The clinical and molecular data were examined to identify patients with known mechanisms of resistance and/or documented imatinib interruption or discontinuation. Of the 584 patients available for investigation, 539 achieved a substantial reduction of BCR-ABL1 during imatinib therapy (< 10% IS) and were further assessed. Among these 539 patients, those who relapsed directly into BC and/or had an emergent BCR-ABL1 mutation, discontinued imatinib after sustained CMR or had a documented dose interruption were identified. Among these patients, doubling times were calculated for those with a BCR-ABL1 rise. The number of patients with a rise is indicated for each group.