Outcome of children with acute myeloid leukaemia (AML) experiencing primary induction failure in the AIEOP AML 2002/01 clinical trial

Paediatric patients with acute myeloid leukaemia (AML) who fail induction due to primary resistance to chemotherapy account for a significant proportion of cases and have a particularly dismal prognosis. We report the clinical and biological data, and final outcome of 48 paediatric patients with primary-resistant AML enrolled in the Associazione Italiana di Ematologia e Oncologia Pediatrica AML 2002/01 clinical trial. These patients had a significantly higher white blood cell count at diagnosis compared to other AML patients. Cytogenetic and molecular features did not differ between patients with primary induction failure and patients allocated to the high-risk group. For the whole patient population, the probability ofoverall survival, event-free survival (EFS) and disease-free survival (DFS)was 21.8%+/- 6.2, 20.4%+/- 5.9, and 49.5%+/- 11.3, respectively. Twenty-eight (58%) patients received haematopoietic stem cell transplantation (HSCT); 3 were autologous and 25 were allogeneic. Patients who underwent HSCT had improved EFS (31.2% vs. 5%, P<0.0001). Only one of the20 patients who did not receive HSCT is alive and disease free. The 19 patients in complete remission at time of HSCT showed significantly betterDFS than the 9 with active disease (46% vs. 0%, P=0.02). This study represents one of the largest series with long-term follow up of paediatric AML patients with primary refractory disease. Children who underwent transplantation had an encouraging long-term outcome. Disease recurrence remains the major cause of treatment failure; a better understanding of the disease biology is desirable to develop more effective treatment strategies.