Mammographic density increase in women receiving different hormone replacement regimens

The epidemiologic factors associated with breast density: A review

In recent years, some studies have evaluated the epidemiologic factors associated with breast density. However, the variant and inconsistent results exist. In addition, breast density has been proved to be a significant risk factor associated with breast cancer. Our review summarized the published studies and emphasized the crucial factors including epidemiological factors associated with breast density. In addition, we also discussed the potential reasons for the discrepant results with risk factors. To decrease the incidence and mortality rates for breast cancer, in clinical practice, breast density should be included for clinical risk models in addition to epidemiological factors, and physicians should get more concentrate on those women with risk factors and provide risk-based breast cancer screening regimens.

Hormone replacement therapy, mammographic density, and breast cancer risk: a cohort study

Purpose

Hormone replacement therapy (HRT) use increases breast cancer risk and mammographic density (MD). We examine whether MD mediates or modifies the association of HRT with the breast cancer.

Methods

For the 4,501 participants in the Danish diet, cancer and health cohort (1993–1997) who attended mammographic screening in Copenhagen (1993–2001), MD (mixed/dense or fatty) was assessed at the first screening after cohort entry. HRT use was assessed by questionnaire and breast cancer diagnoses until 2012 obtained from the Danish cancer registry. The associations of HRT with MD and with breast cancer were analyzed separately using Cox’s regression. Mediation analyses were used to estimate proportion [with 95% confidence intervals (CI)] of an association between HRT and breast cancer mediated by MD.

Results

2,444 (54.3%) women had mixed/dense breasts, 229 (5.4%) developed breast cancer, and 35.9% were current HRT users at enrollment. Compared to never users, current HRT use was statistically significantly associated with having mixed/dense breasts (relative risk and 95% CI 1.24; 1.14–1.35), and higher risk of breast cancer (hazard ratio 1.87; 1.40–2.48). Association between current HRT use and breast cancer risk was partially mediated by MD (percent mediated = 10%; 95% CI 4–22%). The current HRT use-related breast cancer risk was higher in women with mixed/dense (1.94; 1.37–3.87) than fatty (1.37; 0.80–2.35) breasts (p value for interaction = 0.15).

Conclusions

MD partially mediates some of the association between HRT and breast cancer risk. The association between HRT and breast cancer seems to be stronger in women with dense breasts.

Assessment of mammographic density in postmenopausal women during long term hormone replacement therapy

OBJECTIVE

To assess long-term effects of different hormone replacement therapy (HRT) regimens on mammographic density.

METHODS

One hundred sixty-five postmenopausal women were treated with the same HRT during 5 years: 38 received transdermal estradiol, 78 cyclic combined therapy and 49 continuous combined therapy. Mammograms were obtained at baseline, at 1-year and 5-year treatment. Breast density changes were categorized as slight focal increased density, considerable focal increased density, slight diffuse increased density and considerable diffuse increased density.

RESULTS

Mammographic density increased in 7.9% of women receiving estrogen alone versus 25.2% of women receiving combined therapy (p < 0.022) during 1 year, and in 7.9% of women versus 28.3% of women (p < 0.009) after 5 years of therapy, respectively. There were significant statistical differences in women treated with estrogen alone versus those treated with combined HRT after 1 and 5 years. After 5 years of HRT, breast density increased 21.8% in women receiving cyclic combined therapy versus 38.8% in those under continuous combined therapy (p < 0.039).

CONCLUSION

An increase in breast density is significantly more frequent in women receiving combined estrogen-progestin therapy than in women receiving estrogen alone. There are differences between cyclic and continuous combined therapy at 5 years of treatment.

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.

Relationship between breast cancer risk factors and mammographic breast density in the Fernald Community Cohort

Background:

We investigated associations of known breast cancer risk factors with breast density, a well-established and very strong predictor of breast cancer risk.

Methods:

This nested case–control study included breast cancer-free women, 265 with high and 860 with low breast density. Women were required to be 40–80 years old and should have a body mass index (BMI) <35 at the time of the index mammogram. Information on covariates was obtained from annual questionnaires.

Results:

In the overall analysis, breast density was inversely associated with BMI at mammogram (P for trend<0.001), and parity (P for trend=0.02) and positively associated with alcohol consumption (ever vs never: odds ratio 2.0, 95% confidence interval 1.4–2.8). Alcohol consumption was positively associated with density, and the association was stronger in women with a family history of breast cancer (P<0.001) and in women with hormone replacement therapy (HRT) history (P<0.001). Parity was inversely associated with density in all subsets, except premenopausal women and women without a family history. The association of parity with density was stronger in women with HRT history (P<0.001).

Conclusion:

The associations of alcohol and parity with breast density appear to be in reverse direction, but stronger in women with a family history of breast cancer and women who ever used HRT.

Type of hormone therapy and risk of misclassification at mammography screening

OBJECTIVE

Current users of hormone therapy (HT) are known to have a lower accuracy of mammography screening than do never users. We studied whether the risk of misclassification depends on type of hormone, administration, regimen, and dose of the therapy.

METHODS

We linked data from mammography screening registers with drug prescription registers from Fyn, Denmark to identify current and never HT users among screening participants. We compared false-positive risks and interval cancer proportions between current users of different HT preparations, taking women's age, breast density, screen number, and age of comparison mammogram into account.

RESULTS

Estrogen therapy users had a significantly higher false-positive risk when the administration was by injection instead of oral (relative risk [RR], 2.37; 95% CI, 1.37-4.09). Women using sequential estrogen plus progestogen therapy had a significantly higher false-positive risk (RR, 1.94; 95% CI, 1.16-3.26) and a nonsignificantly higher interval cancer proportion (RR, 4.29; 95% CI, 0.69-26.53) when the administration of both hormones was transdermal instead of oral. Using tibolone instead of comparable hormones gave a nonsignificantly lower false-positive risk and a nonsignificantly higher interval cancer proportion.

CONCLUSIONS

Our data showed increased risks of misclassification at mammography screening among women using estrogen injections or transdermal, sequential estrogen plus progestogen. Tibolone seems to offer no advantage regarding accuracy of screening mammography.

Tibolone and breast cancer

Tibolone is a relatively new drug for postmenopausal women, which is structurally related to 19-nortestosterone derivatives and exhibits weak oestrogenic, progestogenic and androgenic activities. The effect of tibolone on breast tissue is still obscure. In vitro studies have shown conflicting results regarding the effects of tibolone on breast cells. On the other hand, although epidemiological studies show an increase in the risk of breast cancer among women treated with tibolone, accumulation of data obtained from radiological studies presents promising results. However, the safety of tibolone with regard to breast tissue needs to be investigated further, especially through well-designed, large-scale, randomised-controlled trials.

Effects of hormone replacement therapy regimens on mammographic breast density: The role of progestins

AIM

To evaluate the effects of different regimens of hormone replacement therapy (HRT) on mammographic breast density.

METHODS

Mammograms of 113 healthy postmenopausal women who were on different HRT regimens were evaluated retrospectively. All women had a baseline mammography and at least one mammogram after at least 12 months of HRT. Four parenchymal patterns were considered mammographically. Quantification of density changes that occurred on follow-up mammograms was done qualitatively and with reference to densities on baseline mammograms.

RESULTS

Sixty women were treated with a continuous estrogen-progestin combination; 16 with a cyclic estrogen-progestin combination and 37 were with estrogen only. Twenty-six women had increased mammographic density after HRT. Mammographic density increase was detected in 23 women (38.3%) of the continuous estrogen-progestin combination group, two women (12.5%) of the cyclic estrogen-progestin combination group and one woman (2.7%) of the estrogen-only group. Mammographic density increase was more common among women in the continuous estrogen-progestin combination group than the other groups and this difference was found to be statistically significant (P < 0.001). Breast density increase was observed in 18 of 30 women (60%) with higher doses of progestin compared to 5 of 30 women (16.7%) with lower dose (P < 0.05).

CONCLUSIONS

Postmenopausal HRT may increase mammographic breast density. Breast density appears to be mostly affected by higher doses and continuous administration of progestin.

Mammographic densities and circulating hormones: A cross-sectional study in premenopausal women

Progestogens appear to influence breast density more than estrogens in postmenopausal women taking hormone replacement therapy (HRT), but little is known about the effect of circulating hormones on mammographic density among premenopausal women. This cross-sectional study explores the relationship of body weight and sex steroids with breast density. Luteal serum samples were analyzed for progesterone, estrone, estradiol, and sex hormone-binding globulin (SHBG). Mammograms were assessed for density using a computer-assisted method. We performed mediation tests using multiple linear regression models. Significant associations of SHBG and estradiol with percentage density disappeared after adjustment for body weight and other covariates, whereas the relationship between progesterone and breast density remained borderline significant. The mediation tests indicated that progesterone has a direct and an indirect effect on mammographic density. Our finding that progesterone shows a stronger association with percentage of mammographic density than estrogen agrees with clinical reports describing denser mammographic patterns among women taking HRT, although these women differ in menopausal status.

Postmenopausal hormone therapy and mammographic breast density

OBJECTIVE

The aim of this study was to evaluate the effects of different types of hormone replacement therapy (HRT) on mammographic density.

MATERIALS AND METHODS

In a prospective 1-year study, 103 postmenopausal women were randomized to receive tibolone 2.5 mg/die, continuous conjugated equine estrogens 0.625 mg/die plus medroxyprogesterone acetate (MPA) 5mg/die or placebo. Mammograms were performed at baseline and after 12 months of treatment. Mammographic density was quantified according to the Wolfe classification.

RESULTS

After 12 months of HRT 16 of the 35 patients (45.1%) receiving continuous combined hormonal therapy showed an increase of breast density change in the Wolfe classification. After treatment with tibolone, an up grading in breast density, according to Wolfe's classification, was found in 2 of the 43 patients (2.3%). No changes were recorded in the 25 patients of the control group. The difference between the group treated with continuous combined hormonal therapy and the control group was highly significant (p<0.001). The difference in breast density between patients in treatment with tibolone and the control group was not statistically significant (p=0.34).

DISCUSSION

Continuous combination HRT may be more commonly associated with an increase of mammography density than tibolone treatment.

Influence of different HRT regimens on mammographic density

OBJECTIVES

A prospective, randomized, open-label study was conducted to evaluate effects on mammographic density in postmenopausal and late perimenopausal women receiving continuous combined or sequential combined hormone replacement therapy (HRT).

METHODS

The subjects were randomized to treatment with low-dose continuous combined HRT containing 1 mg 17beta-estradiol plus 0.5 mg norethisterone acetate (Activelle) or a sequential combined HRT regimen consisting of 0.625 mg conjugated equine estrogens for 28 days plus 5 mg medrogestone for 14 days (Presomen). Mammograms were obtained at baseline and after 9 cycles (each 28 days) of treatment.

RESULTS

The majority of women (approximately two-thirds in each treatment group) had no changes in mammographic breast density between baseline and the final study visit. There were no marked differences between treatment groups. Approximately 20% of women in both groups had a slight increase in mammographic density. Only 10-14% of women in both groups had a pronounced increase in mammographic density. The analyses of the degree of change showed no remarkable differences between treatments.

CONCLUSION

These results indicate that the increase in mammographic density with a low-dose continuous combined HRT regimen is no greater than that with a sequential combined HRT regimen. The type of progestogen does not have an impact on the extent of mammographic density changes.

The effect of tibolone in postmenopausal women receiving tamoxifen after surgery for breast cancer: a randomised, double-blind, placebo-controlled trial

OBJECTIVE

To assess the effects of tibolone on climacteric symptoms, endometrium and serum lipid/lipoproteins in postmenopausal women receiving tamoxifen after surgery for breast cancer.

DESIGN

Double-blind, randomised, placebo-controlled, multicentre pilot study.

SETTING

Hospital outpatient clinic.

SAMPLE

Seventy postmenopausal women receiving tamoxifen following surgery for early breast cancer.

METHODS

Women received 20 mg/day oral tamoxifen plus either 2.5 mg/day oral tibolone or placebo for 12 months.

MAIN OUTCOME MEASURES

Frequency and severity of hot flushes (diary cards); intensity of hot flushes and sweats (Landgren scale); interference of hot flushes and sweats with normal life; frequency and intensity of other climacteric symptoms; endometrial thickness and histology; vaginal bleeding; breast cancer recurrence and serum lipid/lipoproteins.

RESULTS

Daily card data showed no change in the daily number of hot flushes with either tibolone or placebo (P= 0.219) after three months. There was a significant reduction in the severity of flushes with tibolone compared with placebo (-0.4 vs 0.2, P= 0.031). The Landgren scale showed a mean change in the number of hot flushes of -0.6 with tibolone and +1.1 with placebo after 12 months (P= 0.022). Endometrial biopsies were normal and vaginal bleeding was similar in both groups. A significant decrease in triglycerides (-23% vs 1.4%) and HDL (-12% vs 19%) was seen with tibolone compared with placebo after 12 months.

CONCLUSIONS

Tibolone prevented an increase in hot flushes in postmenopausal women given tamoxifen following surgery for breast cancer without untoward effects on the endometrium. Beneficial effects on serum lipid profile were noted.

Hormones and mammographic breast density

Mammographic density reveals information about the hormonal environment along with the heritability in which breast cancer develops. This is made possible by the widespread use of population screening by mammography. Increasingly this is an important observation not just for population studies, which reveal disease determinants, but also for the individual. Density reveals the effect of the intrinsic hormonal environment and its background genetics, and also the effect of pharmaceuticals--agents used for disease control and prevention and hormone replacement therapy (HRT) used for well-being around the menopause. Increasingly this focus on the individual will need methods of measurement of density that can be monitored with greater accuracy than the widely used BI-RADS 4 categories. For this purpose studies are under way to measure volume of dense tissue as a continuous variable. In due course, measurement of density will be used as a biomarker of risk, employed in risk models and to monitor interventions. Before this can happen more knowledge will be needed of the change occurring naturally through the menopause and the differences between individuals. This will need specific study backed up with detailed information about the patient on large numbers of women and their mammograms. Currently the widespread use of HRT has increased the prevalence of the dense patterns and potentially may adversely affect the effectiveness of mammographic screening programmes. There is a large literature recording this from which we see that combined continuous preparations of oestrogen progestin are more likely to cause increased density than oestrogen alone or tibolone. Breast density, measured more accurately, has the potential to be an important adjunct to risk estimation and to monitor interventions for breast cancer prevention with pharmaceuticals (such as SERMS) and by change in lifestyle behaviours.

The effects of tibolone and oestrogen-based HT on breast cell proliferation and mammographic density

Tibolone is a tissue-selective compound used for the treatment of climacteric symptoms and the prevention of osteoporosis in post-menopausal women. In this review some in vitro data and clinical studies indicating that the effects of tibolone on breast tissue are different from those seen with oestrogen-based hormone therapy (HT) are briefly discussed. From a clinical perspective, an increase in mammographic density and breast cell proliferation should be regarded as an unwanted side-effect of HT. Efforts should therefore be made to define treatment regimens for post-menopausal women that have minimal effects on the breast but still maintain the many advantages of HT. Data suggest that tibolone may be such an alternative.

Treatment of menopause-associated vasomotor symptoms: position statement of The North American Menopause Society

OBJECTIVE

To create an evidence-based position statement regarding the treatment of vasomotor symptoms associated with menopause.

DESIGN

The North American Menopause Society (NAMS) enlisted clinicians and researchers acknowledged to be experts in the field of menopause-associated vasomotor symptoms to review the evidence obtained from the medical literature and develop a document for final approval by the NAMS Board of Trustees.

RESULTS

For mild hot flashes, lifestyle-related strategies such as keeping the core body temperature cool, participating in regular exercise, and using paced respiration have shown some efficacy without adverse effects. Among nonprescription remedies, clinical trial results are insufficient to either support or refute efficacy for soy foods and isoflavone supplements (from either soy or red clover), black cohosh, or vitamin E; however, no serious side effects have been associated with short-term use of these therapies. Single clinical trials have found no benefit for dong quai, evening primrose oil, ginseng, a Chinese herbal mixture, acupuncture, or magnet therapy. Few data support the efficacy of topical progesterone cream; safety concerns should be the same as for other progestogen preparations. No clinical trials have been conducted on the use of licorice for hot flashes. Among nonhormonal prescription options, the antidepressants venlafaxine, paroxetine, and fluoxetine and the anticonvulsant gabapentin have demonstrated some efficacy for treating hot flashes and were well tolerated. Two antihypertensive agents, clonidine and methyldopa, have shown modest efficacy but with a relatively high rate of adverse effects. For moderate to severe hot flashes, systemic estrogen therapy, either alone (ET) or combined with progestogen (EPT) or in the form of estrogen-progestin oral contraceptives, has been shown to significantly reduce hot flash frequency and severity. Clinical trials have associated ET/EPT with adverse effects, including breast cancer, stroke, and thromboembolism. Several progestogens (both oral and intramuscular formulations) have shown efficacy in treating hot flashes, including women with a history of breast cancer, although no definitive data are available on long-term safety in these women.

CONCLUSIONS

In women who need relief for mild vasomotor symptoms, NAMS recommends first considering lifestyle changes, either alone or combined with a nonprescription remedy, such as dietary isoflavones, black cohosh, or vitamin E. Prescription systemic estrogen-containing products remain the therapeutic standard for moderate to severe menopause-related hot flashes. Recommended options for women with concerns or contraindications relating to estrogen-containing treatments include prescription progestogens, venlafaxine, paroxetine, fluoxetine, or gabapentin. Clinicians are advised to enlist women's participation in decision making when weighing the benefits, harms, and scientific uncertainties of therapeutic options. Regardless of the management strategy adopted, treatment should be periodically reassessed as menopause-related vasomotor symptoms will abate over time without any intervention in most women.

Effects of tibolone and continuous combined hormone therapy on mammographic breast density and breast histochemical markers in postmenopausal women

OBJECTIVE

To compare changes in mammographic density and the expression of markers of proliferation (Ki67) and apoptosis (Bcl-2) after 1 year of treatment with tibolone and continuous conjugated equine estrogens combined with medroxyprogesterone acetate (CEE-MPA).

DESIGN

Comparative, randomized, evaluator-blinded study.

SETTING

City research hospital.

PATIENT(S)

Thirty-seven postmenopausal women.

INTERVENTION(S)

Tibolone (2.5 mg; n = 18) or continuous conjugated estrogens (0.625 mg) combined with medroxyprogesterone acetate (5 mg; n = 19) for 1 year.

MAIN OUTCOME MEASURE(S)

Mammographic density (BI-RADS density score), expression of immunohistochemical markers Ki67 and Bcl-2.

RESULT(S)

Mean breast density score decreased significantly from 2.22 to 1.67 in the tibolone group, compared with a significant increase in the CEE-MPA-treated group from 1.84 to 2.63. Ki67 expression decreased in 12 of 15, increased in 2 of 15, and remained unchanged in 1 of 15 subjects in the tibolone group, compared with 1 of 19, 15 of 19, and 3 of 19 subjects, respectively, in the CEE-MPA group. Bcl-2 expression decreased in 12 of 15, increased in 2 of 15, and remained unchanged in 1 of 15 subjects in the tibolone group, compared with 5 of 19, 9 of 19, and 5 of 19 subjects, respectively, in the CEE-MPA group.

CONCLUSION(S)

One-year treatment with tibolone induced a decrease in breast density, with a reduction in proliferation and a stimulation of apoptosis, whereas 1-year treatment with CEE-MPA induced an increase in breast density, with stimulation of proliferation and inhibition of apoptosis, indicating that tibolone effects on the breast are different from those of CEE-MPA.

Patients' and clinicians' attitudes after the Women's Health Initiative study

OBJECTIVE

To assess the effect of the publication of the Women's Health Initiative (WHI) study on patients' and physicians' attitudes in relation to hormone therapy (HT).

DESIGN

A survey focused on the degree of knowledge and on the reactions to the WHI study was administered to 600 women allocated in two groups according to their socioeconomic status, high (HSES) or low (LSES). Additionally, 283 physicians were surveyed to determine their attitudes regarding HT after the publication of the WHI study. The rates of HT prescription before and after publication of the study were compared.

RESULTS

Among patients, HT use and knowledge of the WHI study were less common among women of lower socioeconomic status (LSES 16.7% v HSES 47.3%, and LSES 15.7% v HSES 67.3%; P < 0.0001). Of the women in the LSES group who were HT users and had knowledge on the subject of the WHI study (n = 30), 56.7% contacted their physicians and 6.6% abandoned HT. These rates were similar for women in the HSES group. Among physicians, 97.2% of physicians referred to being aware of the WHI study, and 64.7% modified their clinical approach. The main changes were that 21.5% applied more rigorous risk/benefit assessment, 20.1% lowered hormone dosage, 18.8% decreased continuous-combined therapy use, 12.1% shortened the duration of HT, 7.7% abandoned medroxyprogesterone or conjugated estrogen use, and 5.0% increased the use of transdermal estrogens, tibolone, or other alternatives. As for prescriptions, after the publication of the WHI study, there was an 8.6% drop in the rate of HT prescriptions. This decrease was more pronounced for prescriptions based on conjugated equine estrogen and medroxyprogesterone acetate. In contrast, prescription of transdermal estrogens and tibolone increased 5.2% and 16%, respectively.

CONCLUSIONS

There was a significant change in physicians' and patients' attitudes toward HT after publication of the WHI study.

Changes in mammographic and ultrasound image of the breast of women undergoing estrogen replacement therapy

OBJECTIVE

Evaluation of changes in mammographic and ultrasound image of the breast in female patients undergoing estrogen hormonal replacement therapy (ERT).

MATERIAL AND METHODS

126 women with surgical menopause in case of benign disease using ERT and a control group of 100 women in menopause with no hormonal replacement therapy were selected for the study. Changes in the mammographic image were monitored in relation to individual types of breast according to Tabár's typology and with regard to the type of ERT application. In 38 women, changes in ultrasound image were also monitored together with ERT.

RESULTS

In 17 women (13 %) undergoing ERT, an increase in mammographic image density was found. This data was statistically significant in comparison with the control group without ERT (chi2 = 21.566, p < 0.0001). In 103 (82 %) women there was no change in mammographic density and in 6 women (5 %) decreased density despite using of ERT was found. In the group of patients undergoing ERT in peroral form, we found a greater percentage of women with an increased mammographic density (17 %) in comparison with the group of women with intradermally applied ERT (9 %). Increased density of mammographic image was more frequent in women with a prevalence of adipose tissue in their breasts (type II according to Tabár). In 8 patients (21 %) of 38 women with ultrasound examination an enlargement or development of new benign formations in the breast was found; this data was statistically insignificant in comparison with the control group.

CONCLUSION

In women with surgical menopause undergoing ERT, a statistically significant increase in the density of mammographic image was found (chi2 = 21.566, p < 0.0001). Increase in density of mammographic image was most frequent in women with a predominance of adipose tissue in breasts (a type II according to Tabár) and in women undergoing ERT in the peroral form. These data were statistically insignificant in 21 % of women with supplementary ultrasound examination enlargement and development of new benign lesions in the breasts were found.

Role of progestogen in hormone therapy for postmenopausal women: position statement of The North American Menopause Society

OBJECTIVE

To create an evidence-based position statement regarding the role of progestogen in postmenopausal hormone therapy (estrogen plus a progestogen, or EPT) for the management of menopause-related symptoms.

DESIGN

NAMS followed the general principles established for evidence-based guidelines to create this document. Clinicians and researchers acknowledged to be experts in the field of postmenopausal hormone therapy were enlisted to review the evidence obtained from the medical literature and develop a position statement for approval by the NAMS Board of Trustees.

RESULTS

The primary role of progestogen in postmenopausal hormone therapy is endometrial protection. Unopposed estrogen therapy (ET) is associated with a significantly increased risk of endometrial hyperplasia and adenocarcinoma. Adding the appropriate dose and duration of progestogen to ET has been shown to lower that risk to the level found in never-users of ET. The clinical goal of progestogen in EPT is to provide endometrial protection while maintaining estrogen benefits and minimizing progestogen-induced side effects, particularly uterine bleeding. EPT discontinuance correlates with uterine bleeding-women with more days of amenorrhea have higher rates of continuance. All US Food and Drug Administration-approved progestogen formulations will provide endometrial protection if the dose and duration are adequate. Progestogens may diminish the beneficial effects of ET on cardiovascular risk factors. However, no EPT (or ET) regimen should be initiated for the primary or secondary prevention of cardiovascular heart disease. Some progestogens may negatively affect mood. Adding progestogen to ET does not decrease the breast cancer risk, although it does not seem to increase mortality. Progestogen increases mammographic density, which is reversed after discontinuation of use. Progestogen has limited effect on the bone-enhancing action of ET. In general, the side effects of added progestogen are mild, although they may be severe in a small percentage of women.

CONCLUSIONS

Progestogen should be added to ET for all postmenopausal women with an intact uterus to prevent the elevated risk of estrogen-induced endometrial hyperplasia and adenocarcinoma. There is no consensus on a preferred regimen for all women. By changing the progestogen type, route, or regimen, clinicians can individualize therapy to minimize side effects, especially uterine bleeding, and limit any effects on ET benefits while providing adequate endometrial protection.

Progesterone receptors--animal models and cell signalling in breast cancer. Implications for breast cancer of inclusion of progestins in hormone replacement therapies

Progestins are included in menopausal hormone replacement therapy to counteract the increased risk for endometrial cancer associated with estrogen replacement therapy. Studies of hormone replacement therapy and breast cancer risk and of changes in mammographic density according to different regimens of hormone replacement therapy suggest that, for the most part, estrogen-progestin replacement therapy has a more adverse effect on breast cancer risk than does estrogen replacement therapy. Many questions remain unresolved, however, including risk associated with different regimens of estrogen-progestin replacement therapy, and whether the effects vary according to tumor characteristics, such as histology, extent of disease, and hormone receptor status.