Clinical Implications of ESR1 Mutations in Hormone Receptor-Positive Advanced Breast Cancer

Fulvestrant in the treatment of hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: A review

Nearly 75% of breast cancers are hormone receptor-positive (HR+) and human epidermal growth factor receptor type 2-negative (HER2-), making endocrine therapy the mainstay of treatment for HR+ and HER2- combination. Although endocrine therapy, such as therapy with fulvestrant, is widely used in the clinic, endocrine resistance (primary or secondary) is inevitable and poses a serious clinical concern. However, the therapeutic landscape of HR+/HER2- breast cancer is rapidly changing and evolving. In recent years, molecular insights into the genome of HR+/HER2- breast cancer have helped to identify promising targets, such as alterations in signaling pathways [phosphatidylinositide 3-kinase (PI3K/AKT/mammalian target of rapamycin (mTOR)], dysregulation of the cell cycle (CDK4/6), and identification of new ESR1 mutations. These insights have led to the development of newer targeted therapies, which aims at significantly improving survival in these patients. This review summarizes the role and rationale of fulvestrant when used as a monotherapy or in combination with targeted therapies in patients with HR+/HER2- advanced breast cancer. We also discuss other novel agents and potential future combination treatment options.

Targeted mutation detection in breast cancer using MammaSeq™

Background

Breast cancer is the most common invasive cancer among women worldwide. Next-generation sequencing (NGS) has revolutionized the study of cancer across research labs around the globe; however, genomic testing in clinical settings remains limited. Advances in sequencing reliability, pipeline analysis, accumulation of relevant data, and the reduction of costs are rapidly increasing the feasibility of NGS-based clinical decision making.

Methods

We report the development of MammaSeq, a breast cancer-specific NGS panel, targeting 79 genes and 1369 mutations, optimized for use in primary and metastatic breast cancer. To validate the panel, 46 solid tumors and 14 plasma circulating tumor DNA (ctDNA) samples were sequenced to a mean depth of 2311× and 1820×, respectively. Variants were called using Ion Torrent Suite 4.0 and annotated with cravat CHASM. CNVKit was used to call copy number variants in the solid tumor cohort. The oncoKB Precision Oncology Database was used to identify clinically actionable variants. Droplet digital PCR was used to validate select ctDNA mutations.

Results

In cohorts of 46 solid tumors and 14 ctDNA samples from patients with advanced breast cancer, we identified 592 and 43 protein-coding mutations. Mutations per sample in the solid tumor cohort ranged from 1 to 128 (median 3), and the ctDNA cohort ranged from 0 to 26 (median 2.5). Copy number analysis in the solid tumor cohort identified 46 amplifications and 35 deletions. We identified 26 clinically actionable variants (levels 1–3) annotated by OncoKB, distributed across 20 out of 46 cases (40%), in the solid tumor cohort. Allele frequencies of ESR1 and FOXA1 mutations correlated with CA.27.29 levels in patient-matched blood draws.

Conclusions

In solid tumor biopsies and ctDNA, MammaSeq detects clinically actionable mutations (OncoKB levels 1–3) in 22/46 (48%) solid tumors and in 4/14 (29%) of ctDNA samples. MammaSeq is a targeted panel suitable for clinically actionable mutation detection in breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1102-7) contains supplementary material, which is available to authorized users.

Cyclin-dependent kinase 4/6 inhibitors: what have we learnt across studies, therapy situations and substances

PURPOSE OF REVIEW

Cyclin-dependent kinases (CDK) are key regulatory enzymes that control cell cycle and cell division. In the recent years, new therapeutic options selectively targeting CDK 4 and 6 have shown promising clinical activity in several solid tumors. Since 2015, three CDK 4/6 inhibitors have been approved for treatment of hormone receptor-positive HER2-negative metastatic breast cancer: palbociclib, ribociclib and abemaciclib. These drugs share a common mechanism of action and have been evaluated in studies with a similar design. The following review gives a clinical overview of the CDK 4/6 inhibitors in breast cancer therapy and highlight current study data with regard to their antitumor efficacy and toxicities.

RECENT FINDINGS

In clinical trials in the first-line and later-line setting, palbociclib, ribociclib and abemaciclib in combination with endocrine therapy significantly prolonged progression-free survival. The most common adverse events during treatment with CDK 4/6 inhibitors are neutropenia, fatigue and gastrointestinal symptoms.

SUMMARY

CDK 4/6 inhibitors represent a valuable treatment option for patients with metastatic hormone receptor-positive HER2-negative breast cancer. Although the clinical efficacy of the three agents seems similar, their toxicity profiles differ. Therefore, the choice of a CKD 4/6 inhibitor depends on patient's characteristics and individual preferences.

VIDEO ABSTRACT

In the video, the author describes the content of the review and present the main topics discussed in the article (http://links.lww.com/COOG/A44).

FOXA1 levels are decreased in pleural breast cancer metastases after adjuvant endocrine therapy, and this is associated with poor outcome

Estrogen receptor-alpha (ERα)-positive breast cancer is often treated with antihormonal regimens. However, resistance to treatment is common, leading to metastatic disease. ERα activity requires the functional involvement of pioneer factors FOXA1 and GATA3, which enable ERα-chromatin binding and are crucial for ERα-driven cell proliferation. FOXA1 was found increased in metastatic breast cancers in relation to the primary tumor, but a comprehensive clinical assessment thereof, in relation to different metastatic sites and endocrine therapy usage, is currently lacking. Prior cell line-based reports, however, have revealed that FOXA1 is required for tamoxifen-resistant tumor cell proliferation. We studied expression levels of ERα, GATA3, and FOXA1 by immunohistochemistry in samples from both primary tumors and various metastatic sites. For all factors, expression levels varied between the metastatic sites. For pleural metastases, strong variation was found in FOXA1 and GATA3 levels. Although GATA3 levels remained unaltered between primary breast cancer and pleural metastases, FOXA1 levels were reduced exclusively in metastases of patients who received endocrine therapies in the adjuvant setting, even though ERα was still expressed. Importantly, decreased FOXA1 levels in pleural metastases correlated with hormone irresponsiveness in the palliative setting, while no such correlation was found for GATA3. With this, we show divergent clinical correlations of the two ERα pioneer factors FOXA1 and GATA3 in metastatic breast cancer, where endocrine therapy resistance was associated with decreased FOXA1 levels in pleural metastases.

In silico screening for ERα down modulators identifies thioridazine as an anti-proliferative agent in primary, 4OH-tamoxifen-resistant and Y537S ERα-expressing breast cancer cells

PURPOSE

Most breast cancers (BCs) express estrogen receptor α (ERα) and are treated with the endocrine therapy (ET) drugs 4OH-tamoxifen (Tam) and fulvestrant (ICI 182,780; ICI). Unfortunately, a high fraction of ET treated women relapses and becomes resistant to ET. Therefore, additional anti-BC drugs are needed. Recently, we proposed that the identification of novel anti-BC drugs can be achieved using modulation of the intracellular ERα content in BC cells as a pharmacological target. Here, we searched for Food and Drug Administration (FDA)-approved drugs that potentially modify the ERα content in BC cells.

METHODS

We screened in silico more than 60,000 compounds to identify FDA-approved drugs with a gene signature similar to that of ICI. We identified mitoxantrone and thioridazine and tested them in primary, Tam-resistant and genome-edited Y537S ERα-expressing BC cells.

RESULTS

We found that mitoxantrone and thioridazine induced ERα downmodulation and prevented MCF-7 BC cell proliferation. Interestingly, while mitoxantrone was found to be toxic for normal breast epithelial cells, thioridazine showed a preferential activity towards BC cells. Thioridazine also reduced the ERα content and prevented cell proliferation in primary, Tam-resistant and genome-edited Y537S ERα expressing BC cells.

CONCLUSIONS

We suggest that modulation of the intracellular ERα concentration in BC cells can be exploited in in silico screens to identify anti-BC drugs and uncover a re-purposing opportunity for thioridazine in the treatment of primary and metastatic ET resistant BCs.

Fulvestrant in management of hormone receptor-positive metastatic breast cancer

Fulvestrant is a steroidal selective estrogen receptor degrader that was approved by the US FDA in 2002 for treatment of ER-positive metastatic breast cancer (ER + MBC) post-progression on aromatase inhibitors. In 2017, the label was updated to include endocrine therapy naive ER + MBC. While initially fulvestrant was thought to be equivalent to aromatase inhibitors with monthly dose of 250 mg intramuscular injection, several postmarketing trials challenged this understanding. Subsequently, the recommended dose changed to 500 mg monthly plus loading dose, and this was proven to be superior to anastrozole in efficacy. Most recently the results of FALCON trial have further challenged the way fulvestrant is viewed and used. This report provides a historical perspective on this compound, its evolving role in management of ER + MBC and what the future may hold for this drug.

Efficacy and safety of fulvestrant in postmenopausal patients with hormone receptor-positive advanced breast cancer: a systematic literature review and meta-analysis

PURPOSE

This meta-analysis was conducted to compare the efficacy and safety of fulvestrant with aromatase inhibitors in postmenopausal women with hormone receptor-positive (estrogen and/or progesterone receptor positive) advanced breast cancer.

METHODS

Electronic databases were searched for randomized controlled trials comparing the efficacy and safety of fulvestrant with three aromatase inhibitors (anastrozole/letrozole/exemestane) published through August 31, 2017. Time to progression/progression-free survival was the primary outcome, while overall survival and safety were the secondary outcomes. Time to progression/progression-free survival was evaluated in subgroups determined on age, hormone receptor status, visceral metastasis, and measurable disease. Hazard ratios with 95% confidence intervals were analyzed by STATA 12.0.

RESULTS

Total of seven randomized controlled trials, with 3168 patients were included for analysis. In the overall population, fulvestrant and aromatase inhibitors had similar time to progression/progression-free survival (Hazard ratio 0.93; 95% confidence interval 0.86-1.01, P = 0.102); however, time to progression/progression-free survival for fulvestrant 500 mg was significantly longer compared with aromatase inhibitors (hazard ratio 0.75; 95% confidence interval 0.62-0.91, P = 0.003). Subgroup analysis revealed significant prolongation of time to progression/progression-free survival with fulvestrant compared with aromatase inhibitors in the patients of estrogen and progesterone receptor-positive (hazard ratio 0.86; 95% confidence interval, 0.75-0.98, P = 0.022) and patients aged ≥ 65 years (hazard ratio 0.81; 95% confidence interval 0.68-0.96, P = 0.014). Overall survival was similar in both groups (hazard ratio 0.89; 95% confidence interval 0.70, 1.13, P = 0.334).

CONCLUSION

In postmenopausal women with estrogen and/or progesterone receptor-positive advanced breast cancer, fulvestrant 500 mg showed better efficacy than aromatase inhibitor, which was not seen with fulvestrant 250 mg. Compared to aromatase inhibitors, fulvestrant prolonged time to progression/progression-free survival in the subgroups including estrogen and progesterone receptor-positive patients and those aged ≥ 65 years.

Emerging Innovative Therapeutic Approaches Leveraging Cyclin-Dependent Kinase Inhibitors to Treat Advanced Breast Cancer

Estrogen receptor-positive (ER+) tumors represent the most common form of breast cancer. Although endocrine therapy (ET) results in benefit for the majority of these patients, disease progression invariably occurs. The discovery of the relation between cyclin-dependent kinases (CDKs) and the ER pathways is one of the major advances in unveiling mechanisms of resistance to ET. In this article we review the role of CDK4/6 inhibitors in ER + breast cancer patients.

A Computational Assay of Estrogen Receptor α Antagonists Reveals the Key Common Structural Traits of Drugs Effectively Fighting Refractory Breast Cancers

Somatic mutations of the Estrogen Receptor α (ERα) occur with an up to 40% incidence in ER sensitive breast cancer (BC) patients undergoing prolonged endocrine treatments. These polymorphisms are implicated in acquired resistance, disease relapse, and increased mortality rates, hence representing a current major clinical challenge. Here, multi-microseconds (12.5 µs) molecular dynamics simulations revealed that recurrent ERα polymorphisms (i. e. L536Q, Y537S, Y537N, D538G) (mERα) are constitutively active in their apo form and that they prompt the selection of an agonist (active)-like conformation even upon antagonists binding. Interestingly, our simulations rationalize, for the first time, the efficacy profile of (pre)clinically used Selective Estrogen Receptor Modulators/Downregulators (SERMs/SERDs) against these variants, enlightening, at atomistic level of detail, the key common structural traits needed by drugs able to effectively fight refractory BC types. This knowledge represents a key advancement for mechanism-based therapeutics targeting resistant ERα isoforms, potentially allowing the community to move a step closer to ‘precision medicine’ calibrated on patients’ genetic profiles and disease progression.

Precision medicine in breast cancer: reality or utopia?

Many cancers, including breast cancer, have demonstrated prognosis and support advantages thanks to the discovery of targeted therapies. The advent of these new approaches marked the rise of precision medicine, which leads to improve the diagnosis, prognosis and treatment of cancer. Precision medicine takes into account the molecular and biological specificities of the patient and their tumors that will influence the treatment determined by physicians. This new era of medicine is accessible through molecular genetics platforms, the development of high-speed sequencers and means of analysis of these data. Despite the spectacular results in the treatment of cancers including breast cancer, described in this review, not all patients however can benefit from this new strategy. This seems to be related to the many genetic mutations, which may be different from one patient to another or within the same patient. It comes to give new impetus to the research—both from a technological and biological point of view—to make the hope of precision medicine accessible to all.