Postmenopausal hormone therapy with estradiol and norethisterone acetate and mammographic density: findings from a cross-sectional study among Norwegian women

Effects of Hormones on Breast Development and Breast Cancer Risk in Transgender Women

Transgender women experience gender dysphoria due to a gender assignment at birth that is incongruent with their gender identity. Transgender people undergo different surgical procedures and receive sex steroids hormones to reduce psychological distress and to induce and maintain desired physical changes. These persons on feminizing hormones represent a unique population to study the hormonal effects on breast development, to evaluate the risk of breast cancer and perhaps to better understand the precise role played by different hormonal components. In MTF (male to female) patients, hormonal treatment usually consists of antiandrogens and estrogens. Exogenous hormones induce breast development with the formation of ducts and lobules and an increase in the deposition of fat. A search of the existing literature dedicated to hormone regimens for MTF patients, their impact on breast tissue (incidence and type of breast lesions) and breast cancer risk provided the available information for this review. The evaluation of breast cancer risk is currently complicated by the heterogeneity of administered treatments and a lack of long-term follow-up in the great majority of studies. Large studies with longer follow-up are required to better evaluate the breast cancer risk and to understand the precise mechanisms on breast development of each exogenous hormone.

What do TSECs provide in the menopausal hormone therapy?

Tissue-selective estrogen complex (TSEC) is projected as a progestogen-free option for the treatment of estrogen deficiency symptoms in postmenopausal, non-hysterectomized women. TSEC combines the benefits of estrogen with a selective estrogen receptor modulator (SERM), in this case bazedoxifene acetate (BZA), which has an antagonistic effect on the endometrium, thus avoiding the use of progestins. The authorized TSEC combination (conjugated estrogens [CE] 0.45 mg/BZA 20 mg) for the alleviation of vasomotor symptoms has been demonstrated in randomized clinical trials compared with placebo or menopausal hormone therapy (MHT). In addition, TSEC has shown improvements in quality of life and vaginal atrophy. In respect to MHT using progestins, the benefits of TSEC are found mainly in the bleeding pattern, amenorrhea rate, and reduction in mammary repercussion (i.e., breast tenderness and radiological density). The objective of this guide will be to analyze the efficacy and safety of TSEC consisting of CE/BZA in postmenopausal women.

Breast density: why all the fuss?

The term "breast density" or mammographic density (MD) denotes those components of breast parenchyma visualised at mammography that are denser than adipose tissue. MD is composed of a mixture of epithelial and stromal components, notably collagen, in variable proportions. MD is most commonly assessed in clinical practice with the time-honoured method of visual estimation of area-based percent density (PMD) on a mammogram, with categorisation into quartiles. The computerised semi-automated thresholding method, Cumulus, also yielding area-based percent density, is widely used for research purposes; however, the advent of fully automated volumetric methods developed as a consequence of the widespread use of digital mammography (DM) and yielding both absolute and percent dense volumes, has resulted in an explosion of interest in MD recently. Broadly, the importance of MD is twofold: firstly, the presence of marked MD significantly reduces mammographic sensitivity for breast cancer, even with state-of-the-art DM. Recognition of this led to the formation of a powerful lobby group ('Are You Dense') in the US, as a consequence of which 32 states have legislated for mandatory disclosure of MD to women undergoing mammography. Secondly, it is now widely accepted that MD is in itself a risk factor for breast cancer, with a four-to sixfold increased relative risk in women with PMD in the highest quintile compared to those with PMD in the lowest quintile. Consequently, major research efforts are underway to assess whether use of MD could provide a major step forward towards risk-adapted, personalised breast cancer prevention, imaging, and treatment.

Age at Menarche and Late Adolescent Adiposity Associated with Mammographic Density on Processed Digital Mammograms in 24,840 Women

Background: High mammographic density is strongly associated with increased breast cancer risk. Some, but not all, risk factors for breast cancer are also associated with higher mammographic density.Methods: The study cohort (N = 24,840) was drawn from the Research Program in Genes, Environment and Health of Kaiser Permanente Northern California and included non-Hispanic white females ages 40 to 74 years with a full-field digital mammogram (FFDM). Percent density (PD) and dense area (DA) were measured by a radiological technologist using Cumulus. The association of age at menarche and late adolescent body mass index (BMI) with PD and DA were modeled using linear regression adjusted for confounders.Results: Age at menarche and late adolescent BMI were negatively correlated. Age at menarche was positively associated with PD (P value for trend <0.0001) and DA (P value for trend <0.0001) in fully adjusted models. Compared with the reference category of ages 12 to 13 years at menarche, menarche at age >16 years was associated with an increase in PD of 1.47% (95% CI, 0.69-2.25) and an increase in DA of 1.59 cm² (95% CI, 0.48-2.70). Late adolescent BMI was inversely associated with PD (P < 0.0001) and DA (P < 0.0001) in fully adjusted models.Conclusions: Age at menarche and late adolescent BMI are both associated with Cumulus measures of mammographic density on processed FFDM images.Impact: Age at menarche and late adolescent BMI may act through different pathways. The long-term effects of age at menarche on cancer risk may be mediated through factors besides mammographic density. Cancer Epidemiol Biomarkers Prev; 26(9); 1450-8. ©2017 AACR.

Progestogen safety and tolerance in hormonal replacement therapy

INTRODUCTION

Today, it is a mandatory practice to prescribe a combination of estrogens and progestogens for menopausal women requiring hormone therapy and with a uterus. The WHI study and its reanalysis demonstrate a big difference in results between the conjugated equin estrogen (CEE) only vs.CEE plus medroxyprogesterone acetate (MPA) arms in relation with breast cancer and cardiovascular risk. The conclusion is that risk is clearly higher in the arm with MPA than in the CEE only arm. Although the only progestogen used in the WHI study was medroxyprogesterone acetate, side effects and intolerance have been extrapolated as a class effect to all progestogens. Areas covered: Progestogen tolerance and side effects in hormone therapy were reviewed. For that purpose, a limited literature search was conducted on key resources including Pubmed, the Cochrane Library, ECRI, and major international health technology agencies. Expert opinion: Many of the tolerance effects are based on limited data. There are no double-blind randomized trials comparing long-term safety for breast cancer and cardiovascular risk among different progestogens. Short-term clinical studies, observational, and in animal and in vitro studies indicate that both micronized progesterone and dydrogesterone are the safer progestogens with an acceptable metabolic profile.

The Effect of Atorvastatin on Breast Cancer Biomarkers in High-Risk Women

Statins have the potential to reduce breast cancer incidence and recurrence as shown in both epidemiologic and laboratory studies. The purpose of this study was to evaluate the effect of a lipophilic statin, atorvastatin, on breast cancer biomarkers of risk [mammographic density (MD) and insulin growth factor 1 (IGF-1)] in high-risk premenopausal women.Premenopausal women at increased risk for breast cancer received either 40 mg of atorvastatin or placebo for 1 year. Biomarker assessment was performed prior to initiation and at completion of study medication. MD was determined using both Breast Imaging Reporting and Data System and the visual analogue scale. Serum IGF-1 was determined by ELISA assay at the end of the study.Sixty-three women were enrolled between December 2005 and May 2010. Sixteen (25%) women withdrew. The mean age of participants was 43 (range, 35-50), 100% were white, and the average body mass index (BMI) was 26.4. The statin group demonstrated a significant decrease in cholesterol and low-density lipoprotein (LDL), suggesting compliance with study medication. After accounting for BMI, there was no difference in change in MD between groups. There was a significant increase in serum IGF-1 in the statin group.In this multi-institutional randomized prospective clinical trial of premenopausal women at increased risk for breast cancer, we did not see an effect of atorvastatin on MD. Further investigation of statins may be warranted; however, design of prior trials and potential mechanism of action of the agent need to be considered in the design of future trials. Cancer Prev Res; 9(5); 379-84. ©2016 AACR.

Influence of Obesity on Breast Density Reduction by Omega-3 Fatty Acids: Evidence from a Randomized Clinical Trial

Preclinical data indicate that omega-3 fatty acids (n-3FA) potentiate the chemopreventive effect of the antiestrogen (AE) tamoxifen against mammary carcinogenesis. The role of n-3FA in breast cancer prevention in humans is controversial. Preclinical and epidemiologic data suggest that n-3FA may be preferentially protective in obese subjects. To directly test the protective effect of n-3FA against breast cancer, we conducted a 2-year, open-label randomized clinical trial in 266 healthy postmenopausal women (50% normal weight, 30% overweight, 20% obese) with high breast density (BD; ≥25%) detected on their routine screening mammograms. Eligible women were randomized to one of the following five groups (i) no treatment, control; (ii) raloxifene 60 mg; (iii) raloxifene 30 mg; (iv) n-3FA lovaza 4 g; and (v) lovaza 4 g plus raloxifene 30 mg. The 2-year change in BD, a validated biomarker of breast cancer risk, was the primary endpoint of the study. In subset analysis, we tested the prespecified hypothesis that body mass index (BMI) influences the relationship between plasma n-3FA on BD. While none of the interventions affected BD in the intention-to-treat analysis, increase in plasma DHA was associated with a decrease in absolute breast density but only in participants with BMI >29. Our results suggest that obese women may preferentially experience breast cancer risk reduction from n-3FA administration.

Differential impact of body mass index on absolute and percent breast density: implications regarding their use as breast cancer risk biomarkers

Percent breast density (PBD), a commonly used biomarker of breast cancer risk (BCR), is confounded by the influence of non-dense breast tissue on its measurement and factors, such as BMI, which have an impact on non-dense tissue. Consequently, BMI, a potent BCR factor, is, paradoxically, negatively correlated with PBD. We propose that absolute breast density (ABD) is a more accurate biomarker of BCR. We used a volumetric method to compare the correlation between PBD and ABD with baseline demographics and dietary and physical activity variables in a group of 169 postmenopausal women enrolled in a clinical trial prior to any intervention. As expected, a strong negative correlation between PBD and BMI was observed (Rho = -0.5, p < 5e(-12)). In contrast, we observed a strong, previously not well established, positive correlation of BMI with ABD (Rho = 0.41, p < 2.5e(-8)), which supports the use of ABD as a more accurate indicator of BCR. Correction of PBD by BMI did not frequently provide the same information as ABD. In addition, because of the strong influence of BMI on ABD, many correlations between dietary variables and ABD did not emerge, until adjustment was made for BMI. ABD corrected by BMI should be the gold standard BD measurement. These findings identify the optimal measurement of BD when testing the influence of an intervention on BD as a biomarker of BCR.

Mammographic density-a review on the current understanding of its association with breast cancer

There has been considerable recent interest in the genetic, biological and epidemiological basis of mammographic density (MD), and the search for causative links between MD and breast cancer (BC) risk. This report will critically review the current literature on MD and summarize the current evidence for its association with BC. Keywords 'mammographic dens*', 'dense mammary tissue' or 'percent dens*' were used to search the existing literature in English on PubMed and Medline. All reports were critically analyzed. The data were assigned to one of the following aspects of MD: general association with BC, its relationship with the breast hormonal milieu, the cellular basis of MD, the generic variations of MD, and its significance in the clinical setting. MD adjusted for age, and BMI is associated with increased risk of BC diagnosis, advanced tumour stage at diagnosis and increased risk of both local recurrence and second primary cancers. The MD measures that predict BC risk have high heritability, and to date several genetic markers associated with BC risk have been found to also be associated with these MD risk predictors. Change in MD could be a predictor of the extent of chemoprevention with tamoxifen. Although the biological and genetic pathways that determine and perhaps modulate MD remain largely unresolved, significant inroads are being made into the understanding of MD, which may lead to benefits in clinical screening, assessment and treatment strategies. This review provides a timely update on the current understanding of MD's association with BC risk.

Physical activity and mammographic breast density: a systematic review

Studies show a protective relationship between physical activity and breast cancer risk across the life course from menarche to postmenopausal years. Mammographic breast density is a known and strong breast cancer risk factor. Whether the association of physical activity with breast cancer risk is mediated through mammographic breast density is poorly understood. This systematic review summarizes published studies that investigated the association between physical activity and mammographic breast density and discusses the methodological issues that need to be addressed. We included in this review studies that were published before October 31, 2011 that were accessible in full-text format and were published in English. We identified 20 studies through the PubMed Central, BioMed Central, Embase, and Scopus and using the search terms "physical activity and breast density" and "exercise and breast density" as well as through manual searches of the bibliographies of the articles identified in electronic searches. We found no evidence of association between physical activity and breast density across the studies by grouping them first by the timing of physical activity assessment (in adolescence, current/recent, past, and lifetime) and then by women's menopausal status (premenopausal and postmenopausal). Given the strength of the relationship between physical activity and breast cancer and the null findings of this review, it is unlikely that the effect of physical activity is mediated through an effect on breast density.

Rotating night shift work and mammographic density

BACKGROUND

An increased risk of breast cancer has been observed in night shift workers. Exposure to artificial light at night and disruption of the endogenous circadian rhythm with suppression of the melatonin synthesis have been suggested mechanisms. We investigated the hypothesis that rotating night shift work is associated with mammographic density.

METHODS

We conducted a cross-sectional study on the association between rotating night shift work characteristics, 6-sulfatoxymelatonin (MT6s) creatinine adjusted in a spot morning urine sample, and a computer-assisted measure of mammographic density in 640 nurses and midwives ages 40 to 60 years. The associations were evaluated using regression models adjusted for age, body mass index, menopausal status, age at menopause, age at menarche, smoking, and the calendar season of the year when mammography was conducted.

RESULTS

The adjusted means of percentage of mammographic density and absolute density were slightly higher among women working rotating night shifts but not statistically significant [percentage of mammographic density = 23.6%, 95% confidence interval (CI), 21.9%-25.4% vs. 22.5%, 95% CI, 20.8%-24.3%; absolute density = 23.9 cm(2), 95% CI, 21.4-26.4 cm(2) vs. 21.8 cm(2), 95% CI, 19.4-24.3 cm(2) in rotating night shift and day shift nurses, respectively). There were no significant associations between the current or cumulative rotating night shift work exposure metrics and mammographic density. No association was observed between morning MT6s and mammographic density.

CONCLUSIONS

The hypothesis on the link between rotating night shift work, melatonin synthesis disruption, and mammographic density is not supported by the results of the present study.

IMPACT

It is unlikely that the development of breast cancer in nurses working rotating night shifts is mediated by an increase 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.