Postmenopausal hormone therapy and change in mammographic density

[Mammographic density: a valid risk factor for breast cancer?]

Whether estimated or measured, mammographic or breast density, which may be subject to physiological and therapeutic variations, is widely viewed in the literature as an important factor of increased risk for breast cancer. A high breast density, the causes of which are being refined, would increase the relative risk of breast cancer four to six fold, even though some authors direct critics at methodological flaws supporting these results. Three-dimensional imaging will confirm or refute the available results. Meanwhile, radiologists and clinicians must remain vigilant in patients with high breast density.

Can genes for mammographic density inform cancer aetiology?

Mammographic density (MD) reflects variations in fat, stromal and epithelial tissues that are thought to be regulated by several genes. High MD is an established risk factor for breast cancer; therefore, genes that regulate MD may indirectly influence breast cancer. These genes might also be fewer in number and easier to identify than those for breast cancer risk outside of inherited predisposition syndromes. In this Perspective, we review the limited genetic studies of MD and propose future directions.

Could transdermal estradiol + progesterone be a safer postmenopausal HRT? A review

Hormone replacement therapy (HRT) in young postmenopausal women is a safe and effective tool to counteract climacteric symptoms and to prevent long-term degenerative diseases, such as osteoporotic fractures, cardiovascular disease, diabetes mellitus and possibly cognitive impairment. The different types of HRT offer to many extent comparable efficacies on symptoms control; however, the expert selection of specific compounds, doses or routes of administration can provide significant clinical advantages. This paper reviews the role of the non-oral route of administration of sex steroids in the clinical management of postmenopausal women. Non-orally administered estrogens, minimizing the hepatic induction of clotting factors and others proteins associated with the first-pass effect, are associated with potential advantages on the cardiovascular system. In particular, the risk of developing deep vein thrombosis or pulmonary thromboembolism is negligible in comparison to that associated with oral estrogens. In addition, recent indications suggest potential advantages for blood pressure control with non-oral estrogens. To the same extent, a growing literature suggests that the progestins used in association with estrogens may not be equivalent. Recent evidence indeed shows that natural progesterone displays a favorable action on the vessels and on the brain, while this might not be true for some synthetic progestins. Compelling indications also exist that differences might also be present for the risk of developing breast cancer, with recent trials indicating that the association of natural progesterone with estrogens confers less or even no risk of breast cancer as opposed to the use of other synthetic progestins. In conclusion, while all types of hormone replacement therapies are safe and effective and confer significant benefits in the long-term when initiated in young postmenopausal women, in specific clinical settings the choice of the transdermal route of administration of estrogens and the use of natural progesterone might offer significant benefits and added safety.

Automated effect-specific mammographic pattern measures

We investigate the possibility to develop methodologies for assessing effect specific structural changes of the breast tissue using a general statistical machine learning framework. We present an approach of obtaining objective mammographic pattern measures quantifying a specific biological effect, such as hormone replacement therapy (HRT). We compare results using this approach to using standard density measures. We show that the proposed method can quantify both age related effects and effects caused by HRT. Age effects are significantly detected by our method where standard methodologies fail. The separation of HRT subpopulations using our approach is comparable to the best methodology, which is interactive.

Estrogens, progestins, and risk of breast cancer

Obesity is associated with a decreased risk of breast cancer in premenopausal women but an increased risk in postmenopausal women, an effect that increases with time since menopause. Analysis of these effects of obesity shows that there is a ceiling to the carcinogenic effect of estrogen on the breast; increases in nonsex hormone-binding globulin-bound estradiol (non-SHBG bound E2) exceeding approximately 10.2 pg/ml have no further effect on breast cancer risk; this ceiling is lower than the lowest level seen during the menstrual cycle. This suggests that the effects of menopausal estrogen therapy (ET) and menopausal estrogen-progestin therapy (EPT) on a woman's breast cancer risk will greatly depend on her body mass index (BMI; weight in kilograms/height in meters squared, kg/m2) with the largest effects being in slender women. Epidemiological studies confirm this prediction. Our best estimates, per 5 years of use, of the effects of ET on breast cancer risk is a 30% increase in a woman with a BMI of 20 kg/m2 decreasing to an 8% increase in a woman with a BMI of 30 kg/m2; the equivalent figures for EPT are 50% and 26%. The analysis of the effects of estrogen also shows that even reducing the dose of estrogen in ET and EPT by as much as a half will have little or no effect on these risks. Reducing the progestin dose is likely to significantly reduce the risk of EPT: this is possible with an endometrial route of administration.

Investigating the Optimal Soy Protein and Isoflavone Intakes for Women: A Perspective

Traditional soyfoods have been consumed for centuries throughout much of East Asia and, recently, these foods have also become popular in the West. Soyfoods and specific soybean components, such as the protein and isoflavones, have attracted attention for their possible health benefits. Isoflavones are classified as phytoestrogens and have been postulated to be natural alternatives to hormone therapy for menopausal women. To provide guidance on optimal soy intake, this article evaluates Asian soy consumption and both clinical and Asian epidemiologic studies that examined the relationship between soy intake and a variety of health outcomes. On the basis of these data and the standard principles of dietary practice the author suggests that optimal soy protein and isoflavone intakes are 15–20 g/day and 50–90 mg/day, respectively. In addition, an intake of 25 g/day soy protein can be specifically used as the recommendation for cholesterol reduction.

Effect of raloxifene on mammographic density and breast magnetic resonance imaging in premenopausal women at increased risk for breast cancer

BACKGROUND

Mammographic density is a risk factor for breast cancer. Mammographic density and breast magnetic resonance imaging (MRI) volume (MRIV) assess the amount of fibroglandular tissue in the breast. Mammographic density and MRIV can be modulated with hormonal interventions, suggesting that these imaging modalities may be useful as surrogate endpoint biomarkers for breast cancer chemoprevention trials. We evaluated the effect of raloxifene on mammographic density and MRIV in premenopausal women at increased risk for breast cancer.

METHODS

Mammograms and MRI were obtained at baseline and after 1 and 2 years of 60 mg raloxifene by mouth daily for 27 premenopausal women. Mammographic percent dense area was calculated using a semiquantitative thresholding technique. T(1)-weighted spoiled gradient-echo MRI with fat suppression was used to determine breast MRIV using a semiautomatic method. Mean change in mammographic density and median change in MRIV were assessed by the Wilcoxon signed-rank test.

RESULTS

No significant change in mammographic density was seen after treatment with raloxifene. Mean change after 1 year was 1% [95% confidence interval (95% CI), -3 to +5] and after 2 years was 1% (95% CI, -2 to +5). MRIV decreased on raloxifene. Median relative change in MRIV after 1 year was -17% (95% CI, -28 to -9; P = 0.0017) and after 2 years was -16% (95% CI, -31 to -4; P = 0.0004).

CONCLUSIONS

In high-risk premenopausal women, mammographic density did not change on raloxifene, whereas MRIV significantly declined. Our findings suggest that MRIV is a promising surrogate biomarker in premenopausal women at increased risk for breast cancer and should be investigated further in breast cancer prevention trials.

Soy isoflavones, estrogen therapy, and breast cancer risk: analysis and commentary

There has been considerable investigation of the potential for soyfoods to reduce risk of cancer, and in particular cancer of the breast. Most interest in this relationship is because soyfoods are essentially a unique dietary source of isoflavones, compounds which bind to estrogen receptors and exhibit weak estrogen-like effects under certain experimental conditions. In recent years the relationship between soyfoods and breast cancer has become controversial because of concerns – based mostly on in vitro and rodent data – that isoflavones may stimulate the growth of existing estrogen-sensitive breast tumors. This controversy carries considerable public health significance because of the increasing popularity of soyfoods and the commercial availability of isoflavone supplements. In this analysis and commentary we attempt to outline current concerns regarding the estrogen-like effects of isoflavones in the breast focusing primarily on the clinical trial data and place these concerns in the context of recent evidence regarding estrogen therapy use in postmenopausal women. Overall, there is little clinical evidence to suggest that isoflavones will increase breast cancer risk in healthy women or worsen the prognosis of breast cancer patients. Although relatively limited research has been conducted, and the clinical trials often involved small numbers of subjects, there is no evidence that isoflavone intake increases breast tissue density in pre- or postmenopausal women or increases breast cell proliferation in postmenopausal women with or without a history of breast cancer. The epidemiologic data are generally consistent with the clinical data, showing no indication of increased risk. Furthermore, these clinical and epidemiologic data are consistent with what appears to be a low overall breast cancer risk associated with pharmacologic unopposed estrogen exposure in postmenopausal women. While more research is required to definitively allay concerns, the existing data should provide some degree of assurance that isoflavone exposure at levels consistent with historical Asian soyfood intake does not result in adverse stimulatory effects on breast tissue.

Estrogen plus progestin therapy and breast cancer in recently postmenopausal women

The Women's Health Initiative trial found a modestly increased risk of invasive breast cancer with daily 0.625-mg conjugated equine estrogens plus 2.5-mg medroxyprogesterone acetate, with most evidence among women who had previously received postmenopausal hormone therapy. In comparison, observational studies mostly report a larger risk increase. To explain these patterns, the authors examined the effects of this regimen in relation to both prior hormone therapy and time from menopause to first use of postmenopausal hormone therapy ("gap time") in the Women's Health Initiative trial and in a corresponding subset of the Women's Health Initiative observational study. Postmenopausal women with a uterus enrolled at 40 US clinical centers during 1993-1998. The authors found that hazard ratios agreed between the two cohorts at a specified gap time and time from hormone therapy initiation. Combined trial and observational study data support an adverse effect on breast cancer risk. Women who initiate use soon after menopause, and continue for many years, appear to be at particularly high risk. For example, for a woman who starts soon after menopause and adheres to this regimen, estimated hazard ratios are 1.64 (95% confidence interval: 1.00, 2.68) over a 5-year period of use and 2.19 (95% confidence interval: 1.56, 3.08) over a 10-year period of use.

Histologic changes in the breast with menopausal hormone therapy use: correlation with breast density, estrogen receptor, progesterone receptor, and proliferation indices

OBJECTIVE

This retrospective study systematically compared mammographic density with histology in women receiving or not receiving menopausal hormone therapy (HT).

DESIGN

This study was approved by the institutional review board. Twenty-eight postmenopausal women using HT were matched with 28 postmenopausal women not using HT at the time of breast cancer diagnosis. Noncancerous tissue from mastectomy specimens was examined histologically to quantitate the content of fibrous stroma, ducts, and lobule types 1, 2, and 3. Tissue samples were also evaluated for estrogen receptor, progesterone receptor, and Ki67 activity in the ducts and lobules. Breast density was quantified by digitizing the contralateral mammogram and computer-assisted interactive thresholding.

RESULTS

High breast density in women using HT was correlated with greater fibrous stroma (P = 0.020) and lobule type 1 (P = 0.016). Breast density also correlated with Ki67 activity in the ducts (P = 0.031) and lobules (P= 0.023) for both groups combined. Estrogen and progesterone receptors did not correlate with either breast density or HT use.

CONCLUSIONS

Increased fibrous stroma and lobule type 1 are associated with increasing mammographic density in women using HT, independent of estrogen and progesterone receptor up-regulation. These findings suggest that increased breast density may be mediated through a paracrine effect. The increase in breast cancer risk with HT use may be due to an increase in target lobule type 1 cells.

No relationship between circulating levels of sex steroids and mammographic breast density: the Prospect-EPIC cohort

Background

High breast density is associated with increased breast cancer risk. Epidemiologic studies have shown an increase in breast cancer risk in postmenopausal women with high levels of sex steroids. Hence, sex steroids may increase postmenopausal breast cancer risk via an increase of breast density. The objective of the present study was to study the relation between circulating oestrogens and androgens as well as sex hormone binding globulin (SHBG) in relation to breast density.

Methods

We conducted a cross-sectional study among 775 postmenopausal women, using baseline data of a random sample of the Prospect-EPIC study. Prospect-EPIC is one of two Dutch cohorts participating in the European Prospective Investigation into Cancer and Nutrition, and women were recruited via a breast cancer screening programme. At enrolment a nonfasting blood sample was taken and a mammogram was made. Oestrone, oestradiol, dehydroepiandrosterone sulfate, androstenedione, testosterone and SHBG levels were measured, using double-antibody radioimmunoassays. Concentrations of free oestradiol and free testosterone were calculated from the measured oestradiol, testosterone and SHBG levels Mammographic dense and nondense areas were measured using a semiquantitative computerized method and the percentage breast density was calculated. Mean breast measures for quintiles of hormone or SHBG levels were estimated using linear regression analyses.

Results

Both oestrogens and testosterone were inversely related with percent breast density, but these relationships disappeared after adjustment for BMI. None of the sex steroids or SHBG was associated with the absolute measure of breast density, the dense area.

Conclusion

The results of our study do not support the hypothesis that sex steroids increase postmenopausal breast cancer risk via an increase in breast density.

Dietary patterns and breast density in the Minnesota Breast Cancer Family Study

OBJECTIVE

Whether dietary patterns, rather than single foods or nutrients, are associated with breast density is not known. We investigated this in the Minnesota Breast Cancer Family Study.

METHODS

Participants completed a 153-item food frequency questionnaire and provided screening mammograms for breast density assessment using a computer-assisted method. We used multivariate linear regression to quantify dietary pattern-breast density associations.

RESULTS

Among 3,147 women with dietary information, three dietary patterns emerged from principal components analysis: a fruit-vegetable-cereal pattern, a salad-sauce-pasta/grain pattern, and a meat-starch pattern. Among 1,286 women with breast density estimates, the fruit-vegetable-cereal and salad-sauce-pasta/grain patterns were inversely associated with percent breast density only in stratified analyses. The fruit-vegetable-cereal pattern was inversely associated with breast density among premenopausal women (beta = -0.13, p = 0.09; interaction p = 0.009) and current smokers, (beta = -0.30, p = 0.02; interaction p = 0.05), while the salad-sauce-pasta/grain was inversely associated with breast density among current smokers (beta = -0.27, p = 0.06; interaction p = 0.006).

CONCLUSION

Overall our results do not provide strong evidence for associations of dietary patterns with breast density. Suggestive inverse associations for the fruit-vegetable-cereal and salad-sauce-pasta/grain dietary patterns among smokers are consistent with previous reports and leave open the possibility that some dietary patterns influence breast density in population subsets. Nevertheless, these findings require confirmation, and their underlying reasons have yet to be clarified.

Mammary gland development in early pubertal female macaques

Ductal morphogenesis of the mammary gland occurs largely in the early pubertal period under the influence of ovarian sex hormones. In this study we characterized developing ductal structures in breast tissue of 14 female prepubertal or early pubertal rhesus monkeys (average age, 2.6 +/- 0.1 years). Serum estradiol concentrations ranged from < 5.0 to 61.2 pg/ml, while progesterone concentrations were low in all animals (< 0.6 ng/ml). No corpora lutea were seen on ovarian histology. The most immature mammary glands contained multilayered ducts frequently ending in distinctive terminal end bud structures. Transitional ducts had variably stratified columnar epithelium, often with prominent rounded myoepithelial cells and loose periductal stroma. Mature ducts had simple cuboidal luminal epithelium, flattened myoepithelium, and associated lobular development, typical of the premenopausal breast. Expression of estrogen receptor alpha was significantly higher in immature ducts compared to mature ducts, while progesterone receptor expression, epithelial proliferation, and cytokeratin expression did not show a relationship to the maturity of the ducts. These findings identify dynamic morphologic changes occurring in the primate breast during early puberty and suggest that estradiol (rather than progesterone) is the predominant hormonal stimulus for early ductal and lobular development.

Mammographic density. Potential mechanisms of breast cancer risk associated with mammographic density: hypotheses based on epidemiological evidence

There is now extensive evidence that mammographic density is an independent risk factor for breast cancer that is associated with large relative and attributable risks for the disease. The epidemiology of mammographic density, including the influences of age, parity and menopause, is consistent with it being a marker of susceptibility to breast cancer, in a manner similar to the concept of 'breast tissue age' described by the Pike model. Mammographic density reflects variations in the tissue composition of the breast. It is associated positively with collagen and epithelial and nonepithelial cells, and negatively with fat. Mammographic density is influenced by some hormones and growth factors as well as by several hormonal interventions. It is also associated with urinary levels of a mutagen. Twin studies have shown that most of the variation in mammographic density is accounted for by genetic factors. The hypothesis that we have developed from these observations postulates that the combined effects of cell proliferation (mitogenesis) and genetic damage to proliferating cells by mutagens (mutagenesis) may underlie the increased risk for breast cancer associated with extensive mammographic density. There is clearly a need for improved understanding of the specific factors that are involved in these processes and of the role played by the several breast tissue components that contribute to density. In particular, identification of the genes that are responsible for most of the variance in percentage density (and of their biological functions) is likely to provide insights into the biology of the breast, and may identify potential targets for preventative strategies in breast cancer.

Quantifying effect-specific mammographic density

A methodology is introduced for the automated assessment of structural changes of breast tissue in mammograms. It employs a generic machine learning framework and provides objective breast density measures quantifying the specific biological effects of interest. In several illustrative experiments on data from a clinical trial, it is shown that the proposed method can quantify effects caused by hormone replacement therapy (HRT) at least as good as standard methods. Most interestingly, the separation of subpopulations using our approach is considerably better than the best alternative, which is interactive. Moreover, the automated method is capable of detecting age effects where standard methodologies completely fail.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and mammographic density

Mammographic density has been established as a strong risk factor for breast cancer while use of Nonsteroidal Anti-Inflammatory Drugs (NSAIDs) has been associated with a reduction in risk of breast cancer. The hypothesis is that NSAIDs reverses the expression of prostaglandin E2, thereby reducing the local production of estrogens. This report describes the differences in mammographic densities by duration of NSAID use in a multiethnic population. Information for this analysis was available from two previous investigations: a nutritional intervention study with 218 women and a nested case-control study of breast density with 1274 women. On the basis of self-reported medication use from a questionnaire common to both investigations, women were categorized into no use, up to 1 year, 2-5 years, 6-10 years, and 11+ years. Screening mammograms were assessed for density using a computer-assisted method. We applied general linear models to calculate mean percent densities for each medication use category while adjusting for covariates. The analysis of the overall study population did not show a significant association between total NSAID use and mammographic density. Contrary to our hypothesis, women with long-term total NSAID use had non-significantly higher densities than non-users. In addition, the results differed by menopausal status. Whereas the trend of higher densities with longer duration of total NSAID use was significant among postmenopausal women, breast density was slightly lower among premenopausal women with long-term NSAID use. Experimental studies need to be performed to study the effect, if any, of NSAID use on breast density.

Urinary 6-sulfatoxymelatonin and mammographic density in Japanese women

A protective role of melatonin in the etiology of breast cancer has been suggested. The down-regulation of estrogen secretion by melatonin is thought to be a main cause of the link between melatonin and breast cancer risk. The present cross-sectional study examined whether the urinary 6-sulfatoxymelatonin (aMT6-s) level is inversely associated with mammographic density, which is regarded as a marker of breast cancer risk. The study subjects were 289 Japanese women (175 premenopausal and 123 postmenopausal women) who were recruited from participants in a mammographic breast cancer screening. The size of the total breast area and that of the dense area were measured quantitatively using an automated mammographic mass detection method. The concentration of aMT6-s was measured using first-void morning urine. In premenopausal women, the urinary aMT6-s level was significantly positively associated with percent density after controlling for covariates (P for trend=0.02). There was no significant association between urinary aMT6-s level and the percent density in postmenopausal women. We found no evidence that the melatonin level is inversely associated with mammographic density.

Recreational physical activity and mammographic breast density characteristics

Increased mammographic breast density is considered an intermediate marker of breast cancer risk. Physical activity is believed to reduce breast cancer risk; however, its effect on breast density is not well understood. We studied the association between recreational physical activity and mammographic characteristics of the breast among a population of premenopausal and postmenopausal women enrolled as controls (n = 728) in a case-control study of mammographic breast density and breast cancer. Women were enrolled shortly after obtaining their regular screening mammograms, and participants reported their current and lifetime recreational physical activity history using a self-administered, reliable questionnaire at study enrollment. Linear regression was used to determine associations between physical activity variables and the dense breast area, non-dense area, total breast area, and percent density. Age-adjusted analyses revealed significant inverse associations between physical activity variables and the non-dense area and total area and positive associations with percent breast density. These associations were attenuated and nonsignificant after adjustment for body mass index (BMI). Adjustment for additional factors did not substantially change the results. Physical activity was not associated with the dense breast area before or after adjustment for BMI. Self-reported recreational physical activity was not significantly associated with the mammographic characteristics of the breast after adjustment for BMI in this population. These results suggest that the mechanism by which physical activity reduces breast cancer risk may not involve breast density.

Declines in invasive breast cancer and use of postmenopausal hormone therapy in a screening mammography population

Whether a recent large decline in use of postmenopausal hormone therapy after the release of the Women's Health Initiative findings in July 2002 and/or a decline in screening mammography use is related to a recently reported decline in breast cancer incidence in the United States is controversial. We prospectively collected data from four screening mammography registries from January 1997 through December 2003 for 603411 screening mammography examinations performed on women aged 50-69 years. Of these women, 3238 were diagnosed with breast cancer within 12 months of a screening examination. We calculated quarterly rates of self-reported current postmenopausal hormone therapy use and of invasive breast cancer, ductal carcinoma in situ (DCIS), and estrogen receptor (ER)-positive invasive breast cancer adjusted for age, registry, and time between screening examinations. All statistical tests were two-sided. Between 2000 and 2002 and between 2002 and 2003, annual rates of postmenopausal hormone therapy use declined by 7% and 34%, respectively (P(trend) < .001 for both). Between 2000 and 2003, annual rates of invasive cancer declined by 5% (P(trend) = .003). Between 2001 and 2003, annual rates of ER-positive invasive breast cancer declined by 13% (P(trend) = .002). Rates of DCIS were stable during the study period. Our finding of a statistically significant decline in the rate of ER-positive invasive breast cancer in a screening mammography population after the start of a concomitant substantial decline in postmenopausal hormone therapy use suggests that a decline in screening mammography rates is unlikely to account for the recent decline in US breast cancer incidence.

The Association Between Mammographic Breast Density and Bone Mineral Density in the Study of Women's Health Across the Nation

BACKGROUND

Bone mineral density and mammographic breast density are each associated with markers of lifetime estrogen exposure. The association between mammographic breast density and bone mineral density in early perimenopausal women is unknown.

METHODS

We analyzed data from a cohort (n = 501) of premenopausal (no change in menstrual regularity) and early perimenopausal (decreased menstrual regularity in past 3 months) participants of African-American, Caucasian, Chinese, and Japanese ethnicity in the Study of Women's Health Across the Nation. Using multivariable linear regression, we examined the cross-sectional association between percent mammographic density and bone mineral density (BMD).

RESULTS

Percent mammographic density was statistically significantly inversely associated with hip BMD and lumbar spine BMD after adjustment (body mass index, ethnicity, age, study site, parity, alcohol intake, cigarette smoking, physical activity, age at first childbirth) in early perimenopausal, but not premenopausal, women. In early perimenopausal women, every 0.1g/cm(2) greater hip BMD predicted a 2% lower percent mammographic density (95% confidence interval -37.0 to -0.6%, p = 0.04).

CONCLUSION

Mammographic breast density is inversely associated with BMD in the perimenopausal participants of this community-based cohort. The biological underpinnings of these findings may reflect differential responsiveness of breast and bone mineral density to the steroid milieu.

Endogenous hormone levels, mammographic density, and subsequent risk of breast cancer in postmenopausal women

BACKGROUND

Mammographic density and circulating sex hormones are two well-confirmed predictors of breast cancer risk. Whether mammographic density reflects levels of endogenous sex hormones is unclear. We examined whether these predictors are independently associated with breast cancer risk in a prospective study.

METHODS

We conducted a nested case-control study within the Nurses' Health Study cohort of 253 case subjects with breast cancer and 520 control subjects. All participants were postmenopausal women who were not using postmenopausal hormones at the time of both blood collection and mammography. Plasma levels of estradiol, free estradiol, testosterone, and free testosterone were evaluated. Mammographic density was assessed by use of computer-assisted analysis of mammograms. Logistic regression models that were adjusted for matching variables and potential confounders were used to calculate relative risks (RRs) and 95% confidence intervals (CIs). All statistical tests were two-sided.

RESULTS

Levels of circulating sex steroids and mammographic density were both statistically significantly and independently associated with breast cancer risk. The relative risk of breast cancer associated with mammographic density (RR for highest quartile compared with lowest quartile = 3.8, 95% CI = 2.2 to 6.6; P(trend)<.001) changed little when the analysis was adjusted for circulating estradiol (RR = 3.9, 95% CI = 2.2 to 6.9; P(trend)<.001) or circulating testosterone (RR = 4.1, 95% CI = 2.3 to 7.2; P(trend)<.001). Circulating levels of estradiol (RR = 2.4, 95% CI = 1.4 to 4.0) and of testosterone (RR = 2.0, 95% CI = 1.2 to 3.1) were both associated with breast cancer risk, before and after adjustment for mammographic density. In a joint analysis of mammographic density and plasma testosterone, the risk of breast cancer was highest in the highest tertiles of both relative to the lowest tertiles of both (RR = 6.0, 95% CI = 2.6 to 14.0). A similar pattern was observed in the joint analysis of estradiol and mammographic density (RR = 4.1, 95% CI = 1.7 to 9.8).

CONCLUSIONS

Circulating sex steroid levels and mammographic density appear strongly and independently associated with the risk of breast cancer in postmenopausal women.

Effect of ultra-low-dose transdermal estradiol on breast density in postmenopausal women

OBJECTIVE

Women with higher mammographic breast density have increased risk for breast cancer, and there is some evidence that a change in breast density may be a marker for change in risk for breast cancer. The purpose of this study was to determine whether 2 years of treatment with ultra-low-dose transdermal estradiol results in a change in breast density.

DESIGN

The Ultra-Low-dose Transdermal Estradiol Assessment was a randomized, blinded, placebo-controlled trial of 2 years of treatment with unopposed ultra-low-dose (0.014 mg/d) transdermal estradiol for prevention of osteoporosis in 417 postmenopausal women with no history of breast cancer who had not had a hysterectomy. We obtained mammograms at baseline and after 1 and 2 years of treatment from 276 of the participants. Right craniocaudal views were analyzed at a central radiology facility by a trained clinician blinded to treatment group and order of acquisition. Contour analysis was performed to define dense areas versus fatty tissue. Between-group differences in mean change in percent breast density from baseline to 1 and to 2 years of follow-up were assessed using linear regression models adjusted for clinical site.

RESULTS

Participants were 66 +/- 5 years old and 94% were white. The average percent breast density at baseline was 34%. There was no significant difference between treatment groups in change in percent breast density after 1 year (between-group difference, 0.1%; 95% confidence interval, -1.3% to 1.6%) or 2 years of treatment (0.8%; -0.6% to 2.1%).

CONCLUSIONS

Two years of treatment with ultra-low-dose transdermal estradiol did not increase breast density.

Mammographic breast density as a general marker of breast cancer risk

Mammographic breast density is a strong risk factor for breast cancer but whether breast density is a general marker of susceptibility or is specific to the location of the eventual cancer is unknown. A study of 372 incident breast cancer cases and 713 matched controls was conducted within the Mayo Clinic mammography screening practice. Mammograms on average 7 years before breast cancer were digitized, and quantitative measures of percentage density and dense area from each side and view were estimated. A regional density estimate accounting for overall percentage density was calculated from both mammogram views. Location of breast cancer and potential confounders were abstracted from medical records. Conditional logistic regression was used to estimate associations, and C-statistics were used to evaluate the strength of risk prediction. There were increasing trends in breast cancer risk with increasing quartiles of percentage density and dense area, irrespective of the side of the breast with cancer (P(trends) < 0.001). Percentage density from the ipsilateral side [craniocaudal (CC): odds ratios (ORs), 1.0 (ref), 1.7, 3.1, and 3.1; mediolateral oblique (MLO): ORs, 1.0 (ref), 1.5, 2.2, and 2.8] and the contralateral side [CC: ORs, 1.0 (ref), 1.8, 2.2, and 3.7; MLO: ORs, 1.0 (ref), 1.6, 1.9, and 2.5] similarly predicted case-control status (C-statistics, 0.64-65). Accounting for overall percentage density, density in the region where the cancer subsequently developed was not a significant risk factor [CC: 1.0 (ref), 1.3, 1.0, and 1.2; MLO: 1.0 (ref), 1.1, 1.0, and 1.1 for increasing quartiles]. Results did not change when examining mammograms 3 years on average before the cancer. Overall mammographic density seems to represent a general marker of breast cancer risk that is not specific to breast side or location of the eventual cancer.

Associations between soy, diet, reproductive factors, and mammographic density in Singapore Chinese women

Although the evidence is not completely consistent, soy intake has been inversely associated with breast cancer risk, and the strongest results have been observed in certain Asian populations. To address this issue and to examine the association between mammographic density and reproductive factors in this population, we conducted a cross-sectional analysis of mammograms and validated food-frequency questionnaires from 380 Chinese women living in Singapore. Percent mammographic density, a biomarker for breast cancer risk, was assessed using a validated computer-assisted method. We used generalized linear models to estimate mean mammographic density by quartiles of soy intake and intake of other dietary factors while adjusting for potential confounders. Percent mammographic density was inversely associated with age, body mass index, parity, breastfeeding, and soy intake. The difference in mammographic density between the highest and lowest quartiles of soy intake was 4-5%; this difference was statistically significant for soy protein and soy isoflavone intake and is similar in magnitude to what has been reported in Western populations when women undergo menopause or commence hormone therapy. We found no evidence that high fiber, fruit, or vegetable intake has protective effects on mammographic density. Our results suggest that the effect of soy intake on percent mammographic density is moderate but possibly of clinical relevance.

Body size, mammographic density, and breast cancer risk

BACKGROUND

Greater weight and body mass index (BMI) are negatively correlated with mammographic density, a strong risk factor for breast cancer, and are associated with an increased risk of breast cancer in postmenopausal women, but with a reduced risk in premenopausal women. We have examined the associations of body size and mammographic density on breast cancer risk.

METHOD

We examined the associations of body size and the percentage of mammographic density at baseline with subsequent risk of breast cancer among 1,114 matched case-control pairs identified from three screening programs. The effect of each factor on risk of breast cancer was examined before and after adjustment for the other, using logistic regression.

RESULTS

In all subjects, before adjustment for mammographic density, breast cancer risk in the highest quintile of BMI, compared with the lowest, was 1.04 [95% confidence interval (CI), 0.8-1.4]. BMI was associated positively with breast cancer risk in postmenopausal women, and negatively in premenopausal women. After adjustment for density, the risk associated with BMI in all subjects increased to 1.60 (95% CI, 1.2-2.2), and was positive in both menopausal groups. Adjustment for BMI increased breast cancer risk in women with 75% or greater density, compared with 0%, increased from 4.25 (95% CI, 1.6-11.1) to 5.86 (95% CI, 2.2-15.6).

CONCLUSION

BMI and mammographic density are independent risk factors for breast cancer, and likely to operate through different pathways. The strong negative correlated between them will lead to underestimation of the effects on risk of either pathway if confounding is not controlled.

Effects of estradiol with micronized progesterone or medroxyprogesterone acetate on risk markers for breast cancer in postmenopausal monkeys

The addition of the synthetic progestin medroxyprogesterone acetate (MPA) to postmenopausal estrogen therapy significantly increases breast cancer risk. Whether this adverse effect is specific to MPA or characteristic of all progestogens is not known. The goal of this study was to compare the effects of oral estradiol (E2) given with either MPA or micronized progesterone (P4) on risk biomarkers for breast cancer in a postmenopausal primate model. For this randomized crossover trial, twenty-six ovariectomized adult female cynomolgus macaques were divided into social groups and rotated randomly through the following treatments (expressed as equivalent doses for women): (1) placebo; (2) E2 (1 mg/day); (3) E2 + P4 (200 mg/day); and (4) E2 + MPA (2.5 mg/day). Hormones were administered orally, and all animals were individually dosed. Treatments lasted two months and were separated by a one-month washout period. The main outcome measure was breast epithelial proliferation, as measured by Ki67 expression. Compared to placebo, E2 + MPA resulted in significantly greater breast proliferation in lobular (P < 0.01) and ductal (P < 0.01) epithelium, while E2 + P4 did not. Intramammary gene expression of the proliferation markers Ki67 and cyclin B1 was also higher after treatment with E2 + MPA (P < 0.01) but not E2 + P4. Both progestogens significantly attenuated E2 effects on body weight, endometrium, and the TFF1 marker of estrogen receptor activity in the breast. These findings suggest that oral micronized progesterone has a more favorable effect on risk biomarkers for postmenopausal breast cancer than medroxyprogesterone acetate.

Common genetic variation in IGF1, IGFBP-1, and IGFBP-3 in relation to mammographic density: a cross-sectional study

Introduction

Mammographic density is one of the strongest risk factors for breast cancer and is believed to represent epithelial and stromal proliferation. Because of the high heritability of breast density, and the role of the insulin-like growth factor (IGF) pathway in cellular proliferation and breast development, we examined the association between common genetic variation in this pathway and mammographic density.

Methods

We conducted a cross-sectional analysis among controls (n = 1,121) who were between the ages of 42 and 78 years at mammography, from a breast cancer case-control study nested within the Nurses' Health Study cohort. At the time of mammography, 204 women were premenopausal and 917 were postmenopausal. We genotyped 29 haplotype-tagging SNPs demonstrated to capture common genetic variation in IGF1, IGF binding protein (IGFBP)-1, and IGFBP-3.

Results

Common haplotype patterns in three of the four haplotype blocks spanning the gene encoding IGF1 were associated with mammographic density. Haplotype patterns in block 1 (p = 0.03), block 3 (p = 0.009), and block 4 (p = 0.007) were associated with mammographic density, whereas those in block 2 were not. None of the common haplotypes in the three haplotype blocks spanning the genes encoding IGFBP-1/IGFBP-3 were significantly associated with mammographic density. Two haplotype-tagging SNPs in IGF1, rs1520220 and rs2946834, showed a strong association with mammographic density. Those with the homozygous variant genotype for rs1520220 had a mean percentage mammographic density of 19.6% compared with those with the homozygous wild-type genotype, who had a mean percentage mammographic density of 27.9% (p for trend < 0.0001). Those that were homozygous variant for rs2946834 had a mean percentage mammographic density of 23.2% compared with those who were homozygous wild-type with a mean percentage mammographic density of 28.2% (p for trend = 0.0004). Permutation testing demonstrated that results as strong as these are unlikely to occur by chance (p = 0.0005).

Conclusion

Common genetic variation in IGF1 is strongly associated with percentage mammographic density.

Longitudinal Trends in Mammographic Percent Density and Breast Cancer Risk

BACKGROUND

Mammographic density is a strong risk factor for breast cancer. However, whether changes in mammographic density are associated with risk remains unclear.

MATERIALS AND METHODS

A study of 372 incident breast cancer cases and 713 matched controls was conducted within the Mayo Clinic mammography screening practice. Controls were matched on age, exam date, residence, menopause, interval between, and number of mammograms. All serial craniocaudal mammograms 10 years before ascertainment were digitized, and quantitative measures of percent density (PD) were estimated using a thresholding method. Data on potential confounders were abstracted from medical records. Logistic regression models with generalized estimating equations were used to evaluate the interactions among PD at earliest mammogram, time from earliest to each serial mammogram, and absolute change in PD between the earliest and subsequent mammograms. Analyses were done separately for PD measures from the ipsilateral and contralateral breast and also by use of hormone therapy (HT).

RESULTS

Subjects had an average of five mammograms available, were primarily postmenopausal (83%), and averaged 61 years at the earliest mammogram. Mean PD at earliest mammogram was higher for cases (31%) than controls (27%; ipsilateral side). There was no evidence of an association between change in PD and breast cancer risk by time. Compared with no change, an overall reduction of 10% PD (lowest quartile of change) was associated with an odds ratio of 0.9997 and an increase of 6.5% PD (highest quartile of change) with an odds ratio of 1.002. The same results held within the group of 220 cases and 340 controls never using HT. Among the 124 cases and 337 controls known to use HT during the interval, there was a statistically significant interaction between change in PD and time since the earliest mammogram (P = 0.01). However, in all groups, the risk associated with the earliest PD remained a stronger predictor of risk than change in PD.

CONCLUSION

We observed no association between change in PD with breast cancer risk among all women and those never using HT. However, the interaction between change in PD and time should be evaluated in other populations.

Relationships between circulating hormone levels, mammographic percent density and breast cancer risk factors in postmenopausal women

BACKGROUND

Endogenous hormones and insulin-like growth factors (IGF) play a central role in breast cancer development. Mammographic density, an important breast cancer risk factor, has been associated with these biomarkers in premenopausal women. The aim of this study was to assess the relationships between circulating hormones, clinical features related to breast cancer risk and mammographic density in postmenopausal women.

SUBJECTS AND METHODS

The study included 226 postmenopausal women participating in a clinical prevention trial. We performed baseline measurements of mammographic percent density and circulating levels of estradiol, sex-hormone binding globulin (SHBG), follicle stimulating hormone (FSH), prolactin, C-terminal cross-link telopeptide, IGF-I, and IGF binding protein-3.

RESULTS

Median age and time since last menses were 52 years and 15 months, respectively. Median body mass index was 24.1 kg/m(2). After adjusting for age and body mass index, estradiol was the only biomarker significantly correlated with mammographic density (r = 0.17; P = 0.04). Women with normal body mass index had higher mammographic density (P < 0.001), higher SHBG (P < 0.0001), higher FSH (P = 0.002) and lower estradiol levels (P = 0.01) than those who were overweight. Women who had previous biopsies for benign breast disease had a higher mammographic density (P = 0.006).

CONCLUSIONS

In these recently postmenopausal women, mammographic percent density is directly associated with circulating estradiol levels. Our results provide further support to the role of circulating hormones in breast cancer risk.

Reduced mammographic density with use of a gonadotropin-releasing hormone agonist-based chemoprevention regimen in BRCA1 carriers

PURPOSE

Women with a BRCA1 mutation (BRCA1(mut)) need risk reduction options beyond mastectomy and oophorectomy. We evaluated the efficacy, safety, and tolerability of hormonal chemoprevention with a gonadotropin-releasing hormone agonist (GnRHA) with low-dose add-back steroids in BRCA1(mut) carriers.

EXPERIMENTAL DESIGN

The 12-month open label clinical trial used the GnRHA deslorelin, ultra-low-dose estradiol (E(2)), and replacement testosterone, administered via daily intranasal spray in premenopausal women with a BRCA1(mut), and intermittent oral medroxyprogesterone acetate. The end points included mammographic percent density, bone mineral density, endometrial hyperplasia, symptom inventory, and quality of life (Medical Outcomes SF-36 survey).

RESULTS

Six of eight BRCA1(mut) women (mean age, 30.3 years; range, 25-36 years) completed the study. Mammographic percent density was significantly reduced at 12 months (median absolute mammographic percent density decrease, 8.3%; P = 0.043), representing a 29.2% median reduction in mammographic percent density. Bone mineral density remained within reference limits for all participants; there were no cases of atypical endometrial hyperplasia and menses resumed within a median of 67 days (range, 35-110 days) after last drug treatment day. The treatment was well tolerated; hypoestrogenic side effects were minimal and transient; and there were no significant changes in quality of life.

CONCLUSIONS

The GnRHA deslorelin, with low-dose add-back steroids, was well tolerated and significantly decreased mammographic percent density in BRCA1(mut) carriers. This regimen may reduce breast cancer risk and improve the usefulness of mammographic surveillance by reducing density. This is the first demonstration, to our knowledge, of a direct reduction of mammographic densities in young BRCA1(mut) carriers.

Longitudinal measurement of clinical mammographic breast density to improve estimation of breast cancer risk

BACKGROUND

Whether a change over time in clinically measured mammographic breast density influences breast cancer risk is unknown.

METHODS

From January 1993 to December 2003, data that included American College of Radiology Breast Imaging Reporting and Data System (BI-RADS) breast density categories (1-4 in order of increasing density) were collected prospectively on 301,955 women aged 30 and older who were not using postmenopausal hormone replacement therapy and underwent at least two screening mammography examinations; 2639 of the women were diagnosed with breast cancer within 1 year of the last examination. Women's first and last BI-RADS breast density (average 3.2 years apart) and logistic regression were used to model the odds of having invasive breast cancer or ductal carcinoma in situ diagnosed within 12 months of the last examination by change in BI-RADS category. Rates of breast cancer adjusted for age, mammography registry, and time between screening examinations were estimated from this model. All statistical tests were two-sided.

RESULTS

The rate (breast cancers per 1000 women) of breast cancer was higher if BI-RADS breast density category increased from 1 to 2 (5.6, 95% confidence interval [CI] = 4.7 to 6.9) or 1 to 3 (9.9, 95% CI = 6.4 to 15.5) compared to when it remained at BI-RADS density of 1 (3.0, 95% CI = 2.3 to 3.9; P<.001 for trend). Similar and statistically significant trends between increased or decreased density and increased or decreased risk of breast cancer, respectively, were observed for women whose breast density category was initially 2 or 3 and changed categories. BI-RADS density of 4 on the first examination was associated with a high rate of breast cancer (range 9.1-13.4) that remained high even if breast density decreased.

CONCLUSION

An increase in BI-RADS breast density category within 3 years may be associated with an increase in breast cancer risk and a decrease in density category with a decrease in risk compared to breast cancer risk in women in whom breast density category remains unchanged. Two longitudinal measures of BI-RADS breast density may better predict a woman's risk of breast cancer than a single measure.

Unequal risks for breast cancer associated with different hormone replacement therapies: results from the E3N cohort study

Large numbers of hormone replacement therapies (HRTs) are available for the treatment of menopausal symptoms. It is still unclear whether some are more deleterious than others regarding breast cancer risk. The goal of this study was to assess and compare the association between different HRTs and breast cancer risk, using data from the French E3N cohort study. Invasive breast cancer cases were identified through biennial self-administered questionnaires completed from 1990 to 2002. During follow-up (mean duration 8.1 postmenopausal years), 2,354 cases of invasive breast cancer occurred among 80,377 postmenopausal women. Compared with HRT never-use, use of estrogen alone was associated with a significant 1.29-fold increased risk (95% confidence interval 1.02-1.65). The association of estrogen-progestagen combinations with breast cancer risk varied significantly according to the type of progestagen: the relative risk was 1.00 (0.83-1.22) for estrogen-progesterone, 1.16 (0.94-1.43) for estrogen-dydrogesterone, and 1.69 (1.50-1.91) for estrogen combined with other progestagens. This latter category involves progestins with different physiologic activities (androgenic, nonandrogenic, antiandrogenic), but their associations with breast cancer risk did not differ significantly from one another. This study found no evidence of an association with risk according to the route of estrogen administration (oral or transdermal/percutaneous). These findings suggest that the choice of the progestagen component in combined HRT is of importance regarding breast cancer risk; it could be preferable to use progesterone or dydrogesterone.

Postmenopausal hormone therapy and changes in mammographic density

PURPOSE

Hormone therapy (HT) use has been associated with an increased breast cancer risk. We explored the underlying mechanism further by determining the effects of HT on mammographic density, a measure of dense tissue in the breast and a consistent breast cancer risk factor.

PATIENTS AND METHODS

A total of 620 HT users and 620 never users from the Dutch Prospect-European Prospective Investigation into Cancer and Nutrition (EPIC) cohort and 175 HT users and 161 never users from the United Kingdom EPIC-Norfolk cohort were included. For HT users, one mammogram before and one mammogram during HT use was included. For never users, mammograms with similar time intervals were included. Mammographic density was assessed using a computer-assisted method. Changes in density were analyzed using linear regression.

RESULTS

The median time between mammograms was 3.0 years and the median duration of HT use was 1 year. The absolute mean decline in percent density was larger in never users (7.3%) than in estrogen therapy users (6.4%; P = .22) and combined HT users (3.5%; P < .01). The effect of HT appeared to be high in a small number of women, whereas most women were unaffected.

CONCLUSION

Our results suggest that HT use, and especially estrogen and progestin use, slows the changes from dense patterns to more fatty patterns that are normally seen in women with increasing age. Given that it is postulated that lifetime cumulative exposure to high density may be related to breast cancer risk, a delay in density decline in HT users potentially could explain their increased breast cancer risk.

Breast density and polymorphisms in genes coding for CYP1A2 and COMT: the Multiethnic Cohort

Background

Mammographic density is a strong predictor of breast cancer risk and is increased by hormone replacement therapy (HRT). Some associations with genetic polymorphisms in enzymes involved in estrogen metabolism have been described. This cross-sectional analysis examined the relation between mammographic density and the CYP1A2*1F and COMT Val⁵⁸ Met polymorphisms among 332 breast cancer cases and 254 controls in the Hawaii component of the Multiethnic Cohort.

Methods

Mammographic density, before diagnosis in cases, was quantified by using a validated computer-assisted method. Blood samples were genotyped by standard PCR/RFLP methods. Adjusted mean percent density was calculated by genotype using mixed models with the unstructured covariance option.

Results

A positive association between the C allele in the CYP1A2*1F gene and percent density, but not the dense area, was suggested (p = 0.11). The relation was limited to controls (p = 0.045), postmenopausal women not using HRT (p = 0.08), and normal weight subjects (p = 0.046). We did not observe any relation between the COMT Val⁵⁸ Met polymorphism and breast density.

Conclusion

The lack of an association between the CYP1A2 genotype and the size of the dense areas suggests an effect on the non-dense, i.e., fatty breast tissue. The discrepancies among studies may be due to differential susceptibility; changes in enzyme activity as a result of the CYP1A2*1F polymorphism may influence breast tissue differently depending on hormonal status. Larger studies with the ability to look at interactions would be useful to elucidate the influence of genetic variation in CYP1A2 and COMT on the risk of developing breast cancer.

Historical perspectives in postmenopausal hormone therapy: defining the right dose and duration

Recommended dosages of postmenopausal estrogen therapy (ET) and estrogen-progestin therapy (EPT), like those of oral contraceptives, have decreased markedly since oral estrogens were first introduced. Recently, the movement toward lower doses of ET/ EPT has accelerated because of the results of the Women's Health Initiative, which showed that lower-dose ET/EPT may provide similar efficacy and an improved safety profile compared with higher-dose preparations. For example, lower ET/EPT doses effectively relieve vasomotor and vulvovaginal symptoms associated with menopause, prevent bone loss, protect the endometrium, and are better tolerated than commonly prescribed doses. Current guidelines suggest the use of the lowest effective dose for the shortest duration consistent with treatment goals, benefits, and risks for the individual woman. However, the impact of treatment discontinuation should be considered when advising women to use hormone therapy for relieving menopausal symptoms for the shortest possible duration.

Serum prolactin levels are positively associated with mammographic density in postmenopausal women

BACKGROUND

Prolactin is a polypeptide hormone that promotes normal breast proliferation and differentiation, but it is also implicated in the development and growth of mammary tumors. Mammographic density is a strong, independent predictor of breast cancer and, therefore, a potential surrogate indicator of breast cancer risk.

METHODS

To test the hypothesis that serum prolactin is positively related to mammographic density, we conducted a cross-sectional analysis of baseline data from the Postmenopausal Estrogen/Progestin Interventions (PEPI) Mammographic Density Study. Based on prior work, we further hypothesized that this association would be apparent only in women who had not recently used postmenopausal hormone therapy (HT).

RESULTS

In linear regression models adjusted for age, body mass index, race, smoking, alcohol use, parity and physical activity, among the 400 women who were not recent users of HT, prolactin was positively and statistically significantly associated with mammographic density (Beta log base 2 prolactin 0.0369 [95% CI: 0.0094-0.0645]. Thus, for each doubling of serum prolactin, there was an absolute increase in mammographic density of 3.69%. Additional adjustment for serum levels of estradiol, progesterone, sex hormone binding globulin and age at first pregnancy did not affect this result. There was no association between prolactin and mammographic density among the 169 participants who had recently used HT.

CONCLUSION

The correspondence between higher prolactin and higher mammographic density is consistent with prolactin's mitogenic properties and the associations between prolactin and breast tumor promotion. These results support the thesis that prolactin deserves investigation as a target for breast cancer risk reduction.