up, 452 cases of breast cancer were newly diagnosed. No association with breast cancer risk was seen for intake of total fruits and vegetables, cruciferous vegetables, green-leaf vegetables, yellow vegetables, or tomato products in overall or postmenopausal women. Cruciferous vegetable intake was associated with a statistically significant decrease in risk of premenopausal breast cancer [multivariable-RR_{Q4 vs. Q1} = 0.64 (95 % CI = 0.38–1.10; p _trend = .046)] and showed a marginally inverse association with ER+ PR+ tumors [RR_{per 100 g increment} = 0.64 (95 % CI = 0.41–1.00)]. In contrast, positive associations were seen between intake of total fruits and citrus fruits and breast cancer risk in overall and premenopausal women. However, these associations for fruit were all attenuated with additional adjustment for vitamin C intake.

Conclusions

Our results suggest an overall null association between total fruit and vegetable intake and breast cancer risk. Intake of cruciferous vegetable showed a statistically significant association with a decreased risk of breast cancer among premenopausal women.     

Genetic variation at CYP3A is associated with age at menarche and breast cancer risk: a case-control study

Introduction

We have previously shown that a tag single nucleotide polymorphism (rs10235235), which maps to the CYP3A locus (7q22.1), was associated with a reduction in premenopausal urinary estrone glucuronide levels and a modest reduction in risk of breast cancer in women age ≤50 years.

Methods

We further investigated the association of rs10235235 with breast cancer risk in a large case control study of 47,346 cases and 47,570 controls from 52 studies participating in the Breast Cancer Association Consortium. Genotyping of rs10235235 was conducted using a custom Illumina Infinium array. Stratified analyses were conducted to determine whether this association was modified by age at diagnosis, ethnicity, age at menarche or tumor characteristics.

Results

We confirmed the association of rs10235235 with breast cancer risk for women of European ancestry but found no evidence that this association differed with age at diagnosis. Heterozygote and homozygote odds ratios (ORs) were OR = 0.98 (95% CI 0.94, 1.01; P = 0.2) and OR = 0.80 (95% CI 0.69, 0.93; P = 0.004), respectively (P_trend = 0.02). There was no evidence of effect modification by tumor characteristics. rs10235235 was, however, associated with age at menarche in controls (P_trend = 0.005) but not cases (P_trend = 0.97). Consequently the association between rs10235235 and breast cancer risk differed according to age at menarche (P_het = 0.02); the rare allele of rs10235235 was associated with a reduction in breast cancer risk for women who had their menarche age ≥15 years (OR_het = 0.84, 95% CI 0.75, 0.94; OR_hom = 0.81, 95% CI 0.51, 1.30; P_trend = 0.002) but not for those who had their menarche age ≤11 years (OR_het = 1.06, 95% CI 0.95, 1.19, OR_hom = 1.07, 95% CI 0.67, 1.72; P_trend = 0.29).

Conclusions

To our knowledge rs10235235 is the first single nucleotide polymorphism to be associated with both breast cancer risk and age at menarche consistent with the well-documented association between later age at menarche and a reduction in breast cancer risk. These associations are likely mediated via an effect on circulating hormone levels.     

Premenopausal endogenous steroid hormones and breast cancer risk: results from the Nurses' Health Study II

Introduction

Prior research supports an association between endogenous sex steroids and breast cancer among postmenopausal women; the association is less clear among premenopausal women.

Methods

We evaluated the associations between estrogens, androgens, progesterone and sex hormone binding globulin (SHBG) and breast cancer in a nested case-control study in the Nurses'' Health Study II. Between 1996 and 1999, 29,611 participants provided blood samples; 18,521 provided samples timed in early follicular and mid-luteal phases of the menstrual cycle. A total of 634 women, premenopausal at blood collection, developed breast cancer between 1999 and 2009 and were matched to 1,264 controls (514 cases and 1,030 controls with timed samples). We used conditional logistic regression controlling for breast cancer risk factors for overall analyses; unconditional logistic regression additionally controlling for matching factors was used for subgroup analyses.

Results

In analyses of premenopausal estrogens including breast cancers diagnosed both before and after menopause, there was no association between follicular estradiol, estrone and free estradiol and risk of either total or invasive breast cancer. Luteal estradiol was positively associated with estrogen receptor positive (ER+)/progesterone receptor positive (PR+) cancers (5^th vs. 1^st quintile odds ratio (OR): 1.7 (95% confidence interval (CI): 1.0 to 2.9), P_trend = 0.02). Luteal estrone, free estradiol and progesterone were not associated with risk. Androgens were suggestively or significantly associated with risk when the sample was restricted to invasive tumors (for example, testosterone: OR: 1.4 (1.0 to 2.0), P_trend = 0.23) and ER+/PR+ disease (testosterone: OR: 1.7 (1.1 to 2.6) P_trend = 0.10; dehydroepiandrosterone sulfate (DHEAS) OR: 1.3 (0.8 to 2.0) P_trend = 0.05). SHBG was not associated with breast cancer risk. The results varied by menopausal status at diagnosis, with follicular estradiol suggestively positively associated with breast cancers in women premenopausal at diagnosis (OR: 1.1 (0.9 to 1.3) and significantly inversely associated with postmenopausal disease (OR: 0.6 (0.4 to 0.9); P_{heterogeneity} < 0.01).

Conclusions

Androgens were associated with modestly increased risk of breast cancer in this population, with stronger associations for invasive and ER+/PR+ disease. Luteal phase estradiol levels were suggestively associated with ER+/PR+ tumors but no other strong associations were observed with estrogens. Associations with follicular phase estrogens may vary by menopausal status at diagnosis, but case numbers were limited. Additional studies to confirm the role of premenopausal hormones in the etiology of both premenopausal and postmenopausal breast cancer are needed.     

Premenopausal serum androgens and breast cancer risk: a nested case-control study

Introduction

Prospective epidemiologic studies have consistently shown that levels of circulating androgens in postmenopausal women are positively associated with breast cancer risk. However, data in premenopausal women are limited.

Methods

A case-control study nested within the New York University Women's Health Study was conducted. A total of 356 cases (276 invasive and 80 in situ) and 683 individually-matched controls were included. Matching variables included age and date, phase, and day of menstrual cycle at blood donation. Testosterone, androstenedione, dehydroandrosterone sulfate (DHEAS) and sex hormone-binding globulin (SHBG) were measured using direct immunoassays. Free testosterone was calculated.

Results

Premenopausal serum testosterone and free testosterone concentrations were positively associated with breast cancer risk. In models adjusted for known risk factors of breast cancer, the odds ratios for increasing quintiles of testosterone were 1.0 (reference), 1.5 (95% confidence interval (CI), 0.9 to 2.3), 1.2 (95% CI, 0.7 to 1.9), 1.4 (95% CI, 0.9 to 2.3) and 1.8 (95% CI, 1.1 to 2.9; P _trend = 0.04), and for free testosterone were 1.0 (reference), 1.2 (95% CI, 0.7 to 1.8), 1.5 (95% CI, 0.9 to 2.3), 1.5 (95% CI, 0.9 to 2.3), and 1.8 (95% CI, 1.1 to 2.8, P _trend = 0.01). A marginally significant positive association was observed with androstenedione (P = 0.07), but no association with DHEAS or SHBG. Results were consistent in analyses stratified by tumor type (invasive, in situ), estrogen receptor status, age at blood donation, and menopausal status at diagnosis. Intra-class correlation coefficients for samples collected from 0.8 to 5.3 years apart (median 2 years) in 138 cases and 268 controls were greater than 0.7 for all biomarkers except for androstenedione (0.57 in controls).

Conclusions

Premenopausal concentrations of testosterone and free testosterone are associated with breast cancer risk. Testosterone and free testosterone measurements are also highly reliable (that is, a single measurement is reflective of a woman's average level over time). Results from other prospective studies are consistent with our results. The impact of including testosterone or free testosterone in breast cancer risk prediction models for women between the ages of 40 and 50 years should be assessed. Improving risk prediction models for this age group could help decision making regarding both screening and chemoprevention of breast cancer.     

Relations of omega-3 and omega-6 intake with mammographic breast density

Purpose

Omega-3 (n-3) and n-6 fatty acids (FA) intake could influence the occurrence of certain diseases such as breast cancer but little is known about their relation to mammographic density (MD). The purpose of this study is to examine the association of the intake of n-3 FA and n-6 FA with MD among 777 premenopausal and 783 postmenopausal women.

Methods

In this cross-sectional study, FA intake was assessed with a self-administered food-frequency questionnaire and MD was measured using a computer-assisted method. Multivariate analyses were performed by using generalized linear models to evaluate the associations of quartiles of FA intake with MD.

Results

For increasing quartiles of total long-chain n-3 FA intake (< 0.11, 0.11–0.20, 0.21–0.32, and ≥ 0.33 g/day), adjusted mean MD was 29, 29, 27, and 25 %, respectively (P _trend = 0.005). This association remained significant among postmenopausal (P _trend = 0.006) but not among premenopausal (P _trend = 0.21) women. No significant association was found between n-6 FA intake and MD. However, for increasing quartiles of the n-6 FA/long-chain n-3 FA ratio intake (< 31.75, 31.75–52.28, 52.29–94.28, and ≥ 94.29), adjusted mean MD was 26, 27, 29, and 29 %, respectively (P _trend = 0.008).

Conclusions

Higher intake of long-chain n-3 FA was associated with lower MD, suggesting that increased long-chain n-3 FA intake could be a strategy for breast cancer prevention.     

Breast cancer risk in relation to urinary and serum biomarkers of phytoestrogen exposure in the European Prospective into Cancer-Norfolk cohort study

Introduction

Phytoestrogens are a group of compounds found in plants that structurally resemble the hormone oestradiol, and thus have the potential to act as oestrogen agonists or antagonists. Their potential effects may alter the risk of breast cancer, but only a limited range of phytoestrogens has been examined in prospective cohort studies.

Methods

Serum and urine samples from 237 incident breast cancer cases and 952 control individuals (aged 45 to 75 years) in the European Prospective into Cancer-Norfolk cohort were analysed for seven phytoestrogens (daidzein, enterodiol, enterolactone, genistein, glycitein, o-desmethylangolensin, and equol) using liquid chromatography/mass spectrometry. Data on participants' diet, demographics, anthropometrics, and medical history were collected upon recruitment. All models were adjusted for weight, fat and energy intake, family history of breast cancer, social class, analytical batch, and factors related to oestrogen exposure.

Results

Urinary or serum phytoestrogens were not associated with protection from breast cancer in the European Prospective into Cancer-Norfolk cohort. Breast cancer risk was marginally increased with higher levels of total urinary isoflavones (odds ratio = 1.08 (95% confidence interval = 1.00 to 1.16), P = 0.055); among those with oestrogen receptor-positive tumours, the risk of breast cancer was increased with higher levels of urinary equol (odds ratio = 1.07 (95% confidence interval = 1.01 to 1.12), P = 0.013).

Conclusion

There was limited evidence of an association between phytoestrogen biomarkers and breast cancer risk in the present study. There was no indication of decreased likelihood of breast cancer with higher levels of phytoestrogen biomarkers, but the observation that some phytoestrogen biomarkers may be associated with greater risk of breast cancer warrants further study with greater statistical power.     

Plasma amino acid profiles are associated with biomarkers of breast cancer risk in premenopausal Japanese women

Objective

Recently, profiles of plasma amino acids have been utilized to detect diseases including breast cancer. However, there is a possibility that the amino acid status may be associated with the risk of breast cancer. We investigated the relationship of plasma levels of amino acids with levels of sex hormones and insulin-like growth factor (IGF)-1, which are relevant to the etiology of premenopausal breast cancer, in normal premenopausal women.

Methods

Participants were 350 Japanese women who had regular menstrual cycles less than 40-day long. Fasting plasma samples were assayed for estradiol, testosterone, dehydroepiandrosterone sulfate, sex-hormone-binding globulin (SHBG), and IGF-1. A total of 20 amino acids in plasma were quantified by liquid chromatography–mass spectrometry. Information on lifestyle and reproductive factors was obtained using a self-administered questionnaire.

Results

The plasma arginine level was significantly inversely correlated with plasma levels of total and free estradiol and IGF-1 after adjusting for age, body mass index, and phase of the menstrual cycle. Plasma leucine and tyrosine levels were significantly positively correlated with the free testosterone level. The ratio of plasma asparagine to the total amino acids was significantly positively correlated with SHBG level.

Conclusions

Plasma levels of some specific amino acids, such as arginine, leucine, tyrosine, and asparagine, were associated with the levels of sex hormones, SHBG, or IGF-1 in premenopausal women. However, the present cross-sectional study cannot provide a cause–effect relation. The implication of amino acids in the etiology of breast cancer needs to be addressed in future studies.     

Cancer risk factors associated with insulin-like growth factor (IGF)-I and IGF-binding protein-3 levels in healthy women: effect modification by menopausal status

Insulin-like growth factor-I (IGF-I) and IGF-binding protein-3 (IGFBP-3) appear to influence breast cancer risk and are hypothesized to mediate the effects of several cancer risk factors that depend on menopausal status. We investigated associations among cancer risk factors and plasma IGF-I and IGFBP-3 in 882 healthy control women (426 premenopausal, 456 postmenopausal) from two population-based breast cancer case–control studies. Interactions with menopausal status were statistically tested. We observed associations with non-modifiable (age, benign breast disease) and modifiable factors [body mass index (BMI), physical activity, smoking habits, alcohol consumption]. Furthermore, we demonstrated statistical interactions with menopausal status. Premenopausal IGFBP-3 levels increased and postmenopausal levels decreased with age (p-interaction = 0.001). Overweight postmenopausal women had higher IGF-I (p = 0.049) and IGFBP-3 (p = 0.005) levels than women with lower BMI. Postmenopausal IGF-I levels were positively associated with physical activity (p-trend = 0.012, p-interaction = 0.050). Postmenopausal current smokers had lower IGF-I (p = 0.014) and IGFBP-3 levels (p = 0.011). Increasing alcohol consumption was associated with lower premenopausal IGF-I (p-trend = 0.002, p-interaction = 0.004) and higher postmenopausal IGFBP-3 levels (p = 0.019). Benign breast disease was associated with higher premenopausal (p = 0.044) and postmenopausal (p = 0.002) IGF-I levels. IGF-I and/or IGFBP-3 potentially mediate changes in breast cancer risk associated with BMI, benign breast disease, and perhaps alcohol consumption. Other observed associations suggest that neither IGF-I nor IGFBP-3 alone acts as mediator. Consideration of menopausal status may help disentangle carcinogenic pathways involving IGF proteins.     

Association between allergies, asthma, and breast cancer risk among women in Ontario, Canada

Purpose

To investigate the association between allergies, asthma, and breast cancer risk in a large, population-based case–control study.

Methods

Breast cancer cases (n = 3,101) were identified using the Ontario Cancer Registry and population controls (n = 3,471) through random digit dialing. Self-reported histories of allergies, hay fever, and asthma were collected by questionnaire. Logistic regression was used to assess associations between breast cancer risk and history of allergy/hay fever and asthma, with 16 possible confounders examined. Analyses were stratified by menopausal status.

Results

A history of allergies or hay fever was associated with a small reduction in breast cancer risk [age-adjusted odds ratio (AOR) = 0.86, 95 % confidence interval (CI) 0.77–0.96] and did not differ by menopausal status. Asthma was not associated with breast cancer risk overall; however, among premenopausal women, asthma was associated with a reduced risk of breast cancer (AOR = 0.72, 95 % CI 0.54–0.97).

Conclusions

A history of allergies may be associated with a modest reduction in breast cancer risk. Asthma does not appear to be associated with breast cancer risk overall; however, asthma may be associated with reduced breast cancer risk among premenopausal women.     

Plasma free 25-hydroxyvitamin D,vitamin D binding protein,and risk of breast cancer in the Nurses’ Health Study II

Purpose

Prior prospective studies, including our own, have evaluated total plasma 25-hydroxyvitamin D [25(OH)D] and breast cancer risk with inconsistent results. However, recent studies suggest that some vitamin D functions may be more relevant to the unbound (free) fraction of 25(OH)D. Vitamin D binding protein (DBP) influences the free 25(OH)D levels and thus possibly the biological activities of vitamin D.

Methods

We conducted a case–control study nested within the Nurses’ Health Study II to evaluate the association of plasma free 25(OH)D and DBP with breast cancer risk in predominantly premenopausal women. Plasma samples were assayed for 25(OH)D and DBP in 584 case–control pairs. Free 25(OH)D levels were calculated based on plasma levels of total 25(OH)D, DBP, and a constant value representing average albumin levels. Conditional logistic regression was used to estimate relative risks (RRs) and 95 % confidence intervals (CIs).

Results

We found no association between plasma calculated free 25(OH)D and risk of breast cancer overall (highest vs. lowest quartile RR 1.21, 95 % CI 0.83–1.77, trend test p value = 0.50). No association was observed for plasma DBP as well (highest vs. lowest quartile RR 0.95, 95 % CI 0.67–1.36, trend test p value = 0.96). Results were similar by tumor hormone receptor status. Neither the total nor the calculated free 25(OH)D and breast cancer association substantially varied by plasma DBP levels.

Conclusions

Our study does not support an important role of either calculated circulating free 25(OH)D or circulating DBP levels in breast cancer risk among predominantly premenopausal women.     

Assessing the usefulness of a novel MRI-based breast density estimation algorithm in a cohort of women at high genetic risk of breast cancer: the UK MARIBS study

Introduction

Mammographic breast density is one of the strongest known risk factors for breast cancer. We present a novel technique for estimating breast density based on 3D T1-weighted Magnetic Resonance Imaging (MRI) and evaluate its performance, including for breast cancer risk prediction, relative to two standard mammographic density-estimation methods.

Methods

The analyses were based on MRI (n = 655) and mammography (n = 607) images obtained in the course of the UK multicentre magnetic resonance imaging breast screening (MARIBS) study of asymptomatic women aged 31 to 49 years who were at high genetic risk of breast cancer. The MRI percent and absolute dense volumes were estimated using our novel algorithm (MRIBview) while mammographic percent and absolute dense area were estimated using the Cumulus thresholding algorithm and also using a 21-point Visual Assessment scale for one medio-lateral oblique image per woman. We assessed the relationships of the MRI and mammographic measures to one another, to standard anthropometric and hormonal factors, to BRCA1/2 genetic status, and to breast cancer risk (60 cases) using linear and Poisson regression.

Results

MRI percent dense volume is well correlated with mammographic percent dense area (R = 0.76) but overall gives estimates 8.1 percentage points lower (P < 0.0001). Both show strong associations with established anthropometric and hormonal factors. Mammographic percent dense area, and to a lesser extent MRI percent dense volume were lower in BRCA1 carriers (P = 0.001, P = 0.010 respectively) but there was no association with BRCA2 carrier status. The study was underpowered to detect expected associations between percent density and breast cancer, but women with absolute MRI dense volume in the upper half of the distribution had double the risk of those in the lower half (P = 0.009).

Conclusions

The MRIBview estimates of volumetric breast density are highly correlated with mammographic dense area but are not equivalent measures; the MRI absolute dense volume shows potential as a predictor of breast cancer risk that merits further investigation.     

Tumor aromatase expression as a prognostic factor for local control in young breast cancer patients after breast-conserving treatment

Introduction

We sought to determine whether the levels of expression of 17 candidate genes were associated with locoregional control after breast-conserving treatments of early-stage breast cancers in young, premenopausal women.

Methods

Gene expression was measured by using RT-PCR in the breast tumors of a series of 53 young (younger than 40 years), premenopausal patients. All treatments consisted of primary breast-conserving surgery followed by whole-breast radiotherapy (± regional lymph nodes) with or without systemic treatments (chemotherapy ± hormone therapy). The median follow-up was 10 years.

Results

The 10-year locoregional control rate was 70% (95% CI, 57% to 87%). In univariate analysis, no clinical/pathologic prognostic factors were found to be significantly associated with decreased locoregional control. Expression of three genes was found to be significantly associated with an increased locoregional recurrence rate: low estrogen-receptor β, low aromatase, and high GATA3. Two others were associated with only a trend (P < 0.10): low HER1 and SKP2. In multivariate analysis, only the absence of aromatase was significantly associated with an increased locoregional recurrence rate (P = 0.003; relative risk = 0.49; 95% CI 0.29 to 0.82).

Conclusions

Recent data give credit to the fact that breast cancer in young women is a distinct biologic entity driven by special oncogenic pathways. Our results highlight the role of estrogen-signaling pathways (mainly CYP19/aromatase, GATA3, and ER-β) in the risk of locoregional recurrence of breast cancer in young women. Confirmation in larger prospective studies is needed.     

C-reactive protein and postmenopausal breast cancer risk: results from the E3N cohort study

Background

C-reactive protein (CRP), a marker of low-grade inflammation, has been associated with breast cancer risk, but results are scarce and inconsistent.

Methods

A case–control study nested within the E3N prospective cohort included 549 postmenopausal breast cancer cases and 1,040 matched controls, all free of breast cancer at baseline. Serum levels of CRP were measured in samples collected between 1995 and 1999. Unconditional logistic regression models were used to evaluate the association between CRP and breast cancer risk, adjusting for matching factors and known breast cancer risk factors.

Results

No association was observed between CRP levels and breast cancer risk overall. However, a significant interaction was observed between CRP levels and body mass index (BMI). A statistically significant increase in breast cancer risk was observed in overweight and obese women (BMI ≥ 25 kg/m²) (OR 1.92, 95 % CI 1.20–3.08 for CRP ≥ 2.5 mg/L compared with CRP < 1.5 mg/l, p _trend = 0.003, p _interaction between CRP and BMI = 0.03). Similar results were observed in women with waist circumference (WC) ≥ 88 cm (p _trend = 0.01, p _interaction = 0.06) and waist-to-hip ratio (WHR) ≥ 0.80 (p _trend = 0.06, p _interaction = 0.35). CRP levels were not associated with breast cancer risk in women with normal BMI, WC, or WHR.

Conclusions

We found a positive association between CRP levels and postmenopausal breast cancer risk restricted to women with excess adiposity. The suggested relationship between low-grade inflammation, abdominal adiposity, and postmenopausal breast cancer risk deserves further investigation.     

Diet and body constitution in relation to subgroups of breast cancer defined by tumour grade, proliferation and key cell cycle regulators

Background

The general lack of clear associations between diet and breast cancer in epidemiological studies may partly be explained by the fact that breast cancer is a heterogeneous disease that may have disparate genetic associations and different aetiological bases.

Method

A total of 346 incident breast cancers in a prospective cohort of 17,035 women enrolled in the Malmö Diet and Cancer study (Sweden) were subcategorized according to conventional pathology parameters, proliferation and expression of key cell cycle regulators. Subcategories were compared with prediagnostic diet and body measurements using analysis of variance.

Results

A large hip circumference and high body mass index were associated with high grade tumours (P = 0.03 and 0.009, respectively), whereas low energy and unadjusted fat intakes were associated with high proliferation (P = 0.03 and 0.004, respectively). Low intakes of saturated, monounsaturated and polyunsaturated fatty acids were also associated with high proliferation (P = 0.02, 0.004 and 0.003, respectively). Low energy and unadjusted fat intakes were associated with cyclin D₁ overexpression (P = 0.02 and 0.007, respectively), whereas cyclin E overexpression was positively correlated with fat intake. Oestrogen receptor status and expression of the tumour suppressor gene p27 were not associated with either diet or body constitution.

Conclusion

Low energy and low total fat (polyunsaturated fatty acids in particular) intakes, and high body mass index were associated with relatively more malignant breast tumours. Dietary behaviours and body constitution may be associated with specific types of breast cancer defined by conventional pathology parameters and cyclin D₁ and cyclin E expression. Further studies including healthy control individuals are needed to confirm our results.     

Genetic variation in PRL and PRLR, and relationships with serum prolactin levels and breast cancer risk: results from a population-based case-control study in Poland

Introduction

Studies suggest that high circulating levels of prolactin increase breast cancer risk. It is unclear if genetic variations in prolactin (PRL) or prolactin receptor (PRLR) genes also play a role. Thus, we examined the relationship between single nucleotide polymorphisms (SNPs) in PRL and PRLR, serum prolactin levels and breast cancer risk in a population-based case-control study.

Methods

We genotyped 8 PRL and 20 PRLR tag SNPs in 1965 breast cancer cases and 2229 matched controls, aged 20-74, and living in Warsaw or Łódź, Poland. Serum prolactin levels were measured by immunoassay in a subset of 773 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) for genotype associations with breast cancer risk were estimated using unconditional logistic regression, adjusted for age and study site. Geometric mean prolactin levels were estimated using linear regression models adjusted for age, study site, blood collection time, and menstrual cycle day (premenopausal women).

Results

Three SNPs were associated with breast cancer risk: in premenopausal women, PRLR rs249537 (T vs. C per-allele OR 1.39, 95% CI 1.07 - 1.80, P = 0.01); and in postmenopausal women, PRLR rs7718468 (C vs. T per-allele OR 1.16, 95% CI 1.03 - 1.30, P = 0.01) and PRLR rs13436213 (A vs. G per-allele OR 1.13 95% CI 1.01 - 1.26, P = 0.04). However, mean serum prolactin levels for these SNPs did not vary by genotype (P-trend > 0.05). Other SNPs were associated with serum prolactin levels: PRLR rs62355518 (P-trend = 0.01), PRLR rs10941235 (P-trend = 0.01), PRLR rs1610218 (P-trend = 0.01), PRLR rs34024951 (P-trend = 0.02), and PRLR rs9292575 (P-trend = 0.03) in premenopausal controls and PRL rs849872 (P-trend = 0.01) in postmenopausal controls.

Conclusions

Our data provide limited support for an association between common variations in PRLR and breast cancer risk. Altered serum prolactin levels were not associated with breast cancer risk-associated variants, suggesting that common genetic variation is not a strong predictor of prolactin-associated breast cancer risk in this population.     

Genes responsive to both oxidant stress and loss of estrogen receptor function identify a poor prognosis group of estrogen receptor positive primary breast cancers

Introduction

Oxidative stress can modify estrogen receptor (ER) structure and function, including induction of progesterone receptor (PR), altering the biology and clinical behavior of endocrine responsive (ER-positive) breast cancer.

Methods

To investigate the impact of oxidative stress on estrogen/ER-regulated gene expression, RNA was extracted from ER-positive/PR-positive MCF7 breast cancer cells after 72 hours of estrogen deprivation, small-interfering RNA knockdown of ER-α, short-term (8 hours) exposure to various oxidant stresses (diamide, hydrogen peroxide, and menadione), or simultaneous ER-α knockdown and oxidant stress. RNA samples were analyzed by high-throughput expression microarray (Affymetrix), and significance analysis of microarrays was used to define gene signatures responsive to estrogen/ER regulation and oxidative stress. To explore the association of these signatures with breast cancer biology, microarray data were analyzed from 394 ER-positive primary human breast cancers pooled from three independent studies. In particular, an oxidant-sensitive estrogen/ER-responsive gene signature (Ox-E/ER) was correlated with breast cancer clinical parameters and disease-specific patient survival (DSS).

Results

From 891 estrogen/ER-regulated probes, a core set of 75 probes (62 unique genes) responsive to all three oxidants were selected (Ox-E/ER signature). Ingenuity pathway analysis of this signature highlighted networks involved in development, cancer, and cell motility, with intersecting nodes at growth factors (platelet-derived growth factor-BB, transforming growth factor-β), a proinflammatory cytokine (tumor necrosis factor), and matrix metalloproteinase-2. Evaluation of the 394 ER-positive primary breast cancers demonstrated that Ox-E/ER index values correlated negatively with PR mRNA levels (r _p = -0.2; P = 0.00011) and positively with tumor grade (r _p = 0.2; P = 9.741 × e^-5), and were significantly higher in ER-positive/PR-negative versus ER-positive/PR-positive breast cancers (t-test, P = 0.0008). Regardless of PR status, the Ox-E/ER index associated with reduced DSS (n = 201; univariate Cox, P = 0.078) and, using the optimized cut-point, separated ER-positive cases into two significantly different DSS groups (log rank, P = 0.0009).

Conclusion

An oxidant-sensitive subset of estrogen/ER-responsive breast cancer genes linked to cell growth and invasion pathways was identified and associated with loss of PR and earlier disease-specific mortality, suggesting that oxidative stress contributes to the development of an aggressive subset of primary ER-positive breast cancers.