Do Progestogens Reduce The Risk of Breast Cancer? A Review of the Evidence:

Long-term postmenopausal estrogen therapy may be associated with increased risk of breast cancer: a cohort study

Reports of a role of postmenopausal estrogen replacement therapy in the development of breast cancer have been inconsistent. Although many epidemiologic studies have failed to show an association between short-term use of estrogen and breast cancer, there are indications that long-term use may present an increased risk. We undertook a long-term, retrospective cohort study of the incidence of breast cancer in women who had taken long-term estrogen (average 17.2 years), compared to women who had not taken estrogen. Subjects were 454 women born between 1900 and 1915, who were members of a large health maintenance organization in northern California. By the end of 1995, 26 (11.2%) of estrogen users developed breast cancer, as did 9 (4.1%) of the nonusers; the relative risk (RR) for estrogen use was 2.8 [95% confidence interval (95% CI) 1.3-5.9]. Adjustment for age and multiple breast cancer risk factors, including breast cancer surveillance, reduced the RR for estrogen to 2.0 (95% CI 0.9-4.5). We conclude that long-term estrogen use is associated with a substantially increased risk of breast cancer.

Postmenopausal hormone therapy and breast cancer: What is the problem?

Observational studies provide evidence that breast cancer risk is increased with long-term oral use of postmenopausal estrogen replacement therapy (ET). Various large cohort studies have shown that the addition of a progestogen in combined hormone replacement therapy (EPT) increases this risk further. Prospective, randomized controlled trials have confirmed this for the continuous combined regimen. So, why not tell our patients, "Stop using ET and EPT, it is dangerous to your health!"? The answer is: there are too many problems to allow such an oversimplified, definite statement. What is the problem? There is more than one! The problems are as follows: In conclusion, we have a problem as we cannot formulate any general advice that holds for the majority of European postmenopausal women due to lack of consistency, lack of biological plausibility, and lack of relevance of randomized clinical trial data to our daily practical work. So, we have a problem and not a firm basis for undisputable statements.

Breast cancer and post-menopausal hormone therapy

From the introduction of post-menopausal hormone replacement therapy (HRT) there has been great concern that HRT could possibly increase the risk of breast cancer. Prolonged exposure to endogenous oestrogens undeniably increases the risk of breast cancer. Questions that are important and until now only partly answered, are the following. Are oestrogens tumour promoters, as they induce mitosis, lead to proliferation and, therefore, accelerated growth of clinically occult pre-existing tumours? In addition to this, are they genotoxic mutagenic carcinogens, or could they initiate tumours by way of accumulation of incessant DNA-replication damage mechanism? Opinions vary as to the effect of the addition of a progestogen. There is a multitude of different progestogens which could bind with differing affinity to progesterone receptor PR-A or PR-B, and which have different physiological functions via differential gene regulation. The action of a progestogen on the oestrogen-induced cellular mitotic activity could be synergistic or antagonistic (by different pathways: oestrogen receptor downregulation, activating of metabolic pathways within the breast or stimulation of apoptosis)? Over 60 observational studies and two randomized trials provide evidence that the small but significant increase in risk appears with long-term current post-menopausal hormone use. The addition of a progestogen does not decrease the risk as seen with oestrogens alone and might increase the risk further. It is not clear whether there is a difference in risk with sequentially combined versus continuously combined HRT. Many questions nevertheless still remain. Is the risk increase limited to lean women only? What about risk-modifying factors such as alcohol use and a positive family history for breast cancer? Are tumours detected under HRT less aggressive, is there a better prognosis and is the mortality not increased while morbidity is? And is HRT contraindicated for women with a positive family history for breast cancer or in those women who have been treated for breast cancer? And finally, are there alternative options for these women?

The physiology, medical management and oral implications of menopause

BACKGROUND

Approximately 36 million women in the United States are in the postmenopausal phase of life. The vast majority of these women experienced spontaneous cessation of menses between the ages of 47 and 55 years when the production of estrogen decreased because of an inadequate number of functioning follicles within their ovaries. Fewer women entered menopause after surgical removal of both ovaries. This procedure usually is performed prophylactically to prevent ovarian cancer in conjunction with a hysterectomy, which is required to treat abnormal bleeding, endometriosis or pelvic inflammatory disease. The physiological changes associated with spontaneous or surgical menopause cause some women to experience uncomfortable symptoms such as hot flashes, night sweats and vaginal dryness. In addition, estrogen deprivation arising from menopause in association with age-related factors disproportionately increases the risk of developing cardiovascular disease (that is, myocardial infarct, stroke), osteoporosis, Alzheimer's disease and oral disease. Hormone replacement therapy, or HRT (estrogen or estrogen and progestin), often is prescribed on a short-term basis to alleviate the uncomfortable symptoms associated with estrogen deficiency and on a long-term basis to prevent some of the chronic illnesses common to postmenopausal women.

CONCLUSIONS

Dentists who treat women entering menopause need to consider the stressful phase of life their patients are experiencing. Clinical findings of postmenopausal problems on dental examination may include a paucity of saliva, increased dental caries, dysesthesia, taste alterations, atrophic gingivitis, periodontitis and osteoporotic jaws unsuitable for conventional prosthetic devices or dental implants. Panoramic dental radiographs may reveal calcified carotid artery atheromas.

CLINICAL IMPLICATIONS

Dentists have an opportunity to refer women who are not under the care of a gynecologist for an evaluation to determine the appropriateness of HRT for its systemic and oral health benefits.

Women's knowledge of hormone therapy

The aim of this study was to assess women's knowledge of hormone therapy. Two hundred and seven women were interviewed by telephone. The median score to 24 questions concerning the benefits, risks and side effects of therapy was 54.2%. Almost three-quarters of women knew that hormone therapy may decrease the risk of osteoporosis, but half were unaware that it should be taken for at least 10 years for maximum protection against bone loss. While many women knew that hormone therapy may increase the risk of breast cancer, 13.5% believed that it would decrease their risk. Many women overestimated the potential reduction in lifetime risk of hip fracture and the potential increase in lifetime risk of breast cancer with hormone therapy. Women may have insufficient knowledge to make informed choices about hormone therapy. This has implications for physicians who wish to ensure that women are able to participate in informed decision-making.

HRT and breast cancer risk: a clue for interpreting the available data

Epidemiological and biological data on HRT and breast cancer risk are reviewed. Some aspects deserve consideration. (1) The majority of epidemiological data have been gathered from populations where high estrogen doses (> or = 1.25 mg daily of conjugated estrogens) were used as first line therapy. (2) HRT does not increase the risk in overweight women, even in the series in which a risk increase (in longterm users) is found. This could be as a result of the fact that oral estrogens, through their metabolic and hepatocellular effects, reverse some biological features of obesity (e.g. increased insulin-like growth factor I activity and decreased sex hormone binding globulin level) which potentially increase breast cancer risk, so balancing the estrogen stimulation. (3) The progestin addition seems to increase the risk when the 19 nor-testosterone derivatives are used. These androgenic compounds contrast the metabolic and hepatocellular effects of oral estrogens. To sum up, the possibility does exist that even the longterm use of oral estrogens at the right ('low') dose, with the addition of a non-androgenic progestin, will be shown to be associated with a very limited breast cancer risk increase.

Mammographic breast density during hormone replacement therapy: differences according to treatment

OBJECTIVE

Our purpose was to investigate the effects of various hormone replacement regimens on mammographic breast density.

STUDY DESIGN

Mammographic density was recorded in women participating in a population-based screening program. All women were nonusers of hormone replacement therapy at first mammogram and thereafter reported continuous use of the same treatment: estrogen alone (n = 50) or estrogen in cyclic (n = 75) or continuous (n = 50) combination with progestogen. Mammographic density was quantified according to the Wolfe classification.

RESULTS

An increase in mammographic density was much more common among women receiving continuous combination hormone replacement therapy (52%) than among those receiving cyclic (13%) and estrogen-only (18%) treatment. The increase in density was apparent already at first visit after the start of hormone replacement therapy. There was little change in mammographic status during long-term follow-up.

CONCLUSION

Regimens of hormone replacement therapy were shown to have different effects on the normal breast. There is an urgent need to clarify the biologic nature and significance of a change in mammographic density during treatment and, in particular, its relation to symptoms and breast cancer risk.

Hormone replacement therapy: the perspectives for the 21st century

Nowadays different lines of evidence demonstrate the benefits of postmenopausal hormone replacement therapy (HRT). HRT is extremely effective in treating subjective symptoms and can really improve the quality of life of climacteric women. HRT and dementia: Estrogens are potentially relevant to the pathogenesis and treatment of Alzheimer's disease. The effects of different progestogens on cognitive functions and Alzheimer's disease are largely unknown. The prevention of Alzheimer disease might be a major indication to long term HRT. Large prospective, randomized trials will confirm these preliminary data. HRT and osteoporosis: HRT has been strongly correlated with higher bone mineral density and lower fracture incidence. Definite answers in terms of minimum effective dosages, timing and duration of HRT for fracture prevention are needed. HRT and cardiovascular disease: Different lines of evidence suggest that HRT can exert cardioprotective effects with substantial reduction of morbidity and mortality for cardiovascular disease in postmenopausal women. The effects and the role of progestogens in cardiovascular disease prevention are still debated. Prospective, randomized, controlled studies are needed to assess the impact of different HRT regimens on cardiovascular events. HRT and cancer: The major issue in the relationship between HRT and cancer is breast cancer. Long-term and current HRT use are followed by a slight, though significant increase in the risk of breast cancer. Progestogens can modify the cellular response of normal as well as cancer breasts. The possible protective effect of continuous progestogen addition is very interesting and needs further investigation. Alternative to classical HRT: Selective estrogen receptor modulators (SERM). SERMs such as raloxifene (RAL) are a new class of drugs that exert site specific estrogenic or antiestrogenic effects in different target tissues. RAL prevents bone loss and reduces serum cholesterol in postmenopausal women. In contrast to estrogen RAL does not stimulate breast or uterine tissues. In vitro RAL is highly effective at inhibiting the growth of estrogen-dependent breast adenocarcinoma cells. SERMs are expected to represent a major breakthrough for postmenopausal health.

CONCLUSION

HRT can be offered either as a preventive tool or as individualized care on the basis of personal needs. New therapeutic options like the SERMs will offer a substantial medical advancement for the treatment of postmenopausal women.

A cohort study of hormone replacement therapy given to women previously treated for breast cancer

Women who have been previously treated for breast cancer are usually advised to avoid hormone therapy for fear of increasing their risk of tumor recurrence. However, for some women, menopausal symptoms are so severe that their quality of life is poor. Because ethic committees are reticent to permit a double-blind randomized trial, we performed a cohort study of hormone therapy after breast cancer.

METHODS

The study group comprised 1472 women with breast cancer. A total of 167 subjects had used an oral or transdermal estrogen after their treatment for breast cancer. Amongst these estrogen users, 152 (91%) had also used a progestin. In total, 106 other women had used a progestin alone as a treatment for menopausal flushes and not as a treatment for breast cancer. Cox regression analysis was performed using estrogen as a time-dependent covariate with disease-free interval as the outcome.

RESULTS

The uncorrected hazard ratio for the estrogen-progestin users was 0.67 (95% confidence interval (CI) 0.38-1.16) and for the progestin alone users was 0.85 (95% CI 0.44-1.65).

CONCLUSIONS

This study was unable to demonstrate a significant increase in risk of breast cancer recurrence for women who used HRT and suggests that the time is now appropriate for a randomized prospective trial of hormone therapy after breast cancer.

Menopause

The area of menopausal medicine is undergoing rapid evolution as millions of baby boomers enter this life stage. This group came of age at a time when all cultural values and institutions, including the basic assumptions underlying the healthcare of women, underwent intense scrutiny. As a result, alternative approaches to everything from childbirth to menopause have become increasingly mainstream. This article gives the healthcare provider both the philosophical background and practical solutions necessary to assist the menopausal woman in choosing an individualized program to minimize her risk for disease and maximize her postmenopausal health potential by combining the best of both conventional and alternative medical approaches.