Immunohistochemical screening for anaplastic lymphoma kinase (ALK) rearrangement in advanced non-small cell lung cancer patients☆
Introduction
Some genetic alterations such as mutation of epidermal growth factor receptor (EGFR) are well known carcinogenic mechanisms in non-small cell lung cancer (NSCLC). In 2007, the fusion of ALK with echinoderm microtubule-associated protein-like 4 (EML4) was discovered by screening a retroviral complementary DNA expression library [1]. Additional studies, mostly involving East Asian patients, have reported that the detection rate of ALK gene translocation is about 5% in NSCLC [1], [2], [3], [4], [5]. EML4–ALK-positive lung cancer is much more common in young, never or former light smokers. Almost all cases have had adenocarcinoma histology, many with distinct solid or acinar growth pattern with or without signet ring cell histology. With rare exception, EML4–ALK is mutually exclusive with EGFR and KRAS mutations [2], [4], [6], [7], [8]. Moreover, the EML4–ALK rearrangement is reported to be associated with resistance to EGFR tyrosine kinase inhibitor (TKI) therapy [4], [8]. Recently, crizotinib (PF-02341066, Pfizer), a small-molecule dual inhibitor of c-MET and ALK receptor tyrosine kinase, showed a clinical benefit rate of more than 80% of EML4–ALK positive NSCLC patients in phase I clinical trial [9], and has recently been approved by the U.S. FDA for use in locally advanced or metastatic NSCLC.
Several methods including reverse transcriptase (RT)-PCR, fluorescence in situ hybridization (FISH), and immunohistochemistry (IHC) are currently used for identifying ALK translocated NSCLC. RT-PCR is theoretically the most sensitive assay to detect mutant transcript. However, it requires adequate RNA quantity and quality, which are difficult to obtain in routine clinical samples. There is published evidence suggesting a propensity for false positive results in RT-PCR based detection of EML4–ALK [10]. FISH is both sensitive and specific to detect ALK rearrangement. It is the diagnostic method used as an eligibility criterion in ongoing clinical trials of crizotinib [9], [11]; however, it is not readily available in routine pathology practice and is difficult to interpret. FISH may not be practical for screening every NSCLC patient. On the other hand, IHC is an easy and already routine pathology laboratory test, is rapid, and is relatively inexpensive to perform. Therefore, we compared the test concordance of FISH and IHC for ALK and evaluated the role of ALK IHC as a screening tool to identify candidates for ALK inhibitor therapy in advanced NSCLC.
Section snippets
Patient selection
Since EML4–ALK rearrangement is a relatively rare event in unselected NSCLC populations, we limited inclusion criteria for the study population to enrich ALK translocated NSCLC cases. First, we identified 1,166 stage IIIB or IV NSCLC patients with non-squamous cell histology from the Seoul National University Hospital NSCLC database between 2003 and 2009. Then, we selected 262 patients who were either EGFR wild-type or non-responders to previous EGFR TKI therapy (as a proxy for EGFR wild-type
Results
The cohort comprised 105 women and 157 men with mean age of 63.1 years (range, 22–91 years). The histology of the study population consisted of 182 cases of adenocarcinoma, 7 cases of large cell carcinoma, 4 cases of large cell neuroendocrine carcinoma, 5 cases of pleomorphic carcinoma, one case of giant cell carcinoma, and 63 cases of non-small cell carcinoma, not otherwise specified (NOS). All NSCLC, NOS cases were diagnosed by biopsy, including 17 cases with TTF-1 expression, which can be
Discussion
In general, approximately 50% of the NSCLC patients have advanced stage disease at the time of diagnosis and nearly two-thirds of recurrences after curative operation for early stage NSCLC occur at distant sites [14]. Therefore, systemic therapy is one of the important modalities to manage NSCLC patients. Survival improvements have been noted for patients with every stage of NSCLC with the integration of improvements of local therapy and supportive care measures as well as new systemic
Conflict of interest statement
Dong-Wan Kim has acted as a consultant and has received honoraria from Pfizer. Kimary Kulig is an employee of Pfizer.
Acknowledgments
This study was supported by a grant of the Korean Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea (A110057), and was funded in part by an outcomes research agreement with Pfizer.
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2018, Journal of Thoracic OncologyCitation Excerpt :The strength of evidence supporting the use of IHC for ALK testing was adequate. This recommendation is evidence based and was supported by 20 studies,61,111,139–156 comprising 6 PCSs,61,139,141–143,154 3 PRCSs,140,146,155 and 11 RCSs.∗ Of the 20 studies, 19 used FISH as the reference standard when assessing the diagnostic potential of IHC.111,145,147–153,156
A narrative review of methods for the identification of ALK fusions in patients with non-small cell lung carcinoma
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The data of this article was presented in part at the 14th World Conference on Lung Cancer (WCLC) in Amsterdam, The Netherlands (July 3, 2011).
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These authors equally contributed to this work.