Switching from tamoxifen to aromatase inhibitors for adjuvant endocrine therapy in postmenopausal patients with early breast cancer

Prospective Exploratory Study of the Effects of Postoperative Endocrine Medication on the Endometrium in Breast Cancer Patients

Objective

This study aimed to investigate the pathological effects of long-term postoperative endocrine medication on the endometrium in breast cancer patients.

Methods

Data of 99 patients with primary breast cancer who underwent hysteroscopy and obtained endometrial biopsy from 1 June 2018 to 31 December 2021 at the Beijing Obstetrics and Gynecology Hospital, Capital Medical University. Beijing Maternal and Child Health Care Hospital were prospectively collected.

Results

Hysteroscopy was performed followed by endometrial histopathological examination in 99 breast cancer patients, including 44 taking tamoxifen (TAM), 26 taking other endocrine drugs, and 29 not taking endocrine drugs. The endometrial thickness in the TAM group was significantly higher than that in the other endocrine drug groups and the group not taking endocrine drugs (p=0.017). The receiver operating characteristic curves for the abnormal premenopausal endometrial thickening were plotted in this study; an endometrial thickness of 15.5 mm seen on ultrasound could be used as the most accurate ultrasound diagnostic threshold for the diagnosis of abnormal premenopausal endometrial hyperplasia, with an area under the curve of 0.888 (95% CI: 0.716, 1.000), a sensitivity of 100%, and a specificity of 75%, which was consistent with the results of our previous retrospective study. An endometrial thickness of ≥5 mm in postmenopausal women with breast cancer taking TAM was still used as the cut-off value for routine ultrasound diagnosis of abnormal postmenopausal endometrial hyperplasia.

Conclusion

An ultrasound endometrial thickness (proliferative phase) of >15 mm in premenopausal patients can be used as the most accurate ultrasound diagnostic threshold for the diagnosis of abnormal endometrial hyperplasia. After menopause, an ultrasound endometrial thickness of ≥5 mm is still used as the criterion for diagnosing abnormal endometrial hyperplasia. Older patients should be monitored for signs of vaginal bleeding and fluid discharge, and hysteroscopy should be performed if necessary to ascertain the endometrial condition.

Cardiotoxicity of Use of Sequential Aromatase Inhibitors in Women With Breast Cancer

The association between use of aromatase inhibitors (AIs) and cardiovascular outcomes is controversial. While some observational studies have assessed the cardiovascular safety of AIs as upfront treatments, their cardiotoxicity as sequential treatments with tamoxifen remains unknown. Thus, we conducted a population-based cohort study using data from the United Kingdom Clinical Practice Research Datalink linked to the Hospital Episode Statistics and Office for National Statistics databases. We employed a prevalent new-user design to propensity-score match, in a 1:2 ratio, patients switching from tamoxifen to AIs with patients continuing tamoxifen between 1998 and 2016. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals for the study outcomes (myocardial infarction, ischemic stroke, heart failure, and cardiovascular mortality). Overall, 1,962 patients switching to AIs were matched to 3,874 patients continuing tamoxifen. Compared with tamoxifen, AIs were associated with an increased risk of myocardial infarction (hazard ratio (HR) = 2.08, 95% confidence interval (CI): 1.02, 4.27). The hazard ratios were elevated for ischemic stroke (HR = 1.58, 95% CI: 0.85, 2.93) and heart failure (HR = 1.69, 95% CI: 0.79, 3.62) but not cardiovascular mortality (HR = 0.87, 95% CI: 0.49, 1.54), with confidence intervals including the null value. The elevated hazard ratios observed for the cardiovascular outcomes should be corroborated in future large observational studies.

The effects of population-based mammography screening starting between age 40 and 50 in the presence of adjuvant systemic therapy

Adjuvant systemic therapy has been shown to be effective in reducing breast cancer mortality. The additional effect of mammography screening remains uncertain, in particular for women aged 40-49 years. We therefore assessed the effects of screening starting between age 40 and 50, as compared to the effects of adjuvant systemic therapy. The use of adjuvant endocrine therapy, chemotherapy and the combination of endocrine- and chemotherapy, as well as the uptake of mammography screening in the Netherlands was modeled using micro-simulation. The effects of screening and treatment were modeled based on randomized controlled trials. The effects of adjuvant therapy, biennial screening between age 50 and 74 in the presence of adjuvant therapy, and extending the screening programme by starting at age 40 were assessed by comparing breast cancer mortality in women aged 0-100 years in scenarios with and without these interventions. In 2008, adjuvant treatment was estimated to have reduced the breast cancer mortality rate in the simulated population by 13.9%, compared to a situation without treatment. Biennial screening between age 50 and 74 further reduced the mortality rate by 15.7%. Extending screening to age 48 would lower the mortality rate by 1.0% compared to screening from age 50; 10 additional screening rounds between age 40 and 49 would reduce this rate by 5.1%. Adjuvant systemic therapy and screening reduced breast cancer mortality in similar amounts. Expanding the lower age limit of screening would further reduce breast cancer mortality.

Longitudinal trends in utilization of endocrine therapies for breast cancer: an international comparison

WHAT IS KNOWN AND OBJECTIVE

Endocrine therapy is an effective treatment for post-menopausal women with 'oestrogen receptor-positive' invasive breast cancers. There are two main types of endocrine therapies: selective oestrogen receptor modulators (tamoxifen) and aromatase inhibitors (anastrozole, letrozole and exemestane). The aim of this study was to compare the patterns of use of endocrine therapies for breast cancer in women between nine developed countries.

METHODS

A longitudinal, cross-national drug utilization study was conducted. The endocrine therapies included were tamoxifen and the aromatase inhibitors: anastrozole, letrozole and exemestane. Annual drug utilization data were collected from Australia, Denmark, England, Finland, France, Iceland, the Netherlands, Norway and Sweden over the period 2001-2012. Utilization was measured in DDD/1000 inhabitants/day and was also adjusted for breast cancer incidence and female population statistics.

RESULTS AND DISCUSSION

Total use of endocrine therapies either increased or remained steady in all countries. Total endocrine therapy usage was consistently highest in England and France. Norway showed the lowest usage of endocrine therapies overall, using only 1.80 DDD/1000 inhabitants/day in 2012. Downward trends in tamoxifen use and upward trends in aromatase inhibitors were seen across all countries over the study period. By 2012, aromatase inhibitors represented over half of total endocrine therapy use in all countries, and as high as 74% and 80% in France and Denmark, respectively.

WHAT IS NEW AND CONCLUSION

Our analysis found a shift in use of endocrine therapy from tamoxifen to aromatase inhibitors. This trend is consistent with major clinical guidelines endorsing preferential use of aromatase inhibitors in post-menopausal women. Stabilization or small increase in tamoxifen use in the recent years may reflect the recognition of tamoxifen as still an appropriate first-line treatment. The similarity in utilization patterns may be due to the relatively comparable healthcare systems in the countries, namely universal health insurance and pharmaceutical coverage. Differences in utilization observed could be due to differences in breast cancer incidence, prescribing behaviours, interpretation of new trial evidence, and timing of drug marketing approval and reimbursement between countries.

Aromatase inhibitors in the breast cancer clinic: focus on exemestane

Breast cancer is the most prevalent type of cancer in women and responsible for significant female cancer-related mortality worldwide. In the Western world, over 80% of breast cancers are hormone-receptor positive for which endocrine therapy is administered. The main anti-estrogen treatments in use consist of selective estrogen-receptor modulators, such as tamoxifen, and third-generation aromatase inhibitors (AIs), such as exemestane, letrozole, and anastrozole. In this review, the focus will lie on exemestane, its clinical use, and its side-effect profile. Exemestane is the only third-generation steroidal AI. Its efficacy as a first-line treatment in metastatic breast cancer has been demonstrated. Therefore, exemestane could be considered a valid first-line therapeutic option, but it also can be used in second-line or further situations. Exemestane is mostly used as part of sequential adjuvant treatment following tamoxifen, but in this setting it is also active in monotherapy. Furthermore, this AI has been studied in the neoadjuvant setting as presurgical treatment, and even as chemoprevention in high-risk healthy postmenopausal women. It may reverse side effects of tamoxifen, such as endometrial changes and thromboembolic disease but may also cause some inconvenient side effects itself. Additionally, there is a lack of total cross-resistance between exemestane and nonsteroidal AIs as far as their anti-tumoral efficacy is concerned; moreover the two classes of AIs display a nontotal overlapping toxicity profile. Taking together, exemestane can be considered as a useful treatment option at all stages of breast cancer.

Regulation of adipose oestrogen output by mechanical stress

Adipose stromal cells are the primary source of local oestrogens in adipose tissue, aberrant production of which promotes oestrogen receptor-positive breast cancer. Here we show that extracellular matrix compliance and cell contractility are two opposing determinants for oestrogen output of adipose stromal cells. Using synthetic extracellular matrix and elastomeric micropost arrays with tunable rigidity, we find that increasing matrix compliance induces transcription of aromatase, a rate-limiting enzyme in oestrogen biosynthesis. This mechanical cue is transduced sequentially by discoidin domain receptor 1, c-Jun N-terminal kinase 1, and phosphorylated JunB, which binds to and activates two breast cancer-associated aromatase promoters. In contrast, elevated cell contractility due to actin stress fibre formation dampens aromatase transcription. Mechanically stimulated stromal oestrogen production enhances oestrogen-dependent transcription in oestrogen receptor-positive tumour cells and promotes their growth. This novel mechanotransduction pathway underlies communications between extracellular matrix, stromal hormone output, and cancer cell growth within the same microenvironment.

Combined effects of goserelin and tamoxifen on estradiol level, breast density, and endometrial thickness in premenopausal and perimenopausal women with early-stage hormone receptor-positive breast cancer: a randomised controlled clinical trial

Background:

This study is to investigate the effects of geserelin+tamoxifen (TAM) on estradiol level, breast density (BD), endometrial thickness (ET), and blood lipids in premenopausal and perimenopausal women with hormone receptor-positive early-stage breast cancer.

Methods:

This study recruited 110 premenopausal and perimenopausal patients with hormone receptor-positive early-stage breast cancer between 22 June 2008 and 31 December 2009 and randomly assigned them to receive either goserelin plus TAM or TAM alone for 1.5 years. Blood levels of sex hormones and lipids and ET were determined at 0, 3, 6, 12, and 18 months. Contralateral BD was also measured at 0, 12, and 18 months.

Results:

Five participants dropped out of the goserelin plus TAM group, and two participants dropped out of the TAM-alone group before initiation of endocrine therapy. The rest of patients received scheduled treatment and 3 years of median follow-up. No serious adverse effects were observed, and only two local recurrences have been observed in these patients. Estradiol level and BD were lower in the goserelin plus TAM group than in the TAM-alone group (P<0.05). The endometrium in the goserelin plus TAM group was significantly thinner than that in the TAM-alone group (P<0.05), and women in the TAM-alone group exhibited endometrial thickening over the course of the study. Furthermore, no significant differences in blood lipid levels were reported between the two groups.

Conclusion:

The data from the current study demonstrated that the addition of goserelin to TAM results in downregulation of estradiol level, followed by significant reduction in BD and ET in premenopausal and perimenopausal women with hormone receptor-positive breast cancer, which may eventually lead to better outcome in these patients.

Meta-analysis of breast cancer outcome and toxicity in adjuvant trials of aromatase inhibitors in postmenopausal women

The present meta-analysis examines randomized trials of third-generation aromatase inhibitors (AIs) as alternatives to tamoxifen in three treatment settings: monotherapy, sequenced therapy and extended therapy. Eleven randomized controlled trials (RCTs) were chosen based on their similarity in terms of study design and included 34,070 post-menopausal women who had undergone surgery for estrogen-sensitive early breast cancer. DFS was significantly improved by AI monotherapy (Hazard Ratio (HR): 0.89, p = 0.001), sequenced therapy (HR: 0.7, p < 0.00001) and extended therapy (HR: 0.62, p < 0.00001). All of the patients benefited significantly from sequenced therapy (HR: 0.81, p = 0.003), and hormone receptor-positive patients benefited from AI monotherapy (HR = 0.92, p = 0.046) with respect to OS. AI monotherapy conferred significantly lower risks for thromboembolic events (OR = 0.61; p < 0.001) and endometrial cancer (OR = 0.26; p < 0.001) compared with tamoxifen monotherapy; however, there was a greater risk of cardiovascular events (OR = 1.20; p = 0.030). Sequenced therapy was also superior in terms of endometrial cancer but was inferior with respect to fractures, thromboembolic and cardiovascular events.

Gene expression signatures that predict outcome of tamoxifen-treated estrogen receptor-positive, high-risk, primary breast cancer patients: a DBCG study

Background

Tamoxifen significantly improves outcome for estrogen receptor-positive (ER+) breast cancer, but the 15-year recurrence rate remains 30%. The aim of this study was to identify gene profiles that accurately predicted the outcome of ER+ breast cancer patients who received adjuvant Tamoxifen mono-therapy.

Methodology/Principal Findings

Post-menopausal breast cancer patients diagnosed no later than 2002, being ER+ as defined by >1% IHC staining and having a frozen tumor sample with >50% tumor content were included. Tumor samples from 108 patients treated with adjuvant Tamoxifen were analyzed for the expression of 59 genes using quantitative-PCR. End-point was clinically verified recurrence to distant organs or ipsilateral breast. Gene profiles were identified using a model building procedure based on conditional logistic regression and leave-one-out cross-validation, followed by a non-parametric bootstrap (1000x re-sampling). The optimal profiles were further examined in 5 previously-reported datasets containing similar patient populations that were either treated with Tamoxifen or left untreated (n = 623). Three gene signatures were identified, the strongest being a 2-gene combination of BCL2-CDKN1A, exhibiting an accuracy of 75% for prediction of outcome. Independent examination using 4 previously-reported microarray datasets of Tamoxifen-treated patient samples (n = 503) confirmed the potential of BCL2-CDKN1A. The predictive value was further determined by comparing the ability of the genes to predict recurrence in an additional, previously-published, cohort consisting of Tamoxifen-treated (n = 58, p = 0.015) and untreated patients (n = 62, p = 0.25).

Conclusions/Significance

A novel gene expression signature predictive of outcome of Tamoxifen-treated patients was identified. The validation suggests that BCL2-CDKN1A exhibit promising predictive potential.

The growth response to androgen receptor signaling in ERα-negative human breast cells is dependent on p21 and mediated by MAPK activation

Introduction

Although a high frequency of androgen receptor (AR) expression in human breast cancers has been described, exploiting this knowledge for therapy has been challenging. This is in part because androgens can either inhibit or stimulate cell proliferation in pre-clinical models of breast cancer. In addition, many breast cancers co-express other steroid hormone receptors that can affect AR signaling, further obfuscating the effects of androgens on breast cancer cells.

Methods

To create better-defined models of AR signaling in human breast epithelial cells, we took estrogen receptor (ER)-α-negative and progesterone receptor (PR)-negative human breast epithelial cell lines, both cancerous and non-cancerous, and engineered them to express AR, thus allowing the unambiguous study of AR signaling. We cloned a full-length cDNA of human AR, and expressed this transgene in MCF-10A non-tumorigenic human breast epithelial cells and MDA-MB-231 human breast-cancer cells. We characterized the responses to AR ligand binding using various assays, and used isogenic MCF-10A p21 knock-out cell lines expressing AR to demonstrate the requirement for p21 in mediating the proliferative responses to AR signaling in human breast epithelial cells.

Results

We found that hyperactivation of the mitogen-activated protein kinase (MAPK) pathway from both AR and epidermal growth factor receptor (EGFR) signaling resulted in a growth-inhibitory response, whereas MAPK signaling from either AR or EGFR activation resulted in cellular proliferation. Additionally, p21 gene knock-out studies confirmed that AR signaling/activation of the MAPK pathway is dependent on p21.

Conclusions

These studies present a new model for the analysis of AR signaling in human breast epithelial cells lacking ERα/PR expression, providing an experimental system without the potential confounding effects of ERα/PR crosstalk. Using this system, we provide a mechanistic explanation for previous observations ascribing a dual role for AR signaling in human breast cancer cells. As previous reports have shown that approximately 40% of breast cancers can lack p21 expression, our data also identify potential new caveats for exploiting AR as a target for breast cancer therapy.

Eligibility, compliance and persistence of sequential therapy with aromatase inhibitors following 2-3 years of tamoxifen in endocrine adjuvant breast cancer therapy

OBJECTIVE

This study evaluated the eligibility, compliance and persistence of sequential therapy, i.e. a switch to an aromatase inhibitor (AI) following 2-3 years of tamoxifen, in adjuvant endocrine breast cancer (BC) treatment.

METHODS

Data concerning 388 BC patients (age ≤70 years) who started endocrine adjuvant therapy between 1998 and 2008 were analyzed.

RESULTS

From the 263 patients who started therapy with tamoxifen, 167 (63.5%) were eligible for a sequential therapy. Fifty-nine patients (35.3%) were offered a switch by their physicians; women who had their follow-up at oncological units received the offer more often when compared to those treated by general practitioners (p < 0.001). Out of these 59 patients, 50 followed the proposal (compliance 84.7%). Of those who agreed to a sequential therapy, 2 (4%) were non-persistent to endocrine therapy; in 9 cases (18.0%), a re-switch to tamoxifen was done due to AI-related adverse side effects.

CONCLUSIONS

Only a minority of the patients who started an endocrine adjuvant BC therapy was eligible for sequential therapy. Patients who underwent a switch had a high rate of persistence. Efforts should be made to make sure that all physicians, above all general practitioners, who are involved in the treatment of BC patients, are provided with current therapy guidelines.

Breast cancer medications and vision: effects of treatments for early-stage disease

This review concerns the effects on vision and the eye of medications prescribed at three phases of treatment for women with early-stage breast cancer (BC): (1) adjuvant cytotoxic chemotherapy, (2) adjuvant endocrine therapy, and (3) symptomatic relief. The most common side effects of cytotoxic chemotherapy are epiphora and ocular surface irritation, which can be caused by any of several different regimens. Most notably, the taxane docetaxel can lead to epiphora by inducing canalicular stenosis. The selective-estrogen-receptor-modulator (SERM) tamoxifen, long the gold-standard adjuvant-endocrine-therapy for women with hormone-receptor-positive BC, increases the risk of posterior subcapsular cataract. Tamoxifen also affects the optic nerve head more often than previously thought, apparently by causing subclinical swelling within the first 2 years of use for women older than ∼50 years. Tamoxifen retinopathy is rare, but it can cause foveal cystoid spaces that are revealed with spectral-domain optical coherence tomography (OCT) and that may increase the risk for macular holes. Tamoxifen often alters the perceived color of flashed lights detected via short-wavelength-sensitive (SWS) cone response isolated psychophysically; these altered perceptions may reflect a neural-response sluggishness that becomes evident at ∼2 years of use. The aromatase inhibitor (AI) anastrozole affects perception similarly, but in an age-dependent manner suggesting that the change of estrogen activity towards lower levels is more important than the low estrogen activity itself. Based on analysis of OCT retinal thickness data, it is likely that anastrozole increases the tractional force between the vitreous and retina. Consequently, AI users, myopic AI users particularly, might be at increased risk for traction-related vision loss. Because bisphosphonates are sometimes prescribed to redress AI-induced bone loss, clinicians should be aware of their potential to cause scleritis and uveitis occasionally. We conclude by suggesting some avenues for future research into the visual and ocular effects of AIs, particularly as relates to assessment of cognitive function.

Half of breast cancer patients discontinue tamoxifen and any endocrine treatment before the end of the recommended treatment period of 5 years: a population-based analysis

Observational studies on long-term endocrine treatment among breast cancer patients have presented discontinuation rates on tamoxifen, but lack information on the continuance of any endocrine treatment [both tamoxifen and aromatase inhibitors (AIs)] within the same cohort. In this study we determined switching rates from tamoxifen to AIs, discontinuation rates of tamoxifen only, discontinuation rates of any endocrine treatment and determinants of first treatment switch and treatment discontinuation. Patients with early stage breast cancer (stage I-IIIa) starting on tamoxifen were selected from the linked Eindhoven Cancer Registry-PHARMO RLS cohort in the period 1998-2006. Continuous use (allowing a 60 days gap between refills) of tamoxifen only and any endocrine treatment were determined after various follow-up periods: 1, 2, 3, 4, and 5 years. Time to first switch from tamoxifen to an AI was assessed. Cox regression was used to identify determinants of first treatment switch, discontinuation of tamoxifen, and discontinuation of any endocrine treatment. A total of 1,451 new early stage breast cancer patients started on tamoxifen. Of those, 380 had a treatment switch to an AI during follow-up. Of the patients followed for 5 years, 40% continuously used tamoxifen, which was 49% for any endocrine treatment. Older age (older than 70 versus 50-69 years) was independently associated with increased discontinuation of tamoxifen and any endocrine therapy. Patients with two or more concomitant diseases (versus no comorbidity) showed an increased likelihood to stop any endocrine treatment or switch treatment from tamoxifen to an AI. In conclusion, up to half of the breast cancer patients starting tamoxifen continued 5 years of endocrine treatment. Identification of patients at risk of discontinuation will assist in the development of interventions to improve treatment continuation comparable to that of patients included in clinical trials.