Hormone replacement therapy and breast cancer risk in a nationally representative cohort

Modifiable risk factors in women at high risk of breast cancer: a systematic review

BACKGROUND

Modifiable risk factors (alcohol, smoking, obesity, hormone use, and physical activity) affect a woman's breast cancer (BC) risk. Whether these factors affect BC risk in women with inherited risk (family history, BRCA1/2 mutations, or familial cancer syndrome) remains unclear.

METHODS

This review included studies on modifiable risk factors for BC in women with inherited risk. Pre-determined eligibility criteria were used and relevant data were extracted.

RESULTS

The literature search resulted in 93 eligible studies. For women with family history, most studies indicated that modifiable risk factors had no association with BC and some indicated decreased (physical activity) or increased risk (hormonal contraception (HC)/menopausal hormone therapy (MHT), smoking, alcohol). For women with BRCA mutations, most studies reported no association between modifiable risk factors and BC; however, some observed increased (smoking, MHT/HC, body mass index (BMI)/weight) and decreased risk (alcohol, smoking, MHT/HC, BMI/weight, physical activity). However, measurements varied widely among studies, sample sizes were often small, and a limited number of studies existed.

CONCLUSIONS

An increasing number of women will recognize their underlying inherited BC risk and seek to modify that risk. Due to heterogeneity and limited power of existing studies, further studies are needed to better understand how modifiable risk factors influence BC risk in women with inherited risk.

Change in risk of breast cancer after receiving hormone replacement therapy by considering effect-modifiers: a systematic review and dose-response meta-analysis of prospective studies

We synthesize the current literatures and use the power of meta-analysis to examine trends on association between hormone replacement therapy (HRT) and the risk of breast cancer (BC). We performed a comprehensive literature search using PubMed, EMBASE, and Web of Science from their inception until Jan 2017. Prospective studies that provided adjusted risk estimates of HRT and BC risk were eligible. Categorical and dose-response meta-analyses followed the PRISMA were conducted using random effects model and restricted cubic spline model, respectively. Forty-seven publications from thirty-five unique studies were included, involving 3,898,376 of participants and 87,845 of BC cases. Compared with non-users, RR for current estrogen-only therapy (ET) users was 1.14 (95% confidence interval (CI) = 1.05–1.22), and for per year increases was 1.02 (95% CI = 1.02–1.02). Moreover, RR for current estrogen plus progestin therapy (EPT) users was 1.76, (95% CI = 1.56–1.96), and for per year increases was 1.08 (95% CI = 1.08–1.08). Dose-response analyses revealed 8–10 years’ onset peaks, and indicated residual increased BC risk remained after stopping use of ET regimen rather than for EPT. Effect-modifiers like BMI, duration of use, race/ethnicity, routes of administration were recognized. In Conclusions, current use of EP or EPT and ever use of tibolone are associated with an elevated risk of BC. Compared with slim HRT users and non-users, lower BC risks were found among overweight/obese HRT users and former EPT users, respectively. Both ET and EPT users are associated with higher risk of lobular BC than ductal BC, and more ER-positive than negative BC cases were detected among EPT users.

Risk factors of breast cancer: a systematic review and meta-analysis

The etiology of breast cancer might be explained by 2 mechanisms, namely, differentiation and proliferation of breast epithelial cells mediated by hormonal factors. We performed a systematic review and meta-analysis to update effects of risk factors for both mechanisms. MEDLINE and EMBASE were searched up to January 2011. Studies that assessed association between oral contraceptives (OC), hormonal replacement therapy (HRT), diabetes mellitus (DM), or breastfeeding and breast cancer were eligible. Relative risks with their confidence intervals (CIs) were extracted. A random-effects method was applied for pooling the effect size. The pooled odds ratios of OC, HRT, and DM were 1.10 (95% CI = 1.03-1.18), 1.23 (95% CI = 1.21-1.25), and 1.14 (95% CI = 1.09-1.19), respectively, whereas the pooled odds ratio of ever-breastfeeding was 0.72 (95% CI = 0.58-0.89). Our study suggests that OC, HRT, and DM might increase risks, whereas breastfeeding might lower risks of breast cancer.

Hormone replacement therapy: 1815.84 woman-years of follow-up main clinical events

BACKGROUND

One hundred and eighty-five women with a mean age of 50.71 (SD=5.58) years upon initiation of treatment were studied before, and during, treatment.

MATERIALS AND METHODS

Included in the profile of patients under study were family and personal histories, gynecological and breast examinations. Population age: a) <60 years old, 171 women (92.43%), and b) aged 60 years or older, 14 women (7.57%). Dosage comprised both 0.625 mg/daily orally of conjugated equine estrogens and 2.5 or 5 mg/daily of medroxy progesterone acetate. No further specific treatment was prescribed. Mean duration of treatment was 9.82 (SD=5.42) years for all women; 9.70 (SD=5.44) in the younger group. Follow-up comprised 1815.84 woman-years, for 5 years or over (76.75%) on 142 women. Fifty-two women (28.11%) dropped out.

RESULTS

No deaths occurred during treatment. Four cardiovascular events (2.16%) were reported. No spontaneous bone fracture was documented. Nonetheless, there were 12 bone fractures of traumatic origin (6.48%), none of them hip fractures. Five breast cancers were observed. Likewise, one diagnosis of breast cancer for every 37 treated women from our series was evidenced. There were 117 women (63.24%) without any events.

CONCLUSION

A higher risk of breast cancer or of serious cardiovascular events cannot be inferred from statistical analysis of 5 years or more of treatment.

Post-menopausal hormone use and albuminuria

BACKGROUND

Higher levels of urinary albumin excretion predict future hypertension and chronic kidney disease. Post-menopausal hormone use may influence the renin-angiotensin system and renal endothelial function, impacting albumin excretion. The association between post-menopausal hormone use and albuminuria is not well defined.

METHODS

We explored the cross-sectional association between duration of PMH use and albuminuria in 2445 post-menopausal, non-diabetic women from the Nurses' Health Study. Women were categorized as hormone non-users, past users or current users grouped by 3-year intervals of duration of use, from < or =3 years to >15 years. The outcome was the top decile of urine albumin/creatinine ratio (ACR). Multivariate logistic regression was used to assess the association between duration of PMH use and risk of being in the top decile.

RESULTS

The mean age was 66.8 years, and 57% were currently using PMH. The median ACR was 2.9 mg/g, and the 90th percentile was 9.2 mg/g. Compared with women with no history of PMH use, the odds ratio for being in the top ACR decile was lower for women with use of >6-9 years, >9-12 years, >12-15 years and >15 years, but there was no dose-response. The overall odds ratio was 0.55 (95% CI: 0.39-0.77) among women with >6 years of current PMH use compared with non-users. Current hormone use of shorter duration and past hormone use were not associated with albumin excretion.

CONCLUSIONS

Current PMH use of >6 years is associated with a lower urinary ACR in non-diabetic women.

The benefits of oestrogen following menopause: why hormone replacement therapy should be offered to postmenopausal women

Recently, two major epidemiological studies found that hormone replacement therapy (HRT) in postmenopausal women increased the risk of breast cancer. One of the studies also found that HRT increased the risk of cardiovascular disease and thrombosis. As a consequence, women were advised to cease this therapy. However, detailed analysis of these studies suggests that the conclusions may be erroneous. Other studies suggest that the timing of initiation of HRT for healthy women is critical to achieving a beneficial outcome. When begun within 5 years of menopause in healthy women, oestrogen-based HRT results in far greater benefits than adverse outcomes. There is substantial objective evidence that the benefits of HRT include: Reduced distressing symptoms of menopause. Reduced risk of osteoporotic fractures, dementia and colorectal cancer. Improved wellbeing, quality of life; improved vaginal epithelium, sexual enjoyment and bladder capacity. Improved cardiovascular system, with reduced myocardial ischaemia and cardiovascular-related death. Increased longevity. The adverse effects of HRT include: Oral HRT doubles the risk of thromboembolism. HRT promotes growth of pre-existing breast cancer.

Estimating the effect of current, previous and never use of drugs in studies based on prescription registries

PURPOSE

Many studies which investigate the effect of drugs categorize the exposure variable into never, current, and previous use of the study drug. When prescription registries are used to make this categorization, the exposure variable possibly gets misclassified since the registries do not carry any information on the time of discontinuation of treatment.In this study, we investigated the amount of misclassification of exposure (never, current, previous use) to hormone therapy (HT) when the exposure variable was based on prescription data. Furthermore, we evaluated the significance of this misclassification for analysing the risk of breast cancer.

MATERIALS AND METHODS

Prescription data were obtained from Danish Registry of Medicinal Products Statistics and we applied various methods to approximate treatment episodes. We analysed the duration of HT episodes to study the ability to identify discontinuation of therapy from prescription data. Furthermore, we compared to results based on self-reported duration of HT from the Danish Nurse Cohort.Finally, we analysed the effect of HT exposure on time to breast cancer for the different prescription based exposure variables as well as for self-reported HT use.

RESULTS

The results of time to discontinuation varied strongly across the different HT assessments. However, misclassification of HT exposure at baseline was limited and hence analysis of the effect of HT on time to breast cancer showed stability across the different exposure assessments with Hazard Ratios ranging from 1.68 to 1.78 for current use compared to never use.

CONCLUSIONS

The findings suggest that it is possible to estimate the effect of never, current and previous use of HT on breast cancer using prescription data.

The origin of breast cancer

Biological studies confirm that breast cancer is the result of an accumulation of a large number of individual genetic mutations that collectively alter elements of the complex internal signaling system of a cell. These aberrant genetic alterations, when assembled in a single breast cell, disrupt the control system to the extent that the cell functions autonomously in an erratic and irregular manner. Continual replication of a corrupted cell results in the formation of a colony of abnormal cells that may accumulate other aberrant mutations to eventually initiate cancer. What causes these mutations has been the topic of debate over a number of years, but because so many genetic alterations are involved, it is now conceded that one single factor could not possibly initiate all the changes. One plausible explanation involves a sequence of random, accidental, spontaneous mutations during normal stem cell replication. Some of these mutations may be an advantage to the host and their creation advances the functional ability of the breast, whereas abnormal mutations are usually deleted after activation of the complex apoptotic and inhibitory signaling system. When the defense system is corrupted, cells carrying the abnormal genes are able to avoid elimination, eventually passing abnormal mutations from one cell generation to the next. Accumulation of genetic abnormalities, over time, leads to development of a colony of cells that are pathologically abnormal. Biological studies confirm that cultured stem cells are capable of undergoing spontaneous mutations during mitosis, that sex hormones control the rate of mitosis, and that estrogen and progesterone therefore influence the rate that mutations occur. Accumulating the large number of mutations that eventually cause breast cancer can be achieved only if chromosomal abnormalities are carried from one generation of cells to the next to combine with genetic alterations generated spontaneously during stem cell mitosis.

Incidences of breast cancer throughout long-term hormone replacement therapy

OBJECTIVE

To report the main incidences related to diagnosis of breast cancer in a randomly selected cohort population of women treated with conjugated equine estrogens (CEE), always in conjunction with the opposed progestin, medroxy progesterone acetate (MPA) throughout prolonged oral administration.

MATERIAL AND METHODS

One hundred and seventy-eight women were subsequently studied before and during the treatment (cohort study). The profile of studied patients included family and personal histories, gynecological and breast examinations, basal hormonal levels, bone mass concentration (BMC) as well as total cholesterol levels and their fractions. The usual clinical cut off age was applied at the beginning of treatment according to following criteria: (a) women less than 60 years old (91.60%), and (b) women more than 60 years old (8.40%), by assuming that a primary protective effect of HRT might be lost or diminished after surpassing this age threshold. In all the treated women were thoroughly advised about the importance of diet, exercises and self-determination. Both oral CEE 0.625 mg/daily and either 2.5 mg/daily or 5 mg/daily of MPA were administrated in accordance with The American Fertility Society Meeting after 1995 (Seattle) recommendations, following two patterns: (1) cycles or perimenopausal women: from days 1 to 25, and (2) postmenopausal women, from Monday to Friday. No other specific treatments were prescribed. Statistical analysis was performed by using SPSS 12.0 and G-stat 2.0.

RESULTS

Evaluation of basal hormonal levels, BMC, cholesterol levels and their fractions were not included in the current study. Data from the statistical analysis of 178 treated women were as follow: mean duration of treatment 8.06 years for all women; in the younger age group 7.97, and in the older age group 9.04. Total of 1405.5 woman-years of follow-up, 119 women for more than 5 years (66.85%), and more times (68.18%) with CEE plus MPA 5 mg/daily regime. Dropouts occurred in 34 women (19.10%). Main incidences: no deaths occurred during the treatment. Four cardiovascular events (2.24%) were reported. No spontaneous bone fractures were documented. Nonetheless, there were 11 bone fractures of traumatic origin (6.17%), none of them hip fractures. Four breast cancer. Likewise, one diagnosis of breast cancer in each of 45 treated women from our series was evidenced. One hundred and twenty-one women (67.97%) without incidences.

COMMENTS

In our cohort study advices on diet, exercises and self-determination were reinforced for 1405.5 woman-years of follow-up. Combined CEE plus MPA for more than 5 years are no more risk related to breast cancer and cardiovascular events versus shorter treatments. Long-term CEE plus MPA were well tolerated and we did not find statistical evidence which would allow deducing higher rates of morbidity in those entities. Likewise, no deaths were document during the treatments.

Hormone therapy after the Women's Health Initiative: a qualitative study

Background

Publication of results from the Women's Health Initiative study in July 2002 was a landmark event in biomedical science related to postmenopausal women. The purpose of this study was to describe the impact of new hormone therapy recommendations on patients' attitudes and decision-making in a primary care practice.

Methods

A questionnaire including structured and open-ended questions was administered in a family practice office waiting room from August through October 2003. Rationale for taking or not taking hormone therapy was specifically sought. Women 50–70 years old attending for office visits were invited to participate. Data were analyzed qualitatively and with descriptive statistics. Chart review provided medication use rates for the entire practice cohort of which the sample was a subset.

Results

Respondents (n = 127) were predominantly white and well educated, and were taking hormone therapy at a higher rate (38%) than the overall rate (26%) for women of the same age range in this practice. Belief patterns about hormone therapy were, in order of frequency, 'use is risky', 'vindication or prior beliefs', 'benefit to me outweighs risk', and 'unaware of new recommendations'. Twenty-eight out of 78 women continued hormones use after July 2002. Of 50 women who initially stopped hormone therapy after July 2002, 12 resumed use. Women who had stopped hormone therapy were a highly symptomatic group. Responses with emotional overtones such as worry, confusion, anger, and grief were common.

Conclusion

Strategies for decision support about hormone therapy should explicitly take into account women's preferences about symptom relief and the trade-offs among relevant risks. Some women may need emotional support during transitions in hormone therapy use.

Menopausal hormone therapy and risk of breast cancer: a meta-analysis of epidemiological studies and randomized controlled trials

We conducted meta-analyses to assess the impact of menopausal hormone therapy (MHT) on the risk of incident invasive breast cancer (BC) in cohort studies (CS), case-control studies (CCS) and randomized controlled trials (RCTs) published 1989-2004. We used published data providing information upon unopposed estrogen therapy (ET), estrogen-progestin therapy (EPT) or all MHT combined. Major outcomes were MHT-associated overall risk of BC and change of risk per year used. There is a linear increase of overall risk by midterm year of case ascertainment based upon data of all study types for MHT and to a larger extent for EPT, not for ET. Effects are larger in CS than in CCS. Meta-analyses stratified by <1992 versus > or =1992 as midterm year of case ascertainment indicate larger summary risks for the latter period for all MHT analysed, in particular for EPT. Annual increases in BC risk for EPT across study types are 0-9%, for ET 0-3%. In conclusion, there is evidence that relative risks for BC risks by MHT, in particular EPT, have been increasing in recent years. Given the widespread use of MHT, and often long duration, more detailed knowledge about differential BC risks of both estrogens and progestins are necessary to minimize BC risk in symptomatic women who consider MHT.

The impact of the Women's Health Initiative on discontinuation of postmenopausal hormone therapy: the Minnesota Heart Survey (2000-2002)

BACKGROUND

The Women's Health Initiative (WHI) Data Safety and Monitoring Board terminated the trial arm of the estrogen plus progestin combined hormone therapy early after observing an excess of harm relative to benefit of this therapy.

METHODS

To learn how postmenopausal hormone therapy (PMT) use in a community setting was affected by the WHI results, we resurveyed current users of PMT in August 2002 to January 2003 after publication of the WHI findings from our Minnesota Heart Survey (MHS) cohort (2000-2002), a cross-sectional epidemiological survey in the Minneapolis-St. Paul, Minnesota, area. We evaluated women's interpretation of the WHI results, reports of their physicians' recommendations, and the impact of these on PMT use in this group.

RESULTS

We obtained an excellent response rate (97.9%, 185 of 189). Almost a third of women with an intact uterus but few women with a hysterectomy discontinued their PMT regimen within the first 6 months after the WHI research results were released. The majority of women in our study consulted their physician about whether to discontinue PMT. Women in the intact uterus group who started their PMT regimen for menopausal symptoms were less likely to discontinue PMT. Of women who continued their PMT regimen, the majority cited relief of menopausal symptoms or physician recommendation for continuation of PMT or both. Almost a third of the women interviewed reported being confused, worried, or nervous about the media reports of the WHI results.

CONCLUSIONS

These results suggest effective dissemination of WHI information by the media and physicians and significant changes in patterns of PMT use in the community.

Hormone Replacement Therapy and Lung Cancer Risk

PURPOSE

To date, there are few published data regarding the use of hormone replacement therapy (HRT) and lung cancer risk. Therefore, we analyzed data regarding HRT use from a large case-control study designed to study genetic susceptibility to lung cancer to determine whether HRT affected risk of lung cancer.

EXPERIMENTAL DESIGN

In a secondary analysis, we compared self-reported HRT use among 499 women with lung cancer and 519 healthy age-matched controls.

RESULTS

HRT use was associated with an overall reduced risk of 34% [odds ratio (OR), 0.66; 95% confidence interval (CI), 0.51-0.89] of lung cancer, after adjusting for age, ethnicity, smoking status, education, body mass index, and menopausal status. The use of estrogen replacement therapy alone was associated with a 35% reduction in lung cancer risk (OR, 0.65; 95% CI, 0.47-0.89) and the use of combination therapy (estrogen and progestin) was associated with a 39% reduction in lung cancer risk (OR, 0.61; 95% CI, 0.40-0.92). HRT use was also associated with a statistically significantly reduced risk of lung cancer in current smokers (OR, 0.59; 95% CI, 0.38-0.92), but the risk estimates were not statistically significant in never (OR, 0.72; 95% CI, 0.37-1.40) or former smokers (OR, 0.73; 95% CI, 0.46-1.15). In addition, as the cigarette pack-years increased among ever smokers, the protective effect diminished, so that light smokers appeared to benefit the most from HRT use. Decreased lung cancer risks were also evident when the data were stratified by age, ethnicity, and body mass index. The joint effects of HRT use and mutagen sensitivity suggest that HRT use modifies lung cancer risk for genetically susceptible women. HRT use was also associated with a lower risk of death and improved survival compared with the women not taking HRT. To provide a possible biological mechanism to explain our findings, we compared plasma levels of insulin-like growth factor I in users and nonusers, and demonstrated that HRT use was associated with statistically significantly lower insulin-like growth factor I levels for both cases and controls compared with non-HRT users.

CONCLUSIONS

These data suggest an association of HRT use with a decrease in lung cancer risk. However, there are several limitations to this secondary analysis, requiring that the data be viewed with caution, and confirmation is required in well-designed hypothesis driven studies. The biological role of HRT in lung cancer remains understudied, and only extensive research can yield new insights into the mechanisms underlying a protective effect of HRT for lung cancer.

Breast cancer and hormonal replacement therapy

Understanding the association between hormone replacement therapy (HRT), the diagnosis of breast cancer, and the clinical outcome of women who develop breast cancer in the setting of HRT continue to present important challenges for health professionals and the public. The general impression in the medical community is that breast cancer is diagnosed more frequently after prolonged HRT; however, whether a causative relationship exists between HRT and breast cancer remains uncertain. Despite the increase in breast cancer diagnosis, clinical outcome of the disease appears favorable for women who develop breast cancer after HRT; HRT users tend to present with more localized tumors that exhibit favorable histology, and overall death from breast cancer appears reduced. The history of breast cancer constitutes a contraindication for HRT as a general rule, based on the concern that HRT may activate dormant cancer cells. Direct evidence for this practice is very limited; available studies are small and mostly retrospective, but do not indicate an adverse effect of HRT on breast cancer recurrence. In reaching a clinical decision regarding HRT, the expected benefits (largely improvement of menopausal symptoms) must be weighed against the potential risks of HRT (especially breast cancer) for each individual woman.

Mortality from breast carcinoma among US women: the role and implications of socio-economics, heterogeneous insurance, screening mammography, and geography

Despite rapid advances in medicine and beneficial lifestyle changes, the incidence and mortality rate of gynecologic carcinoma remains high worldwide. This paper presents the econometric model findings of the major drivers of breast cancer mortality among US women. The results have implications for public health policy formulation on disease incidence and the drivers of mortality risks. The research methodology is a fixed-effects GLS regression model of breast cancer mortality in US females age 25 and above, using 1990-1997 time-series data pooled across 50 US states and DC. The covariates are age, years schooled, family income, 'screening' mammography, insurance coverage types, race, and US census region. The regressions have strong explanatory powers. Finding education and income to be significantly and positively correlated with mortality supports the 'life in the fast lanes' hypothesis of Phelps. The policy of raising a woman's education at a given income appears more beneficial than raising her income at a given education level. The relatively higher mortality rate for Blacks suggests implementing culturally appropriate set of disease prevention and health promotion programs and policies. Mortality differs across insurance types with Medicaid the worst suggesting need for program reform. Mortality is greater for women ages 25-44 years, females 40-49 years who have had screening mammography, smokers, and residents of some US states. These findings suggest imposing more effective tobacco use control policies (e.g., imposing a special tobacco tax on adult smokers), creating a more tractable screening mammography surveillance system, and designing region-specific programs to cut breast cancer mortality risks.

Progestins and breast cancer

The relationship between the use of menopausal hormone therapy (ERT, unopposed estrogen therapy; HRT, combined estrogen and progestin therapy) and the development of breast cancer remains controversial. Mechanistic studies examining progestins in human breast cancer cell lines have demonstrated a biphasic cellular response to progesterone; initial exposure to hormone results in a proliferative burst with sustained exposure resulting in growth inhibition. To date, there is no definitive evidence that progestins act in the pathogenesis of breast cancer. Epidemiologic studies have produced inconsistent results, and data from randomized, placebo-controlled trials are limited. Although recent results from the continuous combined therapy arm of the Women's Health Initiative trial showed a small increase in the risk of invasive breast cancer in women on therapy for 5 years or more, a clear consensus regarding the relationship between HRT and breast cancer risk cannot yet be drawn from existing data. Studies have consistently documented that HRT use is associated with improved mortality and survival rates for women with breast cancer. Large-scale, randomized studies on different progestin regimens are needed to critically assess the effect of progestin on breast cancer.

The medicalization of menopause: critique and consequences

Menopause is in the process of becoming medicalized. Midlife and older women are being told that natural menopause is actually a deficiency condition requiring replacement hormones to maintain health and increase longevity. The three major diseases that are being linked with the lower estrogen levels of midlife and older women are heart disease, osteoporosis and, most recently, Alzheimer's disease. Primary prevention of these diseases is the rationale used for urging healthy women to take long-term hormones. Although there have been many challenges to these links and warnings against the widespread use of hormones, they have been either ignored or trivialized. In this article, the author examines mortality and morbidity statistics across and within nations and over time, critiques the major arguments used to support the notion that menopause places women at an increased risk of disease and that exogenous hormones reduce this risk, and discusses the adverse consequences of defining all midlife and older women as hormonally deficient and in need of medical intervention.

[Hormone therapy and breast cancer: a review]

PURPOSE

Tamoxifen as adjuvant hormonal therapy after hormonosensitive-breast cancer surgery is well established nowadays, as well as its efficacy in first-line therapy of advanced hormonosensitive breast cancers. Research of drugs which could be effective, with little toxicity, and having a positive impact on cardiovascular disease or bone is an important issue.

CURRENT KNOWLEDGE AND KEY POINTS

New drugs are in development or will soon be on the market to permit second or third lines of treatment with respect to effectiveness and quality of life, such as new anti-estrogens or selective estrogen receptors modulators or aromatase inhibitors. Their principal characteristics are reviewed through recent data.

FUTURE PROSPECTS AND PROJECTS

Prevention of breast cancer is a pertinent question and major publications are presented. Finally, the controversy about the possible reintroduction of replacement hormonal therapy after breast cancer will be questioned through trials.

Hormone replacement therapy and cancer risk

The advantages and disadvantages of hormone replacement therapy (HRT) have been debated nearly as long as the treatment has been in use, especially the relationship between HRT and risk of cancer development. It is hoped that recently published studies will shed more light on this complex issue. Several large population studies suggest that there may be a small but increased risk of developing breast cancer in HRT users, especially in estrogen and progesterone users. This risk appears most pronounced after 5 years of HRT use. Endometrial cancer, which has long been associated with unopposed estrogen use, can be successfully prevented with the addition of progestins to the HRT regimen, provided it is given for at least 10 days each month. Estrogen replacement therapy has also been shown to significantly reduce the risk for colon cancer but not rectal cancers. Finally, a large prospective study has linked HRT with an increase in ovarian cancer mortality.

A population-based cohort study of HRT use and breast cancer in southern Sweden

The overall tumour incidence and breast cancer incidence related to hormone replacement therapy (HRT) were followed in a population-based cohort of 29 508 women, aged 25-65 when interviewed in 1990-92. By the end of the follow up in December 1999, there were 226 611 person-years of observation. A total of 1145 malignant tumours were recorded (expected 1166.6; SIR = 0.98, 95% CI 0.93-1.04). There was a small excess of breast cancer with 434 observed and 387.69 expected (SIR = 1.12, 95% CI 1.02-1.23). Among about 3 663 ever users of HRT, there was no increase in overall tumour incidence (SIR = 0.98, 95% CI 0.86-1.12) but a significant excess of breast cancer (SIR = 1.35, 95% CI 1.09-1.64) compared with never users (SIR = 1.07, 95% CI 0.96-1.19). Breast cancer increased with increasing duration of use and for 48-120 months use the SIR was 1.92 (95% CI 1.32-2.70). There was no significant interaction with family history of breast cancer although an independent additive effect was suggested between HRT use and family history. In a Cox regression model time to breast cancer in relation to duration of HRT use was analysed adjusting for age at menarche, age at menopause, age at first full term pregnancy, parity and age at diagnosis. A significantly higher risk was seen for longer duration of HRT use compared with never users. No increased risk is seen in women beyond 5 years after stopping HRT. There was no interaction between previous use of oral contraceptives and later HRT use.

Media coverage of women's health issues: is there a bias in the reporting of an association between hormone replacement therapy and breast cancer?

Media coverage of scientific research plays a major role in shaping public opinion and influencing medical practice. When an association is controversial, such as with hormone replacement therapy (HRT) and breast cancer, it is important that a balanced picture of the scientific literature be reported. The objective of this study was to assess whether scientific publications that do and do not support an HRT/breast cancer association were cited in the media in proportions similar to those with which they appear in the scientific literature. Scientific publications reporting on the HRT/breast cancer association published from January 1, 1995, to June 30, 2000, were identified through a systematic Medline search. Media reports from newspapers, magazines, television, and radio that reported on HRT and breast cancer were retrieved from an online database. Investigators independently recorded characteristics of the scientific publications and media reports. A total of 32 scientific publications were identified: 20 (62.5%) concluded there was an increased risk of breast cancer associated with HRT (positive publications), and 12 (37.5%) concluded there was no evidence for an association (null publications). Nearly half (47%) of the scientific publications were not cited by the media. There were 203 media citations of scientific publications: 82% were of positive publications and 18% were of null publications, representing a significant excess of citations of positive publications (p < 0.01). Media coverage of this controversial issue is based on a limited sample of the scientific publications. Moreover, the excess of media citations for positive scientific publications suggests a bias against null scientific publications.