Letrozole for brain and scalp metastases from breast cancer—a case report

Hormonal and neuronal interactions shaping the brain metastatic microenvironment

Metastatic progression drives the majority of cancer-related fatalities, and involvement of the central nervous system (CNS) poses especially formidable challenges to patients and clinicians. Brain metastases (BrM), commonly originate from lung, breast and melanoma cancers, and carry disproportionately poor outcomes. Although therapeutic advances have extended survival for many extracranial tumors, BrM incidence continues to climb-underscoring critical knowledge gaps in understanding the unique biology of tumor colonization in the CNS. While definitive evidence remains limited, a growing focus on cancer neuroscience-especially regarding hormone dependent cancer cells in the brain-has begun to reveal that factors normally regulated by sex steroids and neurosteroids may similarly influence the specialized metastatic microenvironment in the CNS. Steroid hormones can permeate the blood-brain barrier (BBB) or be synthesized de novo by astrocytes and other CNS-resident cells, potentially influencing processes such as inflammation, synaptic plasticity, and immune surveillance. However, how these hormonal pathways are co-opted by disseminated cancer cells remains unclear. Here, we review the complex hormonal landscape of the adult brain and examine how neuroendocrine-immune interactions, often regulated by sex hormones, may support metastatic growth. We discuss the interplay between systemic hormones, local steroidogenesis, and tumor adaptation to identify novel therapeutic opportunities.

Breast Cancer Brain Metastasis: A Comprehensive Review

The mechanisms underlying breast cancer brain metastasis (BCBM) development are complex, and its clinical presentation varies depending on the number, location, and size of brain metastases. Common symptoms include headache, neurologic deficits, and seizures. Diagnosis of BCBM typically relies on neuroimaging techniques, such as magnetic resonance imaging and computed tomography scans. Local therapies, such as surgery and stereotactic radiosurgery, can be used to control tumor growth and relieve symptoms. Whole-brain radiotherapy has been a mainstay of treatment for BCBM, but its use has been associated with cognitive decline. Systemic therapy with chemotherapy and targeted agents plays an increasingly important role in the management of BCBM. Novel agents, such as human epidermal growth factor receptor 2 (HER2)-targeted therapies and tyrosine kinase inhibitors, have shown promising results in improving survival for patients with HER2-positive and triple-negative BCBM. This comprehensive review synthesizes current knowledge, clinical insights, and evolving paradigms to provide a robust understanding and roadmap for optimizing the diagnosis and management of BCBM.

Systematic review of the management of brain metastases from hormone receptor positive breast cancer

INTRODUCTION

Brain metastases are a common cause of morbidity and mortality in patients with breast cancer. Local central nervous system (CNS) directed therapies are usually the first line treatment for breast cancer brain metastases (BCBM), but those must be followed by systemic therapies to achieve long-term benefit. Systemic therapy for hormone receptor (HR+) breast cancer has evolved in the last 10 years, but their role when brain metastases occur is uncertain.

METHODS

We performed a systematic review of the literature focused on management of HR+ BCBM by searching Medline/PubMed, EBSCO, and Cochrane databases. The PRISMA guidelines were used for systematic review.

RESULTS

Out of 807 articles identified, 98 fulfilled the inclusion criteria in their relevance to the management of HR+ BCBM.

CONCLUSIONS

Similar to brain metastases from other neoplasms, local CNS directed therapies are the first line treatment for HR+ BCBM. Although the quality of evidence is low, after local therapies, our review supports the combination of targeted and endocrine therapies for both CNS and systemic management. Upon exhaustion of targeted/endocrine therapies, case series and retrospective reports suggest that certain chemotherapy agents are active against HR+ BCBM. Early phase clinical trials for HR+ BCBM are ongoing, but there is a need for prospective randomized trials to guide management and improve patients' outcome.

Systemic treatments for breast cancer brain metastasis

Breast cancer (BC) is the most common cancer in females and BC brain metastasis (BCBM) is considered as the second most frequent brain metastasis. Although the advanced treatment has significantly prolonged the survival in BC patients, the prognosis of BCBM is still poor. The management of BCBM remains challenging. Systemic treatments are important to maintain control of central nervous system disease and improve patients' survival. BCBM medical treatment is a rapidly advancing area of research. With the emergence of new targeted drugs, more options are provided for the treatment of BM. This review features currently available BCBM treatment strategies and outlines novel drugs and ongoing clinical trials that may be available in the future. These treatment strategies are discovered to be more efficacious and potent, and present a paradigm shift in the management of BCBMs.

Advances in the Management of Central Nervous System Metastases from Breast Cancer

Central nervous system (CNS) metastases are common in breast cancer (BC) patients and are particularly relevant as new treatments for BC are prolonging survival. Here, we review advances in the treatment of CNS metastases from BC, including radiotherapy, systemic therapies, and the evolving role of immunotherapy. The use of radiotherapy and chemotherapy is the cornerstone of treatment for CNS metastases. However, new targeted therapies have recently been developed, including anti-HER2 agents and antibody-drug conjugates that have presented promising results for the treatment of these patients.

Systemic Therapy Approaches for Breast Cancer Brain and Leptomeningeal Metastases

OPINION STATEMENT

Brain metastasis arising from breast cancer is associated with a poor prognosis. Various systemic chemotherapy and targeted therapies which are effective against breast cancer often fail to provide benefits against brain metastasis. This is mainly due to limited penetration of the therapies across the blood-brain barrier, and divergent evolution of brain metastasis compared to the primary tumor. Thus, brain metastasis is typically treated upfront with local therapies, such as surgery and radiation, followed by systemic therapies. Systemic therapies with CNS permeability are favored in patients with brain metastasis. This paper reviews various systemic therapy options for breast cancer brain metastasis.

Salvage Treatment for Progressive Brain Metastases in Breast Cancer

Simple Summary

Thirty percent of patients with human epidermal growth factor receptor 2-positive breast cancer and triple-negative breast cancer, and 15% of patients with the remaining subtypes of breast cancer will develop brain metastases. Available treatment methods include surgery and radiotherapy. However, some individuals will experience intracranial progression despite prior local treatment. This situation remains a challenge. In the case of progressing lesions amenable to local therapy, the choice of a treatment method must consider performance status, cancer burden, possible toxicity, and previously applied therapy. Stereotactic radiosurgery or fractionated radiotherapy rather than whole-brain radiotherapy should be used only if feasible. If local therapy is unfeasible, selected patients, especially those with human epidermal growth factor receptor 2-positive breast cancer, may benefit from systemic therapy.

Abstract

Survival of patients with breast cancer has increased in recent years due to the improvement of systemic treatment options. Nevertheless, the occurrence of brain metastases is associated with a poor prognosis. Moreover, most drugs do not penetrate the central nervous system because of the blood–brain barrier. Thus, confirmed intracranial progression after local therapy is especially challenging. The available methods of salvage treatment include surgery, stereotactic radiosurgery (SRS), fractionated stereotactic radiotherapy (FSRT), whole-brain radiotherapy, and systemic therapies. This narrative review discusses possible strategies of salvage treatment for progressive brain metastases in breast cancer. It covers possibilities of repeated local treatment using the same method as applied previously, other methods of local therapy, and options of salvage systemic treatment. Repeated local therapy may provide a significant benefit in intracranial progression-free survival and overall survival. However, it could lead to significant toxicity. Thus, the choice of optimal methods should be carefully discussed within the multidisciplinary tumor board.

Intracranial Response Rate in Patients with Breast Cancer Brain Metastases after Systemic Therapy

Simple Summary

For many years, patients with breast cancer and brain metastases were excluded from participation in clinical trials. It was believed that anticancer drugs could not cross the blood–brain barrier. However, recent evidence strongly suggests that some drugs can act against brain metastases, with the greatest intracranial response rate reported in the case of capecitabine, neratinib plus capecitabine, trastuzumab deruxtecan and tucatinib plus trastuzumab and capecitabine. In this article, we discuss the achievements in systemic therapy of breast cancer patients with brain metastases. We stress on the newest clinical trial results which indicate tremendous progress in HER2-positive breast cancer. On the other hand, in patients with triple-negative breast cancer or hormone-receptor-positive brain metastases, much fewer compounds were discovered. Based on the presented results, patients with active brain metastases should be routinely included in clinical trials with novel agents.

Abstract

Brain metastases are detected in 5% of patients with breast cancer at diagnosis. The rate of brain metastases is higher in HER2-positive and triple-negative breast cancer patients (TNBC). In patients with metastatic breast cancer, the risk of brain metastases is much higher, with up to 50% of the patients having two aggressive biological breast cancer subtypes. The prognosis for such patients is poor. Until recently, little was known about the response to systemic therapy in brain metastases. The number of trials dedicated to breast cancer with brain metastases was scarce. Our review summarizes the current knowledge on this topic including very significant results of clinical trials which have been presented very recently. We focus on the intracranial response rate of modern drugs, including new antibody–drug conjugates, HER2- targeted tyrosine kinase inhibitors and other targeted therapies. We highlight the most effective and promising drugs. On the other hand, we also suggest that further efforts are needed to improve the prognosis, especially patients with TNBC and brain metastases. The information contained in this article can help oncologists make treatment-related decisions.

Targeting brain metastases in breast cancer

Brain metastases (BMs) are an important source of morbidity and mortality in patients with metastatic breast cancer (BC). As survival of patients with advanced BC considerably improved thanks to research advancements and new therapeutic approaches, the apparent incidence of BMs is increasing. Local interventions, in the form of either surgical resection or radiation therapy, remain the mainstay in the management of BMs. Systemic treatments are typically used to complement local strategies to further improve and maintain control of central nervous system (CNS) disease. Although high-level evidence data about the impact of the blood-brain barrier (BBB), as well as the efficacy of anti-cancer agents on BMs and differentials between the systemic compartment and CNS are still scant, our understanding of the activity of systemic treatments with impact on BMs is rapidly evolving. Novel anti-HER2 agents, such as tucatinib, ado-trastuzumab emtansine, trastuzumab deruxtecan and neratinib, have shown intracranial efficacy. Current research efforts are ongoing not only to clarify the activity of existing treatments on the CNS, as well as to develop new drugs and innovative multi-modality approaches. This review will encompass the current treatment landscape of BMs arising from BC, with a focus on recent advancements in the field and investigational approaches.

Is Molecular Tailored-Therapy Changing the Paradigm for CNS Metastases in Breast Cancer?

Breast cancer (BC) is the second most common tumour spreading to the central nervous system (CNS). The prognosis of patients with CNS metastases depends on several parameters including the molecular assessment of the disease. Although loco-regional treatment remains the best approach, systemic therapies are acquiring a role leading to remarkable long-lasting responses. The efficacy of these compounds diverges between tumours with different molecular assessments. Promising agents under investigation are drugs targeting the HER2 pathways such as tucatinib, neratinib, pyrotinib, trastuzumab deruxtecan. In addition, there are several promising agents under investigation for patients with triple-negative brain metastases (third-generation taxane, etirinotecan, sacituzumab, immune-checkpoint inhibitors) and hormone receptor-positive brain metastases (CDK 4/5, phosphoinositide-3-kinase-mammalian target of rapamycin [PI3K/mTOR] inhibitors). Also, the systemic treatment of leptomeningeal metastases, which represents a very negative prognostic site of metastases, is likely to change as several compounds are under investigation, some with interesting preliminary results. Here we performed a comprehensive review focusing on the current management of CNS metastases according to molecular subtypes, site of metastases (leptomeningeal vs brain), and systemic treatments under investigation.

Treatment strategies for breast cancer brain metastases

Brain metastases from breast cancer (BCBM) constitute the second most common cause of brain metastasis (BM), and the incidence of these frequently lethal lesions is currently increasing, following better systemic treatment. Patients with ER-negative and HER2-positive metastatic breast cancer (BC) are the most likely to develop BM, but if this diagnosis remains associated with a worse prognosis, long survival is now common for patients with HER2-positive BC. BCBM represents a therapeutic challenge that needs a coordinated treatment strategy along international guidelines. Surgery has always to be considered when feasible. It is now well established that stereotaxic radiosurgery allows for equivalent control and less-cognitive toxicities than whole-brain radiation therapy, which should be delayed as much as possible. Medical treatment for BCBM is currently a rapidly evolving field. It has been shown that the blood-brain barrier (BBB) is often impaired in macroscopic BM, and several chemotherapy regimens, antibody-drug conjugates and tyrosine-kinase inhibitors have been shown to be active on BCBM and can be part of the global treatment strategy. This paper provides an overview of the therapeutic option for BCBM that is currently available and outlines potential new approaches for tackling these deadly secondary tumours.

Emerging and investigational targeted chemotherapy and immunotherapy agents for metastatic brain tumors

INTRODUCTION

Metastases to the central nervous system are the most common cause of malignant intracranial tumors in adults. Current standard of care includes surgery and radiation, but overall survival remains poor. A range of systemic therapies are emerging as promising treatment options for these patients.

AREAS COVERED

This study reviews novel drug regimens that are under investigation in phase 1 and 2 clinical trials. To identify relevant therapies under clinical investigation, a search was performed on http://clinicaltrials.gov and Pubmed with the keywords brain metastasis, Phase I clinical trial, and Phase II clinical trial from 2016 to 2020. The authors detail the mechanisms of action of all trial agents, outline evidence for their utility, and summarize the current state of the field.

EXPERT OPINION

Current advancements in the medical management of brain metastases can be categorized into targeted therapies, methods of overcoming treatment resistance, novel combinations of therapies, and modulation of the tumor microenvironment with a specific focus on immunotherapy. Each of these realms holds great promise for the field going forward. A more streamlined structure for enrollment into clinical trials will be a crucial step in accelerating progress in this area.

A Brief Overview of Neurosurgical Management for Breast Cancer Metastasis

Despite advances in chemotherapy and radiation, stage IV breast cancer presents a serious challenge to clinicians in light of the continued poor outcomes for patients. Stage IV breast cancer frequently metastasizes to the brain often necessitating neurosurgical intervention. The goals of the neurosurgeon are to adequately address metastatic disease to the central nervous system, limit morbidity for the patients, while preserving as much neurologic function as possible, and to help guide next steps regarding need for radiation and immunotherapy. In this review, we provide a background overview of the role of neurosurgery in managing stage IV metastatic breast cancer involving the brain, discuss what is known about brain metastasis, and highlight avenues for future study and investigation.

Systemic therapy following craniotomy in patients with a solitary breast cancer brain metastasis

Purpose

To describe practice patterns and patient outcomes with respect to the use of postoperative systemic therapy (ST) after resection of a solitary breast cancer brain metastasis (BCBM).

Methods

A multi-institutional retrospective review of consecutive patients undergoing resection of a single BCBM without extracranial metastases was performed to describe subtype-specific postoperative outcomes and assess the impact of types of ST on site of recurrence, progression-free survival (PFS), and overall survival (OS).

Results

Forty-four patients were identified. Stratified estimated survival was 15, 24, and 23 months for patients with triple negative, estrogen receptor positive (ER+), and HER2+ BCBMs, respectively. Patients receiving postoperative ST had a longer median PFS (8 versus 4 months, adjusted p-value 0.01) and OS (32 versus 15 months, adjusted p-value 0.21). Nine patients (20%) had extracranial progression, 23 (52%) had intracranial progression, three (8%) had both, and nine (20%) did not experience progression at last follow-up. Multivariate analysis showed that postoperative hormonal therapy was associated with longer OS (HR 0.26; 95% CI 0.08–0.89; p = 0.03) but not PFS (HR 0.35, 95% CI 0.08–1.47, p = 0.15) in ER+ patients. Postoperative HER2-targeted therapy was not associated with longer OS or PFS in HER2+ patients.

Conclusions

Disease progression occurred intracranially more often than extracranially following resection of a solitary BCBM. In ER+ patients, postoperative hormonal therapy was associated with longer OS. Postoperative HER2-targeted therapy did not show survival benefit in HER2+ patients. These results should be validated in larger cohorts.

Brain metastases from breast cancer may respond to endocrine therapy: report of two cases

Brain metastases from breast cancer have a poor prognosis. There have been few cases reported where patients with breast cancer and brain metastases respond well to endocrine therapy (tamoxifen or letrozole). Here, we report the cases of two breast cancer patients with brain metastases who responded to medroxyprogesterone acetate and fulvestrant, respectively. These cases indicate that endocrine therapy could be very effective in the management of brain metastases from breast carcinoma.

Continued Endocrine Therapy Is Associated with Improved Survival in Patients with Breast Cancer Brain Metastases

PURPOSE

Brain metastases (BMs) are a rare but devastating condition in estrogen receptor (ER)-positive metastatic breast cancer (MBC). Although endocrine therapy (ET) is the mainstay of treatment in this disease subtype, only case reports have been published concerning the activity of ET in BMs henceforth. Therefore, we aimed to systematically investigate the impact of ET after diagnosis of BM on outcome and clinical course of disease in patients with ER-positive MBC.

EXPERIMENTAL DESIGN

Patient characteristics, detailed information about BMs including diagnosis-specific graded prognostic assessment class (DS-GPA), and clinical outcome were obtained by retrospective chart review for all patients treated for ER-positive breast cancer BMs between 1990 and 2017 at an academic care center. Overall survival (OS) was measured as the interval from diagnosis of BM until death or last date of follow-up.

RESULTS

Overall, 198 patients [female: 195/198 (98.5%); male: 3/198 (1.5%)] with ER-positive breast cancer BMs were available for this analysis. Eighty-eight of 198 patients (44.4%) received ET after diagnosis of BM including aromatase inhibitors (AIs; letrozole, anastrozole, exemestane), tamoxifen, and fulvestrant. Median OS was significantly longer in patients receiving ET after diagnosis of BM compared with patients who did not (15 vs. 4 months, P < 0.001; log-rank test). No significant difference in terms of OS was observed between patients receiving AIs, tamoxifen, or fulvestrant. In patients with concomitant leptomeningeal carcinomatosis (LC), ET prolonged median OS significantly as well (7 vs. 3 months, P = 0.012; log-rank test). In a multivariate analysis including DS-GPA and ET, only treatment with ET after diagnosis of BM (HR, 0.69; 95% confidence interval, 0.48-0.99; P = 0.046) was associated with prognosis (Cox regression model).

CONCLUSIONS

Continuing ET after BM diagnosis was associated with a significantly prolonged OS in this large single-center cohort. No substantial differences between substances were observed. These findings should be validated in a prospective cohort.

Systemic therapy for brain metastases

Central nervous system metastases cause grave morbidity in patients with advanced malignancies. Lung cancer, breast cancer, and melanoma are the three most common causes of brain metastases. Although the exact incidence of brain metastases is unclear, there appears to be an increasing incidence which has been attributed to longer survival, better control of systemic disease, and better imaging modalities. Until recently surgical resection of solitary or symptomatic brain metastases, and radiation therapy (either whole-brain radiation therapy or stereotactic radiation) were the mainstay of treatment for patients with brain metastases. The majority of traditional chemotherapies have shown limited activity in the central nervous system, which has been attributed to the blood-brain barrier and the molecular structure of the used agents. The discovery of driver mutations and drugs targeting these mutations has changed the treatment landscape. Several of these targeted small-molecule tyrosine kinase inhibitors do cross the blood-brain barrier and/or have shown activity in the central nervous system. Another major advance in the care of brain metastases has been the advent of new immunotherapeutic agents, for which initial studies have shown intracranial activity. In this chapter, we will review the unique challenges in the treatment of brain metastases. The pertinent clinical studies of chemotherapy in brain metastases will be discussed. The currently reported clinical trials and evidence for use of targeted therapies and immunotherapeutic agents will be emphasized.

Overview of metastatic disease of the central nervous system

In 2016, the American Society of Clinical Oncology reported that 1.7 million Americans were diagnosed with cancer; this number will rise to 2.3 million in the United States and 22 million worldwide in 2030. This rising need is being met by an explosion of new cancer therapies, including: immune checkpoint inhibitors, T-cell therapies, tumor vaccines, antiangiogenic therapies, and various targeted therapies. This armamentarium of targeted therapies has led to better systemic control of disease and longer patient overall survival (OS). The incidence of metastatic disease to the central nervous system (CNS) is rising as patients are living longer with these more effective systemic therapies. Prolonged OS allows increased time to develop CNS metastases. The CNS is also a sanctuary for metastatic tumor cells that are protected from full exposure to therapeutic concentrations of most anticancer agents by the blood-brain barrier, the tumor microenvironment, and immune system. In addition, CNS metastases often develop late in the course of the disease, so patients are frequently heavily pretreated, resulting in drug resistance. Although genomic profiling has led to more effective therapies for systemic disease, the same therapy may not be effective in treating CNS disease, not only due to failure of blood-brain barrier penetration, but from discordance between the molecular profile in systemic and CNS tumor.

Breast Cancer in the Central Nervous System: Multidisciplinary Considerations and Management

Breast cancer is the second most common primary tumor associated with central nervous system (CNS) metastases. Patients with metastatic HER2-positive or triple-negative (estrogen receptor (ER)-negative, progesterone receptor (PR)-negative, HER2-negative) breast cancer are at the highest risk of developing parenchymal brain metastases. Leptomeningeal disease is less frequent but is distributed across breast cancer subtypes, including lobular breast cancer. Initial treatment strategies can include surgery, radiation, intravenous or intrathecal chemotherapy, and/or targeted approaches. In this article, we review the epidemiology of breast cancer brain metastases, differences in clinical behavior and natural history by tumor subtype, and important considerations in the multidisciplinary treatment of these patients. We will highlight new findings that impact current standards of care, clinical controversies, and notable investigational approaches in clinical testing.

A Case of Breast Cancer Brain Metastasis with a 16-Year Time Interval without Evidence of Cancer Recurrence

The median time of brain metastasis from the diagnosis of breast cancer is approximately 3 years. In this case report, a 69-year-old woman demonstrated cerebellar ataxia. Brain magnetic resonance imaging revealed enhanced lesions in bilateral cerebellar hemispheres. She had undergone surgery, radiation, and chemotherapy for uterine and breast cancer 24 years prior and 16 years prior, respectively. Although she had not received any anticancer treatment for 10 years, no recurrences were identified using whole body scans. A partial tumor resection was performed and the histological diagnosis was an adenocarcinoma from breast cancer. As no extracranial lesions were found, gamma-knife irradiation was performed, without additional systemic chemotherapy. One month posttreatment, the tumors dramatically reduced in size and the patient completely recovered from cerebellar ataxia. Systemic chemotherapy is not always required for brain metastasis from breast cancer with a long interval period, as long as no evidence of extracranial recurrence is detected.

Challenges in the treatment of hormone receptor-positive, HER2-negative metastatic breast cancer with brain metastases

Brain metastases are a major cause of morbidity and mortality for women with hormone receptor (HR)-positive breast cancer, yet little is known about the optimal treatment of brain disease in this group of patients. Although these patients are at lower risk for brain metastases relative to those with HER2-positive and triple-negative disease, they comprise the majority of women diagnosed with breast cancer. Surgery and radiation continue to have a role in the treatment of brain metastases, but there is a dearth of effective systemic therapies due to the poor penetrability of many systemic drugs across the blood-brain barrier (BBB). Additionally, patients with brain metastases have long been excluded from clinical trials, and few studies have been conducted to evaluate the safety and effectiveness of systemic therapies specifically for the treatment of HER2-negative breast cancer brain metastases. New approaches are on the horizon, such as nanoparticle-based cytotoxic drugs that have the potential to cross the BBB and provide clinically meaningful benefits to patients with this life-threatening consequence of HR-positive breast cancer.

Developmental therapeutics for patients with breast cancer and central nervous system metastasis: current landscape and future perspectives

Breast cancer is the second-leading cause of metastatic disease in the central nervous system (CNS). Recent advances in the biological understanding of breast cancer have facilitated an unprecedented increase of survival in a subset of patients presenting with metastatic breast cancer. Patients with HER2 positive (HER2+) or triple negative breast cancer are at highest risk of developing CNS metastasis, and typically experience a poor prognosis despite treatment with local and systemic therapies. Among the obstacles ahead in the realm of developmental therapeutics for breast cancer CNS metastasis is the improvement of our knowledge on its biological nuances and on the interaction of the blood–brain barrier with new compounds. This article reviews recent discoveries related to the underlying biology of breast cancer brain metastases, clinical progress to date and suggests rational approaches for investigational therapies.

Systemic therapy of brain metastases: non-small cell lung cancer, breast cancer, and melanoma

Brain metastases (BM) occur frequently in many cancers, particularly non-small cell lung cancer (NSCLC), breast cancer, and melanoma. The development of BM is associated with poor prognosis and has an adverse impact on survival and quality of life. Commonly used therapies for BM such as surgery or radiotherapy are associated with only modest benefits. However, recent advances in systemic therapy of many cancers have generated considerable interest in exploration of those therapies for treatment of intracranial metastases.This review discusses the epidemiology of BM from the aforementioned primary tumors and the challenges of using systemic therapies for metastatic disease located within the central nervous system. Cumulative data from several retrospective and small prospective studies suggest that molecularly targeted systemic therapies may be an effective option for the treatment of BM from NSCLC, breast cancer, and melanoma, either as monotherapy or in conjunction with other therapies. Larger prospective studies are warranted to further characterize the efficacy and safety profiles of these targeted agents for the treatment of BM.

Central nervous system involvement in breast cancer patients: Is the therapeutic landscape changing too slowly?

Central nervous system (CNS) involvement from breast cancer (BC) has been historically considered a relatively rare event. However, the development of new therapeutic strategies with a better control of extra-cranial disease and a longer overall survival (OS) has determined an increased incidence of brain metastases. Patients with HER2-positive or triple negative BC have higher occurrence of CNS involvement than patients with luminal-like disease. Moreover, after development of brain metastases, the prognosis is highly influenced by biological subtype. In patients with multiple brain metastases who experience important neurological symptoms, palliative treatment, with or without whole brain radiation therapy (WBRT), needs to be considered the first step of a multidisciplinary therapeutic approach. Patients with a good performance status and 1-3 brain lesions should be considered for radical surgery; patients technically inoperable with 4-5 metastases smaller than 3cm may undergo stereotactic radiosurgery. The role of systemic therapy in the management of patients with brain metastases is controversial. Preliminary data suggest that systemic therapy after WBRT may improve survival in BC patients with brain lesions. In patients with HER2-positive disease, several retrospective or post hoc analyses showed a longer brain progression-free survival with trastuzumab in combination with or followed by other anti-HER2 drugs (such as pertuzumab, lapatinib, and T-DM1). Until now, no new strategies or drugs are available for triple-negative and luminal-like BC.

Breast cancer brain metastases: the last frontier

Breast cancer is a common cause of brain metastases, with metastases occurring in at least 10–16 % of patients. Longer survival of patients with metastatic breast cancer and the use of better imaging techniques are associated with an increased incidence of brain metastases. Unfortunately, patients who develop brain metastases tend to have poor prognosis with short overall survival. In addition, brain metastases are a major cause of morbidity, associated with progressive neurologic deficits that result in a reduced quality of life. Tumor subtypes play a key role in prognosis and treatment selection. Current therapies include surgery, whole-brain radiation therapy, stereotactic radiosurgery, chemotherapy and targeted therapies. However, the timing and appropriate use of these therapies is controversial and careful patient selection by using available prognostic tools is extremely important. This review will focus on current treatment options, novel therapies, future approaches and ongoing clinical trials for patients with breast cancer brain metastases.

Evaluation of the pharmacological activities of RAD1901, a selective estrogen receptor degrader

Endocrine therapy, using tamoxifen or an aromatase inhibitor, remains a first-line treatment for estrogen receptor 1 (ESR1) positive breast cancer. However, tumor resistance limits the duration of response. The clinical efficacy of fulvestrant, a selective ER degrader (SERD) that triggers receptor degradation, has confirmed that ESR1 often remains engaged in endocrine therapy resistant cancers. Recently developed, selective ER modulators (SERMs)/SERD hybrids (SSHs) that facilitate ESR1 degradation in breast cancer cells and reproductive tissues have been advanced as an alternative treatment for advanced breast cancer, particularly in the metastatic setting. RAD1901 is one SSH currently being evaluated clinically that is unique among ESR1 modulators in that it readily enters the brain, a common site of breast cancer metastasis. In this study, RAD1901 inhibited estrogen activation of ESR1 in vitro and in vivo, inhibited estrogen-dependent breast cancer cell proliferation and xenograft tumor growth, and mediated dose-dependent downregulation of ESR1 protein. However, doses of RAD1901 insufficient to induce ESR1 degradation were shown to result in the activation of ESR1 target genes and in the stimulation of xenograft tumor growth. RAD1901 is an SSH that exhibits complex pharmacology in breast cancer models, having dose-dependent agonist/antagonist activity displayed in a tissue-selective manner. It remains unclear how this unique pharmacology will impact the utility of RAD1901 for breast cancer treatment. However, being the only SERD currently known to access the brain, RAD1901 merits evaluation as a targeted therapy for the treatment of breast cancer brain metastases.

Brain metastases

Brain metastases are the most frequent neurological complication of cancer and the most common brain tumour type. Lung and breast cancers, and melanoma are responsible for up to three-quarters of metastatic brain lesions. Most patients exhibit either headache, seizures, focal deficits, cognitive or gait disorders, which severely impair the quality of life. Brain metastases are best demonstrated by MRI, which is sensitive but non-specific. The main differential diagnosis includes primary tumours, abscesses, vascular and inflammatory lesions. Overall prognosis is poor and depends on age, extent and activity of the systemic disease, number of brain metastases and performance status. In about half of the patients, especially those with widespread and uncontrolled systemic malignancy, death is heavily related to extra-neural lesions, and treatment of cerebral disease doesn't significantly improve survival. In such patients the aim is to improve or stabilize the neurological deficit and maintain quality of life. Corticosteroids and whole-brain radiotherapy usually fulfill this purpose. By contrast, patients with limited number of brain metastases, good performance status and controlled or limited systemic disease, may benefit from aggressive treatment as both quality of life and survival are primarily related to treatment of brain lesions. Several efficacious therapeutic options including surgery, radiotherapy and chemotherapy are available for these patients.

Breast cancer brain metastases: new directions in systemic therapy

The management of patients with brain metastases from breast cancer continues to be a major clinical challenge. The standard initial therapeutic approach depends upon the size, location, and number of metastatic lesions and includes consideration of surgical resection, whole-brain radiotherapy, and stereotactic radiosurgery. As systemic therapies for control of extracranial disease improve, patients are surviving long enough to experience subsequent progression events in the brain. Therefore, there is an increasing need to identify both more effective initial treatments as well as to develop multiple lines of salvage treatments for patients with breast cancer brain metastases. This review summarises the clinical experience to date with respect to cytotoxic and targeted systemic therapies for the treatment of brain metastases, highlights ongoing and planned trials of novel approaches and identifies potential targets for future investigation.

[Systemic treatment of brain metastases from breast cancer: cytotoxic chemotherapy and targeted therapies]

Prevalence of brain metastases is increasing in breast cancer. Brain metastases represent a poor-prognosis disease for which local treatments continue to play a major role. In spite of the presence of a physiological blood-brain barrier limiting their activity, some systemic treatments may display a significant antitumor activity at the central nervous system level. In HER2-positive metastatic breast cancer with brain metastases not previously treated with whole brain radiotherapy, capecitabine and lapatinib combination obtains a volumetric reponse in two thirds of patients (LANDSCAPE study). If confirmed, these results could modify in selected patients the layout of therapeutic strategies. Promoting novel targeted approaches and innovative therapeutic combinations is a critical need to improve survival of breast cancer patients with brain metastases.

Breast cancer brain metastases: differences in survival depending on biological subtype, RPA RTOG prognostic class and systemic treatment after whole-brain radiotherapy (WBRT)

BACKGROUND

Patients with breast cancer brain metastasis are a heterogeneous group in relation to tumor biology and outcome.

MATERIALS AND METHODS

The group of 222 breast cancer patients with brain metastasis was divided into three biological subgroups. The propensity of biological subtypes for metastases to the brain and survivals depending on biological subtype, recursive partitioning analysis of Radiation Therapy Oncology Group (RPA RTOG) prognostic class and the use of systemic treatment after whole-brain radiotherapy were assessed.

RESULTS

The rate of patients with triple-negative, human epidermal growth factor receptor 2 (HER2)-positive and luminal breast cancer with brain metastases was 28%, 53% and 19%, respectively. Median survival from brain metastases in triple-negative, HER2-positive and luminal subtype was 3.7, 9 and 15 months, respectively. Median survival from brain metastases in RPA RTOG prognostic class I, II and III was 15, 11 and 3 months, respectively. In the luminal and in the triple-negative subtype, systemic therapy prolonged survival from 3 to 14 months and from 3 to 4 months, respectively. In HER2-positive subtype, median survival without further treatment, after chemotherapy and after chemotherapy with targeted therapy were 3, 8 and 11 months, respectively.

CONCLUSIONS

HER2-positive and triple-negative breast cancers have special predilection for metastases to the brain. Survival from brain metastases depended on performance status and the use of systemic treatment.

Central nervous system metastases in HER-2-overexpressing metastatic breast cancer: a treatment challenge

With improvements in diagnostic and therapeutic options and a corresponding improvement in survival, central nervous system (CNS) metastasis is becoming a more frequent diagnosis in breast cancer patients. It can be assumed that up to 30% of metastatic breast cancer (MBC) patients may experience CNS metastasis during the course of their disease. Moreover, it has been reported that patients with human epidermal growth factor receptor (HER)-2-overexpressing MBC are at a higher risk for CNS involvement. Whereas locoregional treatment modalities such as surgery, radiosurgery, and whole-brain radiotherapy still must be considered as the treatment of first choice, the armamentarium of systemic treatment modalities has been expanded by the introduction of small molecules such as the tyrosine kinase inhibitors. Rather than analyzing the risk factors for the development of CNS metastasis and reviewing the standard diagnostic and therapeutic approaches in patients with CNS involvement, this review focuses specifically on systemic treatment modalities in patients suffering from CNS metastasis from HER-2-overexpressing MBC.

Chemotherapy in breast cancer patients with brain metastases: have new chemotherapic agents changed the clinical outcome?

Brain metastasis occurs in 15-40% of cancer patients and is present in approximately 10-16% of patients with metastatic breast disease. However, little is known about prognostic factors enabling the early identification of breast cancer patients at risk of CNS metastases. Therapy for brain metastases should be based on several parameters, such as the assessment of prognostic variables, the extent of neurological and systemic disease, and its chemo-sensitivity to previously administered chemotherapy treatments. In view of the known close correlation between metastatic and primary tumor chemosensitivity, the type of chemotherapy chosen should depend more on the tumor histology than on the cerebral distribution of the single drug. More recent drugs with a high impact on the clinical outcome of metastatic breast cancer patients, such as taxanes or trastuzumab, play only a limited role in the treatment of brain metastases.

Excellent response to letrozole in brain metastases from breast cancer

Breast cancer with multiple parenchymal brain metastases carries an extremely poor outcome. Cranial radiotherapy improves survival by only a few months and the role of systemic therapy is marginal and largely unexplored. We report a patient with recurrent carcinoma of breast presenting with multiple bilateral cervical nodes and brain metastases manifesting as a right hemiparesis and facial nerve palsy, who was treated with palliative whole brain irradiation and letrozole. At the follow up at 20 months, neurological function had fully recovered, and both cerebral and extracerebral lesions had completely resolved, with calcification of the cerebral lesions. This report suggests that letrozole has beneficial effects both in extracranial and intracranial disease in hormone responsive metastatic breast cancer.