Combined Use of Assays Identifies Cancer Patient Response to Crizotinib

In screening of a large cohort for anaplastic lymphoma kinase (ALK) fusions through both fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) assays, researchers found many non-small cell lung cancer (NSCLC) patients who had negative and atypical FISH patterns accompanied with positive IHC results, who showed response to crizotinib treatment.

ALK gene rearrangements are found in 3-5% of patients with NSCLC. Identification of appropriate patient population with reliable detective methods is the key to use of targeted therapies. It is routine clinical practice to screen patients with adenocarcinoma NSCLC for ALK rearrangements due to the availability of ALK inhibitors and for their ability to provide remarkable benefit to patients. FISH has long been the gold standard used to screen patients for ALK rearrangements. However, IHC platforms that are used to detect overexpression of protein caused by ALK gene rearrangements have been found to be both highly sensitive and specific in determining ALK status in patients. Further, several studies have shown that patients with tumors that were ALK negative (ALK-) via FISH were ALK positive (ALK+) via IHC, and that those ALK+ patients showed response when treated with the ALK inhibitor crizotinib.

The discordant FISH and IHC phenomenon showed the need for further examination to identify the existence of unknown ALK fusion genes and led to the new study led by investigators at Chinese Academy of Medical Sciences and Peking Union Medical College (Beijing, China). Of the 3,128 cases screened, 2,991 cases were subjected to both FISH and IHC analysis. IHC was performed with the FDA-approved Ventana-D5F3 IHC assay. 14 cases with negative and atypical FISH demonstrated IHC positivity (11 cases were ALK- via FISH and ALK+ via IHC; 3 cases were atypical FISH patterns and ALK+ via IHC). These 14 cases were further investigated using targeted next-generation sequencing (NGS), which revealed that 8 cases housed EML4-ALKfusions, 2 cases revealed novel ALK fusion partners (BIRC6 and PICALM), 1 case had a novel translocation partner (CEBPζ), and 3 patients did not exhibit any type of ALK fusions. Among all 14 patients, 4 patients received crizotinib treatment and demonstrated partial responses at the end of follow-up.

The authors commented that, “The most valuable finding of our study was that patients with EML4-ALK fusion or other novel complicated rearrangements could test negative via FISH and positive via IHC and these patients could possibly benefit from ALK-targeted therapy. Based on these findings, combinational assay of FISH and IHC methods are highly recommended in routine pathological diagnosis and when negative and atypical FISH patterns are accompanied by positivity in IHC.”

The study, by Li W, Zhang J, et al, was published September 7, 2016, online ahead of print in the Journal of Thoracic Oncology.

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Chinese Academy of Medical Sciences and Peking Union Medical College