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M.L. Dalurzo
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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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P3.04-002 - Correlation of ALK Status Between FISH and Immunohistochemistry in Lung Cancer: A Multicenter Study of 738 Cases in Argentina (ID 324)
09:30 - 09:30 | Author(s): M.L. Dalurzo
- Abstract
Background:
Anaplastic lymphoma receptor tyrosine kinase (ALK) gene rearrangements are infrequent alterations in lung cancer occurring in approximately 3-6% of non small cell lung carcinomas (NSCLC). ALK status is an important predictive factor in NSCLC, as ALK rearranged tumors have shown sensitivity to Crizotinib treatment. Even though FISH remains the gold standard for assessment of ALK status, it bears some disadvantages such as availability, need for trained personnel and difficult evaluation in some cases. Currently, this tool is the only approved diagnostic test by the FDA to detect ALK rearrangement. Detection of ALK protein by immunohistochemistry (IHC) is a much more affordable and widespread method. The use of new clones and highly sensitive methods have improved the sensitivity, specificity and predictive values of IHC in the assessment of ALK status.
Methods:
We compared ALK rearrangement in 738 consecutive cases from three Reference center’s surgical pathology laboratories (Hospital Italiano de Buenos Aires, Instituto de Oncología Angel H. Roffo and Hospital Alemán). They were evaluated by FISH and ultra sensitive IHC. FISH was performed on unstained 4 um formalin-fixed paraffin embedded tumor tissue sections using an ALK break-apart probe set (Vysis LSI ALK Dual Color, Break Apart Rearrangement Probe; Abbott Molecular) and paraffin pretreatment IV reagent kit (Vysis, Abbott Molecular). Assays were performed following the manufacturer’s instructions. Positive and negative controls were present in each run. Sections were analyzed by a trained observer under a fluorescence microscope, using appropriate filters. Cases were considered ALK-FISH positive if ≥15% tumor cells showed split red and green signals (separation of 2 diameters or more) and/or single red signals. IHC was performed on an automated Benchmark XT slide stainers, using Ventana anti-ALK D5F3 monoclonal antibody on previously deparaffinized 4um tissue sections. For detection, OptiView DAB IHC Detection Kit and OptiView amplification Kit (Ventana, AZ) was used. Positive and negative controls were present in each run. IHC staining results were interpreted as either negative (weak or no staining present) or positive (strong granular cytoplasmic staining in tumor cells).
Results:
Of 738 cases, 709 were FISH negative and 29 FISH positive (prevalence of ALK rearranged cases 3.92%). Of FISH negative cases, two cases had IHC positive results, and 29 out of 29 FISH positive cases were also IHC positive. For IHC testing, sensitivity was 100%, specificity was 99,71% with a positive predictive value of 93,54% and a negative predictive value of 100%.
Conclusion:
Our results show that IHC has a high sensitivity and specificity to detect ALK rearrangements. Discordant results were unusual, agreeing with the values reported in the literature. While several studies have shown good response to crizotinib in cases with negative FISH and positive IHC, larger studies are needed to validate this association. So far, international guidelines have accepted the use of properly validated IHC as a screening tool in assessing ALK status.
