Estrogens and endometrial cancer. Responses to arguments and current status of an epidemiologic controversy

Development of a new prevention maintenance therapy for postmenopausal women

In spring 1998, breast cancer prevention emerged from being a concept to being a reality. The National Surgical Adjuvant Breast and Bowel Project prevention trial showed that tamoxifen reduced breast cancer by 45% in high-risk women between the ages of 35 and 75. Additionally, an evaluation of 10,550 patients randomized to osteoporosis trials of placebo versus raloxifene demonstrated a 50% reduction in the incidence of breast cancer in woman taking raloxifene. For the future, a Study of Tamoxifen Against Raloxifene (STAR) is ongoing in high-risk postmenopausal women. This chapter describes the biological rationale for the current clinical advances.

The role of ultrasound in the detection of endometrial pathologies in asymptomatic postmenopausal breast cancer patients with tamoxifen treatment

Transvaginal ultrasonography is an effective diagnostic procedure, and thus, it can reasonably be used to determine which asymptomatic, postmenopausal breast cancer patient with tamoxifen treatment will require endometrial sampling. Overall, it seems that the contribution of pulsed Doppler flow in the diagnosis of endometrial pathologies in such patients is nonconclusive. It is suggested that sonohysterography is a useful diagnostic tool for the assessment of specific endometrial pathologies, especially of space-occupying lesions in the endometrial cavity, in such patients.

A realistic clinical perspective of tamoxifen and endometrial carcinogenesis

Tamoxifen has been the endocrine treatment of choice for all stages of breast cancer for nearly a decade. Millions of women are currently receiving tamoxifen worldwide, while large-scale randomised trials have been launched aiming to investigate the drug's merit as a preventive agent. However, there are now concerns about tamoxifen's potential carcinogenicity. The goal of this review is to address these concerns, re-evaluate the available data from laboratory biological models and those from clinical reports and put the whole issue into perspective. Our focus is the association between tamoxifen and the increased frequency of endometrial tumours, while key issues, such as the role of duration of tamoxifen therapy, are also addressed. Finally, we discuss the various monitoring strategies for early detection of endometrial lesions and pertinent problems most likely to be encountered by clinicians taking care of patients who are receiving tamoxifen.

What do we know and what don't we know about tamoxifen in the human uterus

Since its introduction in the early seventies, the list of indications for the use of the antiestrogen tamoxifen has been continuously expanded. Tamoxifen is now used for the treatment of metastatic breast cancer and for long-term and often indefinite administration as an adjuvant therapy. Large clinical trials in three countries are now evaluating the efficacy of tamoxifen as a preventive agent. However, tamoxifen therapy has been associated with an increased incidence of endometrial carcinoma. Laboratory and clinical data available to date on this controversial issue can be summarized as follows: a) Tamoxifen can have an estrogenic effect on endometrium in the presence of low estrogen levels. b) Tamoxifen treatment is probably associated with an increased incidence of endometrial cancer; however, this association appears to be linked to higher tamoxifen doses (40 mg/d). d) It is not known whether tamoxifen causes or allows the identification of occult endometrial carcinoma. e) At the present time there is evidence for a tumor promoting effect of tamoxifen on endometrial cancer at a dose of 20 mg per day. f) Replacement of tamoxifen by 'pure' antiestrogens or coadministration of progestins with tamoxifen do not appear to offer benefit unless clinical trials demonstrate a reduced incidence of endometrial problems. g) Patients must be evaluated for pre-existing endometrical carcinoma before starting tamoxifen therapy. f) Close followup of long-term tamoxifen patients with endometrial biopsies is recommended with individuals who experience symptoms.

Fourteenth Gaddum Memorial Lecture. A current view of tamoxifen for the treatment and prevention of breast cancer

Tamoxifen has been found to be a safe and effective treatment for all stages of breast cancer. Long term tamoxifen therapy is associated with some rare, but potentially serious, side effects so patients should be carefully monitored. However, long term tamoxifen therapy is also associated with a number of physiological benefits over and above its tumouristatic action. These benefits include a decrease in the development of contralateral breast cancer, the maintenance of bone density in postmenopausal women and a decrease in cardiovascular disease. The successful application of tamoxifen to treat breast cancer has increased enthusiasm to test its worth to prevent breast cancer. Although there are individual requests by patients for tamoxifen to prevent breast cancer, individual treatment is inappropriate. Tamoxifen can only be adequately evaluated as a preventive in randomized, double-blind clinical trials. These trials are in place and physicians should encourage women to participate and establish a new therapeutic option as rapidly as possible.

Gynecologic complications associated with long-term adjuvant tamoxifen therapy for breast cancer

The antiestrogen tamoxifen was originally introduced as a therapy for advanced breast cancer. Today, tamoxifen is used to treat selected patients with all stages of breast cancer, and trials are underway to evaluate its effectiveness as a potential breast cancer preventive. When tamoxifen is used as an adjuvant or preventive, extended patient survival times can be expected, and concerns about iatrogenic complications arising from long-term treatment become important. This review discusses currently available laboratory and clinical data regarding the toxicology of tamoxifen and focuses in particular on the gynecologic complications potentially associated with long-term tamoxifen administration.

The epidemiology of endometrial cancer

The descriptive and analytical epidemiology of endometrial cancer is reviewed. Over the last few decades, age-standardized incidence rates have been rising in several countries. The rise has been even greater in terms of absolute numbers of cases, and hence public health implications, due to the aging of the population. Although endometrial cancer rates were found to be higher in richer countries and urban populations, there is now evidence of some changes in the socioeconomic determinants of the disease in developed countries. In etiological terms, any factor that increases exposure to unopposed estrogens (such as menopausal replacement treatment, obesity, and irregular menstrual cycles) tends to increase the risk of the disease, while factors that decrease exposure to estrogens or increase progesterone levels (such as oral contraceptives or smoking) tend to be protective. Less well defined, or more difficult to explain in biological terms, is the role of other factors, such as births, miscarriages, or diabetes and hypertension, and only suggestive evidence is available on diet from analytical epidemiology. The data reviewed herein are discussed in terms of models of carcinogenesis, as well as attributable risks and public health implications.

Osteoporosis and the elderly

Osteoporosis causes significant morbidity and some mortality among the elderly. Although increasing bone content should reduce the rate of osteoporotic fracture, attention should also be paid to other factors (such as falling). Loss of bone mass is a universal phenomenon with aging, and currently we are not able to use risk factor analysis to accurately predict which people are likely to suffer osteoporotic fracture. Bone densitometry cannot be recommended as a useful screening test in elderly patients. When deciding about treatment of osteoporosis in the elderly, it should be noted that few studies have included patients over 75 years of age and that prevention of bone loss is more effective than restoration of lost bone. Although high-dose calcium appears ineffective, patients ingesting low amounts of calcium should be counselled to increase their daily intake to at least 800 mg. Estrogens are very effective at preserving bone mass at least up to age 70 years, and their use is associated with a reduction in hip fractures. Vitamin D at a dose of 600 to 800 IU per day should be given to elderly subjects who do not get significant exposure of their skin to sunlight. Other specific recommendations regarding the prevention and treatment of osteoporosis await the results of further investigation.

The dose-effect relationship between 'unopposed' oestrogens and endometrial mitotic rate: its central role in explaining and predicting endometrial cancer risk

The 'unopposed oestrogen hypothesis' for endometrial cancer maintains that risk is increased by exposure to endogenous or exogenous oestrogen that is not opposed simultaneously by a progestagen, and that this increased risk is due to the induced mitotic activity of the endometrial cells. Investigation of the mitotic rate during the menstrual cycle shows that increases in plasma oestrogen concentration above the relatively low levels of the early follicular phase do not produce any further increase in the mitotic rate of endometrial cells. A modification of the unopposed oestrogen hypothesis which includes this upper limit in the response of endometrial cells to oestrogen is consistent with the known dose-effect relationships between endometrial cancer risk and both oestrogen replacement therapy and postmenopausal obesity; it also suggests that the mechanism by which obesity increases risk in premenopausal women involves progesterone deficiency rather than oestrogen excess, and that the protective effect of cigarette smoking may be greater in postmenopausal than in premenopausal women. Detailed analysis of the age-incidence curve for endometrial cancer in the light of this hypothesis suggests that there will be lifelong effects of even short duration use of exogenous hormones. In particular, 5 years of combination-type oral contraceptive use is likely to reduce a woman's lifetime risk of endometrial cancer by some 60%; whereas 5 years of unopposed oestrogen replacement therapy is likely to increase her subsequent lifetime risk by at least 90%; and even 5 years of 'adequately' opposed therapy is likely to increase subsequent lifetime risk by at least 50%.

The use of combined estrogen-progestin replacement therapy

The evaluation of innovations which use old technology poses different problems than does the evaluation of new technologies. The main necessity is the targeting of its use rather than the technology itself. The need to evaluate the extent of use and its problems is illustrated by the example of progestin use among menopausal and postmenopausal women in the United States. There progestins are not officially approved for use in menopause, even though they have been on the market for a long time with other indications. Estrogen-replacement therapy was widely used from the early 1960s until 1975, when the claim that estrogens cause endometrial cancer notably decreased their use. The use of estrogens increased again in the early 1980s, and one reason for this revival was the claim that progestins offered protection against endometrial cancer. When recommendations for combined estrogen-progestin therapy have been made, other health effects have been ignored. Two consensus conferences as well as the drug control authority have recommended against combined estrogen-progestin therapy until further research is completed. Absence of good research, specialization in medicine, and advantages for prescribers and the drug industry may have contributed to the wide use of this unassessed treatment. Possible solutions for prevention of the diffusion of these kinds of innovations are discussed.