Treatment-free remission (TFR) in patients (pts) with chronic myeloid leukemia in chronic phase (CML-CP) treated with frontline nilotinib: Results from the ENESTFreedom study.

7001Background: In prior clinical trials, ≈40-60% of pts with CML-CP and sustained deep molecular response (MR) maintained TFR after stopping long-term imatinib (median duration: ≈ 5-7 y). The single-arm phase 2 ENESTfreedom study (NCT01784068) is the first to specifically investigate TFR following frontline nilotinib. Methods: Pts with CML-CP with typical b2a2 or b3a2 BCR-ABL1 transcripts, ≥ 2 y of frontline nilotinib, and MR4.5 (BCR-ABL1IS ≤ 0.0032%) at prescreening were eligible. Upon enrollment, pts continued nilotinib for 1 y, with RQ-PCR assessments every 12 wk (consolidation [CONS] phase) at a central standardized laboratory. Pts with no assessment worse than MR4 (BCR-ABL1IS ≤ 0.01%), ≤ 2 assessments between MR4 and MR4.5, and MR4.5 in the last assessment of the CONS phase were eligible to stop treatment (TFR phase). Loss of major MR (MMR [BCR-ABL1IS≤ 0.1%]) triggered re-initiation of nilotinib (ReRx phase). The data cutoff for this analysis was 30 Nov 2015, when all pts who entered the TFR phase h...