Prognosis and outcome of relapsed acute lymphoblastic leukemia: a Hong Kong Pediatric Hematology and Oncology Study Group report.

Background: In 2000, the Hong Kong Pediatric Hematology Oncology Study Group started a new relapsed acute lymphoblastic leukemia (ALL) treatment protocol based on modified ALL-REZ BFM 96 protocol aiming at improving the treatment outcome in Chinese children.
Procedure: All patients in Hong Kong with first relapse of childhood ALL were included. Patients were stratified into four risk groups (S1, S2, S3, and S4) and the treatment consisted of intensive chemotherapy followed by allogeneic hematopoietic stem cell transplantation, if indicated.
Results: Fifty-six patients were recruited and median age at diagnosis of ALL was 4.6 (range, 0.3-17) years. The median time from initial diagnosis to relapse was 2.5 (range, 0.3-9.1) years and follow-up time was 2.7 (range, 0-9.9) years. Forty-nine patients (87.5%) achieved second complete remission (CR2). CR2 rates for S1, S2, S3, and S4 groups were 100%, 93%, 90%, and 67%, respectively. Five-year overall survival (OS) was 50.5 ± 6.9% and event-free survival (EFS) was 41.5 ± 7.1%. There was no significant difference in survival among S1, S2, and S3 groups but S4 patients performed significantly worse with 5-year OS and EFS of 8% and 0%, respectively.
Conclusion: Children with relapsed ALL of S1-S3 risk groups could be successfully treated with intensified treatment protocol. The S4 high risk group needs more innovative approach to improve treatment outcome.
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