Epidemiology of EML4-ALK translocations in a small, German non-small-cell lung cancer patient cohort

Background: Fusions and translocations of the ALK gene are an important genetic marker in different types of cancer and are therapy relevant, especially in lung cancer, as they predict the patient's response to crizotinib therapy. Thereby, EML4-ALK is assumed to be the most frequent fusion of ALK in lung cancer, although ALK is known to be able to fuse with approximately 20 different genes. Patients & methods: Formalin-fixed paraffin-embedded lung tissue from non-small-cell lung cancer patients previously tested positive for EML4-ALK were reanalyzed with three different FISH probe systems that are commercially available. Results: We describe a short series of patients with ALK translocations in which a surprisingly high percentage (66%) of non-EML4-ALK fusions were identified in non-small-cell lung cancer despite an estimated low percentage (similar to 20%) of such translocations. Conclusion: Depending on the diagnostic method used, those patients could receive a false-negative diagnosis and would miss the chance to benefit from novel crizotinib therapy