A Pediatric Treatment of Ph-Negative Acute Lymphoblastic Leukemia (ALL) Is Effective and Safe In Adolescents and Young Adults (AYAs) until 29 Years of Age
Authors: Cluzeau Thomas , Dhedin Nathalie , Huguet Françoise , Raffoux Emmanuel , Maury Sebastien , Lamy Thierry , Mannone Lionel , Guillerm Gaelle , Delannoy Andre , Turlure Pascal , Vey Norbert , Baruchel André , Dombret Herve , Boissel Nicolas 
Published: October 2019

Abstract
Abstract 2125

Background:
Over the last three decades, progress in the treatment of childhood acute lymphoblastic leukemia (ALL) has considerably improved the outcome of children, leading to 5-year OS of more than 80%. Numerous comparisons, including the French LALA/FRALLE (Boissel et al. JCO 2001), have reported a better outcome in teenagers treated with pediatric as compared to standard historical adult ALL protocols. Even if modern pediatric-inspired adult ALL protocols have recently reported impressive improvements, especially in younger patients (Huguet et al. JCO 2009), the issue of whether younger adults (YAs) should be treated according to pediatric or adult protocols remains an open one. The aim of this study was first to evaluate the feasibility and the results of a non-modified pediatric protocol (the French FRALLE 2000) in adolescents and younger adults (AYAs, aged 15–29 years) treated in adult departments.

Methods:
From February 2001 to June 2010, 72 AYAs with Ph-negative ALL were treated according to the pediatric FRALLE 2000-BT protocol in 12 adult hematology units in France and Belgium. After a prednisone prephase and a four-drug induction (prednisone, daunorubicin, vincristine and L-asparaginase), patients in CR received a consolidation, a 1st delayed intensification, an interphase, a 2nd delayed intensification, and a maintenance chemotherapy during two years.

Results:
The median age was 19 years (range, 15–29 years). The cohort was separated in 2 subgroups: 44 adolescents aged 15–19 years and 28 young adults (YAs) aged 20–29 years. There were no significant differences between the adolescent and the YA populations in term of sex ratio, white blood cell count (WBC), central nervous system involvement, and phenotype (BCP- vs T-ALL). As expected, few recurrent cytogenetical abnormalities were identified in this population and did not differed between both subgroups. In the adolescent group, we identified 2 patients with t(4;11), 1 patient with t(1;19), and 3 patients with hypodiploïdy and/or neartriploïdy, whereas this repartition was 2/2/1 in YAs. Rates of good early response to prednisone were in 68% in adolescents and 61% in YAs (p=.52), while rates of good early response to chemotherapy were 80% and 86%, respectively (p=.51). No patient died during induction. Complete remission (CR) rate did not differ between subgroups (98% vs 100%, p=.42). With a median follow up of 4.8 years, 5-year EFS was 57% (41% in adolescents vs 79% in YAs, p=.03) and 5-year OS was 67% (56% and 82% respectively, p=.09). In patients with BCP-ALL, 5-year EFS was 60% (43% in adolescents vs 91% in YAs, p=.02) and 55% in T-ALL (57% vs 50% respectively, p=.81). Twelve patients (17%) received an allogeneic stem cell transplantation (SCT) in first CR (5 adolescents and 7 YAs). Four patients died in first CR, all after SCT, (2 adolescents and 2 YAs). In univariate analysis, a high WBC (continuous variable, p=.02) and a poor early response to chemotherapy (33% vs 63%, p=.02), but not phenotype or poor early response to prednisone, were significantly associated with a shorter EFS. In multivariate analysis, age (adolescents vs YA, p=.04), WBC (continuous variable, p=.0005), and poor early response to chemotherapy (p=.006) had still an impact on EFS. The poor outcome of adolescents compared to YAs, also observed in the French adult GRAALL protocol (not published), was not explained by differences in ALL characteristics, early response to therapy, or treatment-related toxicity.

Conclusion:
The pediatric protocol FRALLE 2000 is effective and safe for the treatment of selected AYAs with Ph-negative ALL referred to adult departments. The results observed in the YA population are promising, warranting prospective comparisons with the more recent pediatric-inspired adult protocols. The unexpected poorer outcome of adolescents deserves further investigations to explore a potential impact of the quality of care delivered in an adult environment.

Disclosures:
No relevant conflicts of interest to declare.