Fusion variants of the ALK gene — the key to modern therapy for patients with ALK-positive non-small-cell lung cancer

Since the discovery of the echinoderm microtubule-associated protein-like 4-anaplastic lymphoma kinase ( EML4 - ALK ) fusion in non-small-cell lung cancer (NSCLC), followed by the identification of many different fusion variants, molecularly targeted therapy has revolutionized treatment for patients with ALK-positive lung cancer. Recent research has focused on understanding how specific variants may influence the biological and molecular behavior of cancer cells and how this knowledge can be used in routine clinical practice. This article explores the current understanding of EML4 - ALK variants and highlights unanswered questions in the field.