Immunocytochemistry used to determine ALK status in lung cancer
ALK immunocytochemistry is highly accurate for detecting ALK-rearranged non-small cell lung cancer (NSCLC) on cytological specimens, according to newly published research. This test continues the trend of personalized medicine for lung cancer patients.
Personalized medicine in lung cancer relies on the identification and characterization of cancer biomarkers and the availability of accurate detection systems and therapies for those biomarkers. The standard procedure for detecting predictive anaplastic lymphoma kinase (ALK) rearrangements is fluorescence in situ hybridization (FISH), but FISH is both expensive and often challenging to interpret. Lung cancer is often diagnosed by cytology, which requires predictive molecular marker analyses on cytological specimens.
In the August issue of the Journal of Thoracic Oncology (2013; doi:10.1097/JTO.0b013e3182936ca9), researchers reported that 41 specimens with available ALK FISH results were retrospectively analyzed with the 5A4 monoclonal antibody on fully automated stained slides. The study population was enriched for consecutive ALK FISH-positive NSCLCs.
The negative controls were 18 consecutive ALK FISH-negative NSCLCs with wild-type epidermal growth factor receptor (EGFR) and KRAS. Because ALK rearrangements are practically mutually exclusive to other known driver mutations, nine consecutive NSCLCs with EGFR mutations were also analyzed by ALK FISH and included as negative controls.
The evaluation of the immunocytochemistry staining was blinded to the FISH results. When ALK immunocytochemistry was compared to ALK FISH, the sensitivity was 93.3%, the specificity was 96%, the positive predictive values were 93.3%, and the negative predictive values were 96%.
The research team, all from Switzerland, concluded that cytological NSCLC specimens are well suited for ALK rearrangement testing. Their technique of ALK immunocytochemistry with the 5A4 monoclonal antibody is feasible and highly accurate for detecting ALK-rearranged NSCLC on conventional cytological specimens and cellblock preparations. Also, it can be used for prescreening NSCLCs.