A comparison of estrogen use by women with endometrial cancer, gynecologic disorders, and other illnesses

Epidemiology of Endometrial Carcinoma: Etiologic Importance of Hormonal and Metabolic Influences

Endometrial carcinoma is the most common gynecologic cancer in developed nations, and the annual incidence is projected to increase, secondary to the high prevalence of obesity, a strong endometrial carcinoma risk factor. Although endometrial carcinomas are etiologically, biologically, and clinically diverse, hormonal and metabolic mechanisms are particularly strongly implicated in the pathogenesis of endometrioid carcinoma, the numerically predominant subtype. The centrality of hormonal and metabolic disturbances in the pathogenesis of endometrial carcinoma, combined with its slow development from well-characterized precursors in most cases, offers a substantial opportunity to reduce endometrial carcinoma mortality through early detection, lifestyle modification, and chemoprevention. In this chapter, we review the epidemiology of endometrial carcinoma, emphasizing theories that link risk factors for these tumors to hormonal and metabolic mechanisms. Future translational research opportunities related to prevention are discussed.

Cost-effectiveness of alternative treatments for women with osteoporosis in Canada

BACKGROUND

During the years following menopause, estrogen levels decline leading to accelerated bone loss and an increased risk of osteoporosis and osteoporosis-related fractures.

METHODS

Using a Markov model and decision analytic techniques, the long-term costs and outcomes of five treatment and secondary prevention strategies for osteoporosis were compared: 'no intervention', alendronate, etidronate, risedronate, and raloxifene. The base case analysis examined postmenopausal (65 year old) osteoporotic women without prior fracture. Probabilistic sensitivity analysis (PSA) was used to incorporate the impact of parameter uncertainty, and deterministic sensitivity analysis (DSA) was used to compare alternative patient populations and modeling assumptions. Life years and Quality Adjusted Life Years (QALYs) were used as measures of effectiveness.

RESULTS

In the base case analysis, risedronate was dominated by etidronate and alendronate. Alendronate and etidronate were projected to have similar costs and QALYs, and the efficiency frontier was represented by 'no intervention', etidronate, alendronate, and raloxifene (Can$32 571, Can$38 623 and Can$114 070 per QALY respectively). Alternative assumptions of raloxifene's impact on CHD and breast cancer, alternative discount rates and alternative patient risk factors (e.g., starting age of therapy, CHD risk, and prior fracture risk) had significant impacts on the overall cost-effectiveness results for both the bisphosphonates and raloxifene.

DISCUSSION

Using conventionally quoted benchmarks and compared to no therapy, alendronate, etidronate, and raloxifene would all be considered cost-effective alternatives for treating women with osteoporosis. Potential limitations of this study include the usual caveats and cautions associated with long-term projection models and the fact that not all inputs into the model are Canadian data sources.

Hormone replacement therapy and risk of malignancy

PURPOSE OF REVIEW

The fact that today our concern is oriented towards the risks rather than the benefits of hormone replacement therapy could be the clearest message about our current position. The safety of hormone replacement therapy, an estrogen-progestin combination which has been sympathetic to and supportive of disturbing menopausal symptoms of women, is seriously challenged.

RECENT FINDINGS

Four randomized trials have now reported on the results of hormone replacement therapy in major potentially fatal conditions, in more than 20,000 women studied for about 5 years. The main concern regarding the increased risk of malignancy in healthy postmenopausal women in western countries has been breast cancer. It is estimated to cause an extra case in about six per 1000 users aged 50-59 and 12 per 1000 aged 60-69. Over the same period the estimated risk of endometrial cancer rates are not increased, with a relative risk of 0.76 per 1000 users aged 50-59. Overall, however, the increased incidence of malignancies is greater than any reduction, one per 230 users aged 50-59 and one per 150 aged 60-69. Randomized trials examining other important but rarer malignancies, like ovarian, gall bladder and urinary bladder cancer, are either nonexistent or too small to reliably describe any effects of hormone replacement therapy.

SUMMARY

Conclusively epidemiological evidence suggests that hormone replacement therapy is associated with a small but substantial increase in breast cancer risk and combined estrogen-progesterone regimens further increase this hazard. Additionally, the evidence from the recent double blind placebo controlled randomized trial on the slight increase in the incidence of adverse cardiovascular events, has turned our orientation away from hormone replacement therapy as a long term therapy in postmenopausal women. In this review, the effort is to approach comprehensively and globally the information on the risks of hormone replacement therapy on several cancer sites.

Perimenopausal use of reproductive hormones effects on breast and endometrial cancer

The effect of reproductive hormone use in the form of oral contraception or HRT on endometrial cancer incidence is not caused by simply bias: the epidemiologic studies are consistent; the effect of ERT is large; the biologic rationale cited is a plausible mechanism; and the response to progestin in oral contraception or combined HRT tends to confirm the biologic mechanism. In contrast, it remains unclear whether changes in breast cancer incidence following use of oral contraception and HRT are caused by hormone exposure or to other factors: the results of epidemiologic studies are not entirely consistent, and the smaller relative effect on risk of breast cancer is susceptible to bias and other sources of error. Although the exact nature of the association between repro ductive hormone use and breast cancer incidence is not yet clear, breast cancer is a common neoplasm in older women. Prescribers and users should take this into account in weighing benefits to ensure that unnecessary risks are avoided.

The effect of the duration of progestin use on the occurrence of endometrial cancer in postmenopausal women

OBJECTIVE

Women who have ever used estrogen replacement therapy (ERT), even at a low dose, have an increased incidence of endometrial cancer. The addition of a progestin to ERT reduces the incidence of endometrial cancer. The duration of progestin administration is more important than the dose.

DESIGN

A MEDLINE review of the literature was performed using the search terms endometrial cancer, epidemiology, and hormone replacement therapy (HRT).

RESULTS

Women who have ever used ERT have an increased incidence of endometrial cancer. The use of HRT for more than 5 years, with a progestin use of <10 days per cycle, has a relative risk = 1.8. Continuous combined HRT, or sequential or cyclic HRT with >10 days of progestin per cycle, appears to decrease the incidence of endometrial cancer to that found in nonusers of HRT.

CONCLUSIONS

The use of HRT in postmenopausal women with a uterus reduces the incidence of endometrial cancer. The duration of progestin administration should be 14 days or more per cycle based on recent epidemiologic data.

High-frequency FSH and LH pulses in obese menopausal women

We studied the pulsatile luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretory patterns, at early or intermediate years of menopause in seven normal women with different degrees of obesity, taking blood samples every minute for 40 min to 2 h. The hormones were assayed with an immunoradiometric assay (IRMA) system, analyzing with the cluster pulse algorithm. All women showed hormone pulses every 8-10 min. In five of them were found periods of discrete pulses with oscillations of high amplitude alternating with periods of pulses of low amplitude. In two cases, the high-frequency oscillatory pattern with low amplitude was found around low mean levels of 22.8 and 25.7 IU/L. The LH oscillatory pattern also had a high frequency, but at a lower level, giving a high FSH/LH ratio. The coincidence index of FSH with LH peaks was 76.6%. We concluded that at menopause, the frequency of FSH and LH secretion increases with a high FSH/LH ratio. Obese menopausal women may have the same high-frequency oscillatory patterns, but at low levels.

Endometrial cancer risk after discontinuing use of unopposed conjugated estrogens (California, United States)

To examine the decline in risk of endometrial cancer after discontinuation of use of conjugated estrogens, we conducted a case-control study in a prepaid health plan. We identified 318 patients who had endometrial cancer but had no history of bilateral oophorectomy and had been in the Southern California (United States) Kaiser Foundation Health Plan for more than 10 years. For each patient, one or two control members were selected, 599 in all, matched for age and duration of membership at the time of cancer detection and who had had neither hysterectomy nor bilateral oophorectomy. A history of prescriptions for conjugated estrogens and of potential confounders was obtained for each subject by reviewing outpatient medical records. Rate ratios (RR) contrasting users with nonusers were estimated by time of latest prescription. We found that estrogen-induced risk of endometrial cancer decreases rapidly as the estrogen-free interval increases. The RR estimates, adjusted for duration of use and potential confounding factors, declined from 5.0 for those receiving their latest prescription within 24 months (95 percent confidence limits [CL] = 2.6-9.8), to 1.8 for those receiving their latest prescription within 24 to 48 months (CL = 0.9-3.7), to values near one for each latest prescription interval earlier than 48 months ago (P for trend = 0.00004). For those who used conjugated estrogens extensively (five or more prescriptions, five to 10 years ago), the RR estimate declined from 5.1 for those whose latest prescription was within two years to 0.6 yr for those whose latest prescription was four to five years previously (P for trend = 0.05).

Postmenopausal unopposed estrogens. Characteristics of use in relation to the risk of endometrial carcinoma

To determine whether treatment regimens for unopposed estrogens can be tailored so as to minimize the excess risk of endometrial cancer, results from 19 published studies of the association between unopposed estrogen use and endometrial cancer were compiled. We sought to examine the influence of duration of use, recency, dose, type of estrogen preparation, and periodic interruption of use on cancer incidence. Estrogen use for 5 years or longer was examined in 18 studies and was associated with a large increase in the risk of endometrial cancer in each one (range in relative risk, 1.8 to 36). Use for shorter durations also was observed to increase risk; however, among women who used estrogens for less than 6 months, any increased risk that may exist appears to be very small in size (six studies; range, 0.6 to 1.4). Risk consistently was seen to decrease with increasing time since cessation of use, although there is evidence from seven of eight studies that some residual excess risk remains long after estrogens have been discontinued. In each of 12 studies that examined the influence of dose, all dose levels of conjugated estrogens increased risk of endometrial cancer substantially. Four of five studies found no differences between oral synthetic estrogens and conjugated estrogens with respect to cancer risk, and all of eight studies found no difference between cyclic and continuous regimens. Based on our review, we conclude that apart from minimizing the duration of use, there is no way of taking unopposed postmenopausal estrogens that reduces their potential to cause endometrial cancer.

Estrogen replacement therapy and the risk of endometrial cancer: remaining controversies

To examine the relationship between exogenous estrogen administration and endometrial cancer, we used data from the Cancer and Steroid Hormone Study, a multicenter, population-based case-control study. Estrogen replacement therapy for greater than or equal to 2 years was associated with an increased risk of both localized and extrauterine cancer (relative risk = 2.8, 95% confidence limits 1.6, 4.6; relative risk = 2.9, 95% confidence limits 0.9, 9.4, respectively). However, the latter finding was based on a small number of cases in which estrogen was used. Women who underwent estrogen replacement therapy for greater than or equal to 2 years had significantly elevated risks of endometrial cancer (2.1 for 2 to 5 years and 3.5 for greater than or equal to 6 years). An elevated risk persisted for greater than or equal to 6 years after discontinuation of therapy. Women who exclusively used conjugated equine estrogen preparations less than or equal to 0.625 mg had no increased risk of endometrial cancer. A history of oral contraceptive use appeared to reduce the risk of endometrial cancer associated with estrogen replacement therapy. However, these latter two potentially important findings were based on a small number of cases in which hormones were used.

The cancer question: an overview of recent epidemiologic and retrospective data

Unopposed estrogen stimulates mitotic activity in endometrial and breast tissue. Numerous case-control studies have evaluated the relationship between estrogen use and the risk of endometrial and breast cancers. In general, exogenous, unopposed estrogen use increases the risk of endometrial cancer by tenfold and of breast cancer by twofold after long-term use of high doses. Estrogen's positive effects on osteoporosis and coronary heart disease must be considered when evaluating the potential risks associated with its use in postmenopausal women.

Effect of sex hormones on NK and ADCC activity of mice

The effect of pharmacologic doses of sex hormones on NK and ADCC activity against YAC-1 lymphoma and CRBC target cells was studied. Estradiol (E) and testosterone (T) administration for 2 weeks caused a substantial reduction of splenic NK activity in TA3 mice of either sex. In prolonging the treatment time, the intensity of suppression was gradually increased. Both E and T have apparently no inhibitory effect on ADCC activity of TA3 mice, although the ADCC activity slightly increased in the early stage of T treatment. The ADCC activity of T-treated male mice was slightly higher than that of E-treated males. Passive transfer of the splenic mononuclear cells and serum of treated mice does not affect the NK and ADCC activity of normal recipient mice. Addition of different concentrations of sex hormones into the culture medium or pre-treatment of effector cells for 12h failed to change the NK and ADCC activity of murine splenic cells.

Smoking, body weight, and early-stage endometrial cancer

The effect of cigarette smoking on the risk of early-stage endometrial cancer was evaluated in a population-based case-control study of women aged 40 to 69 years from upstate New York. Two hundred women with early-stage endometrial cancer diagnosed between 1979 and 1981, and 200 matched community controls were interviewed in person and asked about smoking habits and other risk factors. Statistical analysis revealed a significant decline in relative risk with increased smoking (P less than 0.05). This effect strongly modified the well-known increase in risk with body weight. Among smokers risk did not increase with body weight, whereas among nonsmokers risk increased rapidly with body weight, especially among nonsmokers in whom the peripheral conversion of androgens was the primary source of serum estrogen. Despite this apparent reduced risk for endometrial cancer, smoking remains a major health hazard for women as well as men.

Endometrial carcinogenesis and its relation to oestrogens

The epidemiological evidence suggesting an association between the administration of exogenous oestrogens and an increased risk of developing endometrial adenocarcinoma is critically reviewed and it is concluded that the case for oestrogens being a cause of endometrial cancer is proven. The benefits flowing from preventing postmenopausal osteoporosis by oestrogen replacement therapy are assessed and contrasted with the danger to life posed by endometrial adenocarcinoma: it is pointed out that the type of neoplasm developing in patients taking oestrogens is well differentiated, nonaggressive and easily cured, the survival rate being very high. The addition of progestational agents to the therapeutic regime may prevent the development of endometrial carcinoma but could introduce a risk of cardiovascular disease.

Hormones, medications, and cancer

Hormones have been shown experimentally to act as cocarcinogens or promoters, i.e., they facilitate the carcinogenic event. In the cases of breast and endometrium, those hormones that facilitate growth may also favor carcinogenesis in the human. There is good epidemiologic evidence that use of estrogens after the menopause increases the incidence of breast and endometrial cancer, the risk increasing with increasing duration of use. Periodic progestin-induced withdrawal will probably mitigate the risk of endometrial cancer after the menopause. Prolactin is the important promoter of mammary cancer in the rat and mouse, but its significance in women is still under study. Intermittently elevated prolactin levels have been noted in some women who subsequently developed breast cancer, but epidemiologic studies of women who have received prolactin-releasing drugs such as reserpine and perphenazine have not disclosed increased risk. Diethylstilbestrol is listed as a carcinogen but any estrogen can induce mammary cancer in the rodent or vaginal adenosis in the neonatal mouse (an experimental model of human vaginal adenocarcinoma).