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L. Buffoni
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P3.04 - Poster Session/ Biology, Pathology, and Molecular Testing (ID 235)
- Event: WCLC 2015
- Type: Poster
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
- Moderators:
- Coordinates: 9/09/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P3.04-015 - Immunohistochemistry With 3 ALK Antibodies and Thymidylate Synthase Evaluation of FISH-Positive ALK-Rearranged Lung Adenocarcinomas (ID 1430)
09:30 - 09:30 | Author(s): L. Buffoni
- Abstract
Background:
ALK-rearranged lung tumors represent approximately 2-7% of all Non-Small-Cell Lung Cancers (NSCLCs). Young age, never/light smoking habit, adenocarcinoma (ADK) histology and good response to chemotherapy with pemetrexed characterize ALK-positive patients (pts). Current treatment strategies in this molecular setting are based on ALK-kinase inhibition with small molecules including first (crizotinib/CZT) and second generation TKIs. The FDA-approved companion diagnostic test for CZT treatment is the Vysis break-apart FISH probe, but several works support the immunohistochemistry (IHC) as a sensitive and specific test. The European Medical Agency (EMA) recently approved CZT for second-line treatment of ALK-rearranged NSCLC as detected by "an accurate and validated ALK assay", thus endorsing IHC for eligibility purposes. Here, we retrospectively assessed ALK status in 28 pts with known FISH-positive ALK-rearranged NSCLC performing IHC with 3 different antibodies in order to assess their diagnostic accuracy as compared to the FISH assay. Moreover, we evaluated thymidylate synthase (TS) expression using real-time polymerase chain reaction (RT-PCR) given the conflicting literature data on pemetrexed sensitivity in those tumors. As a secondary end point we will compare molecular and clinical outcomes.
Methods:
FISH was performed with Vysis break-apart FISH probe. IHC was performed with 3 different antibodies: ALK1 (DAKO), 5A4 (Novocastra) and D5F3 (Ventana/Cell Signaling Technology). For ALK1 and 5A4 an IHC scoring value between 0+ and 3+ was used, as previously proposed, while a positive or negative score was used with D5F3 and Ventana KIT. TS gene expression was measured through Real Time PCR, TaqMan method.
Results:
28 specimens of ALK-rearranged ADK diagnosed between 2010 and 2013 from 7 different Italian Oncology Centres were evaluated. Pts median age at diagnosis was 55 (range: 25-78), 9 pts were female. 25/28 (89.3%) specimens were D5F3 positive. 13/28 (46.4%) had 5A4 3+ positivity, 12 (42.8%) showed 2+ positivity while the remaining 3 were negative. 3/28 specimens (10.7%) had ALK1 3+ score, 9 (32.1%) 2+, 13 (46.5%) 1+ and the remaining 3 (10.7%) were negative. Among the 3 FISH-positive and IHC-negative cases, 2 pts underwent CZT treatment, both progressing within 2 weeks and with low percentage of rearranged tumor cells at FISH testing (16-20%) When considering 3+ and 2+ scores as positive, 12 specimens (42.8%) resulted to be positive with all the 3 antibodies, while score 1+ was observed only with ALK1 in 13 (46.4%). Only 3 cases resulted strongly positive with all clones. TS gene expression median value on 25 cases was 6.27 (range 2,8-14-94). 65% of cases had low expression as compared to a population of ALK-negative lung ADK (personal data).
Conclusion:
IHC proved to be a reliable tool to diagnose ALK-rearranged lung tumors, especially with D5F3 and 5A4 antibodies. As the two IHC negative and FISH positive patients who received CZT didn’t respond to treatment, IHC should be used as screening tool or a confirmatory test in case of low-rearranged FISH-positive cases. TS expression appeared to be lower in ALK-positive lung tumors as compared to ALK-negative lung ADK. Further comparisons between clinical and molecular data are ongoing.
