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Importance of 6-mercaptopurine dose in lymphoblastic leukaemia
1Department of Haematology, Children's Hospital, Western Bank, Sheffield.
Insights
Increased 6-mercaptopurine dosage in UK children
Area of Science:
- Pediatric Oncology
- Hematology
- Clinical Pharmacology
Background:
- Acute lymphoblastic leukemia (ALL) is a common childhood cancer.
- Treatment protocols evolve to improve patient outcomes.
- Maintenance therapy, including 6-mercaptopurine, is crucial for ALL remission.
Purpose of the Study:
- To investigate if higher 6-mercaptopurine (6-MP) doses correlate with improved outcomes in UK children with ALL.
- To analyze prescribing patterns of 6-MP in relation to treatment protocols and patient characteristics.
Main Methods:
- Retrospective analysis of 85 children diagnosed with ALL between 1973 and 1987.
- Comparison of 6-MP dosage and relapse-free survival between children diagnosed before and after 1980.
- Analysis of sex-based differences in 6-MP prescription and tolerance.
Main Results:
- Children diagnosed after 1980 showed an 18% improvement in 5-year relapse-free survival.
- Median 6-MP dose increased by 22% in the later group, exceeding protocol recommendations (9%).
- Boys received significantly more 6-MP and experienced fewer dose reductions due to myelosuppression compared to girls.
Conclusions:
- Increased actual 6-MP administration, driven by prescribing guideline changes, likely contributed to improved ALL outcomes post-1980.
- Boys may tolerate 6-MP better than girls, potentially explaining sex-based prognostic differences.
- Findings support optimizing 6-MP dosing within evolving treatment protocols for childhood ALL.
Abstract:
To explore the possibility that higher total dosage of 'maintenance' treatment may have contributed to the recent improvement in outlook of children in the United Kingdom with lymphoblastic leukaemia, details of the amount of 6-mercaptopurine prescribed during the first two years of treatment were studied in an unselected cohort of children diagnosed between 1973 and 1987. Eighty five patients were studied, 30 diagnosed before and 55 after 1980. The group diagnosed after 1980 showed an 18% improvement in relapse free survival at five years. Their median total dose of 6-mercaptopurine had increased by 22%, whereas according to the protocol it should have risen by an average of only 9%. After 1980 boys were prescribed significantly more 6-mercaptopurine than girls, and had fewer dose reductions because of myelosuppression. These findings support the clinical impression that after 1980 an important therapeutic difference resulting from the new United Kingdom acute lymphoblastic leukaemia protocols was an increase in the amount of 6-mercaptopurine that children actually received as a result of changes in prescribing guidelines rather than dose. They also provide further evidence that boys tolerate 6-mercaptopurine better than girls, which may be related to the still unexplained difference in prognosis between the sexes.