Imatinib mesylate selectively targets the causative BCR-ABL oncogene in CML. The results of the IRIS trial indicate that in patients with chronic phase CML treated with first line imatinib, achievement of a complete or partial cytogenetic response (CCyR or PCyR) at 12 months is associated with a significantly better progression free survival (PFS).~Second generation tyrosine kinase inhibitors such as nilotinib can overcome imatinib resistance because of greater potency to bind to BCR-ABL. Recent results indicate that, in patients with previously untreated chronic phase CML, nilotinib results in a faster and higher rate of CCyR or PCyR than imatinib. However, nilotinib use is associated with diet restriction and much higher financial cost. Hence, an appealing strategy is to achieve the high rate of CCyR with first line nilotinib and then to maintain this response with long term imatinib which is user friendly and cost-effective.~The primary objective is to test the ability of imatinib to maintain the cytogenetic response in patients who achieved CCyR or PCyR at 12 months with first line nilotinib. The secondary aims are to assess the effects of this strategy on molecular response, BCR-ABL mutations, and CML progenitors.
The results of the International Randomized Study of Interferon and STI571 (IRIS) trial indicate that in patients with chronic phase CML treated with first line imatinib, achievement of a complete or partial cytogenetic response (CCyR or PCyR) at 12 months is associated with a significantly better progression-free survival (PFS).~Second generation tyrosine kinase inhibitors such as nilotinib can overcome imatinib resistance because of greater potency to bind to BCR-ABL. Recent results indicate that, in patients with previously untreated chronic phase CML, nilotinib results in a faster and higher rate of CCyR or PCyR than imatinib. However, nilotinib use is associated with diet restriction and much higher financial cost.~The primary objective of this study is to evaluate the ability of imatinib to maintain a complete cytogenetic response (CcyR) in patients who achieved a CCyR after 12 months of first-line treatment with nilotinib.