Chemotherapy for metastatic tumors to the central nervous system

Efficacy of tyrosine kinase inhibitors for the treatment of patients with HER2-positive breast cancer with brain metastases: a systematic review and meta-analysis

Background

Brain metastases (BMs) are frequent events in patients with HER2-positive metastatic breast cancer (MBC) and are associated with poor prognosis. Small-molecule anti-HER2 tyrosine kinase inhibitors (TKIs) are promising agents for the treatment of BM. In this study, we assess the clinical outcomes of patients with HER2-positive MBC and BM treated with TKI-containing regimens compared with those treated with non-TKI-containing regimens.

Materials and methods

PubMed, Embase, Cochrane Library, and conference proceedings (ASCO, SABCS, ESMO, and ESMO Breast) were searched up to June 2021. The primary endpoint was progression-free survival (PFS) in patients with BM. Secondary endpoints included PFS in patients without BM and overall survival (OS). The study was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Overall effects were pooled using random-effects models.

Results

This systematic review and meta-analysis included data from 2437 patients (490 with and 1947 without BM at baseline) enrolled in five trials assessing tucatinib-, lapatinib-, pyrotinib-, or afatinib-based combinations. A nonstatistically significant PFS benefit favoring TKI-containing regimens was observed in both patients with BM [hazard ratio (HR) 0.67, 95% confidence interval (CI) 0.41-1.12; P = 0.13] and without BM (HR 0.55, 95% CI 0.24-1.26; P = 0.16). Sensitivity analysis, excluding each study singly, demonstrated a significant PFS benefit favoring TKI-containing regimens in patients with BM after the exclusion of afatinib from the analysis (HR 0.56, 95% CI 0.35-0.90; P = 0.016). No statistically significant differences in OS were observed between the comparison groups.

Conclusions

A trend in PFS favoring TKI-containing regimens was observed in patients with BM. Sensitivity analysis including only trials that evaluated regimens containing tucatinib, lapatinib, or pyrotinib demonstrated a significant PFS benefit favoring TKI-containing regimens in patients with BM.

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The optimal therapy for HER2+ BC BMs remains unknown.

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Anti-HER2 TKIs are effective for treating MBC.

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This study examined the efficacy of TKI for the treatment of patients with BM.

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A trend toward improved PFS favoring TKIs was observed in patients with BM.

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There was no significant difference in OS between TKIs versus non-TKI regimens.

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.

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.

Self-Assembly of Gold Nanoparticles Shows Microenvironment-Mediated Dynamic Switching and Enhanced Brain Tumor Targeting

Inorganic nanoparticles with unique physical properties have been explored as nanomedicines for brain tumor treatment. However, the clinical applications of the inorganic formulations are often hindered by the biological barriers and failure to be bioeliminated. The size of the nanoparticle is an essential design parameter which plays a significant role to affect the tumor targeting and biodistribution. Here, we report a feasible approach for the assembly of gold nanoparticles into ~80 nm nanospheres as a drug delivery platform for enhanced retention in brain tumors with the ability to be dynamically switched into the single formulation for excretion. These nanoassemblies can target epidermal growth factor receptors on cancer cells and are responsive to tumor microenvironmental characteristics, including high vascular permeability and acidic and redox conditions. Anticancer drug release was controlled by a pH-responsive mechanism. Intracellular L-glutathione (GSH) triggered the complete breakdown of nanoassemblies to single gold nanoparticles. Furthermore, in vivo studies have shown that nanospheres display enhanced tumor-targeting efficiency and therapeutic effects relative to single-nanoparticle formulations. Hence, gold nanoassemblies present an effective targeting strategy for brain tumor treatment.

The Biology of Brain Metastasis: Challenges for Therapy

Many patients with lung cancer, breast cancer, and melanoma develop brain metastases that are resistant to conventional therapy. The median survival for untreated patients is 1 to 2 months, which may be extended to 6 months with surgery, radiotherapy, and chemotherapy. The outcome of metastasis depends on multiple interactions of unique metastatic cells with host homeostatic mechanisms which the tumor cells exploit for their survival and proliferation. The blood-brain barrier is leaky in metastases that are larger than 0.5-mm diameter because of production of vascular endothelial growth factor by metastatic cells. Brain metastases are surrounded and infiltrated by microglia and activated astrocytes. The interaction with astrocytes leads to up-regulation of multiple genes in the metastatic cells, including several survival genes that are responsible for the increased resistance of tumor cells to cytotoxic drugs. These findings substantiate the importance of the "seed and soil" hypothesis and that successful treatment of brain metastases must include targeting of the organ microenvironment.

The seed and soil hypothesis revisited--the role of tumor-stroma interactions in metastasis to different organs

The fact that certain tumors exhibit a predilection for metastasis to specific organs has been recognized for well over a century now. An extensive body of clinical data and experimental research has confirmed Stephen Paget's original "seed and soil" hypothesis that proposed the organ-preference patterns of tumor metastasis are the product of favorable interactions between metastatic tumor cells (the "seed") and their organ microenvironment (the "soil"). Indeed, many of the first-line therapeutic regimens, currently in use for the treatment of human cancer are designed to target cancer cells (such as chemotherapy) and also to modulate the tumor microenvironment (such as antiangiogenic therapy). While some types of tumors are capable of forming metastases in virtually every organ in the body, the most frequent target organs of metastasis are bone, brain, liver and the lung. In this review, we discuss how tumor-stromal interactions influence metastasis in each of these organs.

Chemotherapy in brain metastases

The use OF chemotherapy to treat patients with brain metastases has been viewed historically with skepticism. To date, a survival benefit has not been demonstrated with the use of systemic chemotherapy in patients with brain metastases. However, the introduction of novel agents and delivery techniques warrants a reexamination of the role of systemic chemotherapy in the management of brain metastases. Temozolomide has shown encouraging results in patients with nonsmall cell lung cancer, and implanted carmustine wafers have demonstrated excellent local tumor control rates. This review discusses clinical data from the past decade with emphasis on trial design, tumor histology, available agents, and multimodality strategies. In addition, delivery techniques that circumvent the blood-brain barrier are reviewed. Although chemotherapy is usually used as a salvage therapy, it may be considered for use in selected patients with newly diagnosed brain metastases. To better evaluate chemotherapy in brain metastases, future trials should evaluate novel agents in the preirradiation setting. Enhanced regional delivery methods warrant further investigation, and Phase III trials of current regimens stratified by histology and by prognostic factors will establish the role of specific chemotherapy regimens in the treatment of patients with brain metastases.