Treatment Intensification of Traditional BFM Therapy with 3 Chemotherapy Blocks and Double Delayed Intensification (Protocol II) Improves Outcome in Infants with High Risk (HR) Acute Lymphoblastic Leukemia (ALL): Results of Two Consecutive AIEOP Studies.

Introduction: Cure rates of ALL in children aged less than one year (i.e. infants) at diagnosis are in the range of 35–40%. Encouraging results have been recently reported in infants by using intensified treatment, including high dose chemotherapy, with or without allogeneic hematopoietic stem cell transplantation (HSCT) in first complete remission (CR).

Aim: To evaluate the impact of the two treatment strategies adopted in the AIEOP ALL 91 and 95 studies on the outcome of ALL in infants.

Patients and Methods: Fifty-two infants with ALL were enrolled between 1991 and 1999 in two consecutive studies, named AIEOP ALL 91 and ALL 95. Infants with an identified t(4;11) translocation had to be included in the high risk (HR) groups whilst those without this genetic abnormality could be treated in the intermediate (IR) or HR groups according to presenting features and treatment response. Patients belonging to the IR groups received a traditional BFM back-bone based treatment (protocols I, M and II), while those classified in the HR groups underwent an tensified treatment including induction (BFM protocol IA only, in study AIEOP ALL 91, and IA+IB in study ALL 95), consolidation with either 9 blocks of non-cross-resistant drugs (ALL 91) or 3 blocks followed by the 8-drug reinduction regimen - BFM protocol II - repeated twice (ALL 95). All patients were given a continuation phase (reinforced in HR patients of study ALL 95 by vincristine/prednisone pulses). Overall treatment duration was 2 years in both studies.

Results: Infants in studies ALL 91 (n=21) and ALL 95 (n=31) had similar biological and clinical characteristics. The overall event-free survival (EFS) at 5 years was 45.0% (SE 7.0%). The EFS, after censoring for HSCT in 1^st CR, was 38.1% (SE 11.4%) in ALL 91 and 51.6% (SE 9.9%) in ALL 95 (p-value=0.29). Patients treated in the IR arm of the two studies had a similar outcome. Better results were obtained in patients treated in the HR arm of ALL 95 study, where 9/17 chemotherapy-only patients and 3/4 HSCT patients are alive in CCR as compared to 1/7 and 0/2, respectively, in patients treated in the ALL 91 study.

Discussion: These data show that full traditional BFM therapy intensified by 3 post-induction chemotherapy blocks and double protocol II (adopted in study ALL 95), is associated with a better outcome in infants with HR ALL.