Therapy and prophylaxis of brain metastases

Heterogeneity in intracranial relapses after complete resection of lung adenocarcinoma: Distinct features of brain-only relapse versus synchronous extracranial relapse

BACKGROUND

Patients with brain oligometastases have better prognosis than those with synchronous extracranial metastases in non-small cell lung cancer (NSCLC). However, studies focusing on intracranial-only recurrence after curative surgery remained scarce. This study aimed to explore distinct features of patients with exclusive brain relapse after resection of lung adenocarcinoma.

METHODS

Records were retrospectively reviewed of 2809 patients who had complete resection and pathologically confirmed stage IB-IIIA NSCLC in our hospital from October 2012 to September 2019. Patients were enrolled if they were adenocarcinoma and developed intracranial recurrence thereafter. They were divided into two groups depending on whether they had synchronous extracranial metastases. Clinical and pathological features of patients enrolled were collected and compared between groups.

RESULTS

Ninety-seven lung adenocarcinoma patients with intracranial recurrences were enrolled. The median follow-up time was 40 months. Fifty patients (51.5%) had brain oligometastases and 47 patients had synchronous extracranial metastases (ECM). Multivariate logistic regression suggested EGFR-sensitive mutation and male sex were positively correlated to brain-only recurrence (OR = 2.59, 95%CI 1.04-6.84 and OR = 2.58, 95% CI 1.05-6.75), while higher clinical stage was associated with synchronous ECM (stage II (OR = 0.33, 95%CI 0.09-1.14) or stage IIIA (OR = 0.54, 95%CI 0.20-1.38) versus stage I). No other pathological feature (lymphovascular invasion, visceral pleural invasion, low tumor differentiation, etc.) or adjuvant chemotherapy was associated with intracranial-only relapse after complete resection of primary tumor.

CONCLUSION

Among patients with brain relapse after resection of lung adenocarcinoma, patients with EGFR mutations might have intracranial relapse only without synchronous extracranial metastases. Further prospective studies are warranted to verify this.

Tumor lineage-specific immune response in brain metastatic disease: opportunities for targeted immunotherapy regimen?

Metastases in the brain are the most severe and devastating complication of cancer. The incidence of brain metastasis is increasing. Therefore, the need of finding specific druggable targets for brain metastasis is demanding. The aim of this study was to compare the brain (immune) response to brain metastases of the most common tumor lineages, viz., lung adenocarcinoma and breast cancer. Targeted gene expression profiles of 11 brain metastasis of lung adenocarcinoma (BM-LUAD) were compared to 11 brain metastasis of breast cancer (BCBM) using NanoString nCounter PanCancer IO 360™ Panel. The most promising results were validated spatially using the novel GeoMx™ Digital Spatial Profiler (DSP) Technology. Additionally, Immune cell profiles and expression of drug targets were validated by multiplex immunohistochemistry. We found a more active immune response in BM-LUAD as compared to BCBM. In the BM-LUAD, 138 genes were upregulated as compared to BCBM (adj. p ≤ 0.05). Conversely, in BCBM 28 genes were upregulated (adj. p ≤ 0.05). Additionally, genes related to CD45 + cells, T cells, and cytotoxic T cells showed to be expressed higher in BM-LUAD compared to BCBM (adj. p = 0.01, adj. p = 0.023, adj. p = 0.023, respectively). The spatial quantification of the immune cells using the GeoMx DSP technique revealed the significantly higher quantification of CD14 and CD163 in tumor regions of BM-LUAD as compared to BCBM. Importantly, the immune checkpoint VISTA and IDO1 were identified as highly expressed in the BM-LUAD. Multiplex immunohistochemistry confirmed the finding and showed that VISTA is expressed mainly in BM-LUAD tumor cells, CD3 + cells, and to fewer levels in some microglial cells in BM-LUAD. This is the first report on differences in the brain immune response between metastatic tumors of different lineages. We found a far more extensive infiltration of immune cells in BM-LUAD as compared to BCBM. In addition, we found higher expression of VISTA and IDO1 in BM-LUAD. Taken together, targeted immune therapy should be considered to treat patients with BM-LUAD.

Characterization of the immune microenvironment in brain metastases from different solid tumors

BACKGROUND

Brain metastases are one of the most common intracranial neoplasms. Increasing evidence have indicated that systemic immunotherapy may provide long-term benefits for brain metastases. Herein, we presented the results of an immune oncology panel RNA sequencing platform for patients with brain metastases from different primary sites.

METHODS

We investigated 25 samples of human brain metastases from lung cancer (n = 12), breast cancer (n = 6), and colorectal cancer (n = 7). Besides, 13 paired samples of adjacent noncancerous brain tissue (10 from patients with lung cancer and 3 from patients with breast cancer) were collected as controls. By comparing the brain metastases and paired samples of adjacent noncancerous brain tissue from 13 patients, we detected three upregulated and six downregulated genes, representing the malignant properties of cancer cells and increased immune infiltration in the microenvironment. Next, we profiled the immune-related genes in brain metastases from three primary cancer types.

RESULTS

A group of genes were significantly overexpressed in the microenvironment of brain metastases from lung cancer, covering the checkpoint pathways, lymphocyte infiltration, and TCR-coexpression. Especially, immune checkpoint molecules, PD-L1, PD-L2, and IDO1 were expressed at higher levels in brain metastases from lung cancer than those from the other two cancer types.

CONCLUSIONS

This study presents an immune landscape of brain metastases from different cancer types. With high RNA expression levels of PD-1/PD-L1 axis and immune infiltration in brain metastases, it would be worthwhile to explore the efficacy of immune checkpoint blockade for lung cancer patients with intracranial metastases.

Prophylactic TLR9 stimulation reduces brain metastasis through microglia activation

Brain metastases are prevalent in various types of cancer and are often terminal, given the low efficacy of available therapies. Therefore, preventing them is of utmost clinical relevance, and prophylactic treatments are perhaps the most efficient strategy. Here, we show that systemic prophylactic administration of a toll-like receptor (TLR) 9 agonist, CpG-C, is effective against brain metastases. Acute and chronic systemic administration of CpG-C reduced tumor cell seeding and growth in the brain in three tumor models in mice, including metastasis of human and mouse lung cancer, and spontaneous melanoma-derived brain metastasis. Studying mechanisms underlying the therapeutic effects of CpG-C, we found that in the brain, unlike in the periphery, natural killer (NK) cells and monocytes are not involved in controlling metastasis. Next, we demonstrated that the systemically administered CpG-C is taken up by endothelial cells, astrocytes, and microglia, without affecting blood-brain barrier (BBB) integrity and tumor brain extravasation. In vitro assays pointed to microglia, but not astrocytes, as mediators of CpG- C effects through increased tumor killing and phagocytosis, mediated by direct microglia-tumor contact. In vivo, CpG-C-activated microglia displayed elevated mRNA expression levels of apoptosis-inducing and phagocytosis-related genes. Intravital imaging showed that CpG-C-activated microglia cells contact, kill, and phagocytize tumor cells in the early stages of tumor brain invasion more than nonactivated microglia. Blocking in vivo activation of microglia with minocycline, and depletion of microglia with a colony-stimulating factor 1 inhibitor, indicated that microglia mediate the antitumor effects of CpG-C. Overall, the results suggest prophylactic CpG-C treatment as a new intervention against brain metastasis, through an essential activation of microglia.

New developments in brain metastases

Patients with brain metastases (BM) are a population of high clinical need for new therapeutic approaches due to, as yet, very impaired survival prognosis. However, only few clinical trials have specifically addressed this prognostically highly heterogeneous patient population. New developments in the treatment of BM patients aim to reduce the side effects of local therapies, for example, by redefining the indications for stereotactic radiosurgery and whole-brain radiotherapy (WBRT) or introducing new applications like hippocampal sparing WBRT. Furthermore, systemic therapies become a more important treatment approach in patients harboring targetable mutations, as recent BM-specific endpoints in several phase III trials have shown promising intracranial efficacy. In addition, immune-checkpoint inhibitors show promising intracranial efficacy, particularly in patients with melanoma and non-small lung cancer BM. Here, we provide a review on the recent new developments in the local and systemic therapy approaches in BM patients.

Maintaining unperturbed cerebral blood flow is key in the study of brain metastasis and its interactions with stress and inflammatory responses

Blood-borne brain metastases are associated with poor prognosis, but little is known about the interplay between cerebral blood flow, surgical stress responses, and the metastatic process. The intra-carotid inoculation approach, traditionally used in animal studies, involves permanent occlusion of the common carotid artery (CCA). Herein we introduced a novel intra-carotid inoculation approach that avoids CCA ligation, namely - assisted external carotid artery inoculation (aECAi) - and compared it to the traditional approach in C57/BL6 mice, assessing cerebral blood flow; particle distribution; blood-brain barrier (BBB) integrity; stress, inflammatory and immune responses; and brain tumor retention and growth. Doppler flowmetry and two-photon imaging confirmed that only in the traditional approach regional and capillary cerebral blood flux were significantly reduced. Corticosterone and plasma IL-6 levels were higher in the traditional approach, splenic numbers of NK, CD3+, granulocytes, and dendritic cells were lower, and many of these indices were more profoundly affected by surgical stress in the traditional approach. BBB integrity was unaffected. Administration of spherical beads indicated that CCA ligation significantly limited brain distribution of injected particles, and inoculation of D122-LLC syngeneic tumor cells resulted in 10-fold lower brain tumor-cell retention in the traditional approach. Last, while most of the injected tumor cells were arrested in extra-cranial head areas, our method improved targeting of brain-tissue by 7-fold. This head versus brain distribution difference, commonly overlooked, cannot be detected using in vivo bioluminescent imaging. Overall, it is crucial to maintain unperturbed cerebral blood flow while studying brain metastasis and interactions with stress and inflammatory responses.

The brain metastatic niche

Metastasizing cancer cells that arrest in brain microvessels have to face an organ microenvironment that is alien, and exclusive. In order to survive and thrive in this foreign soil, the malignant cells need to successfully master a sequence of steps that includes close interactions with pre-existing brain microvessels, and other nonmalignant cell types. Unfortunately, a relevant number of circulating cancer cells is capable of doing so: brain metastasis is a frequent and devastating complication of solid tumors, becoming ever more important in times where the systemic tumor disease is better controlled and life of cancer patients is prolonged. Thus, it is very important to understand which environmental cues are necessary for effective brain colonization. This review gives an overview of the niches we know, including those who govern cancer cell dormancy, survival, and proliferation in the brain. Colonization of pre-existing niches related to stemness and resistance is a hallmark of successful brain metastasis. A deeper understanding of those host factors can help to identify the most vulnerable steps of the metastatic cascade, which might be most amenable to therapeutic interventions.

Differential role of angiogenesis and tumour cell proliferation in brain metastases according to primary tumour type: analysis of 639 cases

AIM

We aimed to characterize angiogenesis and proliferation and their correlation with clinical characteristics in a large brain metastasis (BM) series.

METHODS

Ki67 proliferation index, microvascular density (MVD) and hypoxia-inducible factor 1 alpha (HIF-1 alpha) index were determined by immunohistochemistry in BM and primary tumour specimens.

RESULTS

Six hundred thirty-nine BM specimens of 639 patients with lung cancer (344/639; 53.8%), breast cancer (105/639; 16.4%), melanoma (67/639; 10.5%), renal cell carcinoma (RCC; 52/639; 8.1%) or colorectal cancer (CRC; 71/639; 11.1%) were available. Specimens of the corresponding primary tumour were available in 113/639 (17.7%) cases. Median Ki67 index was highest in CRC BM and lowest in RCC BM (P < 0.001). MVD and HIF-1 alpha index were both highest in RCC BM and lowest in melanoma BM (P < 0.001). Significantly higher Ki67 indices, MVD and HIF-1 alpha indices in the BM than in matched primary tumours were observed for breast cancer, non-small cell lung cancer (NSCLC) and CRC. Correlation of tissue-based parameters with overall survival in individual tumour types showed a favourable and independent prognostic impact of low Ki67 index [hazard ratio (HR) 1.015; P < 0.001] in NSCLC BM and of low Ki67 index (HR 1.027; P = 0.008) and high angiogenic activity (HR 1.877; P = 0.002) in RCC.

CONCLUSION

Our data argue for differential pathobiological and clinical relevance of Ki67 index, HIF1-alpha index and MVD between primary tumour types in BM patients. An independent prognostic impact of tissue-based characteristics was observed in patients with BM from NSCLC and RCC, supporting the incorporation of these tissue-based parameters into diagnosis-specific prognostic scores.

Macrolide analog F806 suppresses esophageal squamous cell carcinoma (ESCC) by blocking β1 integrin activation

The paucity of new drugs for the treatment of esophageal squamous cell carcinoma (ESCC) limits the treatment options. This study characterized the therapeutic efficacy and action mechanism of a novel natural macrolide compound F806 in human ESCC xenograft models and cell lines. F806 inhibited growth of ESCC, most importantly, it displayed fewer undesirable side effects on normal tissues in two human ESCC xenograft models. F806 inhibited proliferation of six ESCC cells lines, with the half maximal inhibitory concentration (IC50) ranging from 9.31 to 16.43 μM. Furthermore, F806 induced apoptosis of ESCC cells, contributing to its growth-inhibitory effect. Also, F806 inhibited cell adhesion resulting in anoikis. Mechanistic studies revealed that F806 inhibited the activation of β1 integrin in part by binding to a novel site Arg610 of β1 integrin, suppressed focal adhesion formation, decreased cell adhesion to extracellular matrix and eventually triggered apoptosis. We concluded that F806 would potentially be a well-tolerated anticancer drug by targeting β1 integrin, resulting in anoikis in ESCC cells.

Role of the endothelin axis in astrocyte- and endothelial cell-mediated chemoprotection of cancer cells

BACKGROUND

Recent evidence suggests that astrocytes protect cancer cells from chemotherapy by stimulating upregulation of anti-apoptotic genes in those cells. We investigated the possibility that activation of the endothelin axis orchestrates survival gene expression and chemoprotection in MDA-MB-231 breast cancer cells and H226 lung cancer cells.

METHODS

Cancer cells, murine astrocytes, and murine fibroblasts were grown in isolation, and expression of endothelin (ET) peptides and ET receptors (ETAR and ETBR) compared with expression on cancer cells and astrocytes (or cancer cells and fibroblasts) that were co-incubated for 48 hours. Type-specific endothelin receptor antagonists were used to evaluate the contribution of ETAR and ETBR to astrocyte-induced activation of the protein kinase B (AKT)/mitogen-activated protein kinase (MAPK) signal transduction pathways, anti-apoptotic gene expression, and chemoprotection of cancer cells. We also investigated the chemoprotective potential of brain endothelial cells and microglial cells.

RESULTS

Gap junction signaling between MDA-MB-231 cancer cells and astrocytes stimulates upregulation of interleukin 6 (IL-6) and IL-8 expression in cancer cells, which increases ET-1 production from astrocytes and ET receptor expression on cancer cells. ET-1 signals for activation of AKT/MAPK and upregulation of survival proteins that protect cancer cells from taxol. Brain endothelial cell-mediated chemoprotection of cancer cells also involves endothelin signaling. Dual antagonism of ETAR and ETBR is required to abolish astrocyte- and endothelial cell-mediated chemoprotection.

CONCLUSIONS

Bidirectional signaling between astrocytes and cancer cells involves upregulation and activation of the endothelin axis, which protects cancer cells from cytotoxicity induced by chemotherapeutic drugs.

Blockade of SDF-1 after irradiation inhibits tumor recurrences of autochthonous brain tumors in rats

Background

Tumor irradiation blocks local angiogenesis, forcing any recurrent tumor to form new vessels from circulating cells. We have previously demonstrated that the post-irradiation recurrence of human glioblastomas in the brains of nude mice can be delayed or prevented by inhibiting circulating blood vessel–forming cells by blocking the interaction of CXCR4 with its ligand stromal cell-derived factor (SDF)–1 (CXCL12). In the present study we test this strategy by directly neutralizing SDF-1 in a clinically relevant model using autochthonous brain tumors in immune competent hosts.

Methods

We used NOX-A12, an l-enantiomeric RNA oligonucleotide that binds and inhibits SDF-1 with high affinity. We tested the effect of this inhibitor on the response to irradiation of brain tumors in rat induced by n-ethyl-N-nitrosourea.

Results

Rats treated in utero with N-ethyl-N-nitrosourea began to die of brain tumors from approximately 120 days of age. We delivered a single dose of whole brain irradiation (20 Gy) on day 115 of age, began treatment with NOX-A12 immediately following irradiation, and continued with either 5 or 20 mg/kg for 4 or 8 weeks, doses and times equivalent to well-tolerated human exposures. We found a marked prolongation of rat life span that was dependent on both drug dose and duration of treatment. In addition we treated tumors only when they were visible by MRI and demonstrated complete regression of the tumors that was not achieved by irradiation alone or with the addition of temozolomide.

Conclusions

Inhibition of SDF-1 following tumor irradiation is a powerful way of improving tumor response of glioblastoma multiforme.

β1 integrin targeting potentiates antiangiogenic therapy and inhibits the growth of bevacizumab-resistant glioblastoma

Antiangiogenic therapies like bevacizumab offer promise for cancer treatment, but acquired resistance, which often includes an aggressive mesenchymal phenotype, can limit the use of these agents. Upregulation of β1 integrin (ITGB1) occurs in some bevacizumab-resistant glioblastomas (BRG) whereby, mediating tumor-microenvironment interactions, we hypothesized that it may mediate a mesenchymal-type resistance to antiangiogenic therapy. Immunostaining analyses of β1 integrin and its downstream effector kinase FAK revealed upregulation in 75% and 86% of BRGs, respectively, compared with pretreatment paired specimens. Furthermore, flow cytometry revealed eight-fold more β1 integrin in primary BRG cells compared with cells from bevacizumab-naïve glioblastomas (BNG). Fluorescence recovery after photobleaching of cells engineered to express a β1-GFP fusion protein indicated that the mobile β1 integrin fraction was doubled, and half-life of β1 integrin turnover in focal adhesions was reduced markedly in BRG cells compared with bevacizumab-responsive glioblastoma multiforme cells. Hypoxia, which was increased with acquisition of bevacizumab resistance, was associated with increased β1 integrin expression in cultured BNG cells. BRGs displayed an aggressive mesenchymal-like phenotype in vitro. We found that growth of BRG xenograft tumors was attenuated by the β1 antibody, OS2966, allowing a 20-fold dose reduction of bevacizumab per cycle in this model. Intracranial delivery of OS2966 through osmotic pumps over 28 days increased tumor cell apoptosis, decreased tumor cell invasiveness, and blunted the mesenchymal morphology of tumor cells. We concluded that β1 integrin upregulation in BRGs likely reflects an onset of hypoxia caused by antiangiogenic therapy, and that β1 inhibition is well tolerated in vivo as a tractable strategy to disrupt resistance to this therapy.

Chemotherapy in the management of brain metastases: the emerging role of fotemustine for patients with melanoma and NSCLC

INTRODUCTION

An estimated 20 - 40% of cancer patients will develop brain metastases that are the most common intracranial tumors in adults. Patients with cerebral metastases represent a variegate group where selection of the most appropriate treatment depends on many patient- and disease-related factors. The impact of therapeutic option on overall survival is lacking and it is important to consider quality of life (QOL) when treating patients with brain metastases.

AREAS COVERED

A considerable proportion of patients are treated with palliative approaches such as whole-brain radiotherapy. The role of chemotherapy was limited in the past. Recently, several chemotherapeutic agents have been identified as potentially useful. This article examines the pharmacokinetics, efficacy and safety and tolerability of fotemustine (FTM) for the management of patients with cerebral metastasis from melanoma and non-small cell lung cancer (NSCLC).

EXPERT OPINION

FTM is a third-generation nitrosourea that has proved its efficacy on brain metastases of melanoma and showed promising results for the treatment of brain metastasis of NSCLC because of its ability to pass the blood-brain barrier.

Tumor margin identification and prediction of the primary tumor from brain metastases using FTIR imaging and support vector machines

Infrared spectroscopy enables the identification of tissue types based on their inherent vibrational fingerprint without staining in a nondestructive way. Here, Fourier transform infrared microscopic images were collected from 22 brain metastasis tissue sections of bladder carcinoma, lung carcinoma, mamma carcinoma, colon carcinoma, prostate carcinoma and renal cell carcinoma. The scope of this study was to distinguish the infrared spectra of carcinoma from normal tissue and necrosis and to use the infrared spectra of carcinoma to determine the primary tumor of brain metastasis. Data processing follows procedures that have previously been developed for the analysis of Raman images of these samples and includes the unmixing algorithm N-FINDR, segmentation by k-means clustering, and classification by support vector machines (SVMs). Upon comparison with the subsequent hematoxylin and eosin stained tissue sections of training specimens, correct classification rates of the first level SVM were 98.8% for brain tissue, 98.4% for necrosis and 94.4% for carcinoma. The primary tumors were correctly predicted with an overall rate of 98.7% for FTIR images of the training dataset by a second level SVM. Finally, the two level discrimination models were applied to four independent specimens for validation. Although the classification rates are slightly reduced compared to the training specimens, the majority of the infrared spectra of the independent specimens were assigned to the correct primary tumor. The results demonstrate the capability of FTIR imaging to complement histopathological tools for brain tissue diagnosis.

Circulating biomarkers of CNS tumors: an update

CNS tumors comprise approximately 120 histological subtypes. Advances of surgical resection, radiation and systemic therapy have increased the survival rates of distinct types of CNS tumor patients. There is growing interest in identification of diagnostic, prognostic or predictive blood biomarkers in CNS tumor patients, and emerging studies indicate that certain brain tumors are indeed associated with distinct profiles of circulating factors such as proteins (e.g., glial fibrillary acidic protein), DNA fragments (e.g., containing mutated IDH) or miRNAs (e.g., miRNA-21). However, blood biomarker research in neurooncology is, for the most part, at an exploratory level, and adequately powered and well-designed studies are needed to translate the available interesting but preliminary findings into actual clinical use. In this review, the current knowledge on circulating biomarkers of CNS tumors is briefly summarized.

Targeted therapy in brain metastasis

PURPOSE OF REVIEW

To review the state of the art and new developments in the field of targeted agents for brain metastases.

RECENT FINDINGS

The huge amount of information on new molecular compounds and the advances in understanding the molecular pathways that mediate brain colonization have led to an increase of interest in preclinical and clinical investigations in the field of brain metastases. Targeted therapies can be employed either on established brain metastases or in a prevention setting. Targeting angiogenesis is an attractive approach. Up to date, large clinical trial datasets have shown that antiangiogenic agents do not increase the risk of bleeding into the brain. Bevacizumab (an anti-VEGF agent) is undergoing investigation in clinical trials on brain metastases from non-small cell lung cancer (NSCLC), breast cancer and melanoma. Sunitinib, a multitarget small molecule tyrosine kinase inhibitor (TKI), is a promising agent in brain metastases from renal cell cancer. The EGFR inhibitors gefitinib and erlotinib have a definite activity in brain metastases from NSCLC with activating EGFR mutations. Regarding HER2-positive breast cancer patients with established brain metastases, lapatinib (small molecule TKI) seems particularly active in association with capecitabine. Lapatinib alone is attractive in the prevention setting. Brain metastases from melanoma with BRAF V600E mutations respond to a specific inhibitor, such as vemurafenib. The immunomodulator ipilimumab is also active on brain metastases from melanoma.

SUMMARY

The use of targeted agents in brain metastases from solid tumors is promising. The setting of prevention will be probably expanded in the next years. Well designed clinical trials with proper endpoints are needed.

The role of cancer stem cells and miRNAs in defining the complexities of brain metastasis

Researchers and clinicians have been challenged with the development of therapies for the treatment of cancer patients whose tumors metastasized to the brain. Among the most lethal weapons known today, current management of brain metastases involves multiple therapeutic modalities that provide little, if any, for improving the quality of life and overall survival. Recently the role of cancer stem cells (CSCs) in the development of cancer has been studied extensively, and thus its role in the prognosis, diagnosis, and treatment is now being investigated even in the realm of brain metastasis (BM). Recognizing the molecular make-up of CSCs as well as understanding the role of these cells in resistance to treatment modalities is expected to benefit cancer patients. Additionally, past decade has witnessed an increase in awareness and understanding of the role of microRNAs (miRNAs) in various cancer types, and the deregulation miRNAs are critically important for the regulation of genes during the development and progression of human malignancies. The role miRNAs in BM is being investigated, and has also shown tremendous promise for future research. In this review, we discuss the problem and lethality of brain metastases and the current state of management, and further provide insight into novel avenues that are worth considering including the biological complexities of CSCs and miRNAs for designing novel therapies.

Management of brain metastasis: past lessons, modern management, and future considerations

Brain metastasis is a major challenge for patients, physicians, and the broader health care system, with approximately 170,000 new cases per year. After a diagnosis of brain metastasis, patients have a poor prognosis, but modern management has made significant advances in the past two decades to improve palliative efficacy and patient survival through a multidisciplinary approach. A number of factors must be taken into consideration in the treatment approach, including the number of intracranial lesions, the control of extracranial disease, and the patient's overall health, while weighing the benefits of treatment against the toxicities, both acute and chronic. With quality of life as an emphasis, emerging concepts for modern management of brain metastasis have sought to minimize long-term toxicities. The economic impact of such strategies for patients and the health care system has been demonstrated in some studies, but has not been a consistent area of focus. Each of these strategies, as well as novel therapeutics, has embraced the concept of personalized treatment. This review will discuss the current knowledge of modern multidisciplinary management of brain metastasis and look forward to emerging concepts.

Opposing effects of pigment epithelium-derived factor on breast cancer cell versus neuronal survival: implication for brain metastasis and metastasis-induced brain damage

Brain metastases are a significant cause of morbidity and mortality for patients with cancer, yet preventative and therapeutic options remain an unmet need. The cytokine pigment epithelium-derived factor (PEDF) is downregulated in resected human brain metastases of breast cancer compared with primary breast tumors, suggesting that restoring its expression might limit metastatic spread. Here, we show that outgrowth of large experimental brain metastases from human 231-BR or murine 4T1-BR breast cancer cells was suppressed by PEDF expression, as supported by in vitro analyses as well as direct intracranial implantation. Notably, the suppressive effects of PEDF were not only rapid but independent of the effects of this factor on angiogenesis. Paralleling its cytotoxic effects on breast cancer cells, PEDF also exerted a prosurvival effect on neurons that shielded the brain from tumor-induced damage, as indicated by a relative 3.5-fold reduction in the number of dying neurons adjacent to tumors expressing PEDF. Our findings establish PEDF as both a metastatic suppressor and a neuroprotectant in the brain, highlighting its role as a double agent in limiting brain metastasis and its local consequences.

Brain metastases: pathobiology and emerging targeted therapies

Brain metastases (BM) are common in cancer patients and are associated with high morbidity and poor prognosis, even after intensive multimodal therapy including resection, radiotherapy (stereotactic radiosurgery or whole brain radiotherapy) and chemotherapy. However, advances in the understanding of the pathobiology of BM and the development of molecular targeted agents hold promise for improved prophylaxis and therapy of BM. Here we provide a comprehensive review of the current concepts on mechanisms of the brain-metastatic cascade involving hematogenous dissemination of tumor cells, attachment to microvessel endothelial cells, extravasation into the brain, interaction with the local microenvironment, angiogenesis and intraparenchymal proliferation. Transendothelial migration depends on adhesion molecules such as integrins, selectins and chemokines. Tumor cells invade the brain by degrading extracellular matrix components using heparanase and matrix metalloproteinases. Astrocytes and microglial cells exert not only anti-, but also pro-neoplastic effects on brain-invading tumor cells. Some tumor types (e.g. melanoma) show prominent cooption of preexisting vasculature, while other tumor types (e.g. lung cancer) tend to show early angiogenesis after brain invasion. In this article we also critically summarize the data on currently studied targeted therapeutics in BM especially in the context of recent preclinical data. The most promising agents for BM patients include anti-angiogenic drugs, inhibitors of v-RAF murine sarcoma viral oncogene homolog B1 (BRAF) for BRAF V600E mutated melanoma and inhibitors of epithelial growth factor receptor for non-small cell lung cancer. Molecular analysis of the BRAF V600E status of melanoma BM using DNA-based methods or immunohistochemistry may soon enter the routine neuropathological practice.

Immunohistochemical testing of BRAF V600E status in 1,120 tumor tissue samples of patients with brain metastases

Brain metastases (BM) are frequent and carry a dismal prognosis. BRAF V600E mutations are found in a broad range of tumor types and specific inhibitors targeting BRAF V600E protein exist. We analyzed tumoral BRAF V600E-mutant protein expression using the novel mutation-specific antibody VE1 in a series of 1,120 tumor specimens (885 BM, 157 primary tumors, 78 extra-cranial metastases) of 874 BM patients. In 85 cases, we performed validation of immunohistochemical results by BRAF exon 15 gene sequencing. BRAF V600E protein was expressed in BM of 42/76 (55.3%) melanomas, 1/15 (6.7%) ovarian cancers, 4/72 (5.5%) colorectal cancers, 1/355 (0.3%) lung cancers, 2/6 thyroid cancers and 1/2 choriocarcinomas. BRAF V600E expression showed high intra-tumoral homogeneity and was similar in different tumor manifestations of individual patients. VE1 immunohistochemistry and BRAF exon 15 sequencing were congruent in 68/70 (97.1%) cases, but VE1 immunostaining identified small BRAF V600E expressing tumor cell aggregates in 10 cases with inconclusive genetic results. Melanoma patients with BRAF V600E mutant protein expressing tumors were significantly younger at diagnosis of the primary tumor and at operation of BM than patients with non-mutated tumors. In conclusion, expression of BRAF V600E mutant protein occurs in approximately 6% of BM and is consistent in different tumor manifestations of the same patient. Thus, BRAF V600E inhibiting therapies seem feasible in selected BM patients. Immunohistochemical visualization of V600E-mutant BRAF protein is a promising tool for patient stratification. An integrated approach combining both, VE1 immunohistochemistry and genetic analysis may increase the diagnostic accuracy of BRAF mutation analysis.

A review of current management of brain metastases

BACKGROUND

The brain metastasis (BM) represents one of the most common and refractory malignancies worldwide with a rising incidence in all countries. It is generally believed that once a BM has developed, this disease cannot be cured and has a poor prognosis. The challenges of managing this tumor include diagnosis and selective treatment options. In addition, patients with BM frequently have greater expectations of the current therapy outcomes, which hope to get long-term survival and good quality of life.

METHODS

This is a review of current clinical practice based on an exhaustive literature search of PubMed, Embase, and Google Scholar. A series of case studies is presented to provide outcomes of the effective management in BMs that have required treatment for the terminal stage of patients with cancer, and makes recommendations for future practice.

RESULTS

Current technical advances have been made in the diagnosis and treatment of BM. After surgery, radiotherapy, or stereotactic radiosurgery, and for some cases additional systemic chemotherapy for the primary cancer, most patients experience meaningful symptom relief, improved quality of life and longer survival time. An evidence-based summary of recommendations has been produced to guide neurosurgeons and oncologists in managing this particular group of patients.

CONCLUSIONS

On the basis of the available data, this treatment approach for well-selected patients is currently not recommended in the treatment of BMs except in experienced medical centers. Clinical judgment is made balancing surgical, radiotherapy, chemotherapy and management principles to advocacy the best therapy outcome.

Combining temozolomide with other antitumor drugs and target-based agents in the treatment of brain metastases: an unending quest or chasing a chimera?

INTRODUCTION

Medical treatment of brain metastases (BM) is still a controversial issue in cancer therapy being mainly limited by the existence of the BBB. Temozolomide (TMZ) can cross BBB and several clinical trials have been performed attempting to demonstrate the activity of TMZ in combination with whole brain radiotherapy (WBRT) in the treatment of BM.

AREAS COVERED

This review summarizes TMZ-WBRT combination trials highlighting the confounding factors that limit the interpretation of the achieved results and describes the main clinical trials using TMZ in combination with other cytotoxic or biological agents. The main limitations of these trials are: i) patient selection for heterogenous primitive neoplasms and for heterogeneous neuro-functional score; ii) poor penetration across BBB of the other drugs; iii) cumulative toxicity and iv) poor control of extracranial tumor sites.

EXPERT OPINION

Biotechnological, biological and biochemical advances in the management of BM could allow in short time the definition of new schedules based on the rational use of new anticancer weapons. The latter could be cytotoxic agents encapsulated in nanotechnological tools able to cross BBB, lipophilic small kinase inhibitors (lapatinib, sunitinib), mTOR inhibitors and PARP inhibitors combined with old drugs such as TMZ.