Efficacy of T-DM1 for leptomeningeal and brain metastases in a HER2 positive metastatic breast cancer patient: new directions for systemic therapy - a case report and literature review

Radiation therapy, tissue radiosensitization, and potential synergism in the era of novel antibody-drug conjugates

Antibody-drug conjugates (ADCs) represent a therapeutic class of agents designed to selectively deliver cytotoxic payloads to cancer cells. With the increasingly positioning of ADCs in the clinical practice, combinations with other treatment modalities, including radiation therapy (RT), will open new opportunities but also challenges. This review evaluates ADC-RT interactions, examining therapeutic synergies and potential caveats. ADC payloads can be radiosensitizing, enhancing cytotoxicity when used in combination with RT. Antigens targeted by ADCs can have various tissue expressions, resulting in possible off-target toxicities by tissue radiosensitization. Notably, the HER-2-directed ADC trastuzumab emtansine has appeared to increase the risk of radionecrosis when used concomitantly with brain RT, as glial cells can express HER2, too. Other possible organ-specific effects are discussed, such as pulmonary and cardiac toxicities. The lack of robust clinical data on the ADC-RT combination raises concerns regarding specific side effects and the ultimate trade-off of toxicity and safety of some combined approaches. Clinical studies are needed to assess ADC-RT combination safety and efficacy.

Radiation Therapy in the Management of Leptomeningeal Disease From Solid Tumors

Purpose

Leptomeningeal disease (LMD) is clinically detected in 5% to 10% of patients with solid tumors and is a source of substantial morbidity and mortality. Prognosis for this entity remains poor and treatments are palliative. Radiation therapy (RT) is an essential tool in the management of LMD, and a recent randomized trial demonstrated a survival benefit for proton craniospinal irradiation (CSI) in select patients. In the setting of this recent advance, we conducted a review of the role of RT in LMD from solid tumors to evaluate the evidence basis for RT recommendations.

Methods and Materials

In November 2022, we conducted a comprehensive literature search in PubMed, as well as a review of ongoing clinical trials listed on ClinicalTrials.gov, to inform a discussion on the role of RT in solid tumor LMD. Because of the paucity of high-quality published evidence, discussion was informed more by expert consensus and opinion, including a review of societal guidelines, than evidence from clinical trials.

Results

Only 1 prospective randomized trial has evaluated RT for LMD, demonstrating improved central nervous system progression-free survival for patients with breast and lung cancer treated with proton CSI compared with involved-field RT. Modern photon CSI techniques have improved upon historical rates of acute hematologic toxicity, but the overall benefit of this modality has not been prospectively evaluated. Multiple retrospective studies have explored the use of involved-field RT or the combination of RT with chemotherapy, but clear evidence of survival benefit is lacking.

Conclusions

Optimal management of LMD with RT remains reliant upon expert opinion, with proton CSI indicated in patients with good performance status and extra-central nervous system disease that is either well-controlled or for which effective treatment options are available. Photon-based CSI traditionally has been associated with increased marrow and gastrointestinal toxicities, though intensity modulated RT/volumetric-modulated arc therapy based photon CSI may have reduced the toxicity profile. Further work is needed to understand the role of radioisotopes as well as combined modality treatment with intrathecal or central nervous system penetrating systemic therapies.

Long-term response to sequential anti-HER2 therapies including trastuzumab-deruxtecan in a patient with HER2-positive metastatic breast cancer with leptomeningeal metastases: a case report and review of the literature

The incidence of leptomeningeal metastases (LM) is increasing among breast cancer patients, but their prognosis remains dismal. Many therapeutic options are now available to treat HER2-positive (HER2+) metastatic breast cancer (MBC) involving the central nervous system (CNS). This case report illustrates a long-lasting response of more than 2 years in a patient with HER2+ MBC with LM after sequential administration of systemic and intrathecal (IT) anti-HER2 therapies and highlights that an appropriate treatment of HER2+ LM can result in durable survival.

An overview of the therapeutic strategies for neoplastic meningitis due to breast cancer: when and why?

INTRODUCTION

Neoplastic meningitis (NM), also known as leptomeningeal carcinomatosis, is characterized by the infiltration of tumor cells into the meninges, and poses a significant therapeutic challenge owing to its aggressive nature and limited treatment options. Breast cancer is a common cause of NM among solid tumors, further highlighting the urgent need to explore effective therapeutic strategies. This review aims to provide insights into the evolving landscape of NM therapy in breast cancer by collating existing research, evaluating current treatments, and identifying potential emerging therapeutic options.

AREAS COVERED

This review explores the clinical features, therapeutic strategies, recent advances, and challenges of managing NM in patients with breast cancer. Its management includes multimodal strategies, including systemic and intrathecal chemotherapy, radiation therapy, and supportive care. This review also emphasizes targeted drug options and optimal drug concentrations, and discusses emerging therapies. Additionally, it highlights the variability in treatment outcomes and the potential of combination regimens to effectively manage NM in breast cancer.

EXPERT OPINION

Challenges in treating NM include debates over clinical trial end points and the management of adverse effects. Drug resistance and low response rates are significant hurdles, particularly inHER2-negative breast cancer. The development of more precise and cost-effective medications with improved selectivity is crucial. Additionally, global efforts are needed for infrastructure development and cancer control considering the diverse nature of the disease.

Leptomeningeal Carcinomatosis from Solid Tumor Malignancies: Treatment Strategies and Biomarkers

Leptomeningeal metastases/diseases (LMDs) are a late-stage complication of solid tumor or hematologic malignancies. LMD is spread of cancer cells to the layers of the leptomeninges (pia and arachnoid maters) and subarachnoid space seen in 3 to 5% of cancer patients. It is a disseminated disease which carries with it significant neurologic morbidity and mortality. Our understanding of disease pathophysiology is currently lacking; however, advances are being made. As our knowledge of disease pathogenesis has improved, treatment strategies have evolved. Mainstays of treatment such as radiotherapy have changed from involved-field radiotherapy strategies to proton craniospinal irradiation which has demonstrated promising results in recent clinical trials. Systemic treatment strategies have also improved from more traditional chemotherapeutics with limited central nervous system (CNS) penetration to more targeted therapies with better CNS tumor response. Many challenges remain from earlier clinical detection of disease through improvement of active treatment options, but we are getting closer to meaningful treatment.

Safety profile of trastuzumab-emtansine (T-DM1) with concurrent radiation therapy: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

In recent years, the treatment landscape for breast cancer has undergone significant advancements, with the introduction of several new anticancer agents. One such agent is trastuzumab emtansine (T-DM1), an antibody drug conjugate that has shown improved outcomes in both early and advanced breast cancer. However, there is currently a lack of comprehensive evidence regarding the safety profile of combining T-DM1 with radiation therapy (RT). In this study, we aim to provide a summary of the available data on the safety of combining RT with T-DM1 in both early and metastatic breast cancer settings.

MATERIALS AND METHODS

This systematic review and meta-analysis project is part of the consensus recommendations by the European Society for Radiotherapy and Oncology (ESTRO) Guidelines Committee on integrating RT with targeted treatments for breast cancer. A thorough literature search was conducted using the PUBMED/MedLine, Embase, and Cochrane databases to identify original studies focusing on the safety profile of combining T-DM1 with RT.

RESULTS

After applying eligibility criteria, nine articles were included in the meta-analysis. Pooled data from these studies revealed a high incidence of grade 3 + radionecrosis (17%), while the rates of grade 3 + radiation-related pneumonitis (<1%) and skin toxicity (1%) were found to be very low.

CONCLUSION

Although there is some concern regarding a slight increase in pneumonitis when combining T-DM1 with postoperative RT, the safety profile of this combination was deemed acceptable for locoregional treatment in non-metastatic breast cancer. However, caution is advised when irradiating intracranial sites concurrently with T-DM1. There is a pressing need for international consensus guidelines regarding the safety considerations of combining T-DM1 and RT for breast cancer.

A phase II study of concurrent involved-field radiotherapy and intrathecal chemotherapy for leptomeningeal metastasis from solid tumors

BACKGROUND

The role of involved-field radiation therapy (IFRT) and intrathecal chemotherapy (IC) in leptomeningeal metastasis (LM) from solid tumors was gradually underestimated in the era of targeted therapy. This study was aimed to investigate the safety and effectiveness of concurrent IFRT and intrathecal methotrexate (MTX)/cytarabine (Ara-C) for LM, particularly for those who developed LM while receiving targeted therapy.

MATERIALS AND METHODS

Enrolled patients were given induction IC first and then concurrent treatment, which consisted of IFRT (40 Gy total; 2 Gy/f) and IC (MTX 15 mg or Ara-C 50 mg, once per week). Primary endpoint was clinical response rate (RR). Secondary endpoints were safety and overall survival (OS).

RESULTS

Fifty-three patients received induction intrathecal MTX (n = 27) or Ara-C (n = 26). Forty-two patients completed concurrent therapy. Total RR was 34% (18/53). The improvement rate of neurological symptoms and KPS scores were 72% (38/53) and 66% (35/53) respectively. Adverse events (AEs) rate was 28% (15/53). Eight patients (15%, 8/53) showed grade 3-4 AEs, including myelosuppression (n = 4) and radiculitis (n = 5). Median OS was 6.5 months (95% CI, 5.3-7.7 months). Median survival for 18 patients who had clinical response was 7.9 months (95% CI, 4.4-11.4 months), and 0.8 months (95% CI, 0.08-1.5 months) for 6 patients who had LM progression. The median survival in 22 patients who received prior targeted therapy was 6.3 months (95% CI, 4.5-8.1 months).

CONCLUSION

Concurrent IFRT and intrathecal MTX or Ara-C was proved to be a feasible treatment option with an acceptable safety profile for LM from a common tumor entity.

Therapies beyond Physiological Barriers and Drug Resistance: A Pilot Study and Review of the Literature Investigating If Intrathecal Trastuzumab and New Treatment Options Can Improve Oncologic Outcomes in Leptomeningeal Metastases from HER2-Positive Breast Cancer

Leptomeningeal metastases (LM) are a rare but rapidly fatal complication defined by the spread of tumor cells within the leptomeninges and the subarachnoid space, found in approximately 10% of patients with HER2-positive breast cancers. This pilot study evaluated the efficacy of local treatment with intrathecal Trastuzumab (IT) added to systemic treatment. The oncologic outcome of 14 patients with HER2-positive LM is reported. Seven received IT, and seven received standard of care (SOC). The mean number of IT cycles administered was 12.14 ± 4.00. The response rate to CNS after IT treatment + SOC was 71.4%, and three patients (42.8%) obtained durable responses lasting more than 12 months. The median progression-free survival (mPFS) after LM diagnosis was six months, and the median overall survival (mOS) was ten months. The mean values of the PFS in favor of IT therapy (10.6 mo vs. 6.6 mo) and OS (13.7 vs. 9.3 mo) suggest a non-negligible investigation direction in the sense of exploiting intrathecal administration as a possible treatment modality in these patients. Adverse events reported were local pain related to intrathecal administration and one case of arachnoiditis, hematoma, and CSF fistulae. Intrathecal administration of Trastuzumab, alongside systemic treatment and radiotherapy, might improve oncologic outcomes in LM HER2-positive breast cancer with manageable toxicity.

Complete Cerebrospinal Fluid Response to T-DM1 in HER2 Positive Metastatic Breast Cancer: A Case Report

Leptomeningeal carcinomatosis is a rare but serious consequence of pre-existing tumors, such as breast, lung, and gastrointestinal carcinomas. Further, leptomeningeal carcinomatosis is more frequently diagnosed with breast cancers, if only because breast cancers are diagnosed far more often than any other carcinomas. In this paper, we present the case of a leptomeningeal carcinomatosis patient who experienced complete remission following therapy targeted at the Her-2 (human epidermal growth factor receptor 2-positive) receptor. This patient’s diagnosis was complicated by the fact that brain and column MRI imaging were clear, but analysis of the cerebrospinal fluid led to the conclusion of leptomeningeal carcinomatosis. The tests were requested because the patient, under chemotherapy for advanced breast cancer at the time, reported some neurological symptoms. Following the diagnosis of leptomeningeal carcinomatosis and subsequent T-DM1 Her-2 receptor therapy, the patient showed a complete response to leptomeningeal carcinomatosis within 30 days and survived for another 16 months. This case offers compelling evidence that the effect TDM1 Her-2 receptor therapy has on a patient’s remission and long-term survivability is considerably better than other therapies for similar pre-existing conditions diagnosed with leptomeningeal carcinomatosis. Further prospective studies should confirm these findings.

Trastuzumab emtansine vs lapatinib and capecitabine in HER2-positive metastatic breast cancer brain metastases: A real-world study

BACKGROUND

Trastuzumab emtansine (T-DM1) has demonstrated improvements in survival and neurological symptoms in patients with breast cancer with brain metastases (BCBM). This real-world study investigated the effectiveness of T-DM1 versus lapatinib plus capecitabine (LC) in patients with BCBM.

METHODS

This retrospective, observational study evaluated patients with HER2-positive BCBM using a real-world database. Eligible patients had initiated T-DM1 or LC with a prior diagnosis of brain metastasis and ≥1 prior metastatic breast cancer treatment. The primary endpoint was overall survival (OS); secondary endpoints were time to next relevant treatment or death (TTNT) and real-world progression-free survival (rwPFS). An inverse probability of treatment weighting (IPTW) approach was used to account for differences in potential baseline characteristics between treatment groups. Outcomes were described using the Kaplan-Meier method, and the average treatment effect of initiating T-DM1 versus LC was estimated using weighted Cox proportional hazard models and hazard ratio (HR).

RESULTS

A total of 214 patients were available for analysis (T-DM1, n = 161; LC, n = 53). Demographics and baseline characteristics were generally well-balanced between treatment groups after weighting. After weighting, median OS was 17.7 (T-DM1) versus 9.6 (LC) months (HR, 0.55 [95% CI, 0.34-0.89]; P=0.013). Median TTNT was 9.0 (T-DM1) versus 6.0 (LC) months (HR, 0.55 [95% CI, 0.36-0.85]; P = 0.005). After weighting, median rwPFS was 6.0 (T-DM1) versus 4.0 (LC) months (HR, 0.50 [95% CI, 0.36-0.69]; P < 0.001).

CONCLUSIONS

These results support the superior effectiveness and clinical relevance of T-DM1 versus LC in patients with HER2-positive BCBM in the real world.

Leveraging Molecular and Immune-Based Therapies in Leptomeningeal Metastases

Leptomeningeal metastases represent an aggressive stage of cancer with few durable treatment options. Improved understanding of cancer biology, neoplastic reliance on oncogenic driver mutations, and complex immune system interactions have resulted in an explosion in cancer-directed therapy in the last two decades to include small molecule inhibitors and immune checkpoint inhibitors. Most of these therapeutics are underexplored in patients with leptomeningeal metastases, limiting extrapolation of extracranial and even intracranial efficacy outcomes to the unique leptomeningeal space. Further confounding our interpretation of drug activity in the leptomeninges is an incomplete understanding of drug penetration through the blood-cerebrospinal fluid barrier of the choroid plexus. Nevertheless, a number of retrospective studies and promising prospective trials provide evidence of leptomeningeal activity of several small molecule and immune checkpoint inhibitors and underscore potential areas of further therapeutic development for patients harboring leptomeningeal disease.

Leptomeningeal Metastases: New Opportunities in the Modern Era

Leptomeningeal metastases arise from cancer cell entry into the subarachnoid space, inflicting significant neurologic morbidity and mortality across a wide range of malignancies. The modern era of cancer therapeutics has seen an explosion of molecular-targeting agents and immune-mediated strategies for patients with breast, lung, and melanoma malignancies, with meaningful extracranial disease control and improvement in patient survival. However, the clinical efficacy of these agents in those with leptomeningeal metastases remains understudied, due to the relative rarity of this patient population, the investigational challenges associated with studying this dynamic disease state, and brisk disease pace. Nevertheless, retrospective studies, post hoc analyses, and small prospective trials in the last two decades provide a glimmer of hope for patients with leptomeningeal metastases, suggesting that several cancer-directed strategies are not only active in the intrathecal space but also improve survival against historical odds. The continued development of clinical trials devoted to patients with leptomeningeal metastases is critical to establish robust efficacy outcomes in this patient population, define drug pharmacokinetics in the intrathecal space, and uncover new avenues for treatment in the face of leptomeningeal therapeutic resistance.

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.

Treatment of Brain Metastases: The Synergy of Radiotherapy and Immune Checkpoint Inhibitors

Brain metastases are a devastating sequela of common primary cancers (e.g., lung, breast, and skin) and have limited effective therapeutic options. Previously, systemic chemotherapy failed to demonstrate significant benefit in patients with brain metastases, but in recent decades, targeted therapies and more recently immune checkpoint inhibitors (ICIs) have yielded promising results in preclinical and clinical studies. Furthermore, there is significant interest in harnessing the immunomodulatory effects of radiotherapy (RT) to synergize with ICIs. Herein, we discuss studies evaluating the impact of RT dose and fractionation on the immune response, early studies supporting the synergistic interaction between RT and ICIs, and ongoing clinical trials assessing the benefit of combination therapy in patients with brain metastases.

Detection of Circulating Tumor Cells in Cerebrospinal Fluid of Patients with Suspected Breast Cancer Leptomeningeal Metastases: A Prospective Study

BACKGROUND

The diagnosis of breast cancer (BC)-related leptomeningeal metastases (LM) relies on the detection of tumor cells in cerebrospinal fluid (CSF) using conventional cytology (gold standard). However, the sensitivity of this technique is low. Our goal was to evaluate whether circulating tumor cell (CTC) detection in CSF using the CellSearch® system could be used for LM diagnosis.

METHODS

This prospective, monocentric study included adult patients with suspected BC-related LM. The clinical sensitivity and specificity of CTC detection in CSF for LM diagnosis were calculated relative to conventional CSF cytology.

RESULTS

Forty-nine eligible patients were included and 40 were evaluable (CTC detection technical failure: n = 8, eligibility criteria failure: n = 1). Cytology was positive in 18/40 patients. CTCs were detected in these 18 patients (median: 5824 CTC, range: 93 to 45052) and in 5/22 patients with negative cytology (median: 2 CTC, range: 1 to 44). The detection of ≥1 CSF CTC was associated with a clinical sensitivity of 100% (95% CI, 82.4-100) and a specificity of 77.3% (95% CI, 64.3-90.3) for LM diagnosis. HER2+ CTCs were detected in the CSF of 40.6% of patients with HER2- BC (median: 500 CTC, range: 13 to 28 320).

CONCLUSIONS

The clinical sensitivity of CTC detection in CSF with the CellSearch® system for LM diagnosis is higher than that of CSF cytology. CTC detection in patients with negative cytology, however, must be further investigated. The finding of HER2+ CTCs in patients with HER2- BC suggests that the HER2 status of LM should be evaluated to increase the treatment opportunities for these patients.

Current challenges and unmet needs in treating patients with human epidermal growth factor receptor 2-positive advanced breast cancer

Human epidermal growth factor receptor 2 oncogene (HER2-positive) overexpression/amplification occurs in less than 20% of breast cancers and has traditionally been associated with poor prognosis. Development of therapies that target HER2 has significantly improved outcomes for patients with HER2-positive advanced breast cancer (ABC). Currently available HER2-targeted agents include the monoclonal antibodies trastuzumab, pertuzumab, and margetuximab, the small-molecule inhibitors lapatinib, tucatinib, neratinib, and pyrotinib, as well as the antibody-drug conjugates trastuzumab emtansine and trastuzumab deruxtecan. Optimal sequencing of these agents in the continuum of the disease is critical to maximize treatment outcomes. The large body of clinical evidence generated over the past 2 decades aids clinicians in treatment decision-making. However, patients with HER2-positive ABC and specific disease characteristics and/or comorbidities, such as leptomeningeal disease, brain metastases, or cardiac dysfunction, are generally excluded from large randomized clinical trials, and elderly or frail patients are often underrepresented. In addition, there is great inequality in the accessibility of approved drugs across countries. This article addresses various challenging clinical situations when treating patients with HER2-positive ABC. The objective is to provide guidance to clinicians on how and when HER2-targeted therapies and additional treatments can be best implemented in routine clinical practice, on the basis of existing clinical evidence and expert opinion where needed.

Leptomeningeal metastases in patients with human epidermal growth factor receptor 2 positive breast cancer: real-world data from a multicentric European cohort

In patients with human epidermal growth factor receptor 2 positive (HER2+) breast cancer, leptomeningeal metastases (LM) are a rare but often a fatal clinical scenario. In this multicentric study, clinical and pathologic characteristics of patients with HER2+ breast cancer developing LM were described, as well as survival outcomes. Data were gathered retrospectively from medical records of 82 patients with advanced HER2+ breast cancer and LM treated between August 2005 and July 2020. Following LM diagnosis, 79 (96.3%) patients received at least one line of anti‐HER2 therapy, 25 (30.5%) patients received intrathecal therapy and 58 (70.7%) patients received radiotherapy. Overall survival (OS) was 8.3 months (95% confidence interval [CI] 5.7‐11), 1‐year OS was 42%, and 2‐year OS was 21%. At univariate analysis, patients who were treated after 2010, had better Karnofsky performance status, were free of neurological symptoms, had better prognostic, received chemotherapy (OS difference 9.4 months, P = .024), or monoclonal antibodies (trastuzumab ± pertuzumab; OS difference 6.1 months; P = .013) after LM diagnosis, had a statistically significantly longer OS. Presence of neurological symptoms (hazard ratio 3.32, 95% CI 1.26‐8.73; P = .015) and not having received radiotherapy (hazard ratio 2.02, 95% CI 1.09‐3.72; P = .024) were all associated with poorer OS at multivariate analysis. To summarize, not having neurological symptoms and receiving RT at LM diagnosis were associated with prolonged OS in our cohort. Survival seemed to be prolonged with multimodality treatment, which included targeted therapy, chemotherapy, and RT to the LM sites.

Response of Leptomeningeal Metastasis of Breast Cancer With a HER2/neu Activating Variant to Tucatinib: A Case Report

Metastatic breast cancer demonstrates HER2/neu amplification approximately 15% of the time. However, HER2 mutations, which often stimulate tumor growth, occur in only 3% to 5% of patients, and are seen more frequently in metastatic versus primary tumors. They are more frequent in lobular carcinoma, including triple-negative lobular cancer. Many of these variants are resistant to trastuzumab and lapatinib. However, neratinib can be efficacious, and recent data suggest that antibody-drug conjugates (ADCs) such as ado-trastuzumab emtansine (T-DM1) and trastuzumab deruxtecan may also be helpful. Laboratory and clinical data raise the possibility that simultaneous treatment with ADCs plus neratinib may be even more efficacious. Tucatinib, which has demonstrated significant activity in the central nervous system, has also been shown in vitro to be active against a number of these HER2 variants. This report describes a patient with metastatic estrogen receptor-positive, HER2-nonamplified breast cancer with an activating HER2 mutation whose tumor became resistant to neratinib as well as capecitabine, but whose subsequent leptomeningeal disease had a dramatically successful response to tucatinib plus capecitabine. As the frequency of HER2 mutations increases during the evolution of metastatic breast cancer, it is important to obtain genomic evaluation on these tumors with either repeat tissue or liquid biopsy as they progress over time.

Evolving management of HER2+ breast cancer brain metastases and leptomeningeal disease

Patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer are at a particularly high risk of breast cancer brain metastasis (BCBM) and leptomeningeal disease (LMD). Improvements in systemic therapy have translated to improved survival for patients with HER2-positive BCBM and LMD. However, the optimal management of these cases is rapidly evolving and requires a multidisciplinary approach. Herein, a team of radiation oncologists, medical oncologists, neuro-oncologists, and breast surgeon created a review of the evolving management of HER2-positive BCBM and LMD. We assess the epidemiology, diagnosis, and evolving treatment options for patients with HER2-positive BCBM and LMD, as well as the ongoing prospective clinical trials enrolling these patients. The management of HER2-positive BCBM and LMD represents an increasingly common challenge that involves the coordination of local and systemic therapy. Advances in systemic therapy have resulted in an improved prognosis, and promising targeted therapies currently under prospective investigation have the potential to further benefit these patients.

Durable Effect of Pyrotinib and Metronomic Vinorelbine in HER2-Positive Breast Cancer With Leptomeningeal Disease: A Case Report and Literature Review

Leptomeningeal metastases (LM) are rare and catastrophic for metastatic breast cancer (MBC). The prognosis of HER2-positive breast cancer (BC) with LM is extremely poor. There is no high-quality evidence of treatment regimens in HER2-positive BC with LM yet. Here, we present a case of LM in a 50-year-old woman with HER2-positive BC. Immunohistochemistry revealed invasive ductal carcinoma, estrogen receptor negative, progesterone receptor negative, HER2 3+, P53 positive 80%, and Ki-67 positive 35%. Reported for the first time, the patient was given pyrotinib-targeted therapy (400 mg, oral, every day), metronomic vinorelbine (40 mg, oral, three times a week), and intrathecal methotrexate (10 mg, infrequent and irregular use due to poor compliance) synchronously. The patient received and benefited from the treatment regimen for 16 months. And the quality of life, as self-reported, improved significantly. We also comprehensively summarized all the case reports, observational studies, and clinical trials related to HER2-positive BC with LM in the PubMed database and ClinicalTrials.gov. Intrathecal chemotherapy (methotrexate, cytarabine, thiotepa), intrathecal trastuzumab, whole-brain radiotherapy, and systemic therapy are commonly used treatment options according to a review of the literature and research. Pembrolizumab and trastuzumab deruxtecan (DS-8201) as novel drugs are promising in LM. Furthermore, trastuzumab emtansine (T-DM1) and tyrosine kinase inhibitors (TKIs) such as tucatinib and neratinib have exhibited good efficacy in HER2-positive BC with central nervous system (CNS) metastases and deserve further exploration. In our report, combining pyrotinib-targeted therapy with metronomic chemotherapy is a potential regimen, which has presented satisfactory therapeutic efficacy and also warrants additional investigation in HER2-positive BC with LM.

Intramedullary spinal cord metastasis to the cauda equina in a patient with HER2-positive metastatic breast cancer: A case report

The rate of metastasis to the central nervous system is high in human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer patients. Metastatic cauda equina tumors are characterized by rapid progression of symptoms, thus signifying the requirement of their early treatment. However, these tumors are rarely reported, and their optimal treatment options have not been established yet. Here, we report a case study of a patient with HER2-positive breast cancer that metastasized to the cauda equina. The patient underwent urgent surgery to relieve the spinal cord compression. The pain in her back and lower limbs was greatly reduced. Unfortunately, her ability to walk did not improve sufficiently. Overall, surgical treatment may be a favorable option to improve a patient's quality of life.

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.

Autocrine GM-CSF signaling contributes to growth of HER2+ breast leptomeningeal carcinomatosis

Leptomeningeal carcinomatosis (LC) occurs when tumor cells spread to the cerebrospinal fluid-containing leptomeninges surrounding the brain and spinal cord. LC is an ominous complication of cancer with a dire prognosis. Although any malignancy can spread to the leptomeninges, breast cancer, particularly the HER2+ subtype, is its most common origin. HER2+ breast LC (HER2+ LC) remains incurable, with few treatment options, and the molecular mechanisms underlying proliferation of HER2+ breast cancer cells in the acellular, protein, and cytokine-poor leptomeningeal environment remain elusive. Therefore, we sought to characterize signaling pathways that drive HER2+ LC development as well as those that restrict its growth to leptomeninges. Primary HER2+ LC patient-derived ("Lepto") cell lines in co-culture with various central nervous system (CNS) cell types revealed that oligodendrocyte progenitor cells (OPC), the largest population of dividing cells in the CNS, inhibited HER2+ LC growth in vitro and in vivo, thereby limiting the spread of HER2+ LC beyond the leptomeninges. Cytokine array-based analyses identified Lepto cell-secreted granulocyte-macrophage colony-stimulating factor (GM-CSF) as an oncogenic autocrine driver of HER2+ LC growth. Liquid chromatography-tandem mass spectrometry-based analyses revealed that the OPC-derived protein TPP1 proteolytically degrades GM-CSF, decreasing GM-CSF signaling and leading to suppression of HER2+ LC growth and limiting its spread. Lastly, intrathecal delivery of neutralizing anti-GM-CSF antibodies and a pan-Aurora kinase inhibitor (CCT137690) synergistically inhibited GM-CSF and suppressed activity of GM-CSF effectors, reducing HER2+ LC growth in vivo. Thus, OPC suppress GM-CSF-driven growth of HER2+ LC in the leptomeningeal environment, providing a potential targetable axis.

Leptomeningeal Metastases from Solid Tumors: Recent Advances in Diagnosis and Molecular Approaches

Leptomeningeal metastases (LM) from solid tumors represent an unmet need of increasing importance due to an early use of MRI for diagnosis and improvement of outcome of some molecular subgroups following targeted agents and immunotherapy. In this review, we first discussed factors limiting the efficacy of targeted agents in LM, such as the molecular divergence between primary tumors and CNS lesions and CNS barriers at the level of the normal brain, brain tumors and CSF. Further, we reviewed pathogenesis and experimental models and modalities, such as MRI (with RANO and ESO/ESMO criteria), CSF cytology and liquid biopsy, to improve diagnosis and monitoring following therapy. Efficacy and limitations of targeted therapies for LM from EGFR-mutant and ALK-rearranged NSCLC, HER2-positive breast cancer and BRAF-mutated melanomas are reported, including the use of intrathecal administration or modification of traditional cytotoxic compounds. The efficacy of checkpoint inhibitors in LM from non-druggable tumors, in particular triple-negative breast cancer, is discussed. Last, we focused on some recent techniques to improve drug delivery.

Trastuzumab Emtansine (T-DM1) and stereotactic radiation in the management of HER2+ breast cancer brain metastases

Background

Due to recent concerns about the toxicity of trastuzumab emtansine (T-DM1) with stereotactic radiation, we assessed our institutional outcomes treating HER2-positive breast cancer brain metastases (BCBM) with T-DM1 and stereotactic radiation.

Methods

This is a single institution series of 16 patients with HER2-positive breast cancer who underwent 18 stereotactic sessions to 40 BCBM from 2013 to 2019 with T-DM1 delivered within 6 months. The Kaplan-Meier method was used to calculate overall survival (OS), local control (LC), distant intracranial control (DIC), and systemic progression-free survival (sPFS) from the date of SRS. A neuro-radiologist independently reviewed follow-up imaging.

Results

One patient had invasive lobular carcinoma, and 15 patients had invasive ductal carcinoma. All cases were HER2-positive, while 10 were hormone receptor (HR) positive. Twenty-four lesions were treated with stereotactic radiosurgery (SRS) to a median dose of 21 Gy (14–24 Gy). Sixteen lesions were treated with fractionated stereotactic radiation (FSRT) with a median dose of 25 Gy (20-30Gy) delivered in 3 to 5 fractions. Stereotactic radiation was delivered concurrently with T-DM1 in 19 lesions (48%). Median follow up time was 13.2 months from stereotactic radiation. The 1-year LC, DIC, sPFS, and OS were 75, 50, 30, and 67%, respectively. There was 1 case of leptomeningeal progression and 1 case (3%) of symptomatic radionecrosis.

Conclusions

We demonstrate that stereotactic radiation and T-DM1 is well-tolerated and effective for patients with HER2-positive BCBM. An increased risk for symptomatic radiation necrosis was not noted in our series.

Management of Brain and Leptomeningeal Metastases from Breast Cancer

The management of breast cancer (BC) has rapidly evolved in the last 20 years. The improvement of systemic therapy allows a remarkable control of extracranial disease. However, brain (BM) and leptomeningeal metastases (LM) are frequent complications of advanced BC and represent a challenging issue for clinicians. Some prognostic scales designed for metastatic BC have been employed to select fit patients for adequate therapy and enrollment in clinical trials. Different systemic drugs, such as targeted therapies with either monoclonal antibodies or small tyrosine kinase molecules, or modified chemotherapeutic agents are under investigation. Major aims are to improve the penetration of active drugs through the blood-brain barrier (BBB) or brain-tumor barrier (BTB), and establish the best sequence and timing of radiotherapy and systemic therapy to avoid neurocognitive impairment. Moreover, pharmacologic prevention is a new concept driven by the efficacy of targeted agents on macrometastases from specific molecular subgroups. This review aims to provide an overview of the clinical and molecular factors involved in the selection of patients for local and/or systemic therapy, as well as the results of clinical trials on advanced BC. Moreover, insight on promising therapeutic options and potential directions of future therapeutic targets against BBB and microenvironment are discussed.

Emerging treatment strategies for breast cancer brain metastasis: from translational therapeutics to real-world experience

Systemic therapies for primary breast cancer have made great progress over the past two decades. However, oncologists confront an insidious and particularly difficult problem: in those patients with metastatic breast cancer, up to 50% of human epidermal growth factor 2 (HER2)-positive and 25-40% of triple-negative subtypes, brain metastases (BM) kill most of them. Fortunately, standard- of-care treatments for BM have improved rapidly, with a decline in whole brain radiation therapy and use of fractionated stereotactic radiosurgery as well as targeted therapies and immunotherapies. Meanwhile, advances in fundamental understanding of the basic biological processes of breast cancer BM (BCBM) have led to many novel experimental therapeutic strategies. In this review, we describe the most recent clinical treatment options and emerging experimental therapeutic strategies that have the potential to combat BCBM.

Challenges in the treatment of breast cancer brain metastases: evidence, unresolved questions, and a practical algorithm

Breast cancer is the leading cause of brain metastases in women. Large randomized clinical trials that have evaluated local therapies in patients with brain metastases include patients with brain metastases from a variety of cancer types. The incidence of brain metastases in the breast cancer population continues to grow, which is, aside from the rising breast cancer incidence, mainly attributable to improvements in systemic therapies leading to more durable control of extracranial metastatic disease and prolonged survival. The management of breast cancer brain metastases remains challenging, even more so with the continued advancement of local and highly effective systemic therapies. For most patients, a metastases-directed initial approach (i.e., radiation, surgery) represents the most appropriate initial therapy. Treatment should be based on multidisciplinary team discussions and a shared decision with the patients taking into account the risks and benefits of each therapeutic modality with the goal of prolonging survival while maintaining quality of life. In this narrative review, a multidisciplinary group of experts will address challenging questions in the context of current scientific literature and propose a therapeutic algorithm for breast cancer patients with brain metastases.

Advanced Lung Adenocarcinoma Patient with ERBB2 Amplification Identified by Comprehensive Genomic Profiling Benefits from Trastuzumab

For non-small-cell lung cancer (NSCLC) patients without established actionable alterations in genes such as EGFR or ALK, options for targeted therapy remain limited in clinical practice. About 5% of lung adenocarcinoma patients have tumors with ERBB2 genetic alterations, with even fewer patients harboring ERBB2 amplification. Currently, clinical trials mainly use IHC, FISH, or mutation testing to identify potential responders to ERBB2-targeting agents. The use of next-generation sequencing (NGS) to detect ERBB2 alterations, including copy number variants, is rare. In this study, we present an EGFR- and ALK-negative advanced NSCLC case for which we conducted comprehensive tumor genomic profiling to identify potentially actionable alterations. The tumor harbored an ERBB2 amplification, and trastuzumab-based therapy resulted in an excellent response, with a necrotic regression of the patient's lung lesion. Although he developed brain metastasis four months after trastuzumab initiation, he survived for an additional period of eight months without local recurrence or other systemic metastasis. This case report shows that the use of comprehensive genetic testing enables the identification of rare actionable alterations in NSCLC patients without other options for targeted treatment.

Prognostic factors and outcome of HER2+ breast cancer with CNS metastases

Aim: Trastuzumab prolongs progression-free and overall survival in HER2+ breast cancer (BC), but these are associated with increased distant recurrences and central nervous system metastases (CNSm). We retrospectively evaluated outcome and prognostic factors in CNSm and non-CNSm patients. Methods: Records of HER2+ BC treated in 2000-2017 were reviewed. Results: 283/1171 (24%) HER2+ BC patients developed metastatic disease. 109/283 patients (39%) have CNSm associated with worse prognosis and increased risk of death (hazard ratio: 4.7; 95% CI: 3.5-6.4). Prognostic factors were: number of CNSm (single vs multiple lesions; 3-year overall survival 39 vs 18%; p = 0.003); brain radiation (30 vs 14%; p < 0.001); new HER2-targeting therapies (30.6 vs 22.5%; p = 0.025). Conclusion: Prognosis of BC patients with CNSm has improved using HER2-targeting therapies but remains poor.

Systemic therapy for brain metastases

Metastases from cells outside of the central nervous system are the most common cancer found in the brain and are commonly associated with poor prognosis. Although cancer treatment is improving overall, central nervous system metastases are becoming more prevalent and require finesse to properly treat. Physicians must consider the biology of the primary tumor and the complex neurological environment that the metastasis resides in. This can be further complicated by the fact that the practice of cancer management is constantly evolving and therapy that works outside of the blood-brain barrier may not be effective inside of it. Therefore, this review seeks to update the reader on recent advancements made on the three most common sources of brain metastases: lung cancer, breast cancer, and melanoma. Each of these malignancies has been the subject of intriguing and novel avenues of therapy which are reviewed here.

Leptomeningeal carcinomatosis in patients with breast cancer

Leptomeningeal carcinomatosis (LC) is defined as infiltration of the leptomeninges by metastatic carcinoma, a relatively uncommon but devastating complication of many malignancies. Although only 5% of patients with breast cancer develop leptomeningeal involvement, it remains the most common etiology of LC. It can occur as a late-stage complication of systemic progression or present as the first sign of metastatic disease, with or without parenchymal brain metastases. Lobular carcinomas have a higher propensity to metastasize into the meninges when compared to ductal carcinoma, especially the triple-negative subtype, which usually is associated with a shorter interval between metastatic breast cancer diagnosis and the development of LC. Prognosis remains poor, with median survival of 4 months for patients receiving state-of-the-art treatment. The main factors associated with survival are performance status at diagnosis, CSF protein level and triple-negative subtype. Headache is commonly the first clinical presentation of LC, and the diagnostic workup usually requires CSF-cytological analysis and or/MRI. The current management of LC consists of a combination of intra-CSF chemotherapy, systemic therapy, radiotherapy and/or best-supportive care. The standard intra-CSF chemotherapy regimen is methotrexate. Radiotherapy is used for relieving obstruction points on CSF-outflow channels due to ependymal nodules, tumor deposits or bulky disease. Objective responses have been reported with intrathecal administration of trastuzumab for HER2-positive disease, yet this strategy is still under investigation. Further prospective trials are needed to better address the impact of these treatment modalities on overall survival and quality of life.

Clinicopathological and Treatment-Associated Prognostic Factors in Patients with Breast Cancer Leptomeningeal Metastases in Relation to Tumor Biology

BACKGROUND

Breast cancer (BC) is one of the solid tumors most commonly associated with leptomeningeal disease (LMD). LMD carries a devastating prognosis; however, disease presentation and prognostic factors are uncertain.

SUBJECTS, MATERIALS, AND METHODS

In order to describe patient characteristics, treatment patterns, and factors associated with survival in a contemporary multicentric cohort, 153 consecutive BC patients diagnosed with LMD at two European institutions (2002-2017) were included. Time to LMD and overall survival (OS) after LMD diagnosis were evaluated using the Kaplan-Meier method and Cox proportional hazards models.

RESULTS

Median age at LMD diagnosis was 58 years (25-84). Tumor phenotype distribution was as follows: hormone receptor (HR) positive (HR+)/human epidermal growth receptor 2 (HER2) negative 51.0%, triple-negative 15.0%, HR+/HER2 positive (HER2+) 13.1% and HR negative/HER2+ 7.2%. Most patients received active anticancer treatments (radiation therapy [RT] n = 42, systemic therapy n = 110, intrathecal treatment n = 103).Median OS was 3.9 months (95% confidence interval [CI] 2.4-5.5). Eastern Cooperative Oncology Group performance status (ECOG PS) >2, high white blood cells count, low glucose, and high protein in cerebrospinal fluid (CSF) were poor prognostic factors. Having received RT or systemic treatment was associated with better prognosis. In multivariate analysis, ECOG PS (hazard ratio 2.22, 95% CI 1.25-3.94), CSF glucose levels (hazard ratio 1.74, 95% CI 1.05-2.88), and having received systemic treatment (hazard ratio 0.17, 95% CI 0.09-0.32) were confirmed as independent prognostic factors. In HER2+ BC patients, having received systemic HER2-targeted therapy was the only factor maintaining independent prognostication (hazard ratio 0.12, 95% CI 0.02-0.67) in multivariate analysis.

CONCLUSION

Despite being limited by their retrospective nature, these results highlight the need for clinical trials in BC LMD, stratified on tumor biology.

IMPLICATIONS FOR PRACTICE

Leptomeningeal disease (LMD) is a devastating complication of breast cancer (BC), and its optimal therapy is still not defined. Here, patient characteristics, treatment patterns, and prognostic factors from a contemporary cohort of 153 BC-related LMD patients are reported. In multivariate analysis, Eastern Cooperative Oncology Group performance status, cerebrospinal fluid glucose levels, and having received systemic treatment were confirmed as independent prognostic factors in the overall population, whereas in human epidermal growth receptor 2 (HER2) positive BC patients, having received systemic HER2-targeted therapy was the only factor maintaining independent prognostication in multivariate analysis. These results highlight the need to consider stratification on tumor biology in the treatment of BC LMD.

T-DM1 and brain metastases: Clinical outcome in HER2-positive metastatic breast cancer

BACKGROUND

We reported the results of an Italian large retrospective analysis that evaluated the effectiveness and safety of T-DM1 in 'field-practice' breast cancer patients. We performed a sub-analysis to investigate the clinical activity of T-DM1 in patients with brain metastases (BMs).

METHODS

The records of 87 adult women with HER2-positive breast cancer and BMs treated with T-DM1 were reviewed. Their clinical outcomes were compared with those of 216 patients without central nervous system (CNS) involvement.

RESULTS

Response to T-DM1 treatment in BMs was available for 53 patients in the BM group (60.9%): two patients reported a complete response (3.8%), 11 patients obtained partial response (20.7%; overall response rate: 24.5%), 16 patients had a stable disease (30.1%). Regarding extracranial disease, a total of 77 and 191 patients were evaluable for response in BM group and non-BM group, respectively. The overall response rate was 35.1% in the BM group and 38.3% in the non-BM group; disease control rate was 53.3% and 66.6%, respectively. At a median follow-up of 16 months (range: 1-55), median cumulative progression-free survival (PFS) was 7 months (95% CI: 5.4-8.6) in the BM group and 8 months (95% CI: 5.7-10.3) in the non-BM group. In the second-line setting, PFS was 5 (95% CI: 3.1-6.9) versus 11 (95% CI: 7.1-14.9) months (p = 0.01). Overall survival was 14 months (95% CI: 12.2-15.8) in the BM group and 32 months (95% CI: 24.4-39.6) in the non-BM group (p < 0.0001).

CONCLUSIONS

T-DM1 is active in breast cancer patients with BMs.