Long-Term Follow-Up of the Intergroup Exemestane Study

Intracellular Retention of Estradiol is Augmented by GRAM Domain Containing Protein ASTER-B in Breast Cancer Cells

Estrogens are naturally occurring steroid hormones that also act as the primary mitogens for estrogen receptor-positive (ER+) breast cancers. While elevated blood levels of estrogens have been associated with poor prognosis, the relationship between circulating hormone levels in the blood are related to intracellular hormone concentrations. Here, we observed that MCF-7 cells acutely treated with 17β-estradiol (E2) retain a substantial amount of the hormone even upon removal of the hormone from the culture medium. Moreover, global patterns of E2-dependent gene expression are sustained for hours after acute E2 treatment and hormone removal. While circulating E2 is sequestered by sex hormone binding globulin (SHBG), the mechanisms of intracellular E2 retention are poorly understood. We found that a mislocalized GRAM-domain containing protein ASTER-B in the nucleus, which is observed in a subset of patients, is associated with higher cellular E2 retention. Accumulation and retention of hormone are related to the steroidal properties of E2. Finally, we observed that nuclear ASTER-B-mediated E2 retention is required for sustained hormone-induced ERα chromatin occupancy at enhancers and gene expression, as well as subsequent cell growth responses. Our results add intracellular hormone retention as a mechanism controlling E2-dependent gene expression and downstream biological outcomes.

S ignificance

This study advances our understanding of how estradiol can be accumulated and retained intracellularly to drive a pro-proliferative gene expression program in ER+ breast cancer cells. Mechanistically, intracellular E2 retention is mediated in part by mislocalized, nuclear ASTER-B, which is aberrantly localized to the nuclei of cancer cells in some breast cancer patients.

Osteoporotic fracture risk in women with breast cancer treated with aromatase inhibitors: a health insurance claims database study in Japan

BACKGROUND

Hormone therapy with aromatase inhibitors (AIs) for estrogen receptor-dependent breast cancer may expose patients to an increased osteoporosis risk. This study was performed to estimate fracture risk in women with breast cancer to whom AIs were prescribed in Japan.

METHODS

This retrospective study used data from the Japanese Medical Data Vision database. Women with breast cancer prescribed AIs over a 12-month period were identified and matched to women not prescribed AIs using a propensity score. Fracture rates were estimated by a cumulative incidence function and compared using a cause-specific Cox hazard model. The proportion of women undergoing bone density tests was retrieved.

RESULTS

For all fractures sites combined, cumulative fracture incidence at 10 years was 0.19 [95%CI: 0.16-0.22] in women prescribed AIs and 0.18 [95%CI: 0.15-0.21] without AIs. AI prescription was not associated with any changes in risk (adjusted hazard ratio: 1.08 [95%CI: 0.99-1.17] p = 0.08). Women prescribed AI more frequently underwent bone density testing (31.9% [95% CI: 31.2%; 32.6%] versus 2.2% [95% CI: 2.0%; 2.4%]).

CONCLUSIONS

The anticipated association between AI exposure and osteoporotic fracture risk in Japanese women with breast cancer was not seen clearly.

Efficacy of Alternative Dose Regimens of Exemestane in Postmenopausal Women With Stage 0 to II Estrogen Receptor-Positive Breast Cancer: A Randomized Clinical Trial

Importance

Successful therapeutic cancer prevention requires definition of the minimal effective dose. Aromatase inhibitors decrease breast cancer incidence in high-risk women, but use in prevention and compliance in adjuvant settings are hampered by adverse events.

Objective

To compare the noninferiority percentage change of estradiol in postmenopausal women with estrogen receptor-positive breast cancer given exemestane, 25 mg, 3 times weekly or once weekly vs a standard daily dose with a noninferiority margin of -6%.

Design, Setting, and Participants

This multicenter, presurgical, double-blind phase 2b randomized clinical trial evaluated 2 alternative dosing schedules of exemestane. Postmenopausal women with estrogen receptor-positive breast cancer who were candidates for breast surgery were screened from February 1, 2017, to August 31, 2019. Blood samples were collected at baseline and final visit; tissue biomarker changes were assessed from diagnostic biopsy and surgical specimen. Biomarkers were measured in different laboratories between April 2020 and December 2021.

Interventions

Exemestane, 25 mg, once daily, 3 times weekly, or once weekly for 4 to 6 weeks before surgery.

Main Outcomes and Measures

Serum estradiol concentrations were measured by solid-phase extraction followed by liquid chromatography-tandem mass spectrometry detection. Toxic effects were evaluated using the National Cancer Institute terminology criteria, and Ki-67 was assessed by immunohistochemistry.

Results

A total of 180 women were randomized into 1 of the 3 arms; median (IQR) age was 66 (60-71) years, 63 (60-69) years, and 65 (61-70) years in the once-daily, 3-times-weekly, and once-weekly arms, respectively. In the intention-to-treat population (n = 171), the least square mean percentage change of serum estradiol was -89%, -85%, and -60% for exemestane once daily (n = 55), 3 times weekly (n = 56), and once weekly (n = 60), respectively. The difference in estradiol percentage change between the once-daily and 3-times-weekly arms was -3.6% (P for noninferiority = .37), whereas in compliant participants (n = 153), it was 2.0% (97.5% lower confidence limit, -5.6%; P for noninferiority = .02). Among secondary end points, Ki-67 and progesterone receptor were reduced in all arms, with median absolute percentage changes of -7.5%, -5.0%, and -4.0% for Ki-67 in the once-daily, 3-times-weekly, and once-weekly arms, respectively (once daily vs 3 times weekly, P = .31; once daily vs once weekly, P = .06), and -17.0%, -9.0%, and -7.0% for progesterone receptor, respectively. Sex hormone-binding globulin and high-density lipoprotein cholesterol had a better profile among participants in the 3-times-weekly arm compared with once-daily arm. Adverse events were similar in all arms.

Conclusions and Relevance

In this randomized clinical trial, exemestane, 25 mg, given 3 times weekly in compliant patients was noninferior to the once-daily dosage in decreasing serum estradiol. This new schedule should be further studied in prevention studies and in women who do not tolerate the daily dose in the adjuvant setting.

Trial Registration

ClinicalTrials.gov Identifier: NCT02598557; EudraCT: 2015-005063-16.

The Cardiovascular Risks Associated with Aromatase Inhibitors, Tamoxifen, and GnRH Agonists in Women with Breast Cancer

PURPOSE OF REVIEW

Cardiovascular disease accounts for up to 10% of all-cause mortality in women with a diagnosis of breast cancer, and the causes for this are multifaceted. Many women at risk of or with a diagnosis of breast cancer are on endocrine-modulating therapies. It is therefore important to understand the effect of hormone therapies on cardiovascular outcomes in breast cancer patients to mitigate against any adverse effects and to identify those most at risk so that they can be proactively managed. Here we discuss the pathophysiology of these agents, their effect on the cardiovascular system, and the latest evidence on their cardiovascular risks association.

RECENT FINDINGS

Tamoxifen appears to be cardioprotective during treatment but not over the longer term, while the effect of AIs on cardiovascular outcomes remains controversial. Heart failure outcomes remain understudied, and the cardiovascular effects of gonadotrophin-releasing hormone agonists (GNRHa) in women need further research, especially since data from men with prostate cancer have indicated an increased risk of cardiac events in GNRHa users. There remains a need for a greater understanding of the effects of hormone therapies on cardiovascular outcomes in breast cancer patients. Further areas of research in this area include developing evidence to better define the optimal preventive and screening methods for cardiovascular effects and the risk factors for patients on hormonal therapies.

Managing Bone Health in Breast Cancer

OBJECTIVE

Osteoporosis is a common condition that can be caused or exacerbated by estrogen deficiency.

METHODS

This narrative review will discuss optimizing bone health in the setting of adjuvant endocrine treatments for hormone receptor-positive breast cancer and the current use of antiresorptive agents as adjuvant therapy and as bone modifying agents.

RESULTS

Adjuvant endocrine treatments for hormone receptor-positive breast cancer (tamoxifen and aromatase inhibitors) affect bone health. The exact effect depends on the agent used and the menopausal state of the woman. Antiresorptive medications for osteoporosis, bisphosphonates and denosumab, lower the risk of bone loss from aromatase inhibitors. Use of bisphosphonates as adjuvant treatment in breast cancer, regardless of hormone receptor status, is increasing because of benefits seen to cancer relapse and survival.

CONCLUSION

Optimizing bone health in women with breast cancer during and after cancer treatment is informed by an understanding of breast cancer treatment and its skeletal effect.

Long noncoding RNA DIO3OS induces glycolytic-dominant metabolic reprogramming to promote aromatase inhibitor resistance in breast cancer

Aromatase inhibition is an efficient endocrine therapy to block ectopic estrogen production for postmenopausal estrogen receptor (ER)-positive breast cancer patients, but many develop resistance. Here, we show that aromatase inhibitor (AI)-resistant breast tumors display features of enhanced aerobic glycolysis with upregulation of long noncoding RNA (lncRNA) DIO3OS, which correlates with poor prognosis of breast cancer patients on AI therapies. Long-term estrogen deprivation induces DIO3OS expression in ER-positive breast tumor cells, which further enhances aerobic glycolysis and promotes estrogen-independent cell proliferation in vitro and in vivo. Mechanistically, DIO3OS interacts with polypyrimidine tract binding protein 1 (PTBP1) and stabilizes the mRNA of lactate dehydrogenase A (LDHA) by protecting the integrity of its 3'UTR, and subsequently upregulates LDHA expression and activates glycolytic metabolism in AI-resistant breast cancer cells. Our findings highlight the role of lncRNA in regulating the key enzyme of glycolytic metabolism in response to endocrine therapies and the potential of targeting DIO3OS to reverse AI resistance in ER-positive breast cancer.

Role of Exemestane in the Treatment of Estrogen-Receptor-Positive Breast Cancer: A Narrative Review of Recent Evidence

INTRODUCTION

Breast cancer (BC) is the most common type of cancer diagnosed among women worldwide with an estimated 2.3 million new cases every year. Almost two-thirds of all patients with BC have estrogen receptor-positive (ER+) tumors. In this review, the clinical evidence of exemestane in different treatment settings in ER+ BC is presented and summarized.

SEARCH STRATEGY

A search strategy with the keywords "breast cancer [MeSH Terms]" AND "exemestane [Title/Abstract]" was devised and a search was performed in PubMed.

RESULTS

The efficacy of exemestane in different treatment settings has been established by numerous clinical studies. Exemestane is recommended as an adjuvant treatment in postmenopausal women previously treated with tamoxifen in trials comparing 5 years of tamoxifen with 2-3 years of tamoxifen combined with 2-3 years of exemestane, which proved that treatment with exemestane provided better survival outcomes. Similarly, exemestane could be considered as a safe treatment option for neoadjuvant treatment, prevention of chemotherapy, and treatment of advanced BC either alone or in combination with other targeted therapy drugs in both pre- and postmenopausal women.

CONCLUSION

Exemestane could be considered as a reasonable therapeutic option in the treatment of ER+ BC at any stage in pre- and postmenopausal women.

Management of hormone receptor-positive, HER2-negative early breast cancer

The majority of breast cancers are diagnosed at an early stage and are hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative. Significant advances have been made in the management of early stage HR-positive, HER2-negative breast cancer, resulting in improved survival outcomes. In this review, we discuss important factors to consider in the management of this disease. In particular, we discuss the role of adjuvant endocrine therapy, specific endocrine therapy agents, the duration of adjuvant endocrine therapy, treatment-related side effects, and the role of genomic assays and other biomarkers when considering treatment recommendations for individuals with HR-positive, HER2-negative early breast cancer. Finally, we address emerging data to individualize therapeutic decision-making and provide future considerations.

Evolution in the risk of adverse events of adjuvant endocrine therapy in postmenopausal women with early-stage breast cancer

BACKGROUND

Adjuvant endocrine therapy is a gold standard in early-stage, hormone receptor positive breast cancer. In postmenopausal women, aromatase inhibitors (AIs) are associated with improved outcome compared to tamoxifen monotherapy. Differences in the toxicity profiles of these drugs are described; however, little is known about whether the risk of adverse events changes over time.

METHODS

Sequential reports of large, randomized, adjuvant endocrine therapy trials comparing AIs to tamoxifen were reviewed. Data on pre-specified adverse events were extracted including cardiovascular events, bone fractures, cerebrovascular disease, endometrial cancer, secondary malignancies excluding breast cancer, venous thrombosis and death without recurrence. Odds ratios (ORs) were calculated for each adverse event at each time over the course of follow-up. The change in the ORs for adverse events over time was evaluated using weighted linear regression.

RESULTS

Analysis included 21 reports of 7 trials comprising 30,039 patients and reporting outcomes between 28 and 128 months of follow-up. Compared to tamoxifen, AIs use was associated with a significant reduction in the magnitude of increased odds of bone fracture over time (β = - 0.63, p = 0.013). There was a non-significant decrease in the magnitude of reduced odds of secondary malignancies over time (β = 0.448, p = 0.094). The differences in other toxicity profiles between AIs and tamoxifen did not change significantly over time.

CONCLUSIONS

The increased risk of bone fractures associated with adjuvant AIs falls over time and after discontinuation of treatment. Differences in other toxicities between AIs and tamoxifen do not change significantly over time including a persistently elevated risk of cardiovascular events.

Prolonged Time to Adjuvant Chemotherapy Initiation Was Associated with Worse Disease Outcome in Triple Negative Breast Cancer Patients

The optimal time to adjuvant chemotherapy (TTC) for breast cancer (BC) patients remains uncertain. Herein, we aim to evaluate the association between TTC and prognosis among different subtypes in modern era of adjuvant chemotherapy. BC patients receiving operation and adjuvant chemotherapy between January 2009 and December 2015 were included. Enrolled patients were categorized into TTC ≤4 weeks and >4 weeks groups. Relapse-free survival (RFS) and overall survival (OS) were compared according to TTC and analyzed among different BC molecular subtypes. A total of 2611 patients were included. Elder age (P = 0.005), more comorbidities (P <0.001), breast-conserving surgery (P = 0.001), non-invasive ductal carcinoma (P = 0.012), and HER2-positivity (P <0.001) were associated with prolonged TTC. Among whole BC population, no significant difference was observed between two TTC groups in terms of RFS (P = 0.225) or OS (P = 0.355). However, for triple negative (TNBC) patients, TTC >4 weeks was independently related with worse RFS (5-year RFS 81.9% vs 89.3%; HR, 1.89; 95% CI, 1.09 to 3.27; P = 0.024) and OS (5-year OS 84.0% vs 94.0%; HR, 2.49; 95% CI, 1.30 to 4.76; P = 0.006) compared with those TTC ≤4 weeks. Prolonged TTC >4 weeks after BC surgery was not associated with worse survival outcomes in the whole BC patients. However, TTC >4 weeks may increase risk of relapse or death in TNBC patients, which deserves further clinical evaluation.

Preventive drug therapy and contralateral breast cancer: summary of the evidence of clinical trials and observational studies

Background: Breast cancer patients have a lifelong 2-4-fold increased risk of developing a second primary tumor in the contralateral breast compared with the risk for a first primary breast cancer in the general female population. Prevention of contralateral breast cancer (CBC) has received increased attention during recent decades. Here, we summarize and discuss the available literature on drug preventive therapy and CBC.Results: The endocrine-targetting drugs, tamoxifen and aromatase inhibitors are used as standard adjuvant treatment for estrogen receptor (ER)-positive breast cancer. Both are associated with relative risk reductions of CBC of up to 50%, but incur serious side effects. Several prescription drugs originally developed for other purposes, including bisphosphonates, statins, non-steroidal anti-inflammatory drugs, metformin, anti-hypertensives and retinoids, have shown anti-cancer activity in preclinical models. However, results of observational studies on CBC are sparse and inconsistent, with only statins demonstrating promise as preventive agents and a potential treatment option for ER-negative breast cancer patients.Conclusion: Future studies are needed to assess the effect of statins in risk reduction and to identify other drugs with chemopreventive potential against CBC. Eventually, efforts must be directed towards identifying those breast cancer patients likely to benefit most from specific preventive therapies.

Dissecting the predictive value of MAPK/AKT/estrogen-receptor phosphorylation axis in primary breast cancer to treatment response for tamoxifen over exemestane: a Translational Report of the Intergroup Exemestane Study (IES)-PathIES

PURPOSE

The prognostic and predictive values of the MAPK/AKT/ERα phosphorylation axis (pT202/T204MAPK, pT308AKT, pS473AKT, pS118ERα and pS167ERα) in primary tumours were assessed to determine whether these markers can differentiate between patient responses for switching adjuvant endocrine therapy after 2-3 years from tamoxifen to exemestane and continued tamoxifen monotherapy in the Intergroup Exemestane Study (IES).

METHODS

Of the 4724 patients in IES, 1506 were managed in a subset of centres (N = 89) participating in PathIES. These centres recruited 1282 (85%, 1282/1506) women into PathIES of whom 1036 had phospho-marker data. All phospho-markers were analysed by immunohistochemistry staining. Multivariable Cox proportional hazards models of the phospho-markers for disease-free survival (DFS) and overall survival (OS) were adjusted for clinicopathological factors. Treatment effects on the biomarker expression were determined by interaction tests. Benjamini-Hochberg adjustment for multiple testing with a false discovery rate of 10% was applied (pBH).

RESULTS

Phospho-T202/T204MAPK, pS118ERα and pS167ERα were all found to be correlated (pBH = 0.0002). These markers were not associated with either DFS or OS when controlling for the established clinicopathological factors. Interaction terms between the phospho-markers and treatment strategies for either DFS or OS were not statistically significant (pBH > 0.05 for all).

CONCLUSIONS

This PathIES study confirmed previously described associations between the phosphorylation site markers of AKT, MAPK and ERα activity in postmenopausal breast cancer patients. No prognostic correlations between the phosphorylation markers and clinical outcome were found, nor were they predictive for clinical outcomes among patients who switched therapy over those treated with tamoxifen alone.

Adjuvant Letrozole and Tamoxifen Alone or Sequentially for Postmenopausal Women With Hormone Receptor-Positive Breast Cancer: Long-Term Follow-Up of the BIG 1-98 Trial

PURPOSE

Luminal breast cancer has a long natural history, with recurrences continuing beyond 10 years after diagnosis. We analyzed long-term follow-up (LTFU) of efficacy outcomes and adverse events in the Breast International Group (BIG) 1-98 study reported after a median follow-up of 12.6 years.

PATIENTS AND METHODS

BIG 1-98 is a four-arm, phase III, double-blind, randomized trial comparing adjuvant letrozole versus tamoxifen (either treatment received for 5 years) and their sequences (2 years of one treatment plus 3 years of the other) for postmenopausal women with endocrine-responsive early breast cancer. When pharmaceutical company sponsorship ended at 8.4 years of median follow-up, academic partners initiated an observational, LTFU extension collecting annual data on survival, disease status, and adverse events. Information from Denmark was from the Danish Breast Cancer Cooperative Group Registry. Intention-to-treat analyses are reported.

RESULTS

Of 8,010 enrolled patients, 4,433 were alive and not withdrawn at an LTFU participating center, and 3,833 (86%) had at least one LTFU report. For the monotherapy comparison of letrozole versus tamoxifen, we found a 9% relative reduction in the hazard of a disease-free survival event with letrozole (hazard ratio [HR], 0.91; 95% CI, 0.81 to 1.01). HRs for other efficacy end points were similar to those for disease-free survival. Efficacy of letrozole versus tamoxifen for contralateral breast cancer varied significantly over time (0- to 5-, 5- to 10-, and > 10-year HRs, 0.62, 0.47, and 1.35, respectively; treatment-by-time interaction P = .005), perhaps reflecting a longer carryover effect of tamoxifen. Reporting of specific long-term adverse events seemed more effective with national registry than with case-record reporting of clinical follow-up.

CONCLUSION

Efficacy end points continued to show trends favoring letrozole. Letrozole reduced contralateral breast cancer frequency in the first 10 years, but this reversed beyond 10 years. This study illustrates the value of extended follow-up in trials of luminal breast cancer.

Exploration of tumour-infiltrating lymphocytes as a predictive biomarker for adjuvant endocrine therapy in early breast cancer

PURPOSE

Tumour-infiltrating lymphocytes (TILs) have been shown to be prognostic for disease-free survival and predictive for the benefit of chemotherapy in patients with early breast cancer, but have not been studied for endocrine therapy.

EXPERIMENTAL DESIGN

The number of CD8-positive TILs was assessed in a subcohort of 236 patients in the Intergroup Exemestane Study. AQ After 2-3 years of adjuvant tamoxifen, AQpatients were randomized between the schemes of continuation for 5 years on tamoxifen and switching to exemestane. The numbers of CD8-positive TILs were analysed for correlations with disease-free survival (DFS) and overall survival (OS). A similar analysis was performed on 2596 patients in the TEAM trial who were randomized between the sequential scheme and the exemestane monotherapy.

RESULTS

In the first cohort, patients with low (below median) numbers of CD8-positive TILs had a univariate hazard ratio (HR) for DFS of 0.27 (95% CI 0.13-0.55) in favour of treatment with exemestane, whereas this benefit was not observed in patients with high numbers of CD8-positive TILs (HR 1.34, 95% CI 0.71-2.50, HR for interaction 5.02, p = 0.001). In the second cohort, patients with low numbers of CD8-positive TILs showed a benefit of exemestane treatment on recurrence-free survival (RFS HR 0.67, 95% CI 0.45-0.99), and not with above-median numbers of CD8-positive TILs (HR 0.86, 95% CI 0.59-1.26, HR for interaction 1.29, p = 0.36).

CONCLUSIONS

This study is the first to propose the number of CD8-positive TILs as potential predictive markers for endocrine therapy, with the low presence of CD8-positive TILs associated to benefit for exemestane-inclusive therapy. However, treatment-by-marker interactions were only significant in one cohort, indicating the need for further validation.