An unexpected response to second line EGFR inhibitor in relapsing leptomeningeal carcinomatosis from lung adenocarcinoma raises questions on differential mechanisms of action of these agents

Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors for Central Nervous System Metastases from Non-Small Cell Lung Cancer

Central nervous system (CNS) metastases are a common complication in patients with epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC), resulting in a poor prognosis and limited treatment options. Treatment of CNS metastases requires a multidisciplinary approach, and the optimal treatment options and sequence of therapies are yet to be established. Many systemic therapies have poor efficacy in the CNS due to the challenges of crossing the blood-brain barrier (BBB), creating a major unmet need for the development of agents with good BBB-penetrating biopharmaceutical properties. Although the CNS penetration of first- and second-generation EGFR tyrosine kinase inhibitors (TKIs) is generally low, EGFR-TKI treatment has been shown to delay time to CNS progression in patients with CNS metastases from EGFR-mutated disease. However, a major challenge with EGFR-TKI treatment for patients with NSCLC is the development of acquired resistance, which occurs in most patients treated with a first-line EGFR-TKI. Novel EGFR-TKIs, such as osimertinib, have been specifically designed to address the challenges of acquired resistance and poor BBB permeability and have demonstrated efficacy in the CNS. A rational, iterative drug development process to design agents that could penetrate the BBB could prevent morbidity and mortality associated with CNS disease progression. To ensure a consistent approach to evaluating CNS efficacy, special consideration also needs to be given to clinical trial endpoints.

IMPLICATIONS FOR PRACTICE

Historically, treatment options for patients who develop central nervous system (CNS) metastases have been limited and associated with poor outcomes. The development of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) has improved outcomes for patients with EGFR-mutated disease, and emerging data have demonstrated the ability of these drugs to cross the blood-brain barrier and elicit significant intracranial responses. Recent studies have indicated a role for next-generation EGFR-TKIs, such as osimertinib, in the treatment of CNS metastases. In the context of an evolving treatment paradigm, treatment should be individualized to the patient and requires a multidisciplinary approach.

Medical Treatment Options for Patients with Epidermal Growth Factor Receptor Mutation-Positive Non-Small Cell Lung Cancer Suffering from Brain Metastases and/or Leptomeningeal Disease

Brain metastases and/or leptomeningeal disease (LMD) with associated central nervous system (CNS) metastases are known complications of advanced epidermal growth factor receptor (EGFR) mutation-positive non-small cell lung cancer (NSCLC). It is important, therefore, to assess the activity of EGFR tyrosine kinase inhibitors (TKIs) versus such CNS complications. This review explores the literature reporting the intracranial activity of EGFR TKIs, and finds that there is evidence for varying efficacy of the approved agents, erlotinib, gefitinib, afatinib, and osimertinib in patients with CNS metastases. Other EGFR TKIs in development, such as AZD3759, may have a future role as therapeutic options in this setting. Emerging evidence indicates that the second- and third-generation EGFR TKIs, afatinib and osimertinib, effectively penetrate the blood-brain barrier, and therefore represent viable treatment options for CNS lesions, and can reduce the risk of CNS progression. These agents should therefore be considered as first-line treatment options in patients with EGFR mutation-positive NSCLC who have brain metastases and/or LMD. While there are currently no prospective data comparing the intracranial efficacy of second- and third-generation EGFR TKIs in this setting, CNS activity and protection offered by different EGFR TKIs should be an additional consideration when making decisions about the optimal sequence of treatment with EGFR TKIs in order to maximize survival benefit in individual patients.