Analysis of 48 Cases Pediatric Chronic Myeloid Leukemia from China: Results from a Single Institute in China

Objective: Chronic myeloid leukemia (CML) is a rare disease among children. It comprises 3% of childhood leukemias. CML in children is different from CML in adult. Here we analyzed the clinical features and prognosis of pediatric CML in a single institute from China.

Methods: A retrospective study was performed by reviewing clinical records of pediatric CML from 2002 to 2019.

Results: A total of 48 pediatric CML cases were included in the study, with 35 males and 13 females (M: F=2.7:1). Four cases were diagnosed during 2002~2007, 12 cases during 2008~2013 and 32 cases during 2014~2019. Two (4.2%) patients were in accelerate phase (AP) and other 46 patients were in chronic phase (CP) at diagnosis. Median age of onset was 9y (range 1~17y). The most common symptoms were fever (21.6%), fatigue (14.9%) and cough (10.8%). Median size of spleen under left costal margin was 5cm (range 0~21cm). Median WBC count was 15.7/ul, hemoglobin 9.5g/dL, platelet count 58/ul, neutrophils percentage 56% (range 21~74%), basophils percentage 3% (range 1~16%) and median eosinophil percentage was 2% (range 0~19%). Thirty-five patients had done karyotype examination, and 28 cases (80%) with classical Philadelphia chromosome (Ph+). Other 13 patients without Ph chromosome but with BCR/ABL1 fusion gene. In our study, there were 4 patients treated by hydroxyurea and α-interferon, other 44 patients have been used imatinib (IM) 240-340mg/m² per day. Median time from onset to diagnosis was 0.7 months (range 1 day~12 months). Median follow-up time was 52 months (range 1~200 months), while the 5-year overall survival (OS) and event-free survival (EFS) are 100% and 89.1%, respectively. Different gender, age at diagnosis, WBC count, platelet count, karyotype show no difference in OS and EFS. Four patients suffered from blast crisis (BC) (2 patients progressed after using hydroxyurea for 1 and 33 months, 2 patients progressed after using IM for 36 and 6 months, respectively). One patient's BCR/ABL1 transcript level was increased in 36 months after first administration of IM and recovered at 48 months by adding IM dosage from 200mg to 300mg per day. According to the European LeukemiaNet (ELN) criteria, 95.5% patients achieved complete hematologic response (CHR), 90.5% patients achieved complete cytogenetic response (CCyR) and 66.7% patients achieved major molecular response (MMR) at 3, 12, 18 months after IM administration, respectively. There was obvious correlation between WBC count at diagnosis and early molecular response (EMR). Median WBC count was 4.8/ul in patients with EMR and 38.1/ul in patients without EMR. Other clinical features, such as gender, age at diagnosis, hemoglobin count, platelet count and size of spleen, make no difference in EMR.

Conclusion: This is a retrospective study on pediatric CML. The median age at diagnosis is 9 years old. Most of all patients are CML-CP. 5y OS and EFS are 100% and 89.1%. The CHR, CCyR, MMR at 3,12,18 months after IM therapy are 95.5%, 90.5% and 66.7% separately. Until now there is no sufficient data on efficiency and safety specific to pediatric CML patients. Further clinical investigations through international collaboration are need to help more and more patients to achieve treatment-free remission.