Postmenopausal hormone therapy and the risk of breast cancer: the view of an epidemiologist

OBJECTIVES: Postmenopausal hormone therapy (PMH) has been widely used by menopausal women living in western countries for the past several decades. Numerous studies have evaluated the relationship between PMH and breast cancer risk because steroid hormones have been implicated in breast cancer etiology. METHODS: A review of selected studies was performed to evaluate the history of investigations of the association between PMH and breast cancer, with a focus on studies evaluating different PMH regimens and different histologic types of breast cancer. RESULTS: Though studies conducted before the early 1990s suggest that both combined estrogen and progestin (E + P) PMH and unopposed estrogen (E) PMH are associated with an increased risk of breast cancer, more recent observational studies suggest that E + P, particularly current use for 5 years or longer, is more strongly associated with breast cancer risk than is unopposed E. Results from the Women's Health Initiative (WHI) randomized trials have confirmed these findings as they indicate that E + P is causally related to breast cancer (relative risk (RR) = 1.24; 95% confidence interval (CI): 1.01-1.54), while E alone is not (RR = 0.77; 95% CI: 0.59-1.01). CONCLUSIONS: There is clear and consistent evidence that use of E + P increases a woman's risk of breast cancer. Alternatively, current evidence suggests that use of unopposed E is not as strongly associated with breast cancer risk. Further studies are needed though to examine how different PMH regimens, doses, and methods of delivery are related to breast cancer risk, and how PMH impacts the risks of different types of breast cancer.     

Lessons to be learned from animal studies on hormones and the breast

The relation of hormone use by postmenopausal women to breast cancer risk has been controversial and unclear. A recent large randomized trial, the Women's Health Initiative (WHI) and a large observational study (Million Women Study) provided somewhat conflicting answers. The WHI found an increased incidence of breast cancer among women given hormone therapy (conjugated equine estrogen plus medroxyprogesterone acetate) but no increase in those given estrogen only therapy (conjugated equine estrogen alone). Whereas, the Million Women Study found an increased breast cancer risk among the estrogen plus progestin and the estrogen only users. This review brings comparative perspective to the issue of the effects of estrogen plus progestin versus estrogen only effects on breast cancer and is focused particularly on nonhuman primates. Although data from rodents is mixed, studies of monkeys suggest that estrogen only treatment has little or no effect on breast cell proliferation, and by inference, on breast cancer risk. On the other hand, data from both mouse and monkey studies strongly support the conclusion that the co-administration of a progestogen with an estrogen markedly increases breast cell proliferation and the potential for breast cancer promotion.     

New evidence regarding hormone replacement therapies is urgently required transdermal postmenopausal hormone therapy differs from oral hormone therapy in risks and benefits

Controversies about the safety of different postmenopausal hormone therapies (HTs) started 30 years ago and reached a peak in 2003 after the publication of the results from the Women Health Initiative (WHI) trial and the Million Women Study (MWS) [Writing group for the women's health initiative investigations. Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA 2002;288:321-33; Million women study collaborators. Breast cancer and hormone-replacement therapy in the million women study. Lancet 2003;362:419-27]. The single HT formulation used in the WHI trial for non hysterectomized women-an association of oral conjugated equine estrogens (CEE-0.625 mg/day) and a synthetic progestin, medroxyprogesterone acetate (MPA-2.5 mg/day)-increases the risks of venous thromboembolism, cardiovascular disease, stroke and breast cancer. The MWS, an observational study, showed an increased breast cancer risk in users of estrogens combined with either medroxyprogesterone acetate (MPA), norethisterone, or norgestrel. It is unclear and questionable to what extent these results might be extrapolated to other HRT regimens, that differ in their doses, compositions and administration routes, and that were not assessed in the WHI trial and the MWS. Significant results were achieved with the publication of the WHI estrogen-only arm study [Anderson GL, Limacher M, Assaf AR, et al. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women's Health Initiative randomized controlled trial. JAMA 2004;291:1701-1712] in which hormone therapy was reserved to women who had carried out hysterectomy. What emerged from this study will allow us to have some important argument to develop.     

Breast cancer risk in the WHI study: the problem of obesity

In the climacteric, about 40% of the women have occult breast tumors the growth of which may be stimulated by hormones. Many genetic, reproductive and lifestyle factors may influence the incidence of breast cancer. Epidemiological data suggest that the increase in the relative risk (RR) of breast cancer induced by hormone replacement therapy (HRT) is comparable with that associated with early menarche, late menopause, late first birth, alcohol consumption, etc. One of the most important risk factors is obesity which exceeds the effect of HRT by far, and in overweight postmenopausal women the elevated risk of breast cancer is not further increased by HRT. As in the WHI study the majority of women was overweight or obese, this trial was unsuitable for the investigation of breast cancer risk. In the women treated with an estrogen/progestin combination, the RR of breast cancer rose only in those women who have been treated with hormones prior to the study, suggesting a selection bias. In the women not pretreated with hormones, it was not elevated. In the estrogen-only arm of the WHI study, there was no increase but a steady decrease in the RR of breast cancer during 6.8 years of estrogen therapy. This result was unexpected, as estrogens are known to facilitate the development and growth of breast tumors, and the effect is enhanced by the addition of progestins. Obese women are at high risk to develop a metabolic syndrome including insulin resistance and hyperinsulinemia. In postmenopausal women, elevated insulin levels are not only associated with an increased risk for cardiovascular disease, but also for breast cancer. This might explain the effects observed in both arms of the WHI study: HRT with relative low doses of estrogens may improve insulin resistance and, hence, reduce the elevated breast cancer risk in obese patients, whereas this beneficial estrogen effect may be antagonized by progestins. The principal options for the reduction of breast cancer risk in postmenopausal women are the prevention of overweight and obesity to avoid the development of hyperinsulinemia, the medical treatment of insulin resistance, the use of low doses of estrogens and the reduction of exposure to progestins. The latter might include long-cycles with the sequential use of appropriate progestins every 3 months for 14 days. There are large inter-individual variations in the proliferative response to estrogens of the endometrium. Control by vaginalsonography and progestin challenge tests may help to identify those women who may be candidates for low-dose estrogen-only therapy.     

Recent reversal of trends in hormone therapy use in a European population

OBJECTIVE: The impact of the Women's Health Initiative (WHI) randomized trial results published in July 2002 indicating that hormone therapy (HT) is potentially harmful for the heart and the mammary gland of naturally postmenopausal women was assessed for the first time in a European population. DESIGN: This study continuously monitored HT use from 1994 through 2003 in a population-based random sample of 5,758 women aged 35 to 74 years residing in Geneva (city and canton), Switzerland, yielding 1,938 naturally postmenopausal women with an intact uterus and 206 artificially postmenopausal women. Women in the former subgroup weighed substantially less than their WHI trial counterparts but were not otherwise at lower risk for cardiovascular disease. RESULTS: Among the naturally postmenopausal women with an intact uterus, current HT use increased from 29% to 46% (P < 0.0001) through July 2002 and then decreased abruptly to 31% in 2003. Current HT use remained stable (range, 38%-46%; trend P = 0.92) among the artificially postmenopausal women. CONCLUSIONS: Successive annual increases from 1994 through 2001 in the prevalence of current HT use by postmenopausal women living in Geneva were dramatically reversed to the level in 1994 just after the results of the WHI trial were published, but only for naturally postmenopausal women with an intact uterus. Approximately one in three of the latter women who stopped using HT may also have lost its beneficial effects on bone health.     

HRT and gynaecologic cancer after WHI: old stuff or new doubts?

Previous studies had shown that there is little concern about endometrial cancer risk with hormone replacement therapy (HRT), whereas the risk of ovarian cancer is still debated. A new paper based on the women's health initiative (WHI) study devoted to gynaecologic cancers has been published in the October 2003 issue of JAMA, leading to the conclusion that also for endometrial and ovarian cancer risk, as the first WHI publication did for breast cancer risk, the previous large studies have been confirmed. About follow-up the authors conclude that, "The increased burden of endometrial biopsies required to assess vaginal bleeding further limits the acceptability of this regimen." These conclusions deserve a thorough analysis and must be read in the light of the burden of available epidemiological and clinical data and of recommended clinical practice. In the WHI trial the use of continuous combined HRT has resulted in a considerable increase of both imaging and invasive exams, to investigate women with bleeding or spotting, but the findings of these exams have been invariably negative. As far as, all published studies agree on the fact that continuous combined HRT either has no effect or significantly reduces the risk of both endometrial hyperplasia and cancer, there should be no reason to close-watching endometrium of women using this regimen with a different strategy from that employed on any healthy woman.     

Combined conjugated esterified estrogen plus methyltestosterone supplementation and risk of breast cancer in postmenopausal women

Objectives

Testosterone supplementation is being prescribed increasingly to treat symptoms of hormone deficiency in pre- and postmenopausal women; however, studies of the association of testosterone therapy, alone or in combination with estrogen, with risk of breast cancer are limited. The current study assessed the association of combination conjugated esterified estrogen and methyltestosterone (CEE + MT) use and breast cancer risk in postmenopausal women in the Women's Health Initiative (WHI).

Study design

At Year 3 of follow-up, women in the WHI observational study (N = 71,964) provided information on CEE + MT use in the past two years, duration of use, and the brand name of the product. In addition, in each of years 4–8, women were asked whether they had used CEE + MT in the previous year. After 10 years of follow-up, 2832 incident breast cancer cases were identified. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) for the association of CEE + MT use (irrespective of use of other hormones) and of exclusive CEE + MT use in relation to breast cancer risk.

Results

Neither CEE + MT use nor exclusive use of CEE + MT was associated with risk: multivariable-adjusted HR 1.06, 95% CI 0.82–1.36 and HR 1.22, 95% CI 0.78–1.92, respectively. Among women with a natural menopause, the HR for exclusive use was 1.32 (95% CI 0.68–2.55). There was no indication of an association when repeated measures of CEE + MT use were included in a time-dependent covariates analysis.

Conclusion

The present study, the largest prospective study to date, did not show a significant association of CEE + MT supplementation and risk of breast cancer.     

Breast cancer risk with postmenopausal hormonal treatment

This review was designed to determine from the best evidence whether there is an association between postmenopausal hormonal treatment and breast cancer risk. Also, if there is an association, does it vary according to duration and cessation of use, type of regimen, type of hormonal product or route of administration; whether there is a differential effect on risk of lobular and ductal cancer; and whether hormone treatment is associated with breast cancers that have better prognostic factors? Data sources for the review included Medline, the Cochrane Database of Systematic Reviews (Cochrane Library, 2005) and reference lists in the identified citations. Eligible citations addressed invasive breast cancer risk among postmenopausal women and involved use of the estrogen products with or without progestin that are used as treatment for menopausal symptoms. Abstracted data were demographic groupings, categories of hormone use, categories of breast cancer, two-by-two tables of exposure and outcome and adjusted odds ratios, relative risks (RRs) or hazard rates. Average estimates of risk were weighted by the inverse variance method, or if heterogeneous, using a random effects model. The average risk of invasive breast cancer with estrogen use was 0.79 [95% confidence interval (95% CI) = 0.61-1.02] in four randomized trials involving 12 643 women. The average breast cancer risk with estrogen-progestin use was 1.24 (95% CI = 1.03-1.50) in four randomized trials involving 19 756 women. The average risks reported in recent epidemiological studies were higher: 1.18 (95% CI = 1.01-1.38) with current use of estrogen alone and 1.70 (95% CI = 1.36-2.17) with current use of estrogen-progestin. The association of breast cancer with current use was stronger than the association with ever use, which includes past use. For past use, the increased breast cancer risk diminished soon after discontinuing hormones and normalized within 5 years. Reasonably adequate data do not show that breast cancer risk varies significantly with different types of estrogen or progestin preparations, lower dosages or different routes of administration, although there is a small difference between sequential and continuous progestin regimens. Epidemiological studies indicate that estrogen-progestin use increases risk of lobular more than ductal breast cancer, but the number of studies and cases of lobular cancer remains limited. Among important prognostic factors, the stage and grade in breast cancers associated with hormone use [corrected] do not differ significantly from those in non-users, but breast cancers in estrogen-progestin users are significantly more likely to be estrogen receptor (ER) positive. In conclusion, valid evidence from randomized controlled trials (RCTs) indicates that breast cancer risk is increased with estrogen-progestin use more than with estrogen alone. Epidemiological evidence involving more than 1.5 million women agrees broadly with the trial findings. Although new studies are unlikely to alter the key findings about overall breast cancer risk, research is needed, however, to determine the role of progestin, evaluate the risk of lobular cancer and delineate effects of hormone use on receptor presence, prognosis and mortality in breast cancer.     

WHI risks: Any relevance to menopause management?

Two randomised controlled trials of hormone therapy (HT) were conducted within the US Women's Health Initiative. Both were chronic disease prevention trials, undertaken to determine whether HT reduced cardiovascular risk and increased breast cancer risk. Because the majority of subjects in both trials were asymptomatic and many years postmenopausal, and because substantial numbers had received HT prior to recruitment to the trials, care must be taken in drawing conclusions that the observed risks are applicable to women for whom HT is conventionally prescribed. Each of the reported risks must be examined critically to determine its likely applicability to symptomatic women treated for two to three years to relieve symptoms, but sometimes for substantially longer periods. Further, the risks reported in each of the two trials must be considered separately. Concerning cardiovascular disease, many subjects in the trials were at increased baseline risk because of their age, body mass index, smoking status, blood pressure and years since menopause, in contrast to the usual situation for symptomatic perimenopausal women. Therefore the reported overall cardiovascular risks in WHI, in both treatment arms, should be regarded as irrelevant to menopause management. In contrast, breast cancer risk is relevant, providing that proper note is taken of the fact that there was no increased risk after five years of combined hormone therapy in non-prior HT users and there was a tendency to a decreased risk in oestrogen only treated individuals. Other risks are analysed similarly.     

The EMAS 2006/2007 update on clinical recommendations on postmenopausal hormone therapy

This new statement from EMAS presents the findings reported in recent publications from both WHI trials. In general, the reports do not necessitate a revision of the current EMAS advice. They provide further insight into the ongoing controversy around the possibility that hormone therapy (HT) in the form of estrogen (E) alone or estrogen-progestogen (EP) may influence risk of breast cancer differently. They confirm that the increase of breast cancer diagnosis under EP is only significant after a cumulative use of more than 5 years but suggest that there is no increased risk by E within 10 years.     

The incidence of breast cancer and changes in the use of hormone replacement therapy: A review of the evidence

Even though a link between hormone replacement therapy (HRT) and breast cancer has been well documented in the epidemiological literature since the 1980s, it was not until publication of the results of the Women's Health Initiative (WHI) study in 2002 and the Million Women Study in 2003 that women and doctors started reconsidering the use of HRT and sales of HRT started to drop. This paper evaluates the impact of the publication of these two landmark studies on the expected and observed changes in the incidence of breast cancer.Between 2001–2002 and 2005–2006, sharp and significant reductions in the incidence of breast cancer of up to 22% were reported in many US and European populations, temporally consistent with the drop in usage of HRT. Declines in the rates of breast cancer were strongest for 50–60-year-old women (those most likely to be current users of HRT), affected mainly ER+ and PR+ cancers (those most strongly associated with HRT use), and were largest among women with the highest pre-decline prevalence of HRT use and the sharpest decline in its use.A considerable amount of scientific evidence supports the hypothesis that the decline in the incidence of breast cancer is in large part attributable to the sudden drop in HRT use following publication of the WHI and Million Women studies. Nevertheless, the problem of how to advise women contemplating HRT use today remains. Medical relief will remain necessary for many women with menopausal complaints, and so new therapeutic options need to be explored.     

Hormone therapy and coronary heart disease in young women

OBJECTIVE: Because the Women's Health Initiative randomized controlled trial (WHI RCT) primarily studied older women, it is unresolved whether hormone therapy might prevent coronary heart disease in younger women. Given the similarity between our UK General Practice Research Database (GPRD) study of older women and the WHI RCT, the GPRD methodology was used to study a cohort of younger women. DESIGN: Women ages 50 to 55 years were investigated using data from the GPRD to simulate the WHI RCT in a manner similar to our initial study of older women. This study compared 30,102 unexposed and 20,654 exposed women treated with conjugated estrogens and norgestrel. RESULTS: Myocardial infarction was not altered significantly by hormone therapy (adjusted hazard ratio 0.91; 95% CI, 0.69-1.20). Stroke, venous thromboembolic events, breast cancer, and hip fracture were similar to both the GPRD study of older women and the WHI RCT. Although death was decreased in the total cohort, similar to older women, it was not altered significantly in a subset without missing covariate data. CONCLUSION: The similar results of the GPRD studies in younger and older women and between the GPRD and the WHI RCT suggest that hormone therapy does not prevent coronary heart disease in younger postmenopausal women. This study also demonstrates that investigation using a primary care electronic medical record database can expand the generalizability of findings from an RCT.     

Hormone use and patient concerns after the findings of the Women's Health Initiative

OBJECTIVE: To assess behaviors and concerns related to hormone therapy after the findings of the Women's Health Initiative (WHI). DESIGN: A survey was mailed to a random sample of 1,200 women identified through the pharmacy database as taking one of two estrogen + progestogen therapies (EPT) during the 6-month period before the publication of WHI findings. Questions included hormone use history, changes in usage, an assessment of symptoms, symptom changes, health behavior changes, use of alternative therapies, and demographics. RESULTS: The response rate was 70%, with women in their 60s and those receiving hormone therapy for 5 or more years were more likely to respond (P < 0.05). The majority had started hormones for symptom relief (69%) and expected to continue use. Many reported discontinuation (63%) or modifying their medication (18%). Half of these women stopped then restarted, the other half changed products. Women in their 50s were more likely to remain on hormones than older women (P < 0.01), and those taking ethinyl estradiol and norethindrone acetate were more likely to remain on their medication than those on conjugated estrogens (43% vs 29%, P < 0.01). Little change was reported in exercise and 19% increased their calcium intake. Patient concerns fell into five major categories: long-term effects, symptom control, breast cancer risk, bone health, and cognitive function. CONCLUSIONS: Women seem to be heeding the warnings about hormones but remain concerned about the potential long-term sequelae and symptom control. More research is needed to identify safer approaches to symptom relief and to address the concerns expressed.     

Hormone therapy and breast cancer: what factors modify the association?

OBJECTIVE: To determine factors that may modify the association between hormone therapy (HT) and breast cancer risk. DESIGN: Prospective cohort study (the Melbourne Collaborative Cohort Study) of 24,479 women aged 40 to 69 years. History of HT use was collected at baseline and 4 years later by questionnaire. By June 2002, 336 cases of breast cancer were diagnosed among 13,444 women postmenopausal at baseline. Association of breast cancer risk with history of HT use was analyzed using proportional hazards models. RESULTS: The hazard ratio (HR) for recent HT use (current or stopped within the last year) was elevated (HR 1.51; 95% CI, 1.16-1.98) but was not significantly increased for past HT users (HR 1.19; 95% CI, 0.86-1.64). Recent HT use was associated with better differentiated tumors but was not more likely to be associated with estrogen receptor-positive / progesterone receptor-positive tumors. There was little evidence of interactions between recent HT use and body mass index, alcohol intake, parity, and smoking, although the HR for recent HT use in categories of alcohol consumption was greatest in women consuming the most alcohol (HR 2.37; 95% CI, 1.45-3.88 for those consuming > or = 10 g/d versus HR 1.33; 95% CI, 0.85-2.08 for nondrinkers, P interaction = 0.32). CONCLUSIONS: The risk of breast cancer for recent users of HT in this Australian population is increased by approximately 50%. Our results suggest that any potential modifying effect of the association between HT and breast cancer risk by factors such as alcohol intake and body mass index is likely to be modest.     

Continuation of hormone replacement therapy in Slovenia: a prospective, randomized, controlled trial--1-year follow-up

OBJECTIVES: To evaluate the influence of educational intervention on the hormone replacement therapy (HRT) continuation rate in Slovenia after the publication of WHI results. METHODS: We enrolled 125 early postmenopausal women in a 12-month prospective, randomized, controlled, multicentric study in Slovenia. The study group women (n=62) attended educational lectures; the control group women (n=63) did not. Data were collected from three types of questionnaire: before starting HRT, at follow-up visits at 3, 6, 9 and 12 month, after the educational lecture (study group). The continuation rate was measured on the basis of women's self-reports. The results were analyzed according to the "intention-to-treat" principle. The Cox proportional hazard model was used for the final analysis. RESULTS: A gynecologist's suggestion, climacteric symptoms and quality of life were the prevailing reasons for starting HRT. The prevailing factors affecting continuation of HRT were: no or irregular previous OC use (hazard ratio 3.7), no educational lectures (hazard ratio 2.0) and climacteric disorders as the reason for start HRT (hazard ratio 2.1). In the women who discontinued HRT within the first 3 months, the fear of endometrial cancer, breast cancer and bleeding problems were statistically more significant than other factors (P=0.034). In the women who stopped HRT use within 6-12 months, the fear of breast and endometrial cancers increased substantially (P=0.002). CONCLUSIONS: Previous OC use and educational lectures on menopausal problems and HRT significantly improve the HRT continuation rate. The main reason for discontinuing HRT is fear of breast cancer, intensified by media.     

Influence of HRT on prognostic factors for breast cancer: a systematic review after the Women's Health Initiative trial

INTRODUCTION: Mortality due to breast cancer has been reported to be the same or even lower in HRT users than in non-users. This has been attributed to earlier diagnosis and to better prognosis. Nevertheless, more advanced disease in HRT users was reported recently by the Women's Health Initiative (WHI) study. The objective of this study was to assess, using a systematic review of current literature, whether the data of the WHI study are in contradiction to observational data. METHODS: We selected 25 studies, for which we evaluated the methodology, the characteristics of the studied populations, confounding breast cancer risk factors and prognostic indicators. RESULTS: The WHI study, showing a worsening of some prognostic parameters, is in contradiction to most published observational studies. Most observational studies are retrospective, not well matched and did not consider most confounding factors. Their methodology and selection criteria varied considerably and the number of patients was often small. No differences in the distributions of histology, grade or steroid receptors were observed in the WHI trial, while this was the case in some of the observational studies. Other parameters (S phase, protein Neu, Bcl-2 gene, protein p53 and E-cadherin, cathepsin D) were not reported in the WHI trial. CONCLUSIONS: In view of these data, the current clinical message to patients should be changed: one can no longer declare that breast cancers developed while using HRT are of better prognosis.     

Breast cancer incidence in postmenopausal women using testosterone in addition to usual hormone therapy

OBJECTIVE: There is now convincing evidence that usual hormone therapy for ovarian failure increases the risk for breast cancer. We have previously shown that ovarian androgens normally protect mammary epithelial cells from excessive estrogenic stimulation, and therefore we hypothesized that the addition of testosterone to usual hormone therapy might protect women from breast cancer. DESIGN: This was a retrospective, observational study that followed 508 postmenopausal women receiving testosterone in addition to usual hormone therapy in South Australia. Breast cancer status was ascertained by mammography at the initiation of testosterone treatment and biannually thereafter. The average age at the start of follow-up was 56.4 years, and the mean duration of follow-up was 5.8 years. Breast cancer incidence in this group was compared with that of untreated women and women using usual hormone therapy reported in the medical literature and to age-specific local population rates. RESULTS: There were seven cases of invasive breast cancer in this population of testosterone users, for an incidence of 238 per 100,000 woman-years. The rate for estrogen/progestin and testosterone users was 293 per 100,000 woman-years--substantially less than women receiving estrogen/pro-gestin in the Women's Health Initiative study (380 per 100,000 woman-years) or in the "Million Women" Study (521 per 100,000 woman-years). The breast cancer rate in our testosterone users was closest to that reported for hormone therapy never-users in the latter study (283 per 100,000 woman-years), and their age-standardized rate was the same as for the general population in South Australia. CONCLUSIONS: These observations suggest that the addition of testosterone to conventional hormone therapy for postmenopausal women does not increase and may indeed reduce the hormone therapy-associated breast cancer risk-thereby returning the incidence to the normal rates observed in the general, untreated population.     

Menopausal estrogens and breast cancer.

1891 women given conjugated estrogens for the menopause were followed for 12 years (mean) for incidence of breast cancer. Overall, 49 cases were observed; 39.1 were expected on the basis of rates in the general population (relative risk = 1.3, P = 0.06). The relative risk increased with follow-up duration, progressing to 2.0 after 15 years (13/6.6, P = 0.01). The excess risk after 10 years was not due simply to prolonged estrogen use, since there was no clear dose-response relation to accumulated years of use. However, higher risk accrued to women using higher-dose tablets and those taking the medication on an other than daily basis. In addition, after 10 years of follow-up observation, two factors related to low risk of breast cancer, multiparity and oophorectomy, were no longer so related. Finally, estrogen use was related to an especially high risk of breast cancer among women in whom benign disease developed after they had started the drug.     

Testosterone levels in relation to oral contraceptive use and the androgen receptor CAG and GGC length polymorphisms in healthy young women

BACKGROUND: The combined effect from the androgen receptor (AR) CAG and GGC length polymorphisms on testosterone levels has not been studied in young women. METHODS: Testosterone levels were measured in blood drawn on both menstrual cycle days 5-10 and 18-23 in 258 healthy women, aged < or =40 years, from high-risk breast cancer families. CAG and GGC length polymorphisms were analysed by PCR and fragment analyses. All women completed a questionnaire including information on oral contraceptive (OC) use and reproductive factors. RESULTS: OC users had lower median testosterone levels than non-users during cycle days 5-10 and 18-23 (P < or = 0.005 for both). The BRCA mutation status was associated neither with testosterone levels nor with CAG or GGC length polymorphism. The CAG length polymorphism was not associated with testosterone levels. The cumulative number of long GGC alleles (> or =17 repeats) was significantly associated with lower testosterone levels in OC users during cycle days 5-10 (P(trend) =0.014), but not during cycle days 18-23 or in non-users. The interaction between the GGC length polymorphism and OC status was highly significant during cycle days 5-10 (P = 0.002) and near-significant during days 18-23 (P = 0.07). Incident breast cancer was more common in women with two short GGC alleles (log-rank P = 0.003). CONCLUSION: The GGC repeat length was the only significant genetic factor modifying the testosterone levels in current OC users from high-risk families. Homozygosity for the short GGC allele may be linked to the increased risk of early-onset breast cancer after OC exposure in high-risk women.