Postmenopausal hormone therapy and the risk of breast cancer

Hormone replacement therapy use and variations in the risk of breast cancer

OBJECTIVE

To determine the effect of different types and formulations of hormone replacement therapy (HRT) on the risk of breast cancer in postmenopausal women.

DESIGN

Population-based case-control study.

SETTING

UK, 1988-2004.

PARTICIPANTS

Women 50-75 years between 1998 and 2004.

MAIN OUTCOME MEASURES

Breast cancer incidence to estimate the rate ratio (RR) associated with use of various HRTs over a 30-year period.

RESULTS

We identified 6347 incident cases of breast cancer that were matched with 31,516 controls. Cases were on average 61 years at diagnosis and 22% had undergone a hysterectomy. The rate of breast cancer was increased with the use of opposed estrogens in oral form (adjusted RR 1.38; 95% CI 1.27-1.49) in contrast to patch form (RR 1.08; 95% CI 0.81-1.43). This rate was similarly elevated with both continuous (RR 1.29; 95% CI 1.07-1.56) and sequential (RR 1.33; 95% CI 1.21-1.46) forms of opposed estrogen. The rate of breast cancer was not increased among exclusive users of unopposed estrogens (RR 0.97; 95% CI 0.86-1.09) or of tibolone (RR 0.86; 95% CI 0.65-1.13). Users of tibolone who had switched from opposed estrogens, however, had an elevated rate (RR 1.29; 95% CI 1.09-1.52). The rate of breast cancer increased by 25% (95% CI 20-30%) with every ten prescriptions of orally administered opposed estrogen.

CONCLUSIONS

The risk of breast cancer varies with the formulation and preparation of HRT. Opposed estrogens (progesterone-estrogen) in oral form are associated with an increased risk of breast cancer, which increases with use. Transdermal opposed estrogens, unopposed estrogens and tibolone do not increase this risk. However, this study is an observational study that carries risks of various biases, and thus the findings need to be interpreted with caution.

Care of the menopausal patient: A nurse practitioner?s view

PURPOSE

To evaluate the benefits and risks of hormone therapy (HT) and other treatment options for early postmenopausal women.

DATA SOURCES

Published clinical trials, selected peer-reviewed literature, and recent clinical practice guidelines.

CONCLUSIONS

Results of the Women's Health Initiative (WHI) studies on HT may not be directly applicable to healthy, early postmenopausal women suffering from hot flushes. HT is the most effective treatment for menopausal symptoms. The benefits of HT in relieving menopausal symptoms are likely to exceed the risks in this population.

IMPLICATIONS FOR PRACTICE

The results of the WHI reinforce the importance of individualized care based on a woman's medical history, medical needs, and desired outcomes. Nurse practitioners can help their patients put recent results into perspective. When HT is used, nurse practitioners should consider using lower doses and reevaluate the need for therapy annually.

Disruption of androgen receptor signaling by synthetic progestins may increase risk of developing breast cancer

There is now considerable evidence that using a combination of synthetic progestins and estrogens in hormone replacement therapy (HRT) increases the risk of breast cancer compared with estrogen alone. Furthermore, the World Health Organization has recently cited combination contraceptives, which contain synthetic progestins, as potentially carcinogenic to humans, particularly for increased breast cancer risk. Given the above observations and the current trend toward progestin-only contraception, it is important that we have a comprehensive understanding of how progestins act in the millions of women worldwide who regularly take these medications. While synthetic progestins, such as medroxyprogesterone acetate (MPA), which are currently used in both HRT and oral contraceptives were designed to act exclusively through the progesterone receptor, it is clear from both clinical and experimental settings that their effects may be mediated, in part, by binding to the androgen receptor (AR). Disruption of androgen action by synthetic progestins may have serious deleterious side effects in the breast, where the balance between estrogen signaling and androgen signaling plays a critical role in breast homeostasis. Here, we review the role of androgen signaling in the normal breast and in breast cancer and present new data demonstrating that androgen receptor function can be perturbed by low doses of MPA, similar to doses achieved in serum of women taking HRT. We propose that the observed excess of breast malignancies associated with combined HRT may be explained, in part, by synthetic progestins such as MPA acting as endocrine disruptors to negate the protective effects of androgen signaling in the breast. Understanding the role of androgen signaling in the breast and how this is modulated by synthetic progestins is necessary to determine how combined HRT alters breast cancer risk, and to inform the development of optimal preventive and treatment strategies for this disease.

Hormone replacement therapy

HRT should not be used for the prevention or treatment of chronic disease (eg, heart disease, osteoporosis, dementia). HRT is effective in alleviating moderate to severe menopausal symptoms. Clinicians must be aware of the risks and benefits of HRT and discuss them thoroughly with their patients. As new forms and lower doses of hormones become available, additional studies will be needed to compare therapeutic strategies adequately. Studies of younger perimenopausal and menopausal women are needed. Whatever regimen is chosen, the lowest allowable estrogen dose to relieve symptoms for the shortest time is recommended. Alternatives to hormonal therapy are being examined and some may be considered. Table 1 provides an evidence-based summary of current recommendations.

Postmenopausal hormone replacement therapy: endometrial and breast effects

The history of hormone replacement therapy (HRT) dates back to the late 1800s, when animal extracts of ovaries were first used. With the development of synthetic hormones, widespread use in postmenopausal women extended throughout the industrialized world, so that by the late 1900s roughly one-third to one-half of all postmenopausal women in the United States and Europe were taking HRT. Two events changed the course of use of HRT: the association of an increased rate of endometrial carcinoma with estrogen-only HRT and the association of an increased breast cancer rate with combined estrogen and progestin HRT. This review explores the evidence of the effects of HRT on the endometrium and the breast, with emphasis on the pathologic changes.

The effect of low dose hormone therapy on mammographic breast density

OBJECTIVES

To evaluate the effect of two standard and one low dose continuous hormone therapy regimens on mammography.

METHODS

One hundred and thirty-two non-hysterectomized postmenopausal women were randomly allocated either to conjugated equine estrogens 0.625 mg plus medroxyprogesterone acetate 5 mg (CEE/MPA, n=38), 17beta-estradiol 2 mg plus norethisterone acetate 1 mg (E2/NETA, n=44) or 17beta-estradiol 1 mg plus norethisterone acetate 0.5 mg (low E2/NETA, n=50). Treatment was continuous and the study period lasted 12 months. Main outcome measures were the changes according to Wolfe classification between baseline and 12-month mammograms.

RESULTS

Five (13.2%) women in the CEE/MPA group showed an increase in breast density. Fourteen (31.8%) women on E2/NETA and 6 (12.2%) on low E2/NETA treatment revealed an increase in breast density. No woman exhibited an involution of fibroglandular tissue.

CONCLUSIONS

Different hormone therapy regimens have a variable impact on breast density probably depending on the steroid used. Low dose hormone therapy associates with significantly lesser increase in breast density.

The woman patient after WHI

An epidemic of fear and distrust has infected women (and physicians) after publication of the Women's Health Initiative (WHI). The overinflated negative data emerging from the oestroprogestinic arm of WHI have frightened women and gave rise to the most difficult emotions to cope with. Keywords such as cancer, death and hormones combined together, have potentiated an avoidant attitude towards hormonal therapy (HT) driven more emotionally than rationally. This negative aura has not been dissipated by the positive data from the oestrogen-only arm of WHI. This paper will discuss: women's different emotional reactions to and coping strategies for HT-related fear after WHI; the communication skills physicians should use in focusing on positive messages emerging from WHI; predictors of current HT use; the meaning of the higher use of HT in postmenopausal highly-educated women and women gynaecologists; the importance of increasing healthy life-styles as a taking of responsibility towards aging by every woman; shifting from passivity to active sharing of the decision making process with the caring physician; and the use of an individually tailored HT, when appropriate, as part of an active strategy in the pursuit of a longer health expectancy.