Nilotinib As Second-Line Therapy in Patients with Chronic Myeloid Leukemia in Chronic Phase: Thailand Experience

Background: Nilotinib, a second generation tyrosine kinase inhibitor, was proved to have high efficacy on treatment of Philadelphia chromosome positive CML patients who failed or were intolerant to imatinib. Limited data was available on its efficacy and safety in Asian population.

Methods: Chronic phase CML patients who have failure, suboptimal response or intolerance to imatinib according to ELN 2009 guideline were treated with nilotinib 400 mg twice daily on 7 centers in Thailand. Prospective data collection for 24 months was performed.

Results: There were 106 cases participated in this study, 2 cases with initial T315I mutation were excluded from the study, total 104 cases were analysed. The median age was 46 (16-79) years with a slight male predominance over female at the ratio of 1.4:1 respectively. Twenty five percent received imatinib less than 12 months whilst 20% received imatinib longer than 60 months. The median duration of the prior imatinib treatment was 18 months (2-142 months). Best response to imatinib treatment were major molecular response (MMR) 5.8%, complete cytogenetic response (CCyR) 26%, major cytogenetic response (MCyR) 12.5%, complete hematologic response (CHR) 47%, and no CHR 8.7%. The reasons for nilotinib switching were imatinib failure 65%, imatinib intolerance 28%, imatinib suboptimal response 7%. Sixty-eight percent were completed 24 months follow up. Of those, 32% early discontinued treatment mostly because of unsatisfactory results or adverse events. Two patients died of infection and CNS bleeding during the study period.

Evaluation were made every 3 months based on ELN 2009 criteria . Best response to nilotinib treatment included MMR 57%, CCyR 16%, MCyR 6%, CHR 16%, and no CHR 5%. At 3 months, 91%, 35%, and 14% of the patients CHR,CCyR, and MMR, respectively. Achieving CCyR or MMR at 3 months predicted a chance of achieving MMR (P= 0.00001) Those who did not achieve at least CHR at 3 months never achieved MMR, while 86 % of those who achieved CCyR at 3 months achieved MMR and 100% of those achieving MMR at 3 months had sustained MMR throughout the study period (24 months). Imatinib suboptimal response had significantly better outcome as compared to imatinib failure and imatinib intolerance group (P = 0.017). All of suboptimal response cases achieved CCyR , 86% achieved MMR, no early discontinue treatment in this group. While 75% of failure group achieved CCyR, 62% achieved MMR and 62% of intolerance group achieved CCyR, 38% achieved MMR. The reason for poorer response of intolerance group was high rate of early discontinue due to side effects, 17% vs 5% in the imatinib failure group.

Initial BCR-ABL mutation analysis was performed on 90 cases, mutations were found on 16 cases, 2 of them were T315I which were excluded from the study. The cases with mutation significantly had poorer response to treatment than those without mutation (P = 0.001). There was one case with initial G250E mutation, who developed T315I mutation after treatment with nilotinib. At 24 months, 1 case progressed to accelerated phase and 3 cases progressed to blastic transformation. The 2-year progression-free survival and 2-year overall survival was 96% and 98%, respectively.

Skin rash, musculoskeletal pain, and infection were the three most common non-hematologic adverse events found in 18%, 13%, and 6% of the patients, respectively; however, most of them were grade 1-2, except for 4 cases with grade 3-4 infections .Grade 3-4 hematologic adverse events included thrombocytopenia (12%), neutropenia (11%), anemia (5%), and leucopenia (4%); and most of them were manageable. Although biochemical abnormalities were commonly found, most of them were mild. Grade 3-4 events found were hypophosphatemia (6%), hyperglycemia (4%), and elevated serum lipase (4%). Only 10 cases (9%) permanently discontinued nilotinib due to its adverse effects.

Conclusions: Nilotinib, as a second line treatment for Thai patients with chronic phase CML showed excellent efficacy and tolerability. Indication for nilotinib treatment, initial mutation status and depth of response at 3 months after treatment can predict outcomes of the patients.

Author contact: KanchanaChansung M.D. Division of Hematology, Department of Medicine, Faculty of Medicine, Khonkaen University, Khonkaen, Thailand

e-mail: kchansung@gmail.com