Authors: Stephen G. Chun, Kevin S. Choe, Puneeth Iyengar, John S. Yordy and Robert D. Timmerman

Stephen G. Chun

Corresponding author: Stephen.Chun@utsouthwestern.edu
Department of Radiation Oncology; Harold C. Simmons Comprehensive Cancer Center; University of Texas Southwestern Medical Center; Dallas, TX USA

Kevin S. Choe

Department of Radiation Oncology; Harold C. Simmons Comprehensive Cancer Center; University of Texas Southwestern Medical Center; Dallas, TX USA
These authors contributed equally to this work.

Puneeth Iyengar

Department of Radiation Oncology; Harold C. Simmons Comprehensive Cancer Center; University of Texas Southwestern Medical Center; Dallas, TX USA
These authors contributed equally to this work.

John S. Yordy

Department of Radiation Oncology; Harold C. Simmons Comprehensive Cancer Center; University of Texas Southwestern Medical Center; Dallas, TX USA
These authors contributed equally to this work.

Robert D. Timmerman

Department of Radiation Oncology; Harold C. Simmons Comprehensive Cancer Center; University of Texas Southwestern Medical Center; Dallas, TX USA
These authors contributed equally to this work.

Abstract:
Advanced non-small lung cancer (NSCLC) remains almost uniformly lethal with marginal long-term survival despite efforts to target specific oncogenic addiction pathways that may drive these tumors with small molecularly targeted agents and biologics. The EML4-ALK fusion gene encodes a chimeric tyrosine kinase that activates the Ras signaling pathway, and this fusion protein is found in approximately 5% of NSCLC. Targeting EML4-ALK with Crizotinib in this subset of NSCLC has documented therapeutic efficacy, but the vast majority of patients eventually develop recurrent disease that is often refractory to further treatments. We present the clinicopathologic features of three patients with metastatic NSCLC harboring the EML4-ALK translocation that developed isolated central nervous system (CNS) metastases in the presence of good disease control elsewhere in the body. These cases suggest a differential response of NSCLC to Crizotinib in the brain in comparison to other sites of disease, and are consistent with a previous report of poor CNS penetration of Crizotinib. Results of ongoing clinical trials will clarify whether the CNS is a major sanctuary site for EML4-ALK positive NSCLC being treated with Crizotinib. While understanding molecular mechanisms of resistance is critical to overcome therapeutic resistance, understanding physiologic mechanisms of resistance through analyzing anatomic patterns of failure may be equally crucial to improve long-term survival for patients with EML4-ALK translocation positive NSCLC.

Received: August 6, 2012; Accepted: September 17, 2012; Published Online: September 17, 2012

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