BCR-ABL mutation testing to predict response to tyrosine kinase inhibitors in patients with chronic myeloid leukemia.

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML). Although randomized evidence demonstrates that imatinib (a commercially available TKI) prolongs event-free survival in patients with CML, some patients develop imatinib intolerance or resistance. In addition, imatinib is less effective in patients who have progressed to more advanced disease stages, such as accelerated phase and blastic phase CML. For these reasons, 2nd generation TKIs that can inhibit the BCR-ABL protein more effectively or target additional disease mechanisms have been developed. Two such drugs have also been approved for clinical use by the FDA, nilotinib and dasatinib. Resistance to TKI treatment is thought to be mediated through various mechanisms, the most common of which is BCR-ABL1 mutations. Testing for mutations in BCR-ABL1 may predict lack of response to imatinib or may inform the choice between alternative TKIs.