New insights into anaplastic lymphoma kinase-positive nonsmall cell lung cancer.

Abstract

A novel fusion gene of echinoderm microtubule-associated protein-like 4 (EML4) and anaplastic lymphoma kinase (ALK) has been identified in a subset of non-small-cell lung cancers (NSCLCs). Patients with the ALK-EML4 fusion gene demonstrate unique clinicopathological and physiological characteristics. Here we present an analysis of clinicopathological profile of patients of metastatic adenocarcinoma harboring the ALK-EML4 fusion gene and their response to targeted therapy in the form of crizotinib. A retrospective analysis of advanced ALK positive NSCLC, who presented at this tertiary care hospital of armed forces from September 2014 to December 2016 was conducted. The primary goal was to evaluate demographic and clinicopathological profile of ALK positive advanced NSCLC. Detection of ALK fusion was done by IHC on formalin fixed paraffin embedded cell blocks. Out of 20 ALK positive patients, ten patients received upfront cytotoxic chemotherapy, and rest received crizotinib. Patients progressing on cytotoxic chemotherapy received crizotinib as subsequent therapy. Out of 270 patients of NSCLC, fifteen(7.4%) tested positive for ALK-EML4 fusion. Rate of positivity was higher in females(13.7%) than in males (5%). The correlation of the ALK-EML4 fusion gene and clinicopathological characteristics of NSCLC patients demonstrated a significant difference in smoking status, histological types, stage, & metastatic pattern. Median PFS with first line cytotoxic chemotherapy was 5.9 months. Median PFS with upfront crizotinib was not reached, but was significantly superior than cytotoxic chemotherapy. Our analysis indicated that ALK-EML4 positive NSCLC comprised a unique subgroup of adenocarcinomas with distinct clinicopathological characteristics. Incidence of ALK positivity was found to be higher in females and never smokers. These patients have distinct pathological and radiological characteristics. Crizotinib, whether used upfront or as subsequent therapy was found to be superior in PFS (not yet reached at the time of writing this article), and maintaining quality of life as compared to cytotoxic chemotherapy.