Impact of Early Switching to Nilotinib As Second Line TKI in Patients with Chronic Myeloid Leukemia Who Were Intolerant to, Suboptimal to and Failed Imatinib: The Thai Multi-Centered Study

Introduction: To date, the ELN recommendation and NCCN guidelines are the principle mile stones to follow up the treatment response and to make the decision of TKIs switching. However, in real life practice, many factors influence changing the real switching date from the date had an indication. This study aims to analyze the impact of early switching to second line TKI, nilotinib, in real life practice, for the CML patients who failed, had sub-optimal response or were intolerant to imatinib. Methods: This prospective study was conducted through 7 medical centers in Thailand between 1st of September 2009 and 31st of August 2011. Adult CML patients of age ≥ 18 years old, in chronic and accelerated phase, who had failure, suboptimal response or intolerance to imatinib, based on ELN 2009 guideline, were included and were eligible with nilotinib 400 mg twice daily. Prospective data collection for 24 months of each patient was performed. The main objective was to identify the impact of early switching to nilotinib on major molecular response (MMR). The other objectives were to observe the efficacy of nilotinib including overall survival, progression free survival and the safety. The survival results were presented as Kaplan-Meier survival curves. For the comparison of the treatment groups, the Kaplan-Meier estimator with the corresponding log-rank test for equality of survivor functions across treatment group was applied. Results: The final 108 cases were analysed. The median age was 47 (17-79) years with the proportion of male to female of 1.4:1 respectively. The median duration of the prior imatinib treatment was 18 months (2-142 months). The median duration between the date of indication and the date of real switching was 3.1 months (0-62.8 months) with 50% changing less than 3 months, 26.9% between 3 months and 12 months, and 23.1% changing longer than 12 months. The indication of switching included 63.6% failure to imatinib, 29% intolerance to imatinib and 7.4% suboptimal to imatinib. On the nilotinib switching, 70.4% completed 24 months follow-up, and 29.6% discontinued treatment mostly because of unsatisfactory results or adverse events. Evaluation was made every 3 months based on 2009 ELN recommendation. At 3 months, 57%, 20%, and 8% of the patients achieved CHR, CCyR and MMR, respectively. Those who did not achieve CHR at 3 months never achieved MMR, while 86 % of those who achieved CCyR at 3 months achieved MMR. All CML achieving MMR at 3 months had s