Long-Term Outcome of Chronic Phase Chronic Myeloid Leukemia Patients Treated with Nilotinib Front-Line

Nilotinib (NIL) 600 mg daily has demonstrated its superiority over Imatinib 400 mg daily in terms of response and incidence of deep molecular response in the front-line chronic phase (CP) CML setting. In this observational study we have retrospectively analyzed the outcome of in- and out-study 202 patients (pts) treated in this setting with NIL 600 mg front-line, in "real-life" conditions.

All pts with newly diagnosed adult CP-CML receiving NIL 300 mg BID alone front-line between 10/2007 and 06/2020, were eligible for this study. Data were retrospectively collected according to the current French regulations with pts' information. All pts were assessed and followed according to ELN recommendations 2003, 2006, and 2009 along treatment and to the recommendations from the French group of CML (D. Rea et al., Cancer 2018) in case of TFR. In this regard, a TKI was resumed if loss of MMR. All BCR-ABL1 assessments were performed in the 3 reference laboratories, standardised and expressed in % (IS) with ≥32,000 copies of ABL1 as control. The primary endpoints were the rate of molecular responses in the long-term and the (vascular) safety of Nilotinib. Secondary endpoints were the kinetics of molecular response, survival and safety of Nilotinib. Survival (OS, PFS & EFS) was defined according to ELN (J. Guilhot et al. Blood 2012).

Two hundred and two patients were reported with 44% females and 56% males with a median age at diagnosis of 50.4 (17.5-83) years, and 26% of them had cardiovascular risk factors at onset (tobacco abuse 11%, hypercholesterolemia 9.3%, diabetes 1.45%, none with past history of cardiovascular events [CVE]). ELTS scores were high in 14%, intermediate in 31% and low in 55% of pts. Twenty-four (12%) pts harboured additional chromosomal abnormalities at diagnosis. The median follow-up after NIL initiation was 61.5 (1-147.5) months. At last follow-up 113 pts (55%) are not on NIL anymore for toxicities, TFR or resistance reasons. Twenty-eight (14%) pts present an arterial event on NIL (18% PAOD, 14% angina pectoralis, 7% myocardial infarction, 14% stroke, 47% others such as atrial fibrillation, cardiomyopathy...), that occurred after a median of 26 (0.6-98.5) months on NIL. Forty-six (22.5%) pts reached TFR criteria and stopped NIL after a median of 58.5 (27-126) months. The cumulative incidence (CI) rates of MMR at 1, 2 and 5 years were 64 (57-71)%, 79.4 (75.45-83.35)% and 95 (92-98.5)% respectively. For MR4, those were 35.5 (29-42)%, 60 (52-67)% and 82 (74.5-89)% respectively; and for MR4.5, were 14 (9-19)%, 31 (24-28)% and 62 (54-70.5)% respectively. The CI of sustained MR4.5 (i. e. patients eligible for TFR: MR4.5 ≥2 years) was observed in 30 (23-37)% at 3 years, 45.5 (36-55)% at 5 years and 52.5 (41.5-64)% at 6 years (Figure).

The CI of patients entering TFR was 16.75 (10.5-23)% at 5 years and 51.94 (37.31-66.57)% at 10 years with a survival without MMR loss of 70.7 (58- 86)% at 1 year and 65.26 (50.6-84)% at 5 years. Nine (4.5%) pts progressed towards accelerated phase (4 pts) or BC (2 lymphoid, 3 myeloid) responsible for 5 deaths at latest follow-up. Among NIL resistant patients screened, 15 were harbouring ABL1 mutations (5 Y253H, 3 E255K, 3 T315I, 1 M244V, 1 G250E, 1 F359V, 1 V299L). Overall, 10 patients died (5 from CML, 5 from unrelated causes). The probability of OS was 95.75 [95%CI: 92.9-98.7]% at 2 years and 94.8 [91.5-98.3]% at 5 years, for PFS it was 94.92 [91.7-98.2]% at 2 years and 89.5 [84.7-94.6]% at 5 years, and EFS it was 78 [72.3-84]% at 2 years and 60.25 [53.3-68.1]% at 5 years. Regarding sustained MR4.5, univariate analysis showed that female gender (HR=2.46 [1.50-4.02], p<0.001) and low ELTS (HR=0.41 [0.22-0.76], p<0.004) had a significant impact, while multivariate analysis confirmed the role of these 2 factors (HR=2.31 [1.41- 3.79], p=0.001 and HR= 0.52 [0.30- 0.90], p=0.02) in addition to high ELTS (HR= 0.28 [0.14- 0.58], p<0.001). Univariate and multivariate analyses demonstrated that only age impacted on the CI of CVE (HR= 1.07 [1.04-1.10], p<0.001, and HR=1.07 [1.04-1.10], p<0.001).

NIL first-line efficiently limits progression of newly diagnosed CP-CML patients and provides high rates of sustained MR4.5, allowing TFR in a substantial proportion of pts. However, the onset of arterial occlusive events, especially in the elderly is a matter of concern in the choice of this compound at treatment initiation.

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