 Current available data showed that 40 of CML patients with prior stable MR4.5 for 2 years or more will be able to stay imatinib-free for at least 2 years. About 13 of patients without confirmed molecular relapse by the study criteria have low persistent BCR-ABL1 but remain imatinib-free for median follow-up of 22 months range 6 - 35. A few patients with confirmed molecular relapse by study criteria remained drug free on follow-up. This postulates a component of immunity suppressing the leukemic clone. 