Five-Year Outcome of 215 Newly Diagnosed Chronic Myeloid Leukemia Patients Treated Frontline with Nilotinib-Based Regimens: A Gimema CML Working Party Analysis

Background. Nilotinib (NIL) is a potent and selective BCR-ABL inhibitor approved for the frontline treatment of chronic myeloid leukemia (CML) based on the results of the ENESTnd study. The sustained superiority of NIL vs. imatinib (IM) was confirmed after 5 years of follow-up (Hughes et al, abs. 677, EHA 2014). However, few data are available on patients (pts) treated frontline with NIL outside of Company-initiated trials.

Objectives. To analyze the long-term outcome in a large, independent cohort of newly diagnosed CML pts treated frontline with NIL-based regimens.

Methods. We analyzed 215 pts, enrolled in 2 multicenter phase II studies conducted by the GIMEMA CML WP (ClinicalTrials.gov. NCT00481052 and NCT00769327) or treated at the Bologna University Hospital, with NIL 300 mg or 400 mg BID as initial treatment; 123 pts received a sequential treatment with NIL and IM (NIL-IM), with a 3-months (mos) rotation period (all patients received NIL in the first 3 mos). The median age was 53 years (range 18–86). Ten out of 215 pts (5%) had a high EUTOS score. The median follow-up was 57 mos (range 36–81 mos). We assessed: the rates of Complete Cytogenetic Response (CCyR) and Major Molecular Response (MMR); the rates of optimal responders at each milestone according to ELN 2013 recommendations; the overall survival (OS; any death included), progression-free survival (PFS; progression to accelerated/blast phase [AP/BP] and deaths for any cause), failure-free survival (FFS; failures according to ELN 2013 recommendations and deaths for any cause), and event-free survival (EFS; events: failures, permanent discontinuation of NIL for any cause, including deaths). All analysis was made according to the intention-to-treat principle.

Results. The cumulative rates of CCyR and MMR were 93% and 88%, respectively. At 3 mos, 82% of the pts were in Partial Cytogenetic Response and 90% had a BCR-ABL/ABL (IS) < 10%; at 6 mos, 86% were in CCyR and 83% had a BCR-ABL/ABL (IS) < 1%; at 12 mos, 72% were in MMR; all these pts were optimal responders according to ELN 2013 recommendations. Overall, 80 (37%) pts permanently discontinued NIL: 45 (21%) for adverse events or intolerance; 25 (12%) for failures; 7 (3%) while in stable MR⁴; 3 (1%) for other reasons. Cardiovascular adverse events (CVAE) were cause of permanent NIL discontinuation, after a median time of 37 mos, in 13 (6%) pts, and included 4 peripheral arterial occlusive diseases and 3 ischemic coronary diseases; only one pt died for CVAE. Nine (4.1%) pts progressed to AP/BP, 8/9 during the 1st year of therapy and one after 25 mos; all pts subsequently died (after a median of 13 mos, range 1-34 mos). NIL-resistant mutations were identified in 6 of these pts (4 T315I; 1 Y253H; 1 F359V); 7/9 progressions occurred in patients receiving NIL-IM. In addition, 6 pts were classified as failures at 3,6, or 12 mos according to ELN 2013 recommendations; afterwards, 10 pts developed a secondary resistance (3 loss of CHR, 3 loss of CCyR, and 4 confirmed loss of MMR). Overall, 17 (8%) pts died, in 7 cases for reasons unrelated to CML progression. The estimated 6-year OS, PFS, FFS, and EFS were 91%, 91%, 83%, and 59%, respectively.

Conclusions. Our National experience showed that most pts treated frontline with NIL-based regimens were optimal responders according to ELN recommendations and that 91% of the patients were estimated to be alive and progression-free at 6 years. In particular, NIL alone was highly effective in the prevention of AP/BP. Considering that AP/BP had in most cases an early onset and an extremely poor prognosis, its prevention should be the priority of CML treatment, especially in the firsts 2-3 years. However, afterwards, the relatively high number of CVAE observed, suggests to focus, at least in selected patients, on strategies aimed at the prevention of CVAE (NIL dose reduction? switch to IM?).

Acknowledgments. European LeukemiaNet, COFIN, Bologna University, BolognAIL