A randomised study of the effects of letrozole and anastrozole on oestrogen receptor positive breast cancers in postmenopausal women

AMEERA-4: a randomized, preoperative window-of-opportunity study of amcenestrant versus letrozole in early breast cancer

BACKGROUND

Window-of-opportunity (WOO) studies provide insights into the clinical activity of new drugs in breast cancer.

METHODS

AMEERA-4 (NCT04191382) was a WOO study undertaken to compare the pharmacodynamic effects of amcenestrant, a selective estrogen receptor degrader, with those of letrozole in postmenopausal women with newly diagnosed, operable estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer. Women were randomized (1:1:1) to receive amcenestrant 400 mg, amcenestrant 200 mg, or letrozole 2.5 mg once daily for 14 days before breast surgery. The primary endpoint was change in Ki67 between baseline and Day 15 (i.e., day of surgery).

RESULTS

Enrollment was stopped early because of slow recruitment, in the context of the COVID-19 pandemic. The modified intent-to-treat population consisted of 95 study participants with baseline and post-treatment Ki67 values, whereas the safety population included 104 participants who had received at least one dose of study medication. Relative change from baseline in Ki67 was - 75.9% (95% confidence interval [CI] - 81.9 to - 67.9) for amcenestrant 400 mg, - 68.2% (- 75.7 to - 58.4) for amcenestrant 200 mg, and - 77.7% (- 83.4 to - 70.0) for letrozole (geometric least-squares mean [LSM] estimates). Absolute change in ER H-score from baseline (LSM estimate) was - 176.7 in the amcenestrant 400 mg arm, - 202.9 in the amcenestrant 200 mg arm, and - 32.5 in the letrozole arm. There were no Grade ≥ 3 treatment-related adverse events.

CONCLUSIONS

Both amcenestrant and letrozole demonstrated antiproliferative activity in postmenopausal women with previously untreated, operable ER+/HER2- breast cancer and had good overall tolerability.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT04191382 https://clinicaltrials.gov/ct2/show/NCT04191382 . Registered 9 December 2019.

Neoadjuvant endocrine therapy in postmenopausal women with HR+/HER2- breast cancer

INTRODUCTION

While endocrine therapy is the standard-of-care adjuvant treatment for hormone receptor-positive (HR+) breast cancers, there is also extensive evidence for the role of pre-operative (or neoadjuvant) endocrine therapy (NET) in HR+ postmenopausal women.

AREAS COVERED

We conducted a thorough review of the published literature, to summarize the evidence to date, including studies of how NET compares to neoadjuvant chemotherapy, which NET agents are preferable, and the optimal duration of NET. We describe the importance of on-treatment assessment of response, the different predictors available (including Ki67, PEPI score, and molecular signatures) and the research opportunities the pre-operative setting offers. We also summarize recent combination trials and discuss how the COVID-19 pandemic led to increases in NET use for safe management of cases with deferred surgery and adjuvant treatments.

EXPERT OPINION

NET represents a safe and effective tool for the management of postmenopausal women with HR+/HER2- breast cancer, enabling disease downstaging and a wider range of surgical options. Aromatase inhibitors are the preferred NET, with evidence suggesting that longer regimens might yield optimal results. However, NET remains currently underutilised in many territories and institutions. Further validation of predictors for treatment response and benefit is needed to help standardise and fully exploit the potential of NET in the clinic.

Obesity and outcome of post-menopausal women receiving adjuvant letrozole for breast cancer

Introduction

Aromatase enzyme activity is predominant in adipose tissue. This has led to speculation that aromatase activity is elevated in obese women and subsequently decreased the clinical activity of adjuvant aromatase inhibitors (AIs) in women with estrogen receptor positive (ER+) breast cancer (BC). We investigated the effect of obesity on the outcome of this population.

Patients and methods

Records of 320 consecutive post-menopausal (PM) women with ER+ BC starting single agent adjuvant letrozole between years 2005 and 2014 were retrospectively reviewed. Tumour and patients characteristic including body mass index (BMI) on the day of starting letrozole were extracted. Endpoints of main interest were: (1) Frequency of obesity; (2) relapse-free survival (RFS) in nonobese (G1; BMI < 30) and obese (G2; BMI ≥ 30) patients.

Results

Obesity (BMI: 30–34.99) and morbid obesity (BMI ≥ 35) were present in 105/320 (32.8%) and 115/320 (35.9%) women, respectively. Median follow-up of patients was 49 months; RFS at 5 years (G1: 69% versus G2: 78%) and at 8 years (G1: 69% versus G2: 71%). Median RFS is not reached in both groups (Log rank; P = 0.097). There was no correlation between BMI and RFS (correlation coefficient r = 0.075; P = 0.174).

Conclusion

In this cohort, more than two-thirds of PM women starting adjuvant AIs are obese. Obesity did not adversely affect the outcome of women on adjuvant letrozole.

Preoperative Endocrine Therapy

Purpose of Review

Pre-operative endocrine therapy can be used to down-stage large or locally advanced breast cancers in ER+ disease. In the last four decades, it has evolved from a treatment perceived as an alternative to surgery for those too unfit to undergo surgery or chemotherapy, to the present day where it is a valuable and valid option in the treatment of postmenopausal women with ER-rich (Allred score 7–8, or > 50% staining for ER) breast cancer.

Recent Findings

Emerging data from the metastatic setting is translating into neoadjuvant trials, utilising dual endocrine targeting or combinations of endocrine agents and other targeted drugs, including those acting against components of the PI3K pathway and the cell cycle. The routine use of peri-operative endocrine therapy in all ER+ tumours may help to yield important long-term prognostic information, and guide adjuvant endocrine therapy.

Summary

Pre-operative endocrine therapy is an exciting and evolving area with emerging new approaches. In this review, established evidence and emerging data on its applications are discussed.

Recent Progress in the Discovery of Next Generation Inhibitors of Aromatase from the Structure-Function Perspective

Human aromatase catalyzes the synthesis of estrogen from androgen with high substrate specificity. For the past 40 years, aromatase has been a target of intense inhibitor discovery research for the prevention and treatment of estrogen-dependent breast cancer. The so-called third generation aromatase inhibitors (AIs) letrozole, anastrozole, and the steroidal exemestane were approved in the U.S. in the late 1990s for estrogen-dependent postmenopausal breast cancer. Efforts to develop better AIs with higher selectivity and lower side effects were handicapped by the lack of an experimental structure of this unique P450. The year 2009 marked the publication of the crystal structure of aromatase purified from human placenta, revealing an androgen-specific active site. The structure has reinvigorated research activities on this fascinating enzyme and served as the catalyst for next generation AI discovery research. Here, we present an account of recent developments in the AI field from the perspective of the enzyme's structure-function relationships.

Discovery of novel aromatase inhibitors using a homogeneous time-resolved fluorescence assay

AIM

Aromatase is an important target for drugs to treat hormone-dependent diseases, including breast cancer. The aim of this study was to develop a homogeneous time-resolved fluorescence (HTRF) aromatase assay suitable for high-throughput screening (HTS).

METHODS

A 384-well aromatase HTRF assay was established, and used to screen about 7000 compounds from a compound library. Anti-proliferation activity of the hit was evaluated using alamarBlue(R) assay in a hormone-dependent breast cancer cell line T47D. Molecular docking was conducted to elucidate the binding mode of the hit using the Discovery Studio program.

RESULTS

The Z' value and signal to background (S/B) ratio were 0.74 and 5.4, respectively. Among the 7000 compounds, 4 hits (XHN22, XHN26, XHN27 and triptoquinone A) were found to inhibit aromatase with IC50 values of 1.60±0.07, 2.76±0.24, 0.81±0.08 and 45.8±11.3 μmol /L, respectively. The hits XHN22, XHN26 and XHN27 shared the same chemical scaffold of 4-imidazolyl quinoline. Moreover, the most potent hit XHN27 at 10 and 50 μmol/L inhibited the proliferation of T47D cells by 45.3% and 35.2%, respectively. The docking study revealed that XHN27 docked within the active site of aromatase and might form a hydrogen bond and had a π-cation interaction with amino acid residues of the protein.

CONCLUSION

XHN27, an imidazolyl quinoline derivative of flavonoid, is a potent aromatase inhibitor with anti-proliferation activity against breast cancer in vitro. The established assay can be used in HTS for discovering novel aromatase inhibitor.

An international Ki67 reproducibility study

BACKGROUND

In breast cancer, immunohistochemical assessment of proliferation using the marker Ki67 has potential use in both research and clinical management. However, lack of consistency across laboratories has limited Ki67's value. A working group was assembled to devise a strategy to harmonize Ki67 analysis and increase scoring concordance. Toward that goal, we conducted a Ki67 reproducibility study.

METHODS

Eight laboratories received 100 breast cancer cases arranged into 1-mm core tissue microarrays-one set stained by the participating laboratory and one set stained by the central laboratory, both using antibody MIB-1. Each laboratory scored Ki67 as percentage of positively stained invasive tumor cells using its own method. Six laboratories repeated scoring of 50 locally stained cases on 3 different days. Sources of variation were analyzed using random effects models with log2-transformed measurements. Reproducibility was quantified by intraclass correlation coefficient (ICC), and the approximate two-sided 95% confidence intervals (CIs) for the true intraclass correlation coefficients in these experiments were provided.

RESULTS

Intralaboratory reproducibility was high (ICC = 0.94; 95% CI = 0.93 to 0.97). Interlaboratory reproducibility was only moderate (central staining: ICC = 0.71, 95% CI = 0.47 to 0.78; local staining: ICC = 0.59, 95% CI = 0.37 to 0.68). Geometric mean of Ki67 values for each laboratory across the 100 cases ranged 7.1% to 23.9% with central staining and 6.1% to 30.1% with local staining. Factors contributing to interlaboratory discordance included tumor region selection, counting method, and subjective assessment of staining positivity. Formal counting methods gave more consistent results than visual estimation.

CONCLUSIONS

Substantial variability in Ki67 scoring was observed among some of the world's most experienced laboratories. Ki67 values and cutoffs for clinical decision-making cannot be transferred between laboratories without standardizing scoring methodology because analytical validity is limited.

Anastrozole and RU486: Effects on estrogen receptor α and Mucin 1 expression and correlation in the MCF-7 breast cancer cell line

Anastrozole and RU486 are shown to reduce hormone-responsive breast cancer progression when used as adjuvant treatments to surgical intervention, however, a high incidence of cancer recurrence remains. Estrogen receptor alpha (ERα) and Mucin 1 (MUC1), a glycoprotein, are both implicated in breast cancer progression. We assessed whether Anastrozole and RU486 treatment affects the expression of, and relationship between, ERα and MUC1 in the ERα(+) MUC1(+) MCF-7 breast cancer cell line. MCF-7 cells, treated with physiological concentrations of either Anastrozole or RU486 for 18 h or 72 h, were subjected to immunolocalization of both markers. CellProfiler software was used to quantify intensity for statistical analyses. ERα expression increased at both time periods following treatment. MUC1 expression increased with RU486-treatment at both times, whereas Anastrozole induced increased MUC1 expression at 72 h only. The biomarkers demonstrated increased point association at 72 h within treatment groups despite MUC1 diverging from correlation with ERα. We propose that tumor progression is independent of MUC1 and ERα correlation. These preliminary results indicate that withdrawal of adjuvant treatment may result in residual cell populations expressing increased ERα and MUC1. This phenotype may allow enhanced estrogenic and metastatic capacity influencing cancer recurrence, a hypothesis we are investigating further.

An overview of letrozole in postmenopausal women with hormone-responsive breast cancer

Third-generation aromatase inhibitors (AIs) have proven to be superior to tamoxifen in terms of time to disease progression in patients with hormone receptor (HR) positive (HR+) status and, nowadays, are used in the adjuvant and neoadjuvant settings, and first-line therapy for advanced breast cancer. Letrozole is a third generation AI, as are anastrozole and exemestane. In the past, clinical studies had demonstrated that letrozole was effective as a second-line treatment of metastatic breast cancer. In this paper, pharmacokinetic and pharmacodynamic properties of letrozole are reviewed along with its activity in preclinical and clinical settings. Additionally, the results of important clinical trials such as Breast International Group (BIG) 1-98, which tested the optimal initial adjuvant endocrine treatment and the sequential therapy with letrozole and tamoxifen, MA-17 that evaluates the benefits of extended adjuvant therapy, and other important studies in advanced and neoadjuvant disease, are reviewed. Safety comparisons of treatments are also addressed. Interestingly, about 50% of human epidermal growth factor receptor 2-positive (HER2+) breast cancers are HR+. However, HER2 positivity is a marker of antiestrogen treatment resistance. Because of this, a dual treatment is a logical approach when both receptors are overexpressed. The combination of lapatinib and letrozole leads to a significant improvement in the overall disease outcome. Also, the combination of everolimus plus letrozole has been tested in this setting. In fact, the coadministration of both agents seems to increase the efficacy of letrozole in newly-diagnosed HR+ patients. Once resistance to sequential trastuzumab and AI as monotherapy has been found, trastuzumab and letrozole combined in HR+ and HER2+ patients with advanced breast cancer can overcome resistance to both drugs administered as single agents, according to recently reported results.

The mammalian target of rapamycin inhibitor everolimus (RAD001) in early breast cancer: results of a pre-operative study

mTOR plays a key role in tumor cell cycle control, proliferation, and survival. RAD001 (everolimus) is a novel macrolide that inhibits mTOR and thus downstream signaling pathways. 31 post-menopausal women with early breast cancer were given 5 mg RAD001 once daily for 14 days prior to surgery. Biopsies were taken at diagnosis and at surgery (post 14 days of treatment) and assessed for immunohistochemical changes in proliferation (Ki67), apoptosis (active caspase-3), p-AKT (s473), p-S6 (s235/236 and s240/244), p-mTOR (s2448), ER, and PR. Five patients did not complete the 2-week treatment period due to adverse events. All adverse events were grade 1 or 2 (NCIC-CTC scale). RAD001 treatment significantly decreased proliferation (geometric mean reduction 74% from baseline (p = 0.019)), particularly in HER-2 positive tumors. High Ki67 pre-treatment correlated with reduction in Ki67, an increase in apoptosis, a reduction in p-AKT (cytoplasmic) and reduction in p-mTOR following treatment. Nuclear expression of p-AKT was significantly reduced with treatment. Tumors that had a reduction in Ki67 with treatment exhibited a significant reduction in cytoplasmic p-AKT. p-S6 staining was significantly reduced independently of Ki67 (p < 0.001 for two sites of phosphorylation). RAD001 5 mg/daily is safe and tolerable in postmenopausal early breast cancer patients and inhibits the mTOR pathway and its downstream effectors, significantly reducing tumor cell proliferation. Tumors with high Ki67, high p-AKT, and HER-2 positivity may be more responsive to mTOR inhibition with RAD001. This is the first study to report results of RAD001 5 mg as a single agent in early breast cancer.

American Society of Clinical Oncology/College of American Pathologists guideline recommendations for immunohistochemical testing of estrogen and progesterone receptors in breast cancer (unabridged version)

PURPOSE

To develop a guideline to improve the accuracy of immunohistochemical (IHC) estrogen receptor (ER) and progesterone receptor (PgR) testing in breast cancer and the utility of these receptors as predictive markers.

METHODS

The American Society of Clinical Oncology and the College of American Pathologists convened an international Expert Panel that conducted a systematic review and evaluation of the literature in partnership with Cancer Care Ontario and developed recommendations for optimal IHC ER/PgR testing performance.

RESULTS

Up to 20% of current IHC determinations of ER and PgR testing worldwide may be inaccurate (false negative or false positive). Most of the issues with testing have occurred because of variation in pre-analytic variables, thresholds for positivity, and interpretation criteria.

RECOMMENDATIONS

The Panel recommends that ER and PgR status be determined on all invasive breast cancers and breast cancer recurrences. A testing algorithm that relies on accurate, reproducible assay performance is proposed. Elements to reliably reduce assay variation are specified. It is recommended that ER and PgR assays be considered positive if there are at least 1% positive tumor nuclei in the sample on testing in the presence of expected reactivity of internal (normal epithelial elements) and external controls. The absence of benefit from endocrine therapy for women with ER-negative invasive breast cancers has been confirmed in large overviews of randomized clinical trials.

Correlation Between Anthropometric Measures and Biomarker Changes After Neoadjuvant Therapy With Tamoxifen or Anastrozole in Postmenopausal Women With Breast Cancer

Background

Epidemiological studies have reported positive associations between anthropometric measures and risk for developing breast cancers that express hormone receptors and associated mortality. However, the impact of nutritional status on the molecular response to endocrine therapy has yet to be described.

Methods

Body mass index (BMI), waist circumference (WC), hip circumference (HP), and waist-to-hip ratio (WHR) were measured in patients with invasive ductal carcinoma (IDC) before and after neoadjuvant treatment with either tamoxifen or anastrozole, and a possible correlation with prognostic factors, as estrogen receptor (ER), progesterone receptor (PgR), and proliferative index (Ki-67), was analyzed. Fifty-seven patients with palpable ER-positive IDC were randomized into three neoadjuvant treatment groups and received anastrozole or placebo or tamoxifen for twenty-one days. Biomarker status was obtained by comparing the immunohistochemical evaluation of samples collected before and after treatment, using the Allred scoring system. Statistical analysis was performed using the Statistical Package for the Social Sciences (SPSS).

Results and Conclusions

After treatment, the anastrozole group showed reduced ER and PgR expression (p < 0.05), and both the anastrozole and tamoxifen groups showed lower Ki-67 status. A significant reduction in PgR positivity (p < 0.05) was found in women with large WC and HC who were treated with anastrozole. Reduction in PgR positivity also tended to be associated with BMI (p = 0.09) in the anastrozole group. BMI, WC, HC and WHR correlated neither with biomarker levels in the tamoxifen and placebo groups nor with ER and Ki-67 status in the anastrozole group after primary endocrine treatment.

Gene expression profiling of response to mTOR inhibitor everolimus in pre-operatively treated post-menopausal women with oestrogen receptor-positive breast cancer

There is growing evidence that uncontrolled activation of the PI3K/Akt/mTOR pathway contributes to the development and progression of breast cancer. Inhibition of this pathway has antitumour effects in preclinical studies and efficacy in combination with other agents in breast cancer patients. The aim of this study is to characterise the effects of pre-operative everolimus treatment in primary breast cancer patients and to identify potential molecular predictors of response. Twenty-seven patients with oestrogen receptor (ER)-positive breast cancer completed 11-14 days of neoadjuvant treatment with 5-mg everolimus. Core biopsies were taken before and after treatment and analysed using Illumina HumanRef-8 v2 Expression BeadChips. Changes in proliferation (Ki67) and phospho-AKT were measured on diagnostic core biopsies/resection samples embedded in paraffin by immunohistochemistry to determine response to treatment. Patients that responded to everolimus treatment with significant reductions in proliferation (fall in % Ki67 positive cells) also had significant decreases in the expression of genes involved in cell cycle (P = 8.70E-09) and p53 signalling (P = 0.01) pathways. Highly proliferating tumours that have a poor prognosis exhibited dramatic reductions in the expression of cell cycle genes following everolimus treatment. The genes that most clearly separated responding from non-responding pre-treatment tumours were those involved with protein modification and dephosphorylation, including DYNLRB2, ERBB4, PTPN13, ULK2 and DUSP16. The majority of ER-positive breast tumours treated with everolimus showed a significant reduction in genes involved with proliferation, these may serve as markers of response and predict which patients will derive most benefit from mTOR inhibition.

Letrozole: a review of its use in the treatment of postmenopausal women with hormone-responsive early breast cancer

Letrozole (Femara) is a third-generation, nonsteroidal aromatase inhibitor. Adjuvant therapy with letrozole is more effective than tamoxifen in postmenopausal women with hormone-responsive early breast cancer, and extended adjuvant therapy with letrozole after the completion of adjuvant tamoxifen therapy is more effective than placebo in this patient population; letrozole is generally well tolerated. Ongoing trials will help answer outstanding questions regarding the optimal duration of letrozole therapy in early breast cancer and its efficacy compared with other third-generation aromatase inhibitors such as anastrozole. In the meantime, letrozole should be considered a valuable option in the treatment of postmenopausal women with hormone-responsive early breast cancer, both as adjuvant and extended adjuvant therapy.

Trastuzumab plus anastrozole versus anastrozole alone for the treatment of postmenopausal women with human epidermal growth factor receptor 2-positive, hormone receptor-positive metastatic breast cancer: results from the randomized phase III TAnDEM study

PURPOSE

TAnDEM is the first randomized phase III study to combine a hormonal agent and trastuzumab without chemotherapy as treatment for human epidermal growth factor receptor 2 (HER2)/hormone receptor-copositive metastatic breast cancer (MBC).

PATIENTS AND METHODS

Postmenopausal women with HER2/hormone receptor-copositive MBC were randomly assigned to anastrozole (1 mg/d orally) with or without trastuzumab (4 mg/kg intravenous infusion on day 1, then 2 mg/kg every week) until progression. The primary end point was progression-free survival (PFS) in the intent-to-treat population. Results Overall, 103 patients received trastuzumab plus anastrozole; 104 received anastrozole alone. Patients in the trastuzumab plus anastrozole arm experienced significant improvements in PFS compared with patients receiving anastrozole alone (hazard ratio = 0.63; 95% CI, 0.47 to 0.84; median PFS, 4.8 v 2.4 months; log-rank P = .0016). In patients with centrally confirmed hormone receptor positivity (n = 150), median PFS was 5.6 and 3.8 months in the trastuzumab plus anastrozole and anastrozole alone arms, respectively (log-rank P = .006). Overall survival in the overall and centrally confirmed hormone receptor-positive populations showed no statistically significant treatment difference; however, 70% of patients in the anastrozole alone arm crossed over to receive trastuzumab after progression on anastrozole alone. Incidence of grade 3 and 4 adverse events was 23% and 5%, respectively, in the trastuzumab plus anastrozole arm, and 15% and 1%, respectively, in the anastrozole alone arm; one patient in the combination arm experienced New York Heart Association class II congestive heart failure.

CONCLUSION

Trastuzumab plus anastrozole improves outcomes for patients with HER2/hormone receptor-copositive MBC compared with anastrozole alone, although adverse events and serious adverse events were more frequent with the combination.