Outcome of 472 Chronic Myeloid Leukemia Patients Treated with Frontline Nilotinib: A Gimema CML WP Analysis

BACKGROUND: In chronic phase (CP) chronic myeloid leukemia (CML) nilotinib showed better efficacy compared to imatinib. The higher rates of deep molecular response with nilotinib may translate in more patients (pts) eligible for treatment discontinuation. On the other hand, cardiovascular toxicity may limit nilotinib use in selected groups of pts (e.g. elderly pts).

AIM: To investigate the efficacy and safety, overall and according to age, of first-line treatment with nilotinib in CML pts.

METHODS: We analyzed response rates, events and outcome of 472 pts ≥ 18 y of age with CP CML, enrolled in clinical trials of the GIMEMA CML WP with nilotinib frontline. Pts were treated with: nilotinib 300 mg BID (n=276); nilotinib 400 mg BID (n=73); rotation of nilotinib 400 mg BID / imatinib 400 mg OD (3-month periods for each drug)(n=123). The median follow-up was 36 (3-82) months. Pts were further analyzed considering 3 age groups: 18-39 y (98 pts); 40-59 y (217 pts); and ≥ 60 y (157 pts). Definitions: Major molecular response (MR3): BCR-ABL≤0.1% (IS), with > 10.000 ABL copies; MR4: BCR-ABL≤0.01% (IS), with > 10.000 ABL copies. Events: permanent discontinuation of nilotinib for any reason, including adverse events, progression to accelerated/blast phase (AP/BP), or deaths. Arterial thrombotic events (ATEs): peripheral arterial obstructive disease, acute coronary syndrome, chronic ischemic heart disease, significant carotid stenosis and ischemic stroke, or other significant ischemic events.

RESULTS: Overall, the cumulative incidences of MR3 by 12, 24, and 36 months were 75, 88, and 93%, respectively. The cumulative incidences of MR4 by 12, 24, and 36 months were 38, 63, and 76%, respectively. Events leading to permanent nilotinib discontinuation occurred in 132 (27.9%) pts. ATEs occurred in 33 (7% of pts) ATEs, corresponding to 19.7 ATEs/1000 pt-y. Fifteen (3.1%) pts progressed to AP/BP. Overall, 23 (4.9%) pts died, 11 of them after progression to AP/BP. The estimated 5-year OS was 93%.

The sub-analysis according to age showed that: MR3 and MR4 rates were similar across the 3 age groups (cumulative incidences of MR4 by 24 months were 55, 62, and 70% in pts 18-39 y, 40-59 y, and ≥ 60 y, respectively; p=0.25). Progressions to AP/BP were: 6.1% in pts 18-39 y, 2.8% in pts 40-59 y, and 1.9% in pts ≥ 60 y. ATEs were: 0 in pts 18-39y, 4.1% (11.7/1000 pt-years) in pts 40-59 y, and 15.3% (41.3/1000 pt-years) in pts ≥ 60 y (no difference in ATEs was found between pts 60-69 y and those ≥ 70 y). The 5-y OS was 91, 97, and 89% in pts 18-39 y, 40-59 y, and ≥ 60 y, respectively (p=0.065). Death was always leukemia-related in pts 18-39 y (100%), while it was mainly leukemia-unrelated (75%) in pts ≥ 60 y.

SUMMARY/CONCLUSION: Nilotinib as first-line treatment of newly diagnosed CP CML pts showed high rates of deep molecular responses, few progressions to AP/BP, and a high OS. Deep molecular response were similar in all age groups; as expected, ATEs were more frequent in pts > 60 y. These data suggest that: in pts > 60 y, the high efficacy of nilotinib should be weighed against its potential toxicity; in pts < 60 years, nilotinib may be a very good choice, with high efficacy and low toxicity.