Immunohistochemistry May Not Be a Reliable Screening Tool for Identification of ALK Rearrangement (ALKR) in Non-Small Cell Lung Carcinoma (NSCLC)
Chris MJ Conklin, Kenneth J Craddock, Cherry Have, Ming Tsao, Christian Couture, Diana N Ionescu. University of British Columbia, Vancouver, BC, Canada; University Health Network, Toronto General Hospital, Toronto, ON, Canada; IUCPQ (Hôpital Laval), Quebec City, QC, Canada; BC Cancer Agency, Vancouver, BC, Canada
Background: The discovery of EML4-ALK fusion gene in patients with NSCLC was a breakthrough in targeted therapy for lung cancer with significant clinical implications. ALKR is however only seen in a small percentage of NSCLC making identification of these patients challenging and costly.
Design: Using immunohistochemistry (IHC) with mouse monoclonal 5A4 antibody (Ab) from Nikirei Biosciences and fluorescence in situ hybridization (FISH) we screened a tissue microarray built from 593 resected surgical specimens from stage I NSCLC (243 lung adenocarcinoma (ACA), 272 squamous cell carcinoma (SQC), 35 large cell carcinoma, 32 non-small cell carcinoma NOS, and 6 other). IHC was scored as 0 (no staining), 1+ (faint cytoplasmic staining), 2+ (moderate, smooth cytoplasmic staining) and 3+ (intense, granular cytoplasmic staining) in >10% of tumor cells. IHC positive cases were 3+ only. Suspicious and positive cases were confirmed by IHC and FISH on whole section (WS).
Results: Results by FISH were available on 273 cases and by IHC on 385 cases. A total of 11 cases, either positive (N=2) or suspicious (N=9) by at least one methodology, were identified. Cases suspicious by FISH (N=5) were however not suspicious by IHC and cases suspicious by IHC (N=4) were not suspicious by FISH. One case was positive on TMA as well as on WS by IHC and FISH. The only other unequivocally positive FISH case, with an atypical pattern (loss of 5' ALK signal), was not positive or suspicious by IHC. The average age of our 5 males and 5 females was 63 years. There were 4 ACA, 5 SQC and 1 NSCLC NOS, and 3 of all were positive for TTF1.
Conclusions: IHC screening for ALKR in NSCLC with 5A4 antibody may not necessarily identify all cases with gene rearrangement by FISH. As small biopsy/cytology samples are inherently limited for molecular testing the question of finding the best strategy to identify ALKR as well as other clinically relevant molecular anomalies is critical, both in terms of time and cost. These results are currently in the process of being compared to other primary antibody clones (ALK-1 by Dako, 5A4 by Novocastra and D5F3 by Cell Signaling Technology) and revelation systems (FLEX by Dako, CSA II by Dako and ADVANCE by Dako).
Monday, March 19, 2012 9:30 AM
Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 297, Monday Morning