Cerebrospinal Fluid Concentration of Erlotinib and its Active Metabolite OSI-420 in Patients with Central Nervous System Metastases of Non-small Cell Lung Cancer

[Research Progress of EGFR-TKI Therapy for Patients with Central Nervous System Metastases from Non-small Cell Lung Cancer]

Approximately half of all patients with non-small cell lung cancer (NSCLC) develop central nervous system metastases during the course of their disease which indicate poor prognosis. A part of NSCLC patients demonstrates activating epidermal growth factor receptor gene (EGFR) mutations who represent effectiveness and well tolerance of EGFR-specific tyrosine kinase inhibitors (TKIs) therapy. Although the systemic efficacy of targeted agents is established, the efficacy of central nervous system (CNS) metastases is not as well characterized. In this article, we review recent data on the use of EGFR inhibitors for treatment of patients with NSCLC and CNS metastases.

Activity of erlotinib when dosed below the maximum tolerated dose for EGFR-mutant lung cancer: Implications for targeted therapy development

BACKGROUND

Erlotinib is a standard first-line therapy for patients who have metastatic nonsmall cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. The recommended dose of 150 mg daily is the maximum tolerated dose (MTD). Few clinical data are available regarding its efficacy at doses less than the MTD.

METHODS

An institutional database was queried for patients with advanced NSCLC who were positive for EGFR L858R mutations or exon 19 deletions and had received treatment with erlotinib. The treatment course, including the erlotinib dose at initiation of treatment, at 4 months into therapy, and at disease progression, was retrospectively studied. Progression-free survival (PFS) was compared between patients who received the MTD (150 mg) and those who received reduced-dose erlotinib (≤100 mg).

RESULTS

In total, 198 eligible patients were identified. Thirty-one patients (16%) were initiated on reduced-dose erlotinib; they were older (P = .001) and had lower performance status (P = .01) compared with those who were initiated on erlotinib at the MTD. The response rate to reduced-dose erlotinib was 77%. The median PFS of patients initiated on reduced-dose erlotinib was 9.6 months versus 11.4 months for those initiated at the MTD, a difference that was not statistically significant (hazard ratio, 0.81; 95% confidence interval, 0.54-1.21; P = .30). There was a nonsignificant trend toward higher rates of progression within the central nervous system with reduced-dose erlotinib.

CONCLUSIONS

At doses below the MTD, erlotinib treatment results in a high response rate and a prolonged median PFS. Review of the literature indicates that 15 of 30 small-molecule inhibitors that are approved or in late-stage development for cancer therapy have recommended doses below the MTD. When the toxicities of MTD dosing are a concern, an investigation of small-molecule inhibitors at doses below the MTD is warranted. Cancer 2016;122:3456-63. © 2016 American Cancer Society.

Recent developments in the chromatographic bioanalysis of approved kinase inhibitor drugs in oncology

In recent years (2010-present) there has been an increase in the number of publications reporting the development, validation and use of bioanalytical methods in the rapidly expanding drug class of small molecule protein kinase inhibitors. Most reports describe the technological set-up of the methods that have allowed for drug concentration measurements from various sample types. This includes plasma, dried blood-spot, and tissue-analysis. Also method development, exploration of various techniques, as well as measurement and identification of metabolites were addressed. For the bioanalysis, a variety of sample-pretreatment methods like protein-precipitation, liquid-liquid extraction, and solid-phase extraction have been employed, all varying in complexity, cleanliness and time-consumption. Chromatographic separation, nowadays, is more focused on separating components from ion-suppressive effects, since for MS/MS detection, various components do not have to be baseline separated. For detection multiple types of detectors were used, ranging from state-of-the-art high resolution, and tandem mass spectrometry with low picogram per milliliter detection limits to the classical UV-detector with several nanograms per milliliter limits. As new bioanalytical methods have arisen that do rely on chromatographic separation, for example for high-throughput analysis, these are addressed in this review as well.

Blood-brain barrier permeability of gefitinib in patients with brain metastases from non-small-cell lung cancer before and during whole brain radiation therapy

INTRODUCTION

To explore the ability of gefitinib to penetrate blood brain barrier (BBB) during whole brain radiation therapy (WBRT).

PATIENTS AND METHODS

Enrolled in this study were eligible patients who were diagnosed with BM from NSCLC. Gefitinib was given at 250 mg/day for 30 days, then concurrently with WBRT (40 Gy/20 F/4 w), followed by maintenance. Serial CSF and blood samples were collected on 30 day after gefitinib administration, and at the time of 10, 20, 30 and 40 Gy following WBRT. CSF and plasma samples of 13 patients without BM who were treated with gefitinib were collected as control. CSF and plasma gefitinib levels were measured by LC-MS/MS.

RESULTS

Fifteen BM patients completed gefitinib plus WBRT. The CSF-to-plasma ratio of gefitinib in patients with BM was higher than that in patients without BM (1.34% vs. 0.36%, P < 0.001). The CSF-to-plasma ratio of gefitinib increased with the increased dose of WBRT and reached the peak (1.87 ± 0.72%) at 30 Gy, which was significantly higher than that 1.34 ± 0.49% at 0 Gy (P = 0.01). The median time to progression of brain lesions and the median overall survival were 7.07 and 15.4 months, respectively.

CONCLUSION

The BBB permeability of gefitinib increased in accordance with escalated dose of WBRT.

Evaluation on efficacy and safety of tyrosine kinase inhibitors plus radiotherapy in NSCLC patients with brain metastases

Objective

The study was designed to evaluate the efficacy and safety of tyrosine kinase inhibitors (TKIs) plus radiotherapy in patients with brain metastases (BM) of non-small cell lung cancer.

Methods

Medline PubMed, Google Scholar, Web of Science, Oxford Journals Collection, clinical trials and current controlled trials were searched to identify relevant publications. After screening literature and undertaking quality assessment and data extraction, the meta-analysis was performed using RevMan5.3 software.

Results

Eight controlled trials (980 participants) were included in the study. Compared with radiotherapy without TKIs (non-TKI-group), TKIs plus radiotherapy (TKI-group) had a significant benefit on objective response rate (ORR) (RR = 1.56, 95%CI [1.25,2.03]; P =0.0008), significantly prolonged the time to central nerves system progression (CNS-TTP) (HR =0.58, 95% CI [0.35, 0.96]; P =0.03) and median overall survival (MOS) (HR =0.68, 95% CI [0.47, 0.98]; P =0.04) of NSCLC patients with BM. There was no significant difference in overall severe adverse events (Grade≥3) (RR = 1.49, 95% CI [0.88,2.54]; P = 0.14) between two groups.

Conclusion

This meta-analysis showed TKI-group produced superior response rate when compared with non-TKI-group. TKIs plus radiotherapy significantly prolong the CNS-TTP and MOS of patients without enhancing overall severe adverse events.

Impact of whole brain radiation therapy on CSF penetration ability of Icotinib in EGFR-mutated non-small cell lung cancer patients with brain metastases: Results of phase I dose-escalation study

OBJECTIVES

Whole-brain radiation therapy (WBRT) and epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are both treatment options for EGFR-mutated non-small cell lung cancer (NSCLC) patients with brain metastases. However, the dose-escalation toxicity and efficacy of combination therapy, and the effect of WBRT on cerebrospinal fluid (CSF) penetration of EGFR-TKIs are still unclear.

MATERIALS AND METHODS

EGFR-mutated NSCLC patients with brain metastases were enrolled in this study, and the cohorts were constructed with a 3+3 design. The patients received icotinib with escalating doses (125-625mg, tid), and the concurrent WBRT (37.5Gy/15f/3weeks) started a week later. The CSF penetration rates of icotinib were tested before, immediately after, and 4 weeks after WBRT, respectively. Potential toxicities and benefits from dose-escalation treatment were analyzed.

RESULTS

Fifteen patients were included in this study, 3 at each dose level from 125mg-375mg and 6 at 500mg with 3 occurred dose-limiting toxicities. The maximal tolerated dose of icotinib was 375mg tid in this combination therapy. There was a significant correlation between icotinib concentration in the CSF and plasma (R(2)=0.599, P<0.001). The CSF penetration rate of icotinib, from 1.2% to 9.7%, reached a maximum at 375mg (median, 6.1%). There was no significant difference for CSF penetration rates among the three test points (median, 4.1% vs. 2.8% vs. 2.8%, P=0.16). The intracranial objective response rate and median intracranial progression free survival are 80% and 18.9 months.

CONCLUSIONS

WBRT plus concurrent icotinib is well tolerated in EGFR-mutated NSCLC patients with brain metastases, up to an icotinib dose of 375mg tid. The icotinib CSF concentration seemed to have a potential ceiling effect with the dose escalation, and WBRT seemed to have no significant impact on CSF penetration of icotinib till 4 weeks after the treatment.

Radiotherapy plus EGFR TKIs in non-small cell lung cancer patients with brain metastases: an update meta-analysis

Brain metastasis (BM) is the common complication of non‐small cell lung cancer (NSCLC) with a poor prognosis and dismal survival rate. This update meta‐analysis aimed to derive a more precise estimation of radiotherapy plus epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in NSCLC patients with BM. PubMed, EMBASE, Web of Science, Google Scholar, and Cochrane Library were searched to identify any relevant publications. After screening the literature and undertaking quality assessment and data extraction, the meta‐analysis was performed using STATA Version 12.0. In total, 15 studies involving 1552 participants were included. The results indicated that radiotherapy plus EGFR TKIs was more effective at improving response rate and disease control rate (DCR) (risk ratio (RR) = 1.48, 95% confidence interval [CI]: 1.12–1.96, P = 0.005; RR = 1.29, 95% CI: 1.02–1.60, P = 0.035; respectively) than radiotherapy alone or plus chemotherapy. Moreover, radiotherapy plus EGFR TKIs significantly prolonged the time to central nervous system progression (CNS‐TTP) (HR = 0.56, 95% CI [0.33, 0.80]; P = 0.000) and median overall survival (OS) (HR = 0.58, 95% CI [0.42, 0.74]; P = 0.000) but significantly increased adverse events (any grade) (RR = 1.25, 95% CI [1.01, 1.57]; P = 0.009), especially rash and dry skin. These results suggested that radiotherapy plus EGFR TKIs produced superior response rate and DCR and markedly prolonged the CNS‐TTP and OS of NSCLC patients with BM. However, combined groups had the higher rate of incidence of overall adverse effects, especially rash and dry skin.

Pharmacokinetic Properties of Anticancer Agents for the Treatment of Central Nervous System Tumors: Update of the Literature

Despite significant improvement in outcomes for patients with hematologic malignancies and solid tumors over the past 10 years, patients with primary or metastatic brain tumors continue to have a poor prognosis. A primary reason for this is the inability of many chemotherapeutic drugs to penetrate into the brain and brain tumors at concentrations high enough to exert an antitumor effect because of unique barriers and efflux transporters. Several studies have been published recently examining the central nervous system pharmacokinetics of various anticancer drugs in patients with primary and metastatic brain tumors. To summarize recent advances in the field, this review critically presents studies published within the last 9 years examining brain and cerebrospinal fluid penetration of clinically available anticancer agents for patients with central nervous system tumors.

Antacid Use and De Novo Brain Metastases in Patients with Epidermal Growth Factor Receptor-Mutant Non-Small Cell Lung Cancer Who Were Treated Using First-Line First-Generation Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

Background

Antacid treatments decrease the serum concentrations of first-generation epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs), although it is unknown whether antacids affect clinical outcomes. As cerebrospinal fluid concentrations of TKIs are much lower than serum concentrations, we hypothesized that this drug-drug interaction might affect the prognosis of patients with de novo brain metastases.

Materials and Methods

This retrospective study evaluated 269 patients with EGFR-mutant non-small cell lung cancer (NSCLC) who had been diagnosed between December 2010 and December 2013, and had been treated using first-line first-generation EGFR-TKIs. Among these patients, we identified patients who concurrently used H2 receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) as antacids. Patients who exhibited >30% overlap between the use of TKIs and antacids were considered antacid users.

Results

Fifty-seven patients (57/269, 21.2%) were antacid users, and antacid use did not significantly affect progression-free survival (PFS; no antacids: 11.2 months, H2RAs: 9.4 months, PPIs: 6.7 months; p = 0.234). However, antacid use significantly reduced overall survival (OS; no antacids: 25.0 months, H2RAs: 15.5 months, PPIs: 11.3 months; p = 0.002). Antacid use did not affect PFS for various metastasis sites, although antacid users with de novo brain metastases exhibited significantly shorter OS, compared to non-users (11.8 vs. 16.3 months, respectively; p = 0.041). Antacid use did not significantly affect OS in patients with bone, liver, or pleural metastases.

Conclusion

Antacid use reduced OS among patients with EGFR-mutant NSCLC who were treated using first-line first-generation EGFR-TKIs, and especially among patients with de novo brain metastases.

Targeted Therapy in Brain Metastases: Ready for Primetime?

Brain metastasis is a serious complication of cancer that causes significant morbidity for patients. Over the last decade, numerous new driver somatic mutations have been recognized and targeted therapies are changing the landscape of treatment in lung cancer, breast cancer, and melanoma, which are also the three most common cancers that result in brain metastases. The common actionable mutations include the EGFR mutation and anaplastic lymphoma kinase (ALK) translocations in non-small cell lung cancer, the HER2 mutation in breast cancer, and the BRAF mutation in melanoma. However, most of the early trials with targeted agents excluded patients with brain metastases. With a better understanding of the biology, several recent trials of targeted therapy that focus on brain metastases have been reported and others are ongoing. Novel agents with better penetration across the blood-brain barrier are currently being investigated for patients with brain metastases. In this review, we discuss the current state of use and future directions of targeted therapies in brain metastases.

Efficacy of EGFR Tyrosine Kinase Inhibitors in the Adjuvant Treatment for Operable Non-small Cell Lung Cancer by a Meta-Analysis

BACKGROUND

The role of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) in the adjuvant treatment of non-small cell lung cancer (NSCLC) has not been well-established. Our meta-analysis aimed to determine whether the administration of EGFR-TKIs could improve the outcomes of patients with NSCLC undergoing complete resection.

METHODS

We comprehensively searched databases and extracted data from eligible studies. Disease-free survival (DFS) and overall survival (OS) with hazard ratios (HRs) as well as disease relapse with odds ratios (OR) were calculated using random and/or fixed-effects models. Meta-regression analysis and test for interaction between subgroups were also carried out.

RESULTS

A total of 1,960 patients in five studies were included. Adjuvant EGFR-TKI treatment was associated with a significant benefit on DFS (HR, 0.63; 95% CI, 0.41-0.99), corresponding to an absolute benefit of 3.1% at 3 years, yet with significant heterogeneity (I(2) = 83.4%, P < .001). The survival benefit was superior (Pinteraction = .03) in studies with more than an 18-month median treatment duration. EGFR mutation rate was also identified as a source of heterogeneity (P = .017). In the population with EGFR mutations, HR for DFS was 0.48 (95% CI, 0.36-0.65), corresponding to an absolute benefit of 9.5% at 3 years, with a reduced risk of distant metastasis (OR, 0.71; 95% CI, 0.56-0.92). Adjuvant EGFR-TKI treatment resulted in a marginally statistically significant benefit on OS (HR, 0.72; 95% CI, 0.49-1.06). The rate of overall grade 3 or greater adverse events was 42.3% (95% CI, 39.1-45.6).

CONCLUSIONS

Adjuvant EGFR-TKI treatment may enhance disease-free survival and reduce the risk of distant metastasis in patients with EGFR-mutant NSCLC undergoing complete resection.

Oral Targeted Therapies and Central Nervous System (CNS) Metastases

The purpose of our review is to summarize the clinical activity of oral targeted agents against brain metastases. This includes BRAF inhibitors (dabrafenib and vemurafenib), human epidermal growth factor receptor inhibitors (lapatinib, gefitinib, erlotinib, and afatinib), multi-kinase angiogenesis inhibitors (sorafenib, sunitinib, pazopanib, and vandetanib), and ALK/c-MET (crizotinib) and ALK/IGF-1 (ceritinib) inhibitors. Effective systemic therapies are needed for long-term benefit in brain metastases and documentation of intracranial activity for many therapies is poor. Our review provides a summary of the literature with pertinent data for clinicians. This is needed as subjects with brain metastases are often prevented from enrolling in clinical trials and investigations focused on systemic therapies for brain metastases are rare.

Management of dose variability and side effects for individualized cancer pharmacotherapy with tyrosine kinase inhibitors

Molecular-targeted therapies with tyrosine kinase inhibitors (TKIs) have provided a major breakthrough in cancer treatment. These agents are given orally and demonstrated to be substrates for drug transporters. In clinical settings, TKIs are mainly used at a fixed dose, but wide interpatient variability has been observed in their pharmacokinetics and/or pharmacodynamics. Genetic polymorphisms of ABC transporters, drug-drug interaction and adherence are among the factors causing such variation. To overcome these problems, therapeutic drug monitoring has been applied in clinical practice for patient care. Skin disorders are frequently observed as adverse drug reactions when using TKIs, and are commonly managed by symptomatic therapy based on clinical experience. Recent studies have provided some insights into the molecular mechanisms underlying skin disorders induced by TKIs. This review article summarizes the accumulated clinical and basic pharmacological evidence of TKIs, focusing on erlotinib, sorafenib and sunitinib.

LDA-SVM-based EGFR mutation model for NSCLC brain metastases: an observational study

Epidermal growth factor receptor (EGFR) activating mutations are a predictor of tyrosine kinase inhibitor effectiveness in the treatment of non-small-cell lung cancer (NSCLC). The objective of this study is to build a model for predicting the EGFR mutation status of brain metastasis in patients with NSCLC. Observation and model set-up. This study was conducted between January 2003 and December 2011 in 6 medical centers in Southwest China. The study included 31 NSCLC patients with brain metastases. Eligibility requirements were histological proof of NSCLC, as well as sufficient quantity of paraffin-embedded lung and brain metastases specimens for EGFR mutation detection. The linear discriminant analysis (LDA) method was used for analyzing the dimensional reduction of clinical features, and a support vector machine (SVM) algorithm was employed to generate an EGFR mutation model for NSCLC brain metastases. Training-testing-validation (3 : 1 : 1) processes were applied to find the best fit in 12 patients (validation test set) with NSCLC and brain metastases treated with a tyrosine kinase inhibitor and whole-brain radiotherapy. Primary and secondary outcome measures: EGFR mutation analysis in patients with NSCLC and brain metastases and the development of a LDA-SVM-based EGFR mutation model for NSCLC brain metastases patients. EGFR mutation discordance between the primary lung tumor and brain metastases was found in 5 patients. Using LDA, 13 clinical features were transformed into 9 characteristics, and 3 were selected as primary vectors. The EGFR mutation model constructed with SVM algorithms had an accuracy, sensitivity, and specificity for determining the mutation status of brain metastases of 0.879, 0.886, and 0.875, respectively. Furthermore, the replicability of our model was confirmed by testing 100 random combinations of input values. The LDA-SVM-based model developed in this study could predict the EGFR status of brain metastases in this small cohort of patients with NSCLC. Further studies with larger cohorts should be carried out to validate our findings in the clinical setting.

Efficacy of the irreversible ErbB family blocker afatinib in epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI)-pretreated non-small-cell lung cancer patients with brain metastases or leptomeningeal disease

INTRODUCTION

Afatinib is an effective first-line treatment in patients with epidermal growth factor receptor (EGFR)-mutated non-small-cell lung cancer (NSCLC) and has shown activity in patients progressing on EGFR-tyrosine kinase inhibitors (TKIs). First-line afatinib is also effective in patients with central nervous system (CNS) metastasis. Here we report on outcomes of pretreated NSCLC patients with CNS metastasis who received afatinib within a compassionate use program.

METHODS

Patients with NSCLC progressing after at least one line of chemotherapy and one line of EGFR-TKI treatment received afatinib. Medical history, patient demographics, EGFR mutational status, and adverse events including tumor progression were documented.

RESULTS

From 2010 to 2013, 573 patients were enrolled and 541 treated with afatinib. One hundred patients (66% female; median age, 60 years) had brain metastases and/or leptomeningeal disease with 74% having documented EGFR mutation. Median time to treatment failure for patients with CNS metastasis was 3.6 months, and did not differ from a matched group of 100 patients without CNS metastasis. Thirty-five percent (11 of 31) of evaluable patients had a cerebral response, five (16%) responded exclusively in brain. Response duration (range) was 120 (21-395) days. Sixty-six percent (21 of 32) of patients had cerebral disease control on afatinib. Data from one patient with an impressive response showed an afatinib concentration in the cerebrospinal fluid of nearly 1 nMol.

CONCLUSION

Afatinib appears to penetrate into the CNS with concentrations high enough to have clinical effect on CNS metastases. Afatinib may therefore be an effective treatment for heavily pretreated patients with EGFR-mutated or EGFR-TKI-sensitive NSCLC and CNS metastasis.

[Advances in treatment of brain metastases from primary non-small cell lung cancer]

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Clinical utility of erlotinib for the treatment of non-small-cell lung cancer in Japanese patients: current evidence

Gefitinib, an epidermal growth factor tyrosine kinase inhibitor (EGFR-TKI), has been approved in Japan for the treatment of patients with advanced non-small-cell lung cancer (NSCLC) based on Phase II clinical trials since 2002. Erlotinib, another EGFR-TKI, was also approved a few years thereafter. In 2004, activating mutations in the EGFR gene were discovered to be a predictive biomarker for EGFR-TKI treatment, and gefitinib, which is not effective for patients with EGFR wild-type NSCLC, has since been used only in patients with EGFR-mutated NSCLC. In contrast, erlotinib is potentially effective for the treatment of EGFR wild-type NSCLC. Similar to gefitinib, erlotinib is also effective for EGFR-mutated NSCLC and has been used as an initial treatment for patients with advanced EGFR-mutated NSCLC. Both gefitinib and erlotinib can be used in a Japanese clinical setting. The approved daily dose of erlotinib (150 mg) is equal to the maximum tolerated dose of erlotinib. In contrast, the daily dose of gefitinib has been set at 250 mg, which is approximately one-third of the maximum tolerated dose of gefitinib. Accordingly, a higher serum concentration can be achieved using erlotinib, compared with gefitinib. This advantage can be applied to the treatment of central nervous system metastases (brain metastasis and carcinomatous meningitis), the treatment of which is complicated by the difficulty drugs have penetrating the blood-brain barrier. Although patients with EGFR-mutated NSCLC respond dramatically to EGFR-TKIs, some patients have a poor response and the majority eventually undergo disease progression. To overcome such resistance, several novel treatment strategies, such as combination therapy and next-generation EGFR-TKIs, have been attempted.

Favorable response to icotinib in a lung cancer patient with a special mutation at exon 19 of epidermal growth factor receptor

Many studies have illustrated that two types of mutation - deletions in exon 19 and a point mutation in exon 21 (L858R) - have been reported to comprise up to 90% of all activating epidermal growth factor receptor (EGFR) mutations. A point mutation at exon 19 is a rare mutation, and to date there have been no reports investigating the sensitivities of EGFR-tyrosine kinase inhibitors (TKIs) to the mutation. In this case report, we have demonstrated a special mutation, a point mutation at c.2279T>C (p.L760P) in exon 19 of EGFR, which has responded favorably to icotinib in a lung adenocarcinoma patient with brain metastasis. Icotinib is a new type of oral EGFR-TKI developed in China and is the first EGFR-TKI in Asia. Icotinib has the potential to improve the prognosis of lung adenocarcinoma patients and with less toxic-effect.

Bone and brain metastasis in lung cancer: recent advances in therapeutic strategies

Bone and brain metastases are a very common secondary localization of disease in patients with lung cancer. The prognosis of these patients is still poor with a median survival of less than 1 year. Current therapeutic approaches include palliative radiotherapy and systemic therapy with chemotherapy and targeted agents. For bone metastasis, zoledronic acid is the most commonly used bisphosphonate to prevent, reduce the incidence and delay the onset of skeletal-related events (SREs). Recently, denosumab, a fully human monoclonal antibody directed against the receptor activator of nuclear factor κB (RANK) ligand inhibiting the maturation of pre-osteoclasts into osteoclasts, showed increased time to SREs and overall survival compared with zoledronic acid. The treatment of brain metastasis is still controversial. Available standard therapeutic options, such as whole brain radiation therapy and systemic chemotherapy, provide a slight improvement in local control, overall survival and symptom relief. More recently, novel target agents such as the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) erlotinib, gefitinib and afatinib have shown activity in patients with brain metastasis. Inter alia, in patients harboring EGFR mutations, the administration of EGFR TKIs is followed by a response rate of 70-80%, and a longer progression-free and overall survival than those obtained with standard chemotherapeutic regimens. This review is focused on the evidence for therapeutic strategies in bone and brain metastases due to lung cancer.

Epidermal growth factor receptor tyrosine kinase inhibitors in the treatment of central nerve system metastases from non-small cell lung cancer

Brain metastases (BM) are common and disastrous occurrence in patients with non-small cell lung cancer (NSCLC). Currently increasing studies suggest remarkable efficacy and mild toxicity of the epidermal growth factor tyrosine kinase inhibitor (EGFR TKI) in these patients, making targeted therapy an attractive option to BM from NSCLC. We here present a review about the use of EGFR-TKIs in this context and the following questions would be discussed: Are TKIs capable of permeating across brain-blood barrier (BBB)? How to boost exposure of EGFR TKI in cerebrospinal fluid to overcome the resistance of refractory metastases? Would the combination with other treatment like radiotherapy bring about advanced effect? And which patients with BM is the fittest population to EGFR-TKI treatment? In fact, though the administration of EGFR TKI only could achieve certain effect with limited penetration across BBB, increasing dose and combined radiotherapy would carry out better outcome. Unsurprisingly EGFR mutations were still the most important predictor of the sensitivity.

[Therapeutic impact of molecular diagnosis in metastatic non-small cell lung cancer: targeted therapies in 2013]

Recent advances in the molecular characterization of metastatic unresectable lung cancers have markedly improved the management of patients. Today, molecular tests should be performed routinely in all patients with non-squamous non-small cell lung cancer, and in case of squamous cell carcinoma occurring in a non-smoker. In the presence of EGFR mutation or ALK rearrangement, specific inhibitors have shown superior efficacy to chemotherapy in first-line treatment for anti-EGFR (erlotinib and gefitinib) and in second-line treatment for anti-ALK (crizotinib). We will report the most recent clinical trials that aimed to identify effective therapeutic alternatives in case of acquired resistance to first-generation inhibitors (erlotinib, gefitnib, crizotinib), which inevitably occur in a median of 11-13 months at the first line setting and 7 months at the second line setting. Finally, we will describe more recently known molecular alterations such as ROS1 or RET rearrangements and HER2, BRAF, PIK3CA, DDR2 mutations. Some of these alterations are already elegible for dedicated targeted therapies within clinical trials or temporary use authorization (ATU).

Recurrent response to advanced lung adenocarcinoma with erlotinib developing leptomeningeal metastases during gefitinib therapy and two case reports

BACKGROUND

Epidermal growth factor-tyrosine kinase inhibitors (EGFR-TKIs) are one of the effective medicines in advanced lung adenocarcinoma leptomeningeal metastasis (LM) treatment in recent years.

METHODS

This paper reports two cases of advanced lung adenocarcinoma with exon-EGFR19 mutation. LM occurred during gefitinib treatment with an extracranial condition under control. Later, erlotinib was adopted with a recurrent response.

RESULTS

The progression free survival of both patients was over six months and their LM was under control for six and a half and nine months, respectively. LM may be sensitive on different levels to different EGFR-TKIs.

CONCLUSION

Erlotinib can be used to replace gefitinib if intracranial tumor progress occurs during gefitinib treatment. However, our conclusion still needs to be proven by further clinical research.

Phase II study of whole brain radiotherapy with or without erlotinib in patients with multiple brain metastases from lung adenocarcinoma

The aim of this paper is to explore the efficacy of whole brain radiotherapy (WBRT) versus WBRT concurrent with erlotinib in patients with multiple brain metastases of lung adenocarcinoma. WBRT was administered at 30Gy/10f in both arms. In the combination arm, 150 mg erlotinib was given each day, starting the first day of radiotherapy and continuing for 1 month following the end of radiotherapy. Thereafter, pemetrexed or docetaxel monotherapy or the best supportive therapy was given to both arms. The intracranial objective response rate and the local progression-free survival (LPFS) were primary endpoints. Toxicity, progression-free survival (PFS) and overall survival (OS) were secondary endpoints. Thirty-one patients in the WBRT group and 23 patients in the combination group were enrolled from November 2009 to December 2011. In the WBRT and the combination arms, respectively, the objective response rate was 54.84% and 95.65% (P = 0.001), the median local progression-free survival was 6.8 months and 10.6 months (P = 0.003), the median PFS was 5.2 months and 6.8 months (P = 0.009), and median OS was 8.9 months and 10.7 months (P = 0.020). In the combination group, there were no differences of LPFS, PFS, and OS between the epidermal growth factor receptor (EGFR) mutation patients and EGFR wild-type patients. No Grade 4 or higher side effects were observed in either group. A multivariate analysis indicated that erlotinib was the most important prognostic factor for a prolonged survival. Data showed that erlotinib in combination with WBRT had a tolerable toxicity profile and prolonged the LPFS, PFS, and OS of lung adenocarcinoma patients with multiple brain metastases compared with WBRT monotherapy.

The concentration of erlotinib in the cerebrospinal fluid of patients with brain metastasis from non-small-cell lung cancer

It has been demonstrated that erlotinib is effective in treating patients with brain metastasis from non-small-cell lung cancer. However, the number of studies determining the erlotinib concentration in these patients is limited. The purpose of this study was to measure the concentration of erlotinib in the cerebrospinal fluid of patients with brain metastasis from non-small-cell lung carcinoma. Six patients were treated with the standard recommended daily dose of erlotinib (150 mg) for 4 weeks. All the patients had previously received chemotherapy, but no brain radiotherapy. At the end of the treatment period, blood plasma and cerebrospinal fluid samples were collected and the erlotinib concentration was determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The average erlotinib concentration in the blood plasma and the cerebrospinal fluid was 717.7±459.7 and 23.7±13.4 ng/ml, respectively. The blood-brain barrier permeation rate of erlotinib was found to be 4.4±3.2%. In patients with partial response (PR), stable disease (SD) and progressive disease (PD), the average concentrations of erlotinib in the cerebrospinal fluid were 35.5±19.0, 19.1±8.7 and 16.4±5.9 ng/ml, respectively. In addition, the efficacy rate of erlotinib for metastatic brain lesions was 33.3%, increasing to 50% in patients with EGFR mutations. However, erlotinib appeared to be ineffective in cases with wild-type EGFR. In conclusion, a relatively high concentration of erlotinib was detected in the cerebrospinal fluid of patients with brain metastases from non-small-cell lung cancer. Thus, erlotinib may be considered as a treatment option for this patient population.

Peritoneal and meningeal relapse from lung adenocarcinoma after a response to gefitinib: A case report

The prognosis of carcinomatous peritonitis and meningitis is poor since ascites and focal neurological dysfunctions usually do not improve despite the available treatment options for this devastating disease. This is a case report of peritoneal and meningeal relapse from lung adenocarcinoma following a response to gefitinib. A 72-year-old woman was diagnosed with adenocarcinoma in the upper lobe of the left lung, accompanied by a massive carcinomatous pleural effusion. Following a cisplati-based chemotherapy, gefitinib was initiated, achieving satisfactory disease control. At 8 months after gefitinib initiation, the patient developed abdominal distension, gait disturbance and visual disorder of the right eye. Adenocarcinoma cells were detected in the ascitic and pleural fluids. The findings of this case report suggest that clinicians should remain vigilant for this type of metastasis, although it is rarely encountered.

High-dose, pulsatile erlotinib in two NSCLC patients with leptomeningeal metastases--one with a remarkable thoracic response as well

A considerable number of patients with epidermal growth factor receptor (EGFR)-mutated non-small-cell lung cancer (NSCLC) develop leptomeningeal metastases. Leptomeningeal metastases are associated with deterioration of clinical symptoms and poor survival. Traditionally, treatment of metastases in the central nervous system consists of radiotherapy and less frequently, surgery. The role of systemic therapy is limited due to the blood-brain barrier inhibiting pharmacological doses to be reached in the central nervous system. Several case reports have described high-dose, pulsatile tyrosine kinase inhibitors as an effective treatment of leptomeningeal metastases, based on the hypothesis that higher concentrations in the cerebrospinal fluid can be reached by higher systemic concentrations. Here, we describe two patients with EGFR-mutated non-small cell lung cancer, with both clinical and radiological response to this high-dose, pulsatile regimen. Interestingly, one patient showed a remarkable response of intrathoracic response as well.

Phase II trial of erlotinib plus concurrent whole-brain radiation therapy for patients with brain metastases from non-small-cell lung cancer

PURPOSE

Brain metastasis (BM) is a leading cause of death from non-small-cell lung cancer (NSCLC). Reasoning that activation of the epidermal growth factor receptor (EGFR) contributes to radiation resistance, we undertook a phase II trial of the EGFR inhibitor erlotinib with whole-brain radiation therapy (WBRT) in an attempt to extend survival time for patients with BM from NSCLC. Additional end points were radiologic response and safety.

PATIENTS AND METHODS

Eligible patients had BM from NSCLC, regardless of EGFR status. Erlotinib was given at 150 mg orally once per day for 1 week, then concurrently with WBRT (2.5 Gy per day 5 days per week, to 35 Gy), followed by maintenance. EGFR mutation status was tested by DNA sequencing at an accredited core facility.

RESULTS

Forty patients were enrolled and completed erlotinib plus WBRT (median age, 59 years; median diagnosis-specific graded prognostic assessment score, 1.5). The overall response rate was 86% (n = 36). No increase in neurotoxicity was detected, and no patient experienced grade ≥ 4 toxicity, but three patients required dose reduction for grade 3 rash. At a median follow-up of 28.5 months (for living patients), median survival time was 11.8 months (95% CI, 7.4 to 19.1 months). Of 17 patients with known EGFR status, median survival time was 9.3 months for those with wild-type EGFR and 19.1 months for those with EGFR mutations.

CONCLUSION

Erlotinib was well tolerated in combination with WBRT, with a favorable objective response rate. The higher-than-expected rate of EGFR mutations in these unselected patients raises the possibility that EGFR-mutated tumors are prone to brain dissemination.

Local ablative therapy of oligoprogressive disease prolongs disease control by tyrosine kinase inhibitors in oncogene-addicted non-small-cell lung cancer

INTRODUCTION

Many patients with oncogene-driven non-small-cell lung cancer (NSCLC) treated with tyrosine kinase inhibitors experience limited sites of disease progression. This study investigated retrospectively the benefits of local ablative therapy (LAT) to central nervous system (CNS) and/or limited systemic disease progression and continuation of crizotinib or erlotinib in patients with metastatic ALK gene rearrangement (ALK+) or EGFR-mutant (EGFR-MT) NSCLC, respectively.

METHODS

Patients with metastatic ALK+ NSCLC treated with crizotinib (n = 38) and EGFR-MT NSCLC treated with erlotinib (n = 27) were identified at a single institution. Initial response to the respective kinase inhibitors, median progression-free survival (PFS1), and site of first progression were recorded. A subset of patients with either nonleptomeningeal CNS and/or four sites or fewer of extra-CNS progression (oligoprogressive disease) suitable for LAT received either radiation or surgery to these sites and continued on the same tyrosine kinase inhibitors. The subsequent median progression-free survival from the time of first progression (PFS2) and pattern of progression were recorded.

RESULTS

Median progression-free survival in ALK+ patients on crizotinib was 9.0 months, and 13.8 months for EGFR-MT patients on erlotinib. Twenty-five of 51 patients (49%) who progressed were deemed suitable for local therapy (15 ALK+, 10 EGFR-MT; 24 with radiotherapy, one with surgery) and continuation of the same targeted therapy. Post-LAT, 19 of 25 patients progressed again, with median PFS2 of 6.2 months.

DISCUSSION

Oncogene-addicted NSCLC with CNS and/or limited systemic disease progression (oligoprogressive disease) on relevant targeted therapies is often suitable for LAT and continuation of the targeted agent, and is associated with more than 6 months of additional disease control.

Clinical outcomes with erlotinib in patients with epidermal growth factor receptor mutation

The epidermal growth factor receptor (EGFR) mutation is the first recognized molecular target in non-small cell lung cancer that makes personalized therapy feasible. This molecular alteration has been demonstrated to be more frequent in Asians, non-smokers and patients with adenocarcinoma histology. Several retrospective and subgroup analyses of phase III trials have shown the single agent, erlotinib, to be associated with higher response rates and longer progression-free survival in patients harbouring an EGFR mutation. Two prospective randomized phase III studies from China and Europe have confirmed the role of first-line erlotinib in patients with the mutations. Erlotinib has also been evaluated in combination with chemotherapy in either a concurrent or intercalated regimen. Earlier trials were limited by little information on the EGFR mutational status of the enrolled patients, and an ongoing phase III trial with translational biomarker analysis will provide more comprehensive data on the combination.

The impact of initial gefitinib or erlotinib versus chemotherapy on central nervous system progression in advanced non-small cell lung cancer with EGFR mutations

PURPOSE

This retrospective study was undertaken to investigate the impact of initial gefitinib or erlotinib (EGFR tyrosine kinase inhibitor, EGFR-TKI) versus chemotherapy on the risk of central nervous system (CNS) progression in advanced non-small cell lung cancer (NSCLC) with EGFR mutations.

EXPERIMENTAL DESIGN

Patients with stage IV or relapsed NSCLC with a sensitizing EGFR mutation initially treated with gefitinib, erlotinib, or chemotherapy were identified. The cumulative risk of CNS progression was calculated using death as a competing risk.

RESULTS

One hundred and fifty-five patients were eligible (EGFR-TKI: 101, chemotherapy: 54). Twenty-four patients (24%) in the EGFR-TKI group and 12 patients (22%) in the chemotherapy group had brain metastases at the time of diagnosis of advanced NSCLC (P = 1.000); 32 of the 36 received CNS therapy before initiating systemic treatment. Thirty-three patients (33%) in the EGFR-TKI group and 26 patients (48%) in the chemotherapy group developed CNS progression after a median follow-up of 25 months. The 6-, 12-, and 24-month cumulative risk of CNS progression was 1%, 6%, and 21% in the EGFR-TKI group compared with corresponding rates of 7%, 19%, and 32% in the chemotherapy group (P = 0.026). The HR of CNS progression for upfront EGFR-TKI versus chemotherapy was 0.56 [95% confidence interval (CI), 0.34-0.94].

CONCLUSIONS

Our data show lower rates of CNS progression in EGFR-mutant advanced NSCLC patients initially treated with an EGFR-TKI compared with upfront chemotherapy. If validated, our results suggest that gefitinib and erlotinib may have a role in the chemoprevention of CNS metastases from NSCLC.

Clinical outcome in patients with leptomeningeal metastasis from non-small cell lung cancer: Okayama Lung Cancer Study Group

OBJECTIVE

We examined the prognosis of patients with leptomeningeal metastasis (LM) from non-small cell lung cancer (NSCLC) and that stratified by epidermal growth factor receptor (EGFR) mutation status in LM patients receiving EGFR-tyrosine kinase inhibitors (TKIs).

METHODS

We retrospectively analyzed a series of 91 consecutive NSCLC patients with LM between 2001 and 2010.

RESULTS

Most of the LM patients had adenocarcinoma histology and a poor performance status (PS). The median survival time (MST) for all patients was 3.6 months. Adenocarcinoma and TKI treatment were associated with a better prognosis. Among the patients, 51 received EGFR-TKIs. Of these, the EGFR mutation status was assessed in 30 patients; 7 (23%) showed no mutation (group 1), 10 (33%) had a mutation in exon 21 (group 2), and 13 (43%) had deletions in exon 19 (group 3). Interestingly, PS was significantly improved in groups 2 and 3 but not in group 1. The MST in these subgroups was 1.4, 7.1, and 11.0 months in groups 1, 2, and 3, respectively (p<0.001). The median time to progression or symptom deterioration was 0.9, 2.0, and 7.8 months for groups 1, 2, and 3, respectively (p<0.001). A multivariate analysis showed that EGFR-mutant tumors were associated with a better prognosis in patients receiving EGFR-TKIs.

CONCLUSIONS

The prognosis for patients with LM from NSCLC was still poor. Survival after the initiation of EGFR-TKI treatment differed according to the type of EGFR mutation, suggesting the potential benefit of TKIs for patients with EGFR mutations, even though they suffered from LM.

Successful treatment of non-small cell lung cancer with gefitinib after severe erlotinib-related hepatotoxicity

Gefitinib and erlotinib are first-generation small molecular inhibitors of EGFR tyrosine kinase activity. To the best of our knowledge, to date, two reports have stated that patients with NSCLC who develop severe hepatotoxicity secondary to gefitinib treatment can be safely switched to erlotinib. However, the reverse situation has not been reported. Here, we present the first case with non-small cell lung cancer harboring EGFR mutation who developed grade 3/4 hepatotoxicity after initiation of erlotinib, which resolved when therapy was changed to gefitinib. As far as we know, this is the first report showing the efficacy of gefitinib for a non-small cell lung cancer patient who developed severe hepatotoxicity while under erlotinib therapy.

Targeted therapy for brain metastases

The prevention and treatment of brain metastases is an increasingly important challenge in oncology. Improved understanding of the molecular pathogenesis of a number of cancers has led to the development of highly active targeted therapies for patients with specific oncogenic events. Such therapies include EGFR inhibitors for lung cancer, HER2/neu inhibitors for breast cancer, and BRAF inhibitors for melanoma. This review will discuss the development of these targeted therapy approaches, existing data about their role in the management of brain metastasis, and opportunities and challenges for future research in this critical area.

Efficacy of increased-dose erlotinib for central nervous system metastases in non-small cell lung cancer patients with epidermal growth factor receptor mutation

PURPOSE

Recent reports indicate that refractory central nervous system (CNS) metastases of non-small cell lung cancer (NSCLC) are improved by high-dose gefitinib or erlotinib administration. We describe a Japanese woman with NSCLC and CNS metastases who was resistant to 75 mg daily erlotinib, but the metastases were improved by 150 mg daily erlotinib. We investigated the plasma and CSF concentrations of erlotinib at each dose as well as the correlation between the plasma and CSF concentrations of erlotinib.

METHODS

Including this patient, we administered 150 mg erlotinib daily to nine NSCLC patients with CNS metastases and measured the plasma and CSF concentrations just before administration on day 8. The concentrations were determined using high-performance liquid chromatography with ultraviolet detection.

RESULTS

The plasma and CSF concentrations of erlotinib at a dose of 75 mg were 433 and 14 nM, respectively. The plasma and CSF concentrations of erlotinib at a dose of 150 mg were increased to 1,117 and 44 nM, respectively. The mean ± standard deviation of CSF concentrations and penetration rates were 106 ± 59 nM and 4.5 ± 1.5%, respectively. There was a good correlation (R(2) = 0.84) between plasma and CSF concentrations (P = 0.0005).

CONCLUSIONS

This study indicates that CSF concentrations of erlotinib depend on its plasma concentration. As seen in this patient, high CSF concentrations of erlotinib can be achieved by high-dose administration, and this finding suggests the efficacy of high-dose administration, especially to refractory CNS metastases of NSCLC patients.

Two cases of leptomeningeal metastases from lung adenocarcinoma which progressed during gefitinib therapy but responded to erlotinib

We present two patients with leptomeningeal metastases (LM) from lung adenocarcinoma that progressed or newly developed, respectively, during gefitinib therapy which had exhibited substantial antitumor effects on widespread lesions. In both cases, a switch to erlotinib therapy brought about long-lasting dramatic symptomatic improvement and markedly prolonged survival. The first patient is a 46-year-old female who presented with progressive headache and vomiting. Multiple pulmonary, hepatic and bone metastases immediately shrank in response to gefitinib. However, 1 month after completion of concurrent whole brain radiation, dizziness and urinary retention newly emerged, worsening the symptoms observed at presentation. Magnetic resonance imaging (MRI) demonstrated enlargement of ventricles and new gadolinium (Gd)-enhanced disseminated nodules on the surface of the cerebral cortex, suggesting the existence of uncontrollable LM. Sequential erlotinib therapy resulted in symptomatic improvement with a finding of regression of Gd-enhancement on MRI. The beneficial effect lasted for 10 months, though a follow-up brain MRI showed further enlarged ventricles. She finally died due to LM after surviving for 11 months under erlotinib treatment. The other patient is a 55-year-old female in whom headache and vomiting occurred while gefitinib therapy had maintained shrinkage of all pre-existing tumors in the thorax and bones. Brain MRI strongly suggested occurrence of LM with a finding of Gd-enhanced sulci. A switch to erlotinib therapy relieved the symptoms with disappearance of Gd-enhancement. However, the symptoms recurred with a finding of further enlargement of ventricles on brain MRI after 11 months. Finally, she died due to LM after surviving for 12 months under erlotinib treatment.

Brain metastases as preventive and therapeutic targets

The incidence of metastasis to the brain is apparently rising in cancer patients and threatens to limit the gains that have been made by new systemic treatments. The brain is considered a 'sanctuary site' as the blood-tumour barrier limits the ability of drugs to enter and kill tumour cells. Translational research examining metastasis to the brain needs to be multi-disciplinary, marrying advanced chemistry, blood-brain barrier pharmacokinetics, neurocognitive testing and radiation biology with metastasis biology, to develop and implement new clinical trial designs. Advances in the chemoprevention of brain metastases, the validation of tumour radiation sensitizers and the amelioration of cognitive deficits caused by whole-brain radiation therapy are discussed.

Role of ATP-binding cassette and solute carrier transporters in erlotinib CNS penetration and intracellular accumulation

PURPOSE

To study the role of drug transporters in central nervous system (CNS) penetration and cellular accumulation of erlotinib and its metabolite, OSI-420.

EXPERIMENTAL DESIGN

After oral erlotinib administration to wild-type and ATP-binding cassette (ABC) transporter-knockout mice (Mdr1a/b(-/-), Abcg2(-/-), Mdr1a/b(-/-)Abcg2(-/-), and Abcc4(-/-)), plasma was collected and brain extracellular fluid (ECF) was sampled using intracerebral microdialysis. A pharmacokinetic model was fit to erlotinib and OSI-420 concentration-time data, and brain penetration (P(Brain)) was estimated by the ratio of ECF-to-unbound plasma area under concentration-time curves. Intracellular accumulation of erlotinib was assessed in cells overexpressing human ABC transporters or SLC22A solute carriers.

RESULTS

P(Brain) in wild-type mice was 0.27 ± 0.11 and 0.07 ± 0.02 (mean ± SD) for erlotinib and OSI-420, respectively. Erlotinib and OSI-420 P(Brain) in Abcg2(-/-) and Mdr1a/b(-/-)Abcg2(-/-) mice were significantly higher than in wild-type mice. Mdr1a/b(-/-) mice showed similar brain ECF penetration as wild-type mice (0.49 ± 0.37 and 0.04 ± 0.02 for erlotinib and OSI-420, respectively). In vitro, erlotinib and OSI-420 accumulation was significantly lower in cells overexpressing breast cancer resistance protein (BCRP) than in control cells. Only OSI-420, not erlotinib, showed lower accumulation in cells overexpressing P-glycoprotein (P-gp) than in control cells. The P-gp/BCRP inhibitor elacridar increased erlotinib and OSI-420 accumulation in BCRP-overexpressing cells. Erlotinib uptake was higher in OAT3- and OCT2-transfected cells than in empty vector control cells.

CONCLUSION

Abcg2 is the main efflux transporter preventing erlotinib and OSI-420 penetration in mouse brain. Erlotinib and OSI-420 are substrates for SLC22A family members OAT3 and OCT2. Our findings provide a mechanistic basis for erlotinib CNS penetration, cellular uptake, and efflux mechanisms.

Microdialysis for assessing intratumoral drug disposition in brain cancers: a tool for rational drug development

IMPORTANCE OF THE FIELD

many promising targeted agents and combination therapies are being investigated for brain cancer. However, the results from recent clinical trials have been disappointing. A better understanding of the disposition of drug in the brain early in drug development would facilitate appropriate channeling of new drugs into brain cancer clinical trials.

AREAS COVERED IN THIS REVIEW

barriers to successful drug activity against brain cancer and issues affecting intratumoral drug concentrations are reviewed. The use of the microdialysis technique for extracellular fluid (ECF) sampling and its application to drug distribution studies in brain are reviewed using published literature from 1995 to the present. The benefits and limitations of microdialysis for performing neuorpharmacokinetic (nPK) and neuropharmacodynamic (nPD) studies are discussed.

WHAT THE READER WILL GAIN

the reader will gain an appreciation of the challenges involved in identifying agents likely to have efficacy in brain cancer, an understanding of the general principles of microdialysis, and the power and limitations of using this technique in early drug development for brain cancer therapies.

TAKE HOME MESSAGE

a major factor preventing efficacy of anti-brain cancer drugs is limited access to tumor. Intracerebral microdialysis allows sampling of drug in the brain ECF. The resulting nPK/nPD data can aid in the rational selection of drugs for investigation in brain tumor clinical trials.