Brain metastasis in breast cancer: a comprehensive literature review

Current Therapies for Human Epidermal Growth Factor Receptor 2-Positive Metastatic Breast Cancer Patients

The median survival of patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (MBC) has more than doubled, since the discovery of HER2-targeted treatments: it rose from less than 2 years in 2001 (prior introduction of trastuzumab) to more than 4 years in 2017. The initial generation of HER2-targeted therapies included trastuzumab with taxanes in the first line, followed by the addition of lapatinib and by a switch to another cytotoxic agent after progression. Results of CLEOPATRA, EMILIA, and TH3RESA trials have changed this clinical practice. The current consensus includes horizontal dual blockade (trastuzumab + pertuzumab) with taxanes or vinorelbine in the first line, followed by trastuzumab-emtansine (T-DM1) in the second line, with addition of lapatinib in the later lines of treatment. However, the fast and simultaneous development of new drugs led to a relative shortage of clinical evidence to support this sequence. Triple-positive breast cancers (TPBC), which express both hormonal receptors and HER2, constitute nearly half of HER2-positive cases. For these tumors, the current consensus is to add endocrine therapy after completion of cytotoxic treatment. Again, this consensus is not fully evidence-based. In view of the recent progress in treatment of estrogen-receptor positive breast cancers, a series of trials is evaluating addition of CDK4/6 inhibitors, aromatase inhibitors or fulvestrant to HER2-targeted and cytotoxic chemotherapy in TPBC patients. Despite the remarkable progress in treatment of HER2-positive breast cancer, metastatic disease is still incurable in the majority of patients. A wide range of novel therapies are under development to prevent and overcome resistance to current HER2-targeted agents. This review discusses pivotal clinical trials that have shaped current clinical practices, the current consensus recommendations, and the new experimental treatments in metastatic HER2-positive breast cancer.

Foe or friend? Janus-faces of the neurovascular unit in the formation of brain metastases

Despite the potential obstacle represented by the blood-brain barrier for extravasating malignant cells, metastases are more frequent than primary tumors in the central nervous system. Not only tightly interconnected endothelial cells can hinder metastasis formation, other cells of the brain microenvironment (like astrocytes and microglia) can also be very hostile, destroying the large majority of metastatic cells. However, malignant cells that are able to overcome these harmful mechanisms may benefit from the shielding and even support provided by cerebral endothelial cells, astrocytes and microglia, rendering the brain a sanctuary site against anti-tumor strategies. Thus, cells of the neurovascular unit have a Janus-faced attitude towards brain metastatic cells, being both destructive and protective. In this review, we present the main mechanisms of brain metastasis formation, including those involved in extravasation through the brain vasculature and survival in the cerebral environment.

Factores pronósticos en pacientes con cáncer de mama y metástasis cerebral como primer sitio de recurrencia

Objetivo. Evaluar los factores pronósticos (características clínico-patológicas y tratamientos) en las pacientes con cáncer de mama y metástasis al sistema nervioso central (SNC) como primer sitio de afección. Material y métodos. Cohorte retrospectiva, formada por 125 pacientes con cáncer de mama atendidas en el Instituto Nacional de Cancerología durante 2007-2015, quienes presentaron afección en el SNC como primer sitio de metástasis. A través del método Kaplan-Meier y tablas de vida se estimó la supervivencia global. El modelo de riesgos proporcionales de Cox fue utilizado para determinar los factores pronósticos. Resultados. La mediana de super­vivencia global fue de 14.2 meses (IC95% 11.8-26.9). Pacientes clasificadas por inmunohistoquímica como triple negativo (TN) presentaron tiempos de supervivencia más cortos (p<0.004) y con dos veces más riesgo de fallecer, en com­paración con los otros inmunofenotipos (HR= 2.77; IC95% 1.10-6.99); asimismo, se identificó que un grado intermedio en la escala Scarff-Bloom-Richardson incrementa el riesgo de morir en pacientes con metástasis (HR=2.76; IC95% 1.17- 6.51). Conclusiones. La metástasis al SNC continúa siendo un factor de mal pronóstico que reduce la supervivencia y afecta la calidad de vida. Se recomienda vigilar puntualmente la presencia de manifestaciones clínicas neurológicas durante el seguimiento, para una rápida intervención. Las pacientes TN tienen peor pronóstico, y las HER2+ (es decir, con resultado positivo para el receptor 2 del factor de crecimiento humano epidérmico), mejor control a mediano plazo.

Colorectal cancer and brain metastases: An aggressive disease with a different response to treatment

INTRODUCTION

Brain metastases (BM) are rare in colorectal cancer (CRC) and are associated with a dismal prognosis. This work aims to report the rate of BM in CRC patients treated in a single institution, along with survival and prognostic factors.

METHODS

Medical charts for patients with histologically proven CRC were retrospectively reviewed.

RESULTS

A total of 538 patients were identified, of whom 33% developed any metastatic disease and 4.4% presented BM. Lung was the most frequently associated metastatic site (in 68% of the cases). The only factor independently associated with BM development was the presence of metastatic disease at the time of initial presentation. The median duration from initial diagnosis to BM development was 38.6 months (SD 29.1 months). Median survival after BM development was 62 days (95% confidence interval [CI] 56-68). Patients diagnosed with BM within 1 year of cancer diagnosis responded significantly better to treatment than those who acquired BM later, with a median survival after BM diagnosis of 261 days versus 61 days, respectively (p = .002). Patients with BM who received antiangiogenic therapy had an improved median survival compared to those who did not (151 days vs 59 days, p = 0.02; hazard ratio for death 0.29 [95% CI 0.09-0.94]).

CONCLUSION

CRC with BM is an aggressive disease resistant to standard treatment and is associated with poor outcomes. Adding antiangiogenic therapy might be of value for those patients. Patients with BM developing early in the disease course might respond better to treatment.

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

Background

Herein, we report a complete response after whole brain radiotherapy (WBRT) and concomitant T-DM1 in a patient with HER2-positive metastatic breast cancer (MBC) and extensive brain and leptomeningeal involvement.

Case presentation

A 46 years old Caucasian woman with HER2-positive MBC and no baseline CNS involvement, started in August 2015 1^st line therapy with Pertuzumab-Trastuzumab-Docetaxel, with partial response. However, in April 2016 the patient eventually progressed with emergence of brain and leptomeningeal metastases. Hence, she started in May 2016 2^nd line therapy with T-DM1 and concomitant WBRT, with complete response (CR) after 3 courses of therapy, with complete resolution of neurological symptoms and no relevant toxicities. The CR is lasting over 13 months and the patient is out of corticosteroid use.

Conclusions

To the best of our knowledge, this is the first case reporting interesting antitumor activity of T-DM1 and concomitant WBRT in both brain and leptomeningeal metastases, with a favorable safety profile and prolonged extracranial disease control. Further prospective studies should confirm these findings.

Comprehensive molecular biomarker identification in breast cancer brain metastases

Background

Breast cancer brain metastases (BCBM) develop in about 20–30% of breast cancer (BC) patients. BCBM are associated with dismal prognosis not at least due to lack of valuable molecular therapeutic targets. The aim of the study was to identify new molecular biomarkers and targets in BCBM by using complementary state-of-the-art techniques.

Methods

We compared array expression profiles of three BCBM with 16 non-brain metastatic BC and 16 primary brain tumors (prBT) using a false discovery rate (FDR) p < 0.05 and fold change (FC) > 2. Biofunctional analysis was conducted on the differentially expressed probe sets. High-density arrays were employed to detect copy number variations (CNVs) and whole exome sequencing (WES) with paired-end reads of 150 bp was utilized to detect gene mutations in the three BCBM.

Results

The top 370 probe sets that were differentially expressed between BCBM and both BC and prBT were in the majority comparably overexpressed in BCBM and included, e.g. the coding genes BCL3, BNIP3, BNIP3P1, BRIP1, CASP14, CDC25A, DMBT1, IDH2, E2F1, MYCN, RAD51, RAD54L, and VDR. A number of small nucleolar RNAs (snoRNAs) were comparably overexpressed in BCBM and included SNORA1, SNORA2A, SNORA9, SNORA10, SNORA22, SNORA24, SNORA30, SNORA37, SNORA38, SNORA52, SNORA71A, SNORA71B, SNORA71C, SNORD13P2, SNORD15A, SNORD34, SNORD35A, SNORD41, SNORD53, and SCARNA22. The top canonical pathway was entitled, role of BRCA1 in DNA damage response. Network analysis revealed key nodes as Akt, ERK1/2, NFkB, and Ras in a predicted activation stage. Downregulated genes in a data set that was shared between BCBM and prBT comprised, e.g. BC cell line invasion markers JUN, MMP3, TFF1, and HAS2. Important cancer genes affected by CNVs included TP53, BRCA1, BRCA2, ERBB2, IDH1, and IDH2. WES detected numerous mutations, some of which affecting BC associated genes as CDH1, HEPACAM, and LOXHD1.

Conclusions

Using complementary molecular genetic techniques, this study identified shared and unshared molecular events in three highly aberrant BCBM emphasizing the challenge to detect new molecular biomarkers and targets with translational implications. Among new findings with the capacity to gain clinical relevance is the detection of overexpressed snoRNAs known to regulate some critical cellular functions as ribosome biogenesis.

Electronic supplementary material

The online version of this article (10.1186/s12967-017-1370-x) contains supplementary material, which is available to authorized users.

Arachidonic Acid Metabolite as a Novel Therapeutic Target in Breast Cancer Metastasis

Metastatic breast cancer (BC) (also referred to as stage IV) spreads beyond the breast to the bones, lungs, liver, or brain and is a major contributor to the deaths of cancer patients. Interestingly, metastasis is a result of stroma-coordinated hallmarks such as invasion and migration of the tumor cells from the primary niche, regrowth of the invading tumor cells in the distant organs, proliferation, vascularization, and immune suppression. Targeted therapies, when used as monotherapies or combination therapies, have shown limited success in decreasing the established metastatic growth and improving survival. Thus, novel therapeutic targets are warranted to improve the metastasis outcomes. We have been actively investigating the cytochrome P450 4 (CYP4) family of enzymes that can biosynthesize 20-hydroxyeicosatetraenoic acid (20-HETE), an important signaling eicosanoid involved in the regulation of vascular tone and angiogenesis. We have shown that 20-HETE can activate several intracellular protein kinases, pro-inflammatory mediators, and chemokines in cancer. This review article is focused on understanding the role of the arachidonic acid metabolic pathway in BC metastasis with an emphasis on 20-HETE as a novel therapeutic target to decrease BC metastasis. We have discussed all the significant investigational mechanisms and put forward studies showing how 20-HETE can promote angiogenesis and metastasis, and how its inhibition could affect the metastatic niches. Potential adjuvant therapies targeting the tumor microenvironment showing anti-tumor properties against BC and its lung metastasis are discussed at the end. This review will highlight the importance of exploring tumor-inherent and stromal-inherent metabolic pathways in the development of novel therapeutics for treating BC metastasis.

Comparison of immune microenvironments between primary tumors and brain metastases in patients with breast cancer

Background

Immune checkpoint inhibitors are reported to be effective in patients with brain metastases. However, detailed characteristics of the brain metastasis immune microenvironment remain unexplored.

Results

The median tumor-infiltrating lymphocyte (TIL) category in brain metastases was 5% (1–70%). In 46 pair-matched samples, the percentages of TILs were significantly higher in primary breast tumors than in brain metastases (paired t-test, P < 0.01). The numbers of CD4/CD8/Foxp3-positive cells were significantly higher in primary breast tumors than in brain metastases (paired t-test, P < 0.05 for all antibodies). In patients with triple-negative breast cancer specifically, low TIL numbers were associated with significantly shorter overall survival compared to high TIL numbers (log-rank test, P = 0.04).

Materials and Methods

We retrospectively identified 107 patients with breast cancer and brain metastases who had undergone surgery between 2001 and 2012 at 8 institutions, and collected 191 samples including brain metastases alone and primary tumors with pair-matched brain metastasis samples. Hematoxylin and eosin-stained slides were evaluated for TILs and categorized according to the extent of staining. Immunohistochemistry for CD4, CD8, Foxp3, PD-L1, PD-L2, and HLA class I was also performed.

Conclusions

There are significantly fewer TILs in brain metastases than in primary breast tumors.

Neurosurgical management of brain metastases

Brain metastases present a significant public health issue, affecting more than 100,000 patients per year in the U.S. and result in significant morbidity. Brain metastases can occur in a variety of clinical situations ranging from multiple brain metastases with uncontrolled systemic disease to a solitary metastasis in the setting of controlled systemic disease. Additionally, advances in genomics have broadened the opportunities for targeted treatment options and potentially more durable systemic responses. As such, the treatment of brain metastases is now more tailored and multimodal, involving systemic, radiation, and surgical therapies, often in combination. This review discusses the historical and current role of neurosurgical techniques in the treatment of brain metastases.

Effects of FSTL1 on cell proliferation in breast cancer cell line MDA‑MB‑231 and its brain metastatic variant MDA‑MB‑231‑BR

In the past decades, altered Follistatin-like 1 (FSTL1) expression has been documented in a variety of cancers, while its functional roles are poorly understood. Particularly in breast cancer, the expression of FSTL1 and its signaling pathway remain to be determined. In the present study, an elevated FSTL1 expression and a supressed cell proliferation were detected in a specific brain metastatic cell line MDA-MB-231-BR (231-BR), compared with its parental cell line MDA-MB-231. However, this protein was hardly detected in the other three breast cancer cell lines. Next, lentiviral vectors encoding FSTL1 or FSTL1 specific shRNAs were used to overexpress or knock down FSTL1 in MDA-MB-231 or 231-BR, respectively (MDA-MB-231^FSTL1 or 231-BR^{sh FSTL1}). Results showed that overexpression of FSTL1 inhibited MDA-MB-231 cell proliferation, while knockdown of FSTL1 in 231-BR cells promotes cell proliferation, compared with their corresponding control groups. These results were further confirmed in nude mouse xenografts. The tumor volume in 231-BR cell-bearing mice was significantly smaller than that of MDA-MB-231 group, and reduction of tumor volume was detected in MDA-MB-231^FSTL1 cell-bearing mice compared with the control group. Previous studies revealed that TGF-β-Smad2/3 signaling pathway was activated in 231-BR and MDA-MB-231^FSTL1 cells, which may contribute to the inhibited cell proliferation. In addition, Smad3 knockdown could restore the inhibition of cell proliferation induced by FSTL1 overexpression in MDA-MB-231^FSTL1 cells, indicating that the anti-proliferative effect of FSTL1 overexpression may be associated with Smad3 involved TGF-β signaling pathway regulation. This study identified FSTL1 as an inhibitor of cell proliferation in MDA-MB-231 and 231-BR cell lines, which may provide new insights into the development and management of breast cancer.

Comparison of patterns and prognosis among distant metastatic breast cancer patients by age groups: a SEER population-based analysis

To investigate the effects of age at diagnosis on metastatic breast cancer and patients' prognosis, we collected patient data from the Surveillance, Epidemiology, and End Results (SEER) database. We finally identified 4932 eligible metastatic breast cancer patients diagnosed between 2010-2013, including 850 younger patients (<50 years), 2,540 middle-aged patients (50-69 years) and 1,542 elder patients (>69 years). The results revealed that in stage IV patients, elder patients were more likely to have lung metastasis (P < 0.001) and less likely to have only distant lymphatic spread (P = 0.004). Higher proportion of younger (34.9%) and middle-aged (36.2%) patients had multiple metastatic sites than elder patients (28.3%) (P < 0.001). In survival analysis, younger patients presented the best prognosis, while elder patients had the worst both in overall survival (χ² = 121.9, P < 0.001) and breast cancer-specific survival (χ² = 69.8, P < 0.001). Age at diagnosis was an independent prognostic factor for metastatic breast cancer patients. Moreover, patients with bone metastasis only had superior survival compared to other metastatic patients (P < 0.001). Brain metastasis only group and multiple sites metastasis group had the poorest prognosis (P < 0.05). We hope the results will provide insights into a better understanding of distant metastatic breast cancer.

Trastuzumab distribution in an in-vivo and in-vitro model of brain metastases of breast cancer

Background

Drug and antibody delivery to brain metastases has been highly debated in the literature. The blood-tumor barrier (BTB) is more permeable than the blood-brain barrier (BBB), and has shown to have highly functioning efflux transporters and barrier properties, which limits delivery of targeted therapies.

Methods

We characterized the permeability of ¹²⁵I-trastuzumab in an in-vivo, and fluorescent trastuzumab-Rhodamine123 (t-Rho123) in a novel microfluidic in-vitro, BBB and BTB brain metastases of breast cancer model. In-vivo: Human MDA-MB-231-HER2+ metastatic breast cancer cells were grown and maintained under static conditions. Cells were harvested at 80% confluency and prepped for intra-cardiac injection into 20 homozygous female Nu/Nu mice. In-vitro: In a microfluidic device (SynVivo), human umbilical vein endothelial cells were grown and maintained under shear stress conditions in the outer compartment and co-cultured with CTX-TNA2 rat brain astrocytes (BBB) or Met-1 metastatic HER2+ murine breast cancer cells (BTB), which were maintained in the central compartment under static conditions.

Results

Tissue distribution of ¹²⁵I-trastuzumab revealed only ~3% of injected dose reached normal brain, with ~5% of injected dose reaching brain tumors. No clear correlation was observed between size of metastases and the amount of ¹²⁵I-trastuzumab localized in-vivo. This heterogeneity was paralleled in-vitro, where the distribution of t-Rho123 from the outer chamber to the central chamber of the microfluidic device was qualitatively and quantitatively analyzed over time. The rate of t-Rho123 linear uptake in the BBB (0.27 ± 0.33 × 10⁴) and BTB (1.29 ± 0.93 × 10⁴) showed to be significantly greater than 0 (p < 0.05). The BTB devices showed significant heterogenetic tendencies, as seen in in-vivo.

Conclusions

This study is one of the first studies to measure antibody movement across the blood-brain and blood-tumor barriers, and demonstrates that, though in small and most likely not efficacious quantities, trastuzumab does cross the blood-brain and blood-tumor barriers.

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.

Comparative membrane proteomics analyses of breast cancer cell lines to understand the molecular mechanism of breast cancer brain metastasis

Breast cancer is the leading type of cancer in women. Breast cancer brain metastasis is currently considered an issue of concern among breast cancer patients. Membrane proteins play important roles in breast cancer brain metastasis, involving cell adhesion and penetration of blood-brain barrier. To understand the mechanism of breast cancer brain metastasis, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was employed in conjunction with enrichment of membrane proteins to analyze the proteomes from five different breast cancer and a brain cancer cell lines. Quantitative proteomic data of all cell lines were compared with MDA-MB-231BR which is a brain seeking breast cancer cell line, thus representing brain metastasis characteristics. Label-free proteomics of the six cell lines facilitates the identification of 1238 proteins and the quantification of 899 proteins of which more than 70% were membrane proteins. Unsupervised principal component analysis (PCA) of the label-free proteomics data resulted in a distinct clustering of cell lines, suggesting quantitative differences in the expression of several proteins among the different cell lines. Unique protein expressions in 231BR were observed for 28 proteins. The up-regulation of STAU1, AT1B3, NPM1, hnRNP Q, and hnRNP K and the down-regulation of TUBB4B and TUBB5 were noted in 231BR relative to 231 (precursor cell lines from which 231BR is derived). These proteins might contribute to the breast cancer brain metastasis. Ingenuity pathway analysis (IPA) supported the great brain metastatic propensity of 231BR and suggested the importance of the up-regulation of integrin proteins and down-regulation of EPHA2 in brain metastasis.

Clinical outcome of brain metastases differs significantly among breast cancer subtypes

Brain metastases in patients with breast cancer are associated with a poor survival rate. A small number of studies have challenged this premise, suggesting that survival times following brain metastasis differ significantly between breast cancer subtypes. In the current study, overall survival (OS), brain metastases-free survival (BMFS) and survival following brain metastases (SFBM) were found to be associated with the intrinsic breast cancer subtype. A total of 1,147 patients with invasive breast cancer who were treated at the Hannover Medical School between January 2004 and December 2010 were included, from which 54 patients with brain metastases were identified. The Kaplan-Meier method or Cox regression analyses were performed for analysis of survival. OS was found to differ significantly between breast cancer subtypes: OS was significantly shorter in patients with triple-negative (TN) cancer compared with patients with human epidermal growth factor receptor (HER2)-enriched tumors (P<0.001). In addition, median BMFS times differed significantly between luminal (1,003 days), HER2-enriched (514 days) and TN breast cancer patients (460 days) (P=0.045). The median durations of SFBM were 386 days in luminal, 310 days in HER2-enriched and 147 days in TN breast cancer patients (P=0.029). The results suggested that patients with luminal breast cancer have a lower risk of brain metastases and the most favorable outcome with regard to BMFS, whereas patients with HER2-positive or TN breast cancer have a significantly higher risk of developing brain metastases. Compared with TN breast cancer, the duration of SFBM was doubled in HER2-enriched cancers. These findings may have important implications for treatment and follow-up strategies in patients with breast cancer.

Clinicopathological factors associated with survival in patients with breast cancer brain metastasis

Brain metastasis from breast cancer generally represents a catastrophic event yet demonstrates substantial biological heterogeneity. There have been limited studies solely focusing on the prognosis of patients with such metastasis. In this study, we carried out a comprehensive analysis in 108 consecutive patients with breast cancer brain metastases between 1997 and 2012 to further define clinicopathological factors associated with early onset of brain metastasis and survival outcomes after development of them. We found that lobular carcinoma, higher clinical stages at diagnosis, and lack of coexisting bone metastasis were significantly associated with a worse brain relapse-free survival when compared with brain-only metastasis. High histologic grade, triple-negative breast cancer, and absence of visceral involvement were unfavorable prognostic factors after brain metastasis. Furthermore, high histologic grade, advanced tumor stages, and lack of coexisting bone involvement indicated a worse overall survival. Thus, the previously established prognostic factors in early stage or advanced breast cancers may not entirely apply to patients with brain metastases. Furthermore, the prognostic significance of the clinicopathological factors differed before and after a patient develops brain metastasis. This knowledge might help in establishing an algorithm to further stratify patients with breast cancer into prognostically significant categories for optimal prevention, screening, and treatment of their brain metastasis.

Management of breast cancer brain metastases: Focus on human epidermal growth factor receptor 2-positive breast cancer

After the introduction of trastuzumab, a monoclonal antibody that binds to human epidermal growth factor receptor 2 (HER2), the overall survival (OS) among patients with HER2-positive breast cancer has been substantially improved. However, among these patients, the incidence of brain metastases (BM) has been increasing and an increased proportion of them have died of intracranial progression, which makes HER2-positive breast cancer brain metastases (BCBM) a critical issue of concern. For local control of limited BM, stereotactic radiosurgery (SRS) and surgical resection are available modalities with different clinical indications. Postoperative or preoperative radiation is usually delivered in conjunction with surgical resection to boost local control. Adjuvant whole-brain radiotherapy (WBRT) should be deferred for limited BM because of its impairment of neurocognitive function while having no benefit for OS. Although WBRT is still the standard treatment for local control of diffuse BM, SRS is a promising treatment for diffuse BM as the technique continues to improve. Although large molecules have difficulty crossing the blood brain barrier, trastuzumab-containing regimens are critical for treating HER2-positive BCBM patients because they significantly prolong OS. Tyrosine kinase inhibitors are more capable of crossing into the brain and they have been shown to be beneficial for treating BM in HER2-positive patients, especially lapatinib combined with capecitabine. The antiangiogenic agent, bevacizumab, can be applied in the HER2-positive BCBM scenario as well. In this review, we also discuss several strategies for delivering drugs into the central nervous system and several microRNAs that have the potential to become biomarkers of BCBM.

Breast carcinoma subtypes show different patterns of metastatic behavior

The aim of our retrospective study was to analyze patterns of subtype specific metastatic spread and to identify the time course of distant metastases. A consecutive series of 490 patients with breast cancer who underwent surgery and postoperative treatment at Semmelweis University, Hungary, and diagnosed between the years 2000 and 2007 was identified from the archives of the 2nd Department of Pathology, Hungary. Molecular subtypes were defined based on the 2011 St. Gallen recommendations. Statistical analysis was performed with SPSS Statistics for Windows, Version 22.0. Distant metastasis free survival (DMFS) was defined as the time elapsed between the first pathological diagnosis of the tumor and the first distant metastasis detection. Distant metastases were detected in 124 patients. Mean time to develop metastasis was 29 months (range 0-127 months). The longest DMFS was observed in the Luminal A (LUMA) subtype (mean 39 months) whereas the shortest was seen in the HER2-positive (HER2+) subtype (mean 21 months; p = 0.012). We confirmed that HER2+ tumors carry a higher risk for distant metastases (42.1%). LUMA-associated metastases were found to be solitary in 59% of cases, whereas HER2+ tumors showed multiple metastases in 79.2% of cases. LUMA tumors showed a preference for bone-only metastasis as compared with HER2+ and triple negative breast cancer (TNBC) cases, which exhibited a higher rate of brain metastasis. The most frequent second metastatic sites of hormone receptor (HR) positive tumors were the lung and liver, whereas the brain was the most affected organ in HR-negative (HR-) cases. Tumor subtypes differ in DMFS and in pattern of distant metastases. HER2+ tumors featured the most aggressive clinical course. Further identification of subtype-specific factors influencing prognosis might have an impact on clinical care and decision-making.

Clinical features of brain metastases in breast cancer: an implication for hippocampal-sparing whole-brain radiation therapy

Objective

The objectives of this study were to describe the distribution of brain metastases (BM) in breast cancer patients and investigate the risk factors for perihippocampal metastases (PHM).

Patients and methods

Retrospective analysis of the clinicopathological characteristics and patterns of BM was performed. Associations between clinicopathological characteristics and PHM (the hippocampus plus 5 mm margin) were evaluated using logistic regression analyses.

Results

A total of 1,356 brain metastatic lesions were identified in 192 patients. Patients with 1–3 BM, 4–9 BM, and ≥10 BM accounted for 63.0%, 18.8%, and 18.2%, respectively. There were only 7 (3.6%) patients with hippocampal metastases (HM) and 14 (7.3%) patients with PHM. On logistic regression, the number of BM was an independent risk factor for PHM. Patients with ≥10 BM had a significantly higher risk of PHM compared with those with <10 BM. Breast cancer subtype (BCS) was not associated with PHM. The number of BM was significantly correlated with various BCSs. Patients with hormone receptor (HR)+/human epidermal growth factor receptor 2 (HER2)+, HR−/HER2+, and HR−/HER2− subtypes had a higher probability of ≥10 BM, relative to patients with an HR+/HER2− subtype.

Conclusion

Our study suggests that a low incidence of PHM may be acceptable to perform hippocampal-sparing whole-brain radiation therapy for breast cancer patients. Patients with extensive diffuse metastases (≥10 BM) were associated with higher odds of PHM.

Vinorelbine Delivery and Efficacy in the MDA-MB-231BR Preclinical Model of Brain Metastases of Breast Cancer

PURPOSE

To evaluate vinorelbine drug exposure and activity in brain metastases of the human MDA-MB-231BR breast cancer model using integrated imaging and analysis.

METHODS

Brain and systemic metastases were created by administration of cancer cells in female NuNu mice. After metastases developed, animals were administered vinorelbine at the maximal tolerated dose (12 mg/kg), and were evaluated thereafter for total and unbound drug pharmacokinetics, biomarker TUNEL staining, and barrier permeability to Texas red.

RESULTS

Median brain metastasis drug exposure was 4-fold greater than normal brain, yet only ~8% of non-barrier systemic metastases, which suggests restricted brain exposure. Unbound vinorelbine tissue/plasma partition coefficient, K_p,uu, equaled ~1.0 in systemic metastases, but 0.03-0.22 in brain metastases, documenting restricted equilibration. In select sub-regions of highest drug-uptake brain metastases, K_p,uu approached 1.0, indicating complete focal barrier breakdown. Most vinorelbine-treated brain metastases exhibited little or no positive early apoptosis TUNEL staining in vivo. The in vivo unbound vinorelbine IC₅₀ for TUNEL-positive staining (56 nM) was 4-fold higher than that measured in vitro (14 nM). Consistent with this finding, P-glycoprotein expression was observed to be substantially upregulated in brain metastasis cells in vivo.

CONCLUSIONS

Vinorelbine exposure at maximum tolerated dose was less than one-tenth that in systemic metastases in >70% of brain metastases, and was associated with negligible biomarker effect. In small subregions of the highest uptake brain metastases, compromise of blood-tumor barrier appeared complete. The results suggest that restricted delivery accounts for 80% of the compromise in drug efficacy for vinorelbine against this model.