Cause or prevention of breast cancer with estrogens: analysis from tumor biologic data, growth kinetic model and Women's Health Initiative study

Randomized trials of estrogen-alone and breast cancer incidence: a meta-analysis

PURPOSE

In the Women's Health initiative (WHI) randomized clinical trial, conjugated equine estrogen (CEE)-alone significantly reduced breast cancer incidence (P = 0.005). As cohort studies had opposite findings, other randomized clinical trials were identified to conduct a meta-analysis of estrogen-alone influence on breast cancer incidence.

METHODS

We conducted literature searches on randomized trials and: estrogen, hormone therapy, and breast cancer, and searches from a prior meta-analysis and reviews. In the meta-analysis, for trials with published relative risks (RR) and 95% confidence intervals (CI), each log-RR was multiplied by weight = 1/V, where V = variance of the log-RR, and V was derived from the corresponding 95% CI. For smaller trials with only breast cancer numbers, the corresponding log-RR = (O - E)/weight, where O is the observed case number in the oestrogen-alone group and E the corresponding expected case number, E = nP.

RESULTS

Findings from 10 randomized trials included 14,282 participants and 591 incident breast cancers. In 9 smaller trials, with 1.2% (24 of 2029) vs 2.2% (33 of 1514) randomized to estrogen-alone vs placebo (open label, one trial) (RR 0.65 95% CI 0.38-1.11, P = 0.12). For 5 trials evaluating estradiol formulations, RR = 0.63 95% CI 0.34-1.16, P = 0.15. Combining the 10 trials, 3.6% (262 of 7339) vs 4.7% (329 of 6943) randomized to estrogen-alone vs placebo (overall RR 0.77 95% CI 0.65-0.91, P = 0.002).

CONCLUSION

The totality of randomized clinical trial evidence supports a conclusion that estrogen-alone use significantly reduces breast cancer incidence.

Why does hormonal contraception and menopausal hormonal treatment have such a small effect on breast cancer risk?

Oestrogen is considered by many to be a major cause of breast cancer, and yet hormonal contraception and menopausal hormonal therapy have a paradoxically small effect on breast cancer risk. Also, in the oestrogen-only arm of the Women's Health Initiative, subjects given oestrogen had a reduced risk of breast cancer compared to controls. Initiation of breast cancer likely begins early in life, in the long-lived ER-PR- breast stem cell. The main mitogen of ER+PR+ breast cancers is oestrogen derived from local breast fat and the tumour itself, rather than circulating oestrogens. Progesterone is relatively breast neutral, but progestins in the laboratory have been shown to expand malignant breast stem cell number.

Menopausal Hormone Therapy and the Breast: A Review of Clinical Studies

Background

Women in the peri- or postmenopause can experience symptoms related to the gradual degradation of ovarian function. Hormone replacement therapy (HRT) is the most effective therapy to treat common menopausal symptoms such as hot flashes and vaginal discomfort. However, safety concerns have been raised revolving, among others also, around the risk of breast cancer.

Methods

This article is based on a selective literature search for relevant studies regarding HRT use and the risk of breast cancer in the general population or BRCA carriers, the risk of breast cancer recurrence, or the risk of breast cancer in situ.

Summary

HRT can lead to little or no increase in breast cancer risk. The risk depends on the duration and composition of the HRT and decreases after stopping the treatment. Data assessing the oncological safety of HRT after breast cancer are inconsistent. According to current knowledge, HRT is fundamentally contraindicated after breast cancer but can be individually considered after a risk-benefit assessment and when nonhormonal therapies have failed. The same applies to HRT after DCIS, which should not be routinely offered but nonetheless can be considered in individual cases. HRT can be offered up to the age of natural menopause for BRCA mutation carriers who are undergoing risk-reducing bilateral salpingo-oophorectomy and do not have a personal history of breast cancer, but is contraindicated in BRCA mutation carriers who have already had breast cancer.

The Women's Health Initiative randomized trials of menopausal hormone therapy and breast cancer: findings in context

IMPORTANCE AND OBJECTIVE

The menopausal hormone therapy (MHT) association with breast cancer has been controversial for more than 40 years. Most recently, findings from cohort studies have been discordant compared with those from the Women's Health Initiative (WHI) randomized trials. In cohort studies, both estrogen therapy and estrogen plus progestin were associated with higher breast cancer incidence. In contrast, in the WHI randomized trials, findings for estrogen plus progestin are concordant with cohort study reports, whereas estrogen therapy significantly reduced breast cancer incidence. In addition, concerns have been raised regarding the WHI findings from both trials. In this report, we briefly summarize findings for MHT on breast cancer from cohort studies and the WHI randomized trials. The report focus is addressing, point-by-point, concerns raised regarding the WHI findings.

METHODS

For cohort studies, we relied on the latest findings from (1) the meta-analysis of the Collaborative Group on Hormonal Factors in Breast Cancer and (2) the Million Women's Study. To identify commentaries and editorials, "Menopause" and "Climacteric" were searched from 2002 to present; PubMed and Google Scholar were searched for commentaries, editorials, and breast cancer, MHT, estrogen, conjugated equine estrogen, estradiol, "hormone replacement therapy," and "HRT."

DISCUSSION AND CONCLUSIONS

Thirty commentaries challenging WHI findings were identified. All were reviewed, and issues needing response were identified. Findings from the meta-analysis from the Collaborative Group on Hormonal Factors in Breast Cancer and the Million Women Study were summarized and compared with finding in the two WHI randomized trials evaluating estrogen therapy and estrogen plus progestin. Based on the randomized clinical trials, estrogen therapy, for women with prior hysterectomy, decreases breast cancer incidence and mortality. In contrast, estrogen plus progestin increases breast cancer incidence, which persists through two decades. Women considering estrogen plus progestin use for vasomotor symptoms should understand the breast cancer risk.

Identification of Candidate Genes in Breast Cancer Induced by Estrogen Plus Progestogens Using Bioinformatic Analysis

Menopausal hormone therapy (MHT) was widely used to treat menopause-related symptoms in menopausal women. However, MHT therapies were controversial with the increased risk of breast cancer because of different estrogen and progestogen combinations, and the molecular basis behind this phenomenon is currently not understood. To address this issue, we identified differentially expressed genes (DEGs) between the estrogen plus progestogens treatment (EPT) and estrogen treatment (ET) using the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas (TCGA) data. As a result, a total of 96 upregulated DEGs were first identified. Seven DEGs related to the cell cycle (CCNE2, CDCA5, RAD51, TCF19, KNTC1, MCM10, and NEIL3) were validated by RT-qPCR. Specifically, these seven DEGs were increased in EPT compared to ET (p < 0.05) and had higher expression levels in breast cancer than adjacent normal tissues (p < 0.05). Next, we found that estrogen receptor (ER)-positive breast cancer patients with a higher CNNE2 expression have a shorter overall survival time (p < 0.05), while this effect was not observed in the other six DEGs (p > 0.05). Interestingly, the molecular docking results showed that CCNE2 might bind to 17β-estradiol (−6.791 kcal/mol), progesterone (−6.847 kcal/mol), and medroxyprogesterone acetate (−6.314 kcal/mol) with a relatively strong binding affinity, respectively. Importantly, CNNE2 protein level could be upregulated with EPT and attenuated by estrogen receptor antagonist, acolbifene and had interactions with cancer driver genes (AKT1 and KRAS) and high mutation frequency gene (TP53 and PTEN) in breast cancer patients. In conclusion, the current study showed that CCNE2, CDCA5, RAD51, TCF19, KNTC1, MCM10, and NEIL3 might contribute to EPT-related tumorigenesis in breast cancer, with CCNE2 might be a sensitive risk indicator of breast cancer risk in women using MHT.

Estrogen therapy and breast cancer in randomized clinical trials: a narrative review

IMPORTANCE AND OBJECTIVE

In the Women's Health Initiative (WHI) randomized trial with 10,739 postmenopausal women with prior hysterectomy, conjugated equine estrogen (CEE) alone significantly reduced breast cancer incidence and breast cancer mortality. In contrast, epidemiological studies in a meta-analysis from the Collaborative Group on Hormonal Factors in Breast Cancer (Collaborative Group) with 108,647 breast cancers and the Million Women's Study cohort significantly associated estrogen-alone therapy with higher breast cancer incidence and breast cancer mortality. The Collaborative Group included a meta-analysis of five smaller randomized trials and the WHI randomized trial; however, findings were restricted to the Collaborative Group appendix. Our objective is to facilitate understanding of these discordant results.

METHODS

Data sources supporting our review findings include the randomized WHI CEE-alone trial and the meta-analysis of five smaller randomized trials evaluating estrogen alone. We summarize the smaller randomized trials' details of breast cancer relevance and place the findings in clinical context. We review findings of the WHI randomized trial evaluating CEE alone in the context of issues raised by Collaborative Group and the Million Women Study authors. We trace the evolution of the time-from-menopause, "window of opportunity" concept and augment the Collaborative Group meta-analysis by including the most recent WHI findings.

DISCUSSION AND CONCLUSIONS

Consideration of the smaller randomized trials evaluating estrogen alone with breast cancer signals that the WHI findings of lower breast cancer incidence and lower breast cancer mortality with CEE-alone use are not a "stand-alone" outcome or due to the play of chance. The serial reports of consistent favorable breast cancer findings through 20 years of cumulative follow-up suggest CEE-alone use initiates changes that persist. After full consideration of risks and benefits, randomized trial evidence provides reassurance for postmenopausal women with prior hysterectomy who are close to menopause considering estrogen alone for climacteric symptom management.

Management of menopause: a view towards prevention

Women spend approximately one-third of their lives with menopause, which occurs around 50 years of age. It is now appreciated that several important metabolic and cardiovascular disease risks emerge during the menopausal transition. Many important conditions occur 10-15 years after menopause, including weight gain and obesity, metabolic syndrome, diabetes, osteoporosis, arthritis, cardiovascular disease, dementia, and cancer; therefore, the occurrence of menopause heralds an important opportunity to institute preventative strategies. These strategies will lead to improved quality of life and decreased mortality. Various strategies are presented for treating symptoms of menopause and diseases that are asymptomatic. Among several strategies is the use of hormone therapy, which has efficacy for symptoms and osteoporosis, and can improve metabolic and cardiovascular health. When instituted early, which is key, in younger postmenopausal women (under 60 years) oestrogen has been found to consistently decrease mortality with a favourable risk-benefit profile in low-risk women. Prospective data show that long-term therapy might not be required for this benefit.

Individual Benefits and Risks of Intravaginal Estrogen and Systemic Testosterone in the Management of Women in the Menopause, With a Discussion of Any Associated Risks for Cancer Development

ABSTRACT

Several formulations of intravaginal oestrogen are available for the treatment of genitourinary syndrome of menopause (GSM). These are safe and effective treatments for the symptoms of GSM. Licensed doses of intravaginal oestrogen do not elevate systemic estradiol levels above the normal postmenopausal range with long term use and there is no evidence of an increased risk of coronary heart disease, stroke, thromboembolism, colorectal cancer, endometrial cancer, breast cancer or breast cancer recurrence with their use. This should reassure both women and their healthcare professionals and should lead to more women receiving these localised, vaginally administered hormonal treatments. Available evidence also suggests a positive safety profile for transdermal testosterone treatment when delivered at physiological concentrations.

Mathematical model for the estrogen paradox in breast cancer treatment

Estrogen is known to stimulate the growth of breast cancer, but is also effective in treating the disease. This is referred to as the"estrogen paradox". Furthermore, short-term treatment with estrogen can successfully eliminate breast cancer, whereas long-term treatment can cause cancer recurrence. Studies highlighted clinical correlations between estrogen and the protein p53 which plays a pivotal role in breast cancer suppression. We sought to investigate how the interplay between estrogen and p53 impacts the dynamics of breast cancer, and further explore if this could be a plausible explanation for the estrogen paradox and the paradoxical tumor recurrence that results from prolonged treatment with estrogen. For this, we propose a novel ODE based mathematical model that accounts for dormant and active cancer cells, along with the estrogen hormone and the p53 protein. We analyze the model's global stability behavior using the Poincaré-Bendixson theorem and results from differential inequalities. We also perform a bifurcation analysis and carry out numerical simulations that elucidate the roles of estrogen and p53 in the estrogen paradox and its long term estrogen paradoxical effect. The mathematical and numerical analyses suggest that the apparent paradoxical role of estrogen could be the result of an interplay between estrogen and p53, and provide explicit conditions under which the paradoxical effect of long-term treatment may be prevented.

Breast Cancer Prevention: Time for Change

Agency breast cancer prevention guidelines for other than hereditary cancers have not materially changed in 20 years; endocrine-targeted agents (then, tamoxifen; now, adding raloxifene and aromatase inhibitors) reduce good prognosis estrogen receptor (ER)-positive, progesterone receptor (PR)-positive cancers without reducing deaths from breast cancer. Across three tamoxifen placebo-controlled prevention trials (N = 23,360) begun almost 30 years ago, although there were 226 fewer breast cancer cases, there were nine more deaths from breast cancer in the tamoxifen groups. Following clinical advances, currently more than half of breast cancer cases are solved problems with extremely low risk of death. As endocrine-targeted agents commonly prevent these cancers, widespread implementation of current prevention strategies may not reduce deaths from breast cancer. Compared with other breast cancers, ER-positive, PR-negative cancers and triple-negative cancers have inferior survival (90.6% v 83.8% v 78.1%, respectively; P < .001). Against this background, in the Women's Health Initiative Dietary Modification randomized trial (N = 48,835), ER-positive, PR-negative cancers were statistically significantly reduced in the intervention group (hazard ratio, 0.77; 95% CI, 0.64 to 0.94) and deaths from breast cancer were reduced 21% (P = .02). In the Women's Health Initiative randomized, placebo-controlled trial evaluating conjugated equine estrogen (N = 10,739), ER-positive, PR-negative cancers were statistically significantly reduced in the intervention group (hazard ratio, 0.44; 95% CI, 0.27 to 0.74) and deaths from breast cancer were reduced 40% (P = .04). These findings suggest that reexamination of breast cancer risk reduction strategies and clinical practice is needed.

Association of Menopausal Hormone Therapy With Breast Cancer Incidence and Mortality During Long-term Follow-up of the Women's Health Initiative Randomized Clinical Trials

IMPORTANCE

The influence of menopausal hormone therapy on breast cancer remains unsettled with discordant findings from observational studies and randomized clinical trials.

OBJECTIVE

To assess the association of prior randomized use of estrogen plus progestin or prior randomized use of estrogen alone with breast cancer incidence and mortality in the Women's Health Initiative clinical trials.

DESIGN, SETTING, AND PARTICIPANTS

Long-term follow-up of 2 placebo-controlled randomized clinical trials that involved 27 347 postmenopausal women aged 50 through 79 years with no prior breast cancer and negative baseline screening mammogram. Women were enrolled at 40 US centers from 1993 to 1998 with follow-up through December 31, 2017.

INTERVENTIONS

In the trial involving 16 608 women with a uterus, 8506 were randomized to receive 0.625 mg/d of conjugated equine estrogen (CEE) plus 2.5 mg/d of medroxyprogesterone acetate (MPA) and 8102, placebo. In the trial involving 10 739 women with prior hysterectomy, 5310 were randomized to receive 0.625 mg/d of CEE alone and 5429, placebo. The CEE-plus-MPA trial was stopped in 2002 after 5.6 years' median intervention duration, and the CEE-only trial was stopped in 2004 after 7.2 years' median intervention duration.

MAIN OUTCOMES AND MEASURES

The primary outcome was breast cancer incidence (protocol prespecified primary monitoring outcome for harm) and secondary outcomes were deaths from breast cancer and deaths after breast cancer.

RESULTS

Among 27 347 postmenopausal women who were randomized in both trials (baseline mean [SD] age, 63.4 years [7.2 years]), after more than 20 years of median cumulative follow-up, mortality information was available for more than 98%. CEE alone compared with placebo among 10 739 women with a prior hysterectomy was associated with statistically significantly lower breast cancer incidence with 238 cases (annualized rate, 0.30%) vs 296 cases (annualized rate, 0.37%; hazard ratio [HR], 0.78; 95% CI, 0.65-0.93; P = .005) and was associated with statistically significantly lower breast cancer mortality with 30 deaths (annualized mortality rate, 0.031%) vs 46 deaths (annualized mortality rate, 0.046%; HR, 0.60; 95% CI, 0.37-0.97; P = .04). In contrast, CEE plus MPA compared with placebo among 16 608 women with a uterus was associated with statistically significantly higher breast cancer incidence with 584 cases (annualized rate, 0.45%) vs 447 cases (annualized rate, 0.36%; HR, 1.28; 95% CI, 1.13-1.45; P < .001) and no significant difference in breast cancer mortality with 71 deaths (annualized mortality rate, 0.045%) vs 53 deaths (annualized mortality rate, 0.035%; HR, 1.35; 95% CI, 0.94-1.95; P= .11).

CONCLUSIONS AND RELEVANCE

In this long-term follow-up study of 2 randomized trials, prior randomized use of CEE alone, compared with placebo, among women who had a previous hysterectomy, was significantly associated with lower breast cancer incidence and lower breast cancer mortality, whereas prior randomized use of CEE plus MPA, compared with placebo, among women who had an intact uterus, was significantly associated with a higher breast cancer incidence but no significant difference in breast cancer mortality.

Update on Menopausal Hormone Therapy for Fracture Prevention

PURPOSE OF REVIEW

The goal of the review is to assess the appropriateness of menopausal hormone therapy (MHT) for the primary prevention of bone loss in women at elevated risk in the early years after menopause.

RECENT FINDINGS

Estrogen alone or combined with progestin to protect the uterus from cancer significantly reduces the risk of osteoporosis-related fractures. MHT increases type 1 collagen production and osteoblast survival and maintains the equilibrium between bone resorption and bone formation by modulating osteoblast/osteocyte and T cell regulation of osteoclasts. Estrogens have positive effects on muscle and cartilage. Estrogen, but not antiresorptive therapies, can attenuate the inflammatory bone-microenvironment associated with estrogen deficiency. However, already on second year of administration, MHT is associated with excess breast cancer risk, increasing steadily with duration of use. MHT should be considered in women with premature estrogen deficiency and increased risk of bone loss and osteoporotic fractures. However, MHT use for the prevention of bone loss is hindered by increase in breast cancer risk even in women younger than 60 years old or who are within 10 years of menopause onset.