Intermediate dose of imatinib in combination with chemotherapy followed by allogeneic stem cell transplantation improves early outcome in paediatric Philadelphia chromosome-positive acute lymphoblastic leukaemia (ALL): results of the Spanish Cooperative Group SHOP studies ALL-94, ALL-99 and ALL-2005

Summary Philadelphia-chromosome acute lymphoblastic leukaemia (Ph+ ALL) is a subgroup of ALL with very high risk of treatment failure. We report here the results of the Sociedad Espanola de Hematologia y Oncologia Pediatricas (SEHOP/SHOP) in paediatric Ph+ ALL treated with intermediate-dose imatinib concurrent with intensive chemotherapy. The toxicities and outcome of these patients were compared with historical controls not receiving imatinib. Patients with Ph+ ALL aged 1–18 years were enrolled in three consecutive ALL/SHOP trials (SHOP-94/SHOP-99/SHOP-2005). In the SHOP-2005 trial, imatinib (260 mg/m2 per day) was given on day-15 of induction. Allogeneic haematopoietic stem-cell transplantation (HSCT) from a matched related or unrelated donor was scheduled in first complete remission (CR1). Forty-three patients were evaluable (22 boys, median age 6·8 years, range, 1·2–15). Sixteen received imatinib whereas 27 received similar chemotherapy without imatinib. Seventeen of 27 and 15 of 16 patients in the non-imatinib and imatinib cohort, respectively, underwent HSCT in CR1. With a median follow-up of 109 and 39 months for the non-imatinib and imatinib cohorts, the 3-year event-free survival (EFS) was 29·6% and 78·7%, respectively (P = 0·01). These results show that, compared to historical controls, intermediate dose of imatinib given concomitantly with chemotherapy and followed by allogeneic HSCT markedly improved early EFS in paediatric Ph+ ALL.