Postmenopausal hormone therapy and change in mammographic density

Tamoxifen-induced reduction in mammographic density and breast cancer risk reduction: a nested case-control study

BACKGROUND

Mammographic breast density is a strong risk factor for breast cancer. Tamoxifen, which reduces the risk of breast cancer in women at high risk, also reduces mammographic breast density. However, it is not known if tamoxifen-induced reductions in breast density can be used to identify women who will benefit the most from prophylactic treatment with this drug.

METHODS

We conducted a nested case-control study within the first International Breast Cancer Intervention Study, a randomized prevention trial of tamoxifen vs placebo. Mammographic breast density was assessed visually and expressed as a percentage of the total breast area in 5% increments. Case subjects were 123 women diagnosed with breast cancer at or after their first follow-up mammogram, which took place 12-18 months after trial entry, and control subjects were 942 women without breast cancer. Multivariable logistic regression was used to adjust for other risk factors. All statistical tests were two-sided.

RESULTS

In the tamoxifen arm, 46% of women had a 10% or greater reduction in breast density at their 12- to 18-month mammogram. Compared with all women in the placebo group, women in the tamoxifen group who experienced a 10% or greater reduction in breast density had 63% reduction in breast cancer risk (odds ratio = 0.37, 95% confidence interval = 0.20 to 0.69, P = .002), whereas those who took tamoxifen but experienced less than a 10% reduction in breast density had no risk reduction (odds ratio = 1.13, 95% confidence interval = 0.72 to 1.77, P = .60). In the placebo arm, there was no statistically significant difference in breast cancer risk between subjects who experienced less than a 10% reduction in mammographic density and subjects who experienced a greater reduction.

CONCLUSION

The 12- to 18-month change in mammographic breast density is an excellent predictor of response to tamoxifen in the preventive setting.

Assessment of mammographic density before and after first full-term pregnancy

Mammographic density (MD) has consistently been found as one of the strongest breast cancer risk factors. In our study, both qualitative and quantitative density measurements were performed in a hospital-based group of premenopausal women before and after first full-term pregnancy providing an opportunity for direct evaluation of the effects of one pregnancy on MD. Mammograms were obtained from 23 women before and after first full-term pregnancy and from 28 nulliparous controls. MD was determined by a standard qualitative assessment method using the Breast Imaging Reporting and Data System, and a quantitative computer-based threshold method (0-100%). The mean age at mammography before and after pregnancy was 31 and 34 years, respectively, with a mean difference of 40 months between mammographies. The quantitative density assessment showed a significant reduction in relative MD after pregnancy of 12 percentage points (8.6-15.4), compared with 3.1 (0.0-6.2) in the nulliparous control group (P<0.001). A reduction in MD of more than 10% was seen in 52% of the patients, compared with 18% of the controls. The qualitative density assessment confirmed a reduction in MD after pregnancy by one Breast Imaging Reporting and Data System category (P=0.02). This longitudinal study showed that MD can be influenced by one full-term pregnancy. This effect was seen with both quantitative and qualitative assessment methods. It may be hypothesized that breast cancer risk reduction associated with pregnancy is mediated through a direct reduction of MD, and MD assessment might be incorporated in individualizing risk assessment and prevention.

Circulating levels of inflammatory markers and mammographic density among postmenopausal women

Mammographic density is strongly associated with breast cancer risk. Inflammation is involved in breast carcinogenesis, perhaps through effects on mammographic density. We evaluated associations between inflammatory markers interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and C-reactive protein (CRP) and mammographic density among postmenopausal women. Plasma IL-6, TNF-α, and CRP levels were measured in 145 women with benign breast disease (benign controls) and 397 women with a negative screening mammogram (well controls) enrolled in the Mammograms and Masses Study. Associations between the inflammatory markers and mammographic density were evaluated separately for benign and well controls through correlation analyses and linear regressions. Age-adjusted mean CRP levels were higher among benign controls (2.07 μg/ml) compared to well controls (1.63 μg/ml; P = 0.02), while IL-6 and TNF-α levels were similar between groups. Using linear regression, IL-6, TNF-α, and CRP were not statistically significantly associated with dense breast area within either group. Statistically significant positive associations were observed between all three markers and nondense breast area in both groups; statistically significant negative associations were observed between IL-6 and percent density among benign controls, and between all three markers and percent density among well controls. These associations were all attenuated and non-significant upon adjustment for body mass index. IL-6, TNF-α, and CRP levels were not independently associated with dense breast area, nondense breast area, or percent density in this study population. Our results suggest that these inflammatory factors do not impact breast carcinogenesis through independent effects on mammographic density.

High-density lipoprotein cholesterol, obesity, and mammographic density in Korean women: the Healthy Twin study

Background

High-density lipoprotein cholesterol (HDL-C) is reported to be associated with breast cancer risk. To better understand this association, we examined the relationship between HDL-C and mammographic density, a putative intermediate risk factor for breast cancer.

Methods

The study subjects were 711 Korean women from the Healthy Twin study. Lipid parameters were assayed enzymatically in fresh sera, and percent dense area (PDA) and absolute dense area were measured from digital mammograms using a computer-assisted method.

Results

PDA was positively associated with HDL-C in both premenopausal and postmenopausal women in a multivariable-adjusted linear mixed model, but the association did not persist when the model was additionally adjusted for body mass index (BMI). BMI was inversely associated with PDA, and this association did not change after additional adjustment for any lipid parameter. Multivariable-adjusted analysis showed that there were significant additive genetic cross-trait correlations between PDA and both HDL-C (coefficient, 0.175) and triglyceride (coefficient, −0.262). However, those correlations disappeared after additional adjustment for BMI.

Conclusions

HDL-C alone is unlikely to increase the risk of breast cancer in Korean women, particularly through changes in breast parenchyma that are apparent in mammographic density. BMI should be included in studies using analytical models where mammographic density is used as an intermediate risk factor for breast cancer.

Effects of isoflavones on breast density in pre- and post-menopausal women: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Isoflavones from soy and red clover exert modest hormonal effects in women, but the relevance to risk of breast cancer is unclear. The aim of this meta-analysis was to assess the effects of isoflavone-rich foods or supplements on a biomarker of breast cancer risk, women's mammographic density.

METHODS

Electronic searches were performed on The Cochrane Library, Medline and EMBASE (to June 2009), and reference lists and trial investigators were consulted to identify further studies. Randomized controlled trials (RCTs) of isoflavone-rich foods or supplements versus placebo with a duration of at least 6 months were included in our analysis. Inclusion/exclusion, data extraction and validity assessment were carried out independently in duplicate, and meta-analysis used to pool study results. Subgrouping, sensitivity analysis, assessment of heterogeneity and funnel plots were used to interpret the results.

RESULTS

Eight RCTs (1287 women) compared isoflavones with placebo for between 6 months and 3 years. Meta-analysis suggested no overall effect of dietary isoflavones on breast density in all women combined [mean difference (MD) 0.69%, 95% confidence interval (CI) -0.78 to 2.17] or post-menopausal women (MD -1.10%, 95% CI -3.22 to 1.03). However, there was a modest increase in mammographic density in premenopausal women (MD 1.83%, 95% CI 0.25-3.40) without heterogeneity but this effect was lost in one of three sensitivity analyses.

CONCLUSIONS

Isoflavone intake does not alter breast density in post-menopausal women, but may cause a small increase in breast density in premenopausal women. Larger, long-term trials are required to determine if these small effects are clinically relevant.

RANK ligand mediates progestin-induced mammary epithelial proliferation and carcinogenesis

RANK ligand (RANKL), a TNF-related molecule, is essential for osteoclast formation, function and survival through interaction with its receptor RANK. Mammary glands of RANK- and RANKL-deficient mice develop normally during sexual maturation, but fail to form lobuloalveolar structures during pregnancy because of defective proliferation and increased apoptosis of mammary epithelium. It has been shown that RANKL is responsible for the major proliferative response of mouse mammary epithelium to progesterone during mammary lactational morphogenesis, and in mouse models, manipulated to induce activation of the RANK/RANKL pathway in the absence of strict hormonal control, inappropriate mammary proliferation is observed. However, there is no evidence so far of a functional contribution of RANKL to tumorigenesis. Here we show that RANK and RANKL are expressed within normal, pre-malignant and neoplastic mammary epithelium, and using complementary gain-of-function (mouse mammary tumour virus (MMTV)-RANK transgenic mice) and loss-of function (pharmacological inhibition of RANKL) approaches, define a direct contribution of this pathway in mammary tumorigenesis. Accelerated pre-neoplasias and increased mammary tumour formation were observed in MMTV-RANK transgenic mice after multiparity or treatment with carcinogen and hormone (progesterone). Reciprocally, selective pharmacological inhibition of RANKL attenuated mammary tumour development not only in hormone- and carcinogen-treated MMTV-RANK and wild-type mice, but also in the MMTV-neu transgenic spontaneous tumour model. The reduction in tumorigenesis upon RANKL inhibition was preceded by a reduction in pre-neoplasias as well as rapid and sustained reductions in hormone- and carcinogen-induced mammary epithelial proliferation and cyclin D1 levels. Collectively, our results indicate that RANKL inhibition is acting directly on hormone-induced mammary epithelium at early stages in tumorigenesis, and the permissive contribution of progesterone to increased mammary cancer incidence is due to RANKL-dependent proliferative changes in the mammary epithelium. The current study highlights a potential role for RANKL inhibition in the management of proliferative breast disease.

Comparison of breast density measured by dual energy X-ray absorptiometry with mammographic density among adult women in Hawaii

BACKGROUND

While use of mammography is limited, due to concerns related to radiation exposure, dual energy X-ray absorptiometry (DXA), commonly available in medical care settings, is characterized by low radiation exposure.

METHODS

In the current paper, we compared breast density measured by DXA with mammographic density in 101 adult women who had a screening mammogram during the last 2 years. DXA scans of both breasts were taken using a clinical DXA system calibrated to measure breast density. The total projected breast area was manually delineated on each image and percent fibroglandular volume density (%FGV), absolute fibroglandular volume, total breast area and volume were computed. After digitizing mammographic films, total breast area, dense area, and percent density (PD) were estimated using computer-assisted mammographic density assessment.

RESULTS

Both DXA and mammographic measures showed high correlations between left and right breasts ranging from 0.85 to 0.98 (p<0.0001). Mean %FGV was 38.8±14.3%, and mean percent density was 31.9±18.2% for craniocaudal views and 28.3±16.2% for mediolateral views. The correlation between the two measures was 0.76 for both views (p<0.0001). Associations with common risk factors showed similar patterns for DXA and mammographic densities; in particular, the inverse associations with BMI and age at menarche were evident for both methods. Multilinear regression with stepwise selection indicated an explained variance of 0.56 for %FGV alone and of 0.58 for %FGV plus number of children.

CONCLUSION

Despite some differences in methodology, the current comparison suggests that DXA may provide a low-radiation option in evaluating breast density.

Breast cancer risk by breast density, menopause, and postmenopausal hormone therapy use

PURPOSE

We determined whether the association between breast density and breast cancer risk and cancer severity differs according to menopausal status and postmenopausal hormone therapy (HT) use.

METHODS

We collected data on 587,369 women who underwent 1,349,027 screening mammography examinations; 14,090 women were diagnosed with breast cancer. We calculated 5-year breast cancer risk from a survival model for subgroups of women classified by their Breast Imaging Reporting and Data System (BIRADS) breast density, age, menopausal status, and current HT use, assuming a body mass index of 25 kg/m(2). Odds of advanced (ie, IIb, III, IV) versus early (ie, I, IIa) stage invasive cancer was calculated according to BIRADS density.

RESULTS

Breast cancer risk was low among women with low density (BIRADS-1): women age 55 to 59 years, 5-year risk was 0.8% (95% CI, 0.6 to 0.9%) for non-HT users and 0.9% (95% CI, 0.7% to 1.1%) for estrogen and estrogen plus progestin users. Breast cancer risk was high among women with very high density (BIRADS-4), particularly estrogen plus progestin users: women age 55 to 59 years, 5-year risk was 2.4% (95% CI, 2.0% to 2.8%) for non-HT users, 3.0% (95% CI, 2.6% to 3.5%) for estrogen users, and 4.2% (95% CI, 3.7% to 4.6%) for estrogen plus progestin users. Advanced-stage breast cancer risk was increased 1.7-fold for postmenopausal HT users who had very high density (BIRADS-4) compared to those with average density (BIRADS-2).

CONCLUSION

Postmenopausal women with high breast density are at increased risk of breast cancer and should be aware of the added risk of taking HT, especially estrogen plus progestin.

Breast tissue composition and susceptibility to breast cancer

Breast density, as assessed by mammography, reflects breast tissue composition. Breast epithelium and stroma attenuate x-rays more than fat and thus appear light on mammograms while fat appears dark. In this review, we provide an overview of selected areas of current knowledge about the relationship between breast density and susceptibility to breast cancer. We review the evidence that breast density is a risk factor for breast cancer, the histological and other risk factors that are associated with variations in breast density, and the biological plausibility of the associations with risk of breast cancer. We also discuss the potential for improved risk prediction that might be achieved by using alternative breast imaging methods, such as magnetic resonance or ultrasound. After adjustment for other risk factors, breast density is consistently associated with breast cancer risk, more strongly than most other risk factors for this disease, and extensive breast density may account for a substantial fraction of breast cancer. Breast density is associated with risk of all of the proliferative lesions that are thought to be precursors of breast cancer. Studies of twins have shown that breast density is a highly heritable quantitative trait. Associations between breast density and variations in breast histology, risk of proliferative breast lesions, and risk of breast cancer may be the result of exposures of breast tissue to both mitogens and mutagens. Characterization of breast density by mammography has several limitations, and the uses of breast density in risk prediction and breast cancer prevention may be improved by other methods of imaging, such as magnetic resonance or ultrasound tomography.

Changes and tracking of mammographic density in relation to Pike's model of breast tissue aging: a UK longitudinal study

Percent mammographic density (PMD) is a strong marker of breast cancer risk. It may be a correlate of the rate of breast tissue aging, as proposed by Pike to explain breast cancer age-incidence. We examined longitudinal changes in PMD in 645 breast screening attendees in London, UK, in which each had between 2 and 5 screens spanning 3-12 years at ages 50-65 years and compare these to Pike's model. Within-woman PMD declined during these ages, with a slowing rate of decline. Annual rates of decline were 1.4% (95% confidence interval: 1.2-1.6), 0.7% (0.6-0.9) and 0.1% (-0.2 to 0.4) at ages 50, 57 and 64. Dense area declined similarly, but the absolute magnitude of the rate of increase of nondense area was almost double that of dense area. PMD dropped by 2.4% (1.4-3.4) on menopausal transition and increased by 2.4% (1.4-3.5) with the use of hormone therapy. Higher body mass index, greater parity and being Afro-Caribbean or South Asian ethnicities were associated with lower PMD, but did not affect rate of change of PMD at these ages. Within-woman rank correlation of PMD was 0.80 for readings taken 9 years apart. Effects of menopause and parity and the lack of effect of menarche on age-specific PMD at these ages are consistent with the predicted determinants in Pike's model. A high degree of tracking of PMD indicates that at ages 50-65 years high-risk women could be identified by a single early screen at age older than 50.

Association of body size measurements and mammographic density in Korean women: the Healthy Twin study

BACKGROUND

Both greater body size and higher mammographic density seem to be associated with a risk of breast cancer. To understand a mechanism through which body size confers a higher risk of breast cancer, associations between mammographic measures and various measures of body size were examined.

METHOD

Study subjects were 730 Korean women selected from the Healthy Twin study. Body size measurements were completed according to standard protocol. Mammographic density was measured from digital mammograms using a computer-assisted method from which the total area and the dense area of the breast were calculated, and nondense area and percent of dense area were straightforwardly derived. Linear mixed models considering familial correlations were used for analyses.

RESULTS

Total and nondense areas were positively associated with current body mass index (BMI), BMI at 35 years, total fat percent, waist circumference, and waist-hip ratio, whereas percent dense area was inversely associated with these characteristics in both premenopausal and postmenopausal women. Height was not associated with any mammographic measure. Total and nondense areas had strong positive genetic correlations with current BMI, total fat percent, waist circumference, and waist-hip ratio, whereas percent dense area had strong inverse genetic correlations with these body size measurements.

CONCLUSION

Mammographic density and obesity are inversely associated with each other possibly from common genetic influences that have opposite effects on mammographic density and obesity in Korean women.

IMPACT

The association between obesity and breast cancer does not seem to be mediated through mammographic density.

Risk factors for ductal, lobular, and mixed ductal-lobular breast cancer in a screening population

BACKGROUND

Biological distinctions between histologic subtypes of breast cancer suggest etiologic differences, although few studies have been powered to examine such differences. We compared associations between several factors and risk of ductal, lobular, and mixed ductal-lobular breast cancers.

METHODS

We used risk factor data from the Breast Cancer Surveillance Consortium for 3,331,744 mammograms on 1,211,238 women, including 19,119 women diagnosed with invasive breast cancer following mammography (n = 14,818 ductal, 1,602 lobular, and 1,601 mixed ductal-lobular). Histologic subtype-specific risk factor associations were evaluated using Cox regression.

RESULTS

Significant positive associations with family history and breast density were similar across subtypes. Hormone therapy use was associated with increased risk of all subtypes, but was most strongly associated with lobular cancer [hazard ratio (HR) = 1.46; 95% confidence interval (CI), 1.25-1.70]. Relative to nulliparous women, parous women had lower risk of ductal and mixed but not lobular cancers (HR = 0.80; 95% CI, 0.76-0.84; HR = 0.79; 95% CI, 0.68-0.93; HR = 0.96; 95% CI, 0.81-1.15, respectively). Late age at first birth was associated with increased risk of all subtypes.

CONCLUSIONS

Similarities in risk factor associations with ductal, lobular, and mixed breast cancer subtypes were more pronounced than differences. Distinctions between subtype-specific associations were limited to analyses of hormone therapy use and reproductive history.

IMPACT

The results of this study indicate that the strongest risk factors for breast cancer overall (that is, family history and breast density) are not histologic subtype specific. Additional studies are needed to better characterize subtype-specific associations with genetic, hormonal, and nonhormonal factors.

Family history, mammographic density, and risk of breast cancer

PURPOSE

Mammographic density is a strong and highly heritable risk factor for breast cancer. The purpose of this study was to examine the extent to which mammographic density explains the association of family history of breast cancer with risk of the disease.

SUBJECTS AND METHODS

We carried out three nested case-control studies in screening programs that included in total 2,322 subjects (1,164 cases and 1,158 controls). We estimated the independent and combined associations of family history and percent mammographic density at baseline with subsequent breast cancer risk.

RESULTS

After adjustment for age and other risk factors, compared with women with no affected first-degree relatives, percent mammographic density was 3.1% greater for women with one affected first-degree relative, and 7.0% greater for women with two or more affected relatives (P = 0.001 for linear trend across family history categories). The odds ratios for breast cancer risk were 1.37 [95% confidence interval (95% CI), 1.10-1.72] for having one affected relative, and 2.45 (95% CI, 1.30-4.62) for having two or more affected relatives (P for trend = 0.0002). Adjustment for percent mammographic density reduced these odds ratios by 16% and 14%, respectively. Percent mammographic density explained 14% (95% CI, 4-39%) of the association of family history (at least one affected first-degree relative) with breast cancer risk.

CONCLUSIONS

Percent mammographic density has features of an intermediate marker for breast cancer, and some of the genes that explain variation in percent mammographic density might be associated with familial risk of breast cancer.

Decrease in breast density in the contralateral normal breast of patients receiving neoadjuvant chemotherapy: MR imaging evaluation

PURPOSE

To investigate the change of breast density with quantitative magnetic resonance (MR) imaging in the contralateral normal breast of patients receiving neoadjuvant chemotherapy.

MATERIALS AND METHODS

This study was approved by the institutional review board and was HIPAA compliant. Informed consent was obtained. Fifty-four patients with breast cancer (mean age, 47 years; age range, 30-74 years) treated with NAC protocol and enrolled in a breast MR imaging research study were studied. The density in the contralateral normal breast was analyzed by using an MR imaging-based segmentation method. The effect of chemotherapy on the change of density following the doxorubicin and cyclophosphamide (AC) and the AC and taxane regimen was evaluated. The dependence on age was investigated by using a multivariate regression model.

RESULTS

In patients who underwent both AC and taxane follow-up, the mean percentage of change from the individual's baseline density was -10% (95% confidence interval: -12.8%, -7.2%) after AC and -12.7% (95% confidence interval: -16%, -9.4%) after AC and taxane. In patients who underwent both follow-up studies after one to two and four cycles of AC, the mean percentage of change was -9.4% (95% confidence interval: -13.5%, -5.3%) after one to two cycles of AC and -14.7% (95% confidence interval: -20.6%, -8.7%) after four cycles of AC. The percentage reduction of density was significantly dependent on age. Patients younger than 40 years had a greater reduction after chemotherapy than patients older than 55 years (P = .01).

CONCLUSION

By using three-dimensional MR imaging, patients receiving chemotherapy showed reduction of breast density, and the effects were significant after initial treatment with one to two cycles of the AC regimen.

Mammographic density change with 1 year of aerobic exercise among postmenopausal women: a randomized controlled trial

BACKGROUND

The Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial examined the influence of aerobic exercise on biological factors that are associated with breast cancer risk. Mammographic density, a secondary outcome, is reported here.

METHODS

The ALPHA Trial was a parallel group randomized controlled trial conducted between May 2003 and July 2007. Postmenopausal, sedentary women ages 50 to 74 years (n = 320) were evenly randomized to aerobic exercise (45 minutes, 5 days per week) or control (usual life-style) for 1 year. Dense fibroglandular tissue and nondense fatty tissue were measured from mammograms at baseline and 1 year using computer-assisted thresholding software for area measurements and a new technique that relies on the calibration of mammography units with a tissue-equivalent phantom for volumetric measurements.

RESULTS

Nondense volume decreased in the exercise group relative to the control group (difference between groups = -38.5 cm(3); 95% confidence interval, -61.6 to 15.4; P = 0.001). Changes in total body fat accounted for this decrease. Changes in dense area and dense volume, measures that have previously been associated with breast cancer risk, were not significantly different between the groups (P > or = 0.26).

CONCLUSIONS

Achieving changes in mammographic measures may require more exercise or a study population with higher baseline levels of sex hormones or a wider range of mammographic density. The data from this study, however, suggest that the protective effect of exercise on breast cancer risk may operate through a mechanism other than mammographic density.

Genotypes and haplotypes in the insulin-like growth factors, their receptors and binding proteins in relation to plasma metabolic levels and mammographic density

BACKGROUND

Increased mammographic density is one of the strongest independent risk factors for breast cancer. It is believed that one third of breast cancers are derived from breasts with more than 50% density. Mammographic density is affected by age, BMI, parity, and genetic predisposition. It is also greatly influenced by hormonal and growth factor changes in a woman's life cycle, spanning from puberty through adult to menopause. Genetic variations in genes coding for hormones and growth factors involved in development of the breast are therefore of great interest. The associations between genetic polymorphisms in genes from the IGF pathway on mammographic density and circulating levels of IGF1, its binding protein IGFBP3, and their ratio in postmenopausal women are reported here.

METHODS

Samples from 964 postmenopausal Norwegian women aged 55-71 years were collected as a part of the Tromsø Mammography and Breast Cancer Study. All samples were genotyped for 25 SNPs in IGF1, IGF2, IGF1R, IGF2R, IGFALS and IGFBP3 using Taqman (ABI). The main statistical analyses were conducted with the PROC HAPLOTYPE procedure within SAS/GENETICS (SAS 9.1.3).

RESULTS

The haplotype analysis revealed six haploblocks within the studied genes. Of those, four had significant associations with circulating levels of IGF1 or IGFBP3 and/or mammographic density. One haplotype variant in the IGF1 gene was found to be associated with mammographic density. Within the IGF2 gene one haplotype variant was associated with levels of both IGF1 and IGFBP3. Two haplotype variants in the IGF2R were associated with the level of IGF1. Both variants of the IGFBP3 haplotype were associated with the IGFBP3 level and indicate regulation in cis.

CONCLUSION

Polymorphisms within the IGF1 gene and related genes were associated with plasma levels of IGF1, IGFBP3 and mammographic density in this study of postmenopausal women.

The effect of age, menopausal state, and breast density on (18)F-FDG uptake in normal glandular breast tissue

Theoretically, the degree of (18)F-FDG uptake in the glandular tissues of the normal breast can affect the detection of breast cancer. The aim of this prospective study was to investigate relationships among age, menopausal state, and breast density and determine whether they affect (18)F-FDG uptake in normal glandular breast tissue.

METHODS

Among 250 newly diagnosed breast cancer patients, 149 patients (mean age +/- SD, 50.9 +/- 9.70 y; range, 32-77 y) were analyzed because they had normal contralateral breasts confirmed by MRI, mammography, and (18)F-FDG PET examinations. PET images were acquired 60 +/- 2 min after the administration of (18)F-FDG (5.2 MBq/kg of body weight). The maximum and average standardized uptake value (SUVmax and SUVavg, respectively) of (18)F-FDG were calculated in the normal breast. Patients were divided into groups according to qualitative breast density and menopausal state. Descriptive statistics and 2-factorial analysis of covariance were used to assess the effects of qualitative breast density, menopausal state, and age on SUVmax and SUVavg. Pearson chi(2) was used to test the relationship between menopausal state and qualitative breast density.

RESULTS

The average age of patients with nondense breasts was significantly higher than that of patients with dense breasts (P < 0.01). Also, breast density related to menopausal state (P < 0.05). Dense breasts had an average SUVmax of 1.243 and mean SUVavg of 0.694, whereas nondense breasts had a mean SUVmax of 0.997 and mean SUVavg of 0.592. Analysis of covariance indicated that density and the linear effect of age were significant with regard to both SUVmax and SUVavg. After removing the linear effect of age, menopausal state had no effect on SUVmax and SUVavg.

CONCLUSION

(18)F-FDG uptake significantly decreases as age increases and breast density decreases. Age and qualitative breast density are independent factors and significantly affect (18)F-FDG uptake for both SUVmax and SUVavg. Menopausal state had no effect on SUVmax and SUVavg.

Birth weight and mammographic density among postmenopausal women in Sweden

Birth weight is a significant predictor of breast cancer risk in adult life and mammary gland mass could be an intermediate stage in this long process. We have studied the association of birth size measurements with mammographic density, a marker of mammary gland mass. For a population-based sample of 893 postmenopausal women without previous cancer in Sweden, we retrieved information on birth size from birth records and their most recent mammography. Film mammograms of the medio-lateral oblique view were digitized and the Cumulus software was used for computer-assisted semi-automated thresholding of mammographic density. Results were analyzed using generalized linear models controlling for possible confounders. Mean percent mammographic density increased when comparing the extreme categories of birth weight (from 15.6% to 18.6%) and head circumference (from 15.5% to 20.4%), and the corresponding linear trends were statistically significant (p values 0.02 and 0.007, respectively). The associations were particularly strong when the cutoff for high versus low mammographic density was set at the relatively high value of 50%. Compared to women weighing 3001-3500 grams at birth, women with birth weights >4000g were at almost 3-fold risk of developing high mammographic density (odds ratio: 2.9, 95% confidence interval 1.1 to 7.9). No association with mammographic density was evident with respect to birth length which, however, is known to be less accurately measured. These results indicate that adult breast density, a powerful predictor of breast cancer risk, has intrauterine roots, as reflected in birth size.

Epidemiologic studies of isoflavones & mammographic density

Isoflavones, phytoestrogens in soy beans with estrogen-like properties, have been examined for their cancer protective effects. Mammographic density is a strong predictor of breast cancer. This review summarizes studies that have examined the association between isoflavones and breast density. Observational investigations in Hawaii and Singapore suggest slightly lower breast density among women of Asian descent with regular soy intake, but two larger studies from Japan and Singapore did not observe a protective effect. The findings from seven randomized trials with primarily Caucasian women indicate that soy or isoflavones do not modify mammographic density. Soy foods and isoflavone supplements within a nutritional range do not appear to modify breast cancer risk as assessed by mammographic density.

Circulating carotenoids, mammographic density, and subsequent risk of breast cancer

Mammographic density is one of the strongest predictors of breast cancer risk. Recently, it has been suggested that reactive oxygen species may influence breast cancer risk through its influence on mammographic density. In the current study, we addressed this hypothesis and also assessed if the association between carotenoids and breast cancer risk varies by mammographic density. We conducted a nested case-control study consisting of 604 breast cancer cases and 626 controls with prospectively measured circulating carotenoid levels and mammographic density in the Nurses' Health Study. Circulating levels of alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were measured. We used a computer-assisted thresholding method to measure percent mammographic density. We found no evidence that circulating carotenoids are inversely associated with mammographic density. However, mammographic density significantly modified the association between total circulating carotenoids and breast cancer (P heterogeneity = 0.008). Overall, circulating total carotenoids were inversely associated with breast cancer risk (P trend = 0.01). Among women in the highest tertile of mammographic density, total carotenoids were associated with a 50% reduction in breast cancer risk (odds ratio, 0.5; 95% confidence interval, 0.3-0.8). In contrast, there was no inverse association between carotenoids and breast cancer risk among women with low mammographic density. Similarly, among women in the highest tertile of mammographic density, high levels of circulating alpha-carotene, beta-cryptoxanthin, lycopene, and lutein/zeaxanthin were associated with a significant 40% to 50% reduction in breast cancer risk (P trend < 0.05). Our results suggest that plasma levels of carotenoids may play a role in reducing breast cancer risk, particularly among women with high mammographic density.

Conjugated equine estrogen influence on mammographic density in postmenopausal women in a substudy of the women's health initiative randomized trial

PURPOSE

Increased mammographic density is associated with increased breast cancer risk and reduced sensitivity of screening mammography and is related to hormone exposure. However, the effects of conjugated equine estrogens (CEEs) alone on mammographic density in diverse racial/ethnic populations are not established. We examined the effect of CEE alone on mammographic density in a subsample of the Women's Health Initiative (WHI) clinical trial participants.

PATIENTS AND METHODS

In the WHI trial, women were randomly assigned to daily CEE 0.625 mg or placebo. The effect of CEE on mammographic percent density was determined over 1 and 2 years in a stratified random sample of 435 racially and ethnically diverse participants from 15 of 40 WHI clinics.

RESULTS

Use of CEE resulted in mean increase in mammographic percent density of 1.6 percentage points (95% CI, 0.8 to 2.4) at year 1 compared with a mean decrease of 1.0 percentage point (95% CI, -1.7 to -0.4) in the placebo group (P < .001). The effect persisted for 2 years, with a mean increase of 1.7 percentage points (95% CI, 0.7 to 2.7) versus a mean decrease of 1.2 percentage points (95% CI, -1.8 to -0.5; P < .001) in the hormone and placebo groups, respectively. These effects were greater in women age 60 to 79 years (P = .03 for interaction across age).

CONCLUSION

Use of CEE results in a modest but statistically significant increase in mammographic density that is sustained over at least a 2-year period. The clinical significance of the CEE effect on mammographic density remains to be determined.

New-onset breast tenderness after initiation of estrogen plus progestin therapy and breast cancer risk

BACKGROUND

Estrogen plus progestin therapy increases breast cancer incidence and breast tenderness. Whether breast tenderness during estrogen plus progestin therapy is associated with breast cancer risk is uncertain.

METHODS

We analyzed data from the Women's Health Initiative Estrogen + Progestin Trial, which randomized postmenopausal women with an intact uterus to receive daily conjugated equine estrogens, 0.625 mg, plus medroxyprogesterone acetate, 2.5 mg (n = 8506), or placebo (n = 8102). At baseline and annually, participants underwent mammography and clinical breast examination. Self-reported breast tenderness was assessed at baseline and at 12 months. The incidence of invasive breast cancer was confirmed by medical record review (mean follow-up of 5.6 years).

RESULTS

Of women without baseline breast tenderness (n = 14,538), significantly more assigned to receive conjugated equine estrogens plus medroxyprogesterone vs placebo experienced new-onset breast tenderness after 12 months (36.1% vs 11.8%, P < .001). Of women in the conjugated equine estrogens plus medroxyprogesterone group, breast cancer risk was significantly higher in those with new-onset breast tenderness compared with those without (hazard ratio, 1.48; 95% confidence interval, 1.08-2.03; P = .02). In the placebo group, breast cancer risk was not significantly associated with new-onset breast tenderness (P = .97).

CONCLUSIONS

New-onset breast tenderness during conjugated equine estrogens plus medroxyprogesterone therapy was associated with increased breast cancer risk. The sensitivity and specificity of the association between breast tenderness and breast cancer were similar in magnitude to those of the Gail model. Trial Registration clinicaltrials.gov Identifier: NCT00000611.

Low-dose transdermal estradiol induces breast density and heterogeneity changes comparable to those of raloxifene

The aim of this study was to investigate whether transdermal low-dose estradiol treatment induces changes in mammographic density or heterogeneity compared with raloxifene, whether if these changes relate to changes in bone formation/resorption markers, and whether these findings indicate elevation of breast cancer risk by treatment.

METHODS

Digitized mammograms of 2 x 135 completers of a 2-year, randomized trial formed the base of the present analysis. Active treatments were transdermal estradiol releasing 0.014 mg estradiol (E2)/week and orally administered raloxifene hydrochloride 60 mg/day, respectively. Influence of the therapies on breast density was assessed with categorical scores Breast Imaging Reporting and Data System, area percentage density, and computer-based (E2-specific) heterogeneity examination of radiographs. These where related to physical and systemic markers.

RESULTS

At baseline, no mammography scoring methodology or other marker could separate the two treatment groups of transdermal estradiol and raloxifene. No treatment induced significant density changes measured by Breast Imaging Reporting and Data System. Both treatments made the area percentage density increase and the estradiol significantly. Both treatments induced significant changes in E2-specific heterogeneity scoring (E2-specific heterogeneity examination of radiograph), and the raloxifene treatment induced a significantly higher change. At baseline, the mammographic markers showed negative correlation with body mass index and positive correlation with serum type I collagen crosslinks C-telopeptide. The changes in mammographic markers did not essentially exhibit correlations to changes in bone markers in either treatment group.

CONCLUSIONS

Low-dose transdermal estradiol and raloxifene induced comparable changes in breast density and heterogeneity. Baseline correlations may be explained through relations to obesity. The current study does not yield evidence against the hypothesis that "neither raloxifene nor low dose transdermal estradiol treatment increases the breast cancer risk."

Hormone therapy, mammographic density, and breast cancer risk

Percent mammographic density (PMD) is a strong independent risk factor for breast cancer. The effects of age, parity and menopause on PMD are consistent with it being a marker of susceptibility to breast cancer. In this review, we describe the association of PMD with breast cancer, the biological plausibility of this association, and discuss the extent to which PMD meets the criteria for a surrogate marker for the effects of exogenous hormones on risk of breast cancer. Combined hormone therapy is associated with a small increase in both PMD and the risk of breast cancer. However there is evidence that the associations of blood estradiol levels and HRT with breast cancer risk are independent of the association of PMD with risk, suggesting that different biological pathways may be involved. Tamoxifen, an anti-estrogenic drug, reduces both the risk of breast cancer and PMD, but the potential mediation of the effects of anti-estrogens on breast cancer risk by their effects on PMD has not yet been examined. Given the evidence that estradiol and PMD are independently associated with breast cancer risk, it seems unlikely that an effect of these agents on PMD mediates their effects on risk. We thus find that the available evidence is insufficient to conclude that PMD can be used as a surrogate marker for the effect of exogenous hormones on breast cancer. Further research to examine the potential role of PMD as a mediator of the effects of other risk factors is required.

Sex steroid metabolism polymorphisms and mammographic density in pre- and early perimenopausal women

Introduction

We examined the association between mammographic density and single-nucleotide polymorphisms (SNPs) in genes encoding CYP1A1, CYP1B1, aromatase, 17β-HSD, ESR1, and ESR2 in pre- and early perimenopausal white, African-American, Chinese, and Japanese women.

Methods

The Study of Women's Health Across the Nation is a longitudinal community-based cohort study. We analyzed data from 451 pre- and early perimenopausal participants of the ancillary SWAN Mammographic Density study for whom we had complete information regarding mammographic density, genotypes, and covariates. With multivariate linear regression, we examined the relation between percentage mammographic breast density (outcome) and each SNP (primary predictor), adjusting for age, race/ethnicity, parity, cigarette smoking, and body mass index (BMI).

Results

After multivariate adjustment, the CYP1B1 rs162555 CC genotype was associated with a 9.4% higher mammographic density than the TC/TT genotype (P = 0.04). The CYP19A1 rs936306 TT genotype was associated with 6.2% lower mammographic density than the TC/CC genotype (P = 0.02). The positive association between CYP1A1 rs2606345 and mammographic density was significantly stronger among participants with BMI greater than 30 kg/m² than among those with BMI less than 25 kg/m² (P_interaction = 0.05). Among white participants, the ESR1 rs2234693 CC genotype was associated with a 7.0% higher mammographic density than the CT/TT genotype (P = 0.01).

Conclusions

SNPs in certain genes encoding sex steroid metabolism enzymes and ESRs were associated with mammographic density. Because the encoded enzymes and ESR1 are expressed in breast tissue, these SNPs may influence breast cancer risk by altering mammographic density.

Hormone therapy and breast cancer risk

Hormone therapy (HT) is the most efficacious intervention for the relief of climacteric symptoms. Controversies surrounding HT have left many women puzzled and afraid. Gynecologists are faced with long-standing beneficial assumptions challenged by an abundance of robust detrimental new data, with little guidance on how to interpret these findings. Prescriptions for HT (and incidence of breast cancers in some areas) have fallen over the last 3 years due to anxiety provoked about breast cancer risk and recurrence. The current 'clinical climate' is against HT. Due to a lack of effective alternatives, women suffering from estrogen-deficiency symptoms are still requesting objective information about HT, particularly those at higher risk of breast cancer or those with a past history of breast cancer. In this situation, discussion of the current clinical uncertainty surrounding the use of HT must be undertaken to ensure that women are adequately informed. The objective of this presentation is to provide a framework for understanding breast cancer risk associated with HT. What are the precise molecular mechanisms of estrogen and progestin in the initiation of breast cancer? Does the risk of estrogen-only therapy on breast cancer vary by dose, constituent, route and duration of administration and cessation of use? Does HT, in addition to increasing risk for breast cancer, affect the type of breast cancer (lobular and ductal) diagnosed? Is HT associated with breast cancers that have better prognostic factors? How relevant are the changes in mammographic breast density associated with HT for the evaluation of breast cancer risk? What is the additional global health risk/benefit ratio associated with the selective use of progesterone or progestin that may confer a significant cardiovascular benefit, such as drospirenone? It is currently assumed and tested that new hormones with particular pharmacological profiles may ultimately achieve their therapeutic goal of relieving climacteric symptoms without an associated moderate increased risk of breast cancer.

Differences in measured mammographic density in the menstrual cycle

BACKGROUND

In premenopausal women, the sensitivity of screening mammography for detecting breast cancer has been reported to be greater in the follicular phase than in the luteal phase of the menstrual cycle, which may be due to differences in mammographic density. To examine this possible effect, we compared mammographic density in premenopausal women who had mammograms at different phases of the menstrual cycle.

METHODS

We recruited premenopausal women ages 40 to 49 years from two mammography units in Toronto, recorded the first day of the last menstrual period (LMP) and measured mammographic density using Cumulus software. We classified the time of the mammography examination as having occurred in one of four intervals, 1 (first week after LMP), 2 (second week after LMP), 3 (third week after LMP) and 4 (>3 weeks after LMP), and compared mammographic density across intervals.

RESULTS

Of the 936 women included in the analysis, 620 were examined by film and 316 by digital mammography. There were small and statistically nonsignificant variations in breast dense, nondense area, and percent density over the menstrual cycle in women examined by film mammography. Marginally significant variation in percent density was observed in the digital subset due to significant differences in the amount of nondense tissue over the menstrual cycle.

CONCLUSION

Variations in mammographic density over the menstrual cycle were small and nonsignificant for women examined by either film or digital mammography. Thus, timing of mammography in menstrual cycle is unlikely to have a significant influence in breast cancer detection by screening mammography.

Mammographic density and epithelial histopathologic markers

BACKGROUND

We explored the association of mammographic density, a breast cancer risk factor, with hormonal and proliferation markers in benign tissue from tumor blocks of pre-and postmenopausal breast cancer cases.

METHODS

Breast cancer cases were recruited from a case-control study on breast density. Mammographic density was assessed on digitized prediagnostic mammograms using a computer-assisted method. For 279 participants of the original study, we obtained tumor blocks and prepared tissue microarrays (TMA), but benign tissue cores were only available for 159 women. The TMAs were immunostained for estrogen receptor alpha (ERalpha) and beta (ERbeta), progesterone receptor (PR), HER2/neu, Ki-67, and Proliferating Cell Nuclear Antigen (PCNA). We applied general linear models to compute breast density according to marker expression.

RESULTS

A substantial proportion of the samples were in the low or no staining categories. None of the results was statistically significant, but women with PR and ERbeta staining had 3.4% and 2.4% higher percent density. The respective values for Caucasians were 5.7% and 11.6% but less in Japanese women (3.5% and -1.1%). Percent density was 3.4% higher in women with any Ki-67 staining and 2.2% in those with positive PCNA staining.

CONCLUSION

This study detected little evidence for an association between mammographic density and expression of steroid receptors and proliferation markers in breast tissue, but it illustrated the problems of locating tumor blocks and benign breast tissue samples for epidemiologic research. Given the suggestive findings, future studies examining estrogen effects in tissue, cell proliferation, and density in the breast may be informative.

Various doses of soy isoflavones do not modify mammographic density in postmenopausal women

Soy isoflavones have functional similarity to human estrogens and may protect against breast cancer as a result of their antiestrogenic activity or increase risk as a result of their estrogen-like properties. We examined the relation between isoflavone supplementation and mammographic density, a strong marker for breast cancer risk, among postmenopausal women. The Osteoporosis Prevention Using Soy (OPUS) study, a multi-site, randomized, double-blinded, and placebo-controlled trial assigned 406 postmenopausal women to 80 or 120 mg/d of isoflavones each or a placebo for 2 y. Percent densities were assessed in digitized mammograms using a computer-assisted method. The mammogram reader did not know the treatment status and the time of mammograms. We applied mixed models to compare breast density by treatment while considering the repeated measures. The mammographic density analysis included 358 women, 88.2% of the OPUS participants; 303 had a complete set of 3 mammograms, 49 had 2, and 6 had only 1 mammogram. At baseline, the groups were similar in age, BMI, and percent density, but mean breast density differed by study site (P = 0.02). A model with all mammograms did not show a treatment effect on any mammographic measure, but the change over time was significant; breast density decreased by 1.6%/y across groups (P < 0.001). Stratification by age and BMI did not reveal any effects in subgroups. In this randomized 2-y trial, isoflavone supplements did not modify breast density in postmenopausal women. These findings offer reassurance that isoflavones do not act like hormone replacement medication on breast density.

Perspectives on the soy-breast cancer relation

There has been considerable investigation of the potential for soy foods to reduce risk of breast cancer. Initial enthusiasm for this research was partially based on the historically low incidence rates of breast cancer and high soy food intake in Japan. There are several putative soybean chemopreventive agents, but most cancer research has focused on isoflavones. Isoflavones possess both hormonal and nonhormonal properties relevant to carcinogenesis. Recent epidemiologic analyses indicate that among Asians high soy intake is associated with an approximate one-third reduction in the risk of both pre- and postmenopausal breast cancer. However, several lines of evidence suggest that to derive maximum protection against breast cancer, soy must be consumed early in life. This evidence is consistent with the lack of significant effects noted in clinical studies that have evaluated the effects of isoflavone-containing products on breast cancer risk markers. Isoflavones may exert their putative protective effects by stimulating breast cell differentiation in a manner similar to that which is thought to occur during early pregnancy. Finally, the ability of the isoflavone genistein to stimulate the growth of mammary tumors in ovariectomized athymic nude mice implanted with estrogen-sensitive breast cancer cells has raised concern that soy foods, and especially isoflavone supplements, are contraindicated for patients with breast cancer and women at high risk of breast cancer. However, findings from clinical studies, in which breast biopsies have been taken or breast tissue density measured after isoflavone exposure, are reassuring and contrast with the proliferative effects of conventional combined hormone therapy, although understanding of the effect of soy and isoflavones on breast tissues remains imprecise.

Long term hormone therapy for perimenopausal and postmenopausal women

BACKGROUND

Hormone therapy (HT) is widely used for controlling menopausal symptoms and has also been used for the management and prevention of cardiovascular disease, osteoporosis and dementia in older women. This is an updated version of the original Cochrane review first published in 2005.

OBJECTIVES

To assess the effect of long-term HT on mortality, cardiovascular outcomes, cancer, gallbladder disease, cognition, fractures and quality of life.

SEARCH STRATEGY

We searched the following databases to November 2007: Trials Register of the Cochrane Menstrual Disorders and Subfertility Group, Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, Biological Abstracts. Also relevant non-indexed journals and conference abstracts.

SELECTION CRITERIA

Randomised double-blind trials of HT versus placebo, taken for at least one year by perimenopausal or postmenopausal women. HT included oestrogens, with or without progestogens, via oral, transdermal, subcutaneous or transnasal routes.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data.

MAIN RESULTS

Nineteen trials involving 41,904 women were included. In relatively healthy women, combined continuous HT significantly increased the risk of venous thrombo-embolism or coronary event (after one year's use), stroke (after three years), breast cancer and gallbladder disease. Long-term oestrogen-only HT significantly increased the risk of venous thrombo-embolism, stroke and gallbladder disease (after one to two years, three years and seven years' use respectively), but did not significantly increase the risk of breast cancer. The only statistically significant benefits of HT were a decreased incidence of fractures and (for combined HT) colon cancer, with long-term use. Among women aged over 65 who were relatively healthy (i.e. generally fit, without overt disease) and taking continuous combined HT, there was a statistically significant increase in the incidence of dementia. Among women with cardiovascular disease, long-term use of combined continuous HT significantly increased the risk of venous thrombo-embolism.One trial analysed subgroups of 2839 relatively healthy 50 to 59 year old women taking combined continuous HT and 1637 taking oestrogen-only HT, versus similar-sized placebo groups. The only significantly increased risk reported was for venous thrombo-embolism in women taking combined continuous HT: their absolute risk remained low, at less than 1/500. However, this study was not powered to detect differences between groups of younger women.

AUTHORS' CONCLUSIONS

HT is not indicated for the routine management of chronic disease. We need more evidence on the safety of HT for menopausal symptom control, though short-term use appears to be relatively safe for healthy younger women.

The relative importance of genetics and environment on mammographic density

BACKGROUND

Although several environmental factors predict mammographic density, estimates of its heritability have been quite high. We investigated whether part of the presumed heritability might be attributed to differential sharing of modifiable risk factors in monozygotic (MZ) and dizygotic (DZ) twins.

METHODS

We measured percent and absolute mammographic density using mammograms from 257 MZ and 296 DZ twin pairs. The correlation of intrapair mammographic density was compared according to zygosity across strata of modifiable risk factors. Portions of variance attributable to additive genetic factors, shared environment, and individual environment were calculated using a variance component methodology in the entire set, and within twin pairs stratified by environmental trait similarity.

RESULTS

Both percent density and absolute mammographic density were more highly correlated between MZ twins than DZ twins, but the correlations varied across strata. Body mass index (BMI) and parity strongly predicted differences in mammographic density within MZ twin pairs. After adjusting for covariates, 53% of the total variance in percent density and 59% of that in absolute density seemed attributable to genetic effects, but these estimates varied greatly by stratum. For twins dissimilar on BMI (difference >2.5 kg/m(2)), the additive genetic component of absolute density was estimated at only 20% (+/-19%), and the common and individual environment at 21% (+/-14%) and 49%, respectively (P value for heterogeneity across BMI = 0.0001).

CONCLUSION

Our results confirm that the genome is an important determinant of mammographic density but suggest that an unknown portion of the mammographic density effect attributed to the genome may be due to shared modifiable environmental factors.

Parenchymal texture analysis in digital breast tomosynthesis for breast cancer risk estimation: a preliminary study

RATIONALE AND OBJECTIVES

Studies have demonstrated a relationship between mammographic parenchymal texture and breast cancer risk. Although promising, texture analysis in mammograms is limited by tissue superposition. Digital breast tomosynthesis (DBT) is a novel tomographic x-ray breast imaging modality that alleviates the effect of tissue superposition, offering superior parenchymal texture visualization compared to mammography. The aim of this study was to investigate the potential advantages of DBT parenchymal texture analysis for breast cancer risk estimation.

MATERIALS AND METHODS

DBT and digital mammographic (DM) images of 39 women were analyzed. Texture features, shown in previous studies with mammograms to correlate with cancer risk, were computed from the retroareolar breast region. The relative performances of the DBT and DM texture features were compared in correlating with two measures of breast cancer risk: (1) the Gail and Claus risk estimates and (2) mammographic breast density. Linear regression was performed to model the association between texture features and increasing levels of risk.

RESULTS

No significant correlation was detected between parenchymal texture and the Gail and Claus risk estimates. Significant correlations were observed between texture features and breast density. Overall, the DBT texture features demonstrated stronger correlations with breast percent density than DM features (P < or = .05). When dividing the study population into groups of increasing breast percent density, the DBT texture features appeared to be more discriminative, having regression lines with overall lower P values, steeper slopes, and higher R(2) estimates.

CONCLUSION

Although preliminary, the results of this study suggest that DBT parenchymal texture analysis could provide more accurate characterization of breast density patterns, which could ultimately improve breast cancer risk estimation.

Mediterranean diet and breast density in the Minnesota Breast Cancer Family Study

Mediterranean populations' lower breast cancer incidence has been attributed to a traditional Mediterranean diet, but few studies have quantified Mediterranean dietary pattern intake in relation to breast cancer. We examined the association of a Mediterranean diet scale (MDS) with mammographic breast density as a surrogate marker for breast cancer risk. Participants completed a dietary questionnaire and provided screening mammograms for breast density assessment using a computer-assisted method. Among 1,286 women, MDS was not clearly associated with percent density in multivariate linear regression analyses. Because of previous work suggesting dietary effects limited to smokers, we conducted stratified analyses and found MDS and percent density to be significantly, inversely associated among current smokers (beta = -1.68, P = 0.002) but not among nonsmokers (beta = -0.08, P = 0.72; P for interaction = 0.008). Our results confirm a previous suggestion that selected dietary patterns may be protective primarily in the presence of procarcinogenic compounds such as those found in tobacco smoke.

Is there a difference in the association between percent mammographic density and subtypes of breast cancer? Luminal A and triple-negative breast cancer

BACKGROUND

Mammographic density is a potentially modifiable risk factor for breast cancer. To what extent mammographic density is a predictor for both hormone receptor-positive and hormone receptor-negative tumors is unclear. Even less is known about whether mammographic density predicts subtypes of breast cancer defined by expression status of the three receptors: estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2).

METHODS

We estimated the association of percent mammographic density with subtypes of invasive breast cancer among 479 population-based female breast cancer patients and 376 control subjects ages 35 to 64 years. The expression status of ER, PR, and HER-2 was assessed using immunohistochemistry methods in a single laboratory. We considered ER+ or PR+ plus HER-2- tumors as luminal A breast cancer and ER-/PR-/HER-2- tumors as triple-negative breast cancer. We used unconditional logistic regression methods to estimate odd ratios (95% confidence intervals) for both case-control and case-case comparisons.

RESULTS

Mammographic density was associated with increased risk of both invasive breast cancer subtypes, luminal A and triple-negative, in the case-control analysis. Results from case-case comparisons yielded no differences between the two subtypes among all women combined or in analyses done separately by race (White versus African American women) or menopausal status (premenopausal versus postmenopausal women; all P values > 0.05).

CONCLUSIONS

Our results suggest that percent mammographic density is positively associated with both luminal A and triple-negative breast cancer.

Green tea, soy, and mammographic density in Singapore Chinese women

There is increasing evidence from observational studies that breast cancer risk is inversely associated with soy and green tea consumption. We investigated the effects of these two dietary agents on mammographic density, a well-established biomarker for breast cancer risk, in a cross-sectional analysis of mammograms and validated food frequency questionnaires from 3,315 Chinese women in Singapore. Percent mammographic density (PMD) was assessed using a reproducible computer-assisted method. We used generalized linear models to estimate PMD by intake of soy, green tea, and black tea while adjusting for potential confounders. Daily green tea drinkers showed statistically significantly lower PMD (19.5%) than non-tea drinkers (21.7%; P = 0.002) after adjusting for relevant covariates. This difference in PMD between daily green tea drinkers and non-tea drinkers remained statistically significant after adjustment for soy (P = 0.002); the effect was more apparent among lower soy consumers (Q1-Q3; 21.9% versus 19.4%; P = 0.002) than in higher (Q4) consumers (20.9% versus 19.5%; P = 0.32). Black tea intake was unrelated to PMD. Only among postmenopausal women who reported very high soy intake (Q4) compared with those with less soy intake was there any association noted between PMD and soy intake (18.9% versus 20.5%; P = 0.035). Following adjustment for green tea intake, the association between soy and PMD was no longer statistically significant (P = 0.52). Our findings suggest that both regular green tea and high soy intake may have beneficial effects on the breast; the effect of green tea on PMD may be stronger than the effect of soy.

Early intake appears to be the key to the proposed protective effects of soy intake against breast cancer

There is a large variation in breast cancer incidence and mortality rates worldwide. Migration studies have indicated that this variation is primarily the result of lifestyle influences. Although there has been much research conducted, definitively identifying dietary factors that impact breast cancer risk has proven difficult. In part this may be because most clinical and epidemiologic studies have focused on adult dietary exposure. However, evidence suggests that childhood and/or adolescence is the period of life when the breast is most sensitive to dietary influences. Further, the available epidemiologic and animal data suggest that early soy intake reduces breast cancer risk. Soy foods are unique dietary sources of isoflavones, diphenolic compounds that exert estrogen-like effects under certain experimental conditions. The protection effects of soy may result from the soybean isoflavones stimulating differentiation of the breast in much the same way that the elevated estrogen levels do during pregnancy. More specifically, in rats, the primary isoflavone genistein reduces mammary tumorigenesis and increases mammary tissue differentiation by leading to a reduction in the number of terminal end buds (TEB) and an increase in the number of differentiated lobules. There is need and justification for continued investigation of the early soy intake hypothesis, particularly to determine the cellular targets of soy action and to identify the signaling pathways mediating the effects on mammary gland morphology and susceptibility to breast cancer.

Exogenous and endogenous hormones, mammographic density and breast cancer risk: can mammographic density be considered an intermediate marker of risk?

Elevated mammographic density measures are a well-established, relatively strong risk factor for breast cancer development. A systematic review of prospective cohort studies and cross-sectional studies strikingly establishes parallels between the associations of combined postmenopausal estrogen and progestin replacement therapy with, on the one hand, mammographic densities and, on the other hand, breast cancer risk. Other parallel observations were the inverse associations of both mammographic density and breast cancer risk with the selective estrogen receptor modulator tamoxifen, and direct associations with prolactin. Paradoxically, however, high mammographic density has been found associated with higher risks of both estrogen- and progesterone-receptor positive (ER+/ PR+) and negative (ER-/PR-) breast cancers, while hormone replacement therapy (HRT) use, but also circulating (blood) levels of androgens, estrogens, and prolactin appear to be associated more specifically to the risk of ER+ tumors. The effects of aromatase inhibitors and gonadotropin-releasing hormone agonists on breast density, as well as on breast cancer risk, still require further investigation. Regarding circulating levels of insulin-like growth factor (IGF)-I or IGFBP-3, studies did not show fully consistent relationships with mammographic density measures and breast cancer risk. In view of these various findings, it is impossible, at present, to propose mammographic density measures as an intermediate risk-related phenotype, integrating the effects of exogenous and/or endogenous hormones on the risk of developing breast cancer.

Increases in serum estrone sulfate level are associated with increased mammographic density during menopausal hormone therapy

BACKGROUND

Menopausal hormone therapy increases mammographic density. We determined whether increases in serum estrone sulfate (E(1)S) levels during menopausal hormone therapy predict increased mammographic density.

METHODS

We measured percent mammographic density and serum E(1)S levels in 428 participants of the Postmenopausal Estrogen/Progestin Interventions study who were randomly assigned to daily conjugated equine estrogen (CEE) 0.625 mg alone, CEE + daily medroxyprogesterone acetate (MPA) 2.5 mg, CEE + cyclical MPA (10 mg days 1-12 per 28-day cycle), or CEE + cyclical micronized progesterone (10 mg days 1-12). Serum E(1)S levels were determined by RIA. Information about covariates was determined by annual questionnaire. Using linear regression, we determined the association between change in E(1)S level from baseline to 12 months and change in percent mammographic density (by semiquantitative interactive threshold method).

RESULTS

After controlling for baseline mammographic density, age, body mass index, alcohol intake, parity, smoking, ethnicity, physical activity, and age at first pregnancy, mammographic density increased by 1.3% for every 1 ng/mL increase in E(1)S level (P < 0.0001). The association between change in E(1)S level and change in mammographic density differed by treatment group (greater effect in CEE + cyclical MPA group versus CEE group; P = 0.05). After controlling for treatment group, change in the ratio of E(1)S to E(1) was also positively associated with change in mammographic density.

CONCLUSIONS

Increases in serum E(1)S levels during menopausal hormone therapy are associated with increases in mammographic density. The relative contribution of E(1)S and E(1) to stimulation of breast tissue awaits further elucidation.

Mammographic breast density--evidence for genetic correlations with established breast cancer risk factors

Previous twin and family studies indicate that the familial aggregation of breast density is due (in part) to genetic factors. Whether these genetic influences are shared with other breast cancer risk factors, however, is not known. Using standard film-screen mammography, we screened 550 women, including 611 pairs of sisters, from the Old Order Amish population of Lancaster County, Pennsylvania. We digitized mammograms and quantified the dense and nondense areas of the breast using a computer-assisted method. Information about other breast cancer risk factors was collected via questionnaires and a physical exam. Using pedigree-based variance component methods, we estimated the genetic contributions to several breast cancer risk factors, including breast density, and evaluated the evidence for shared genetic influences between them. After adjusting for covariates, genetic effects accounted for >33% of the total variance of each risk factor (P < 0.001), including breast density, and the dense and nondense areas of the breast were significantly genetically correlated with parity [genetic correlation (rho(G)) = -0.47; P = 0.013] and age at menarche (rho(G) = -0.38; P = 0.008), respectively. The nondense area of the breast and, in turn, breast density, expressed as a ratio of dense area to total area, were also genetically correlated with most measures of adiposity but in opposite directions (rho(G) > or = 0.75; P < 10(-7) for nondense area). We conclude that the genetic components that influence breast density are not independent of the genetic components that influence other breast cancer risk factors. This shared genetic architecture should be considered in future genetic studies of breast density.