Treatment Outcome of Children over 10 Years and Young Adults with ALL in Sweden: A Comparison between Paediatric- and Adult Protocols.

On behalf of the Swedish Adult ALL Group and the Swedish Childhood Leukemia Group. Several recent studies have shown superior outcome for older teenagers and young adults with acute lymphoblastic leukemia (ALL) treated in pediatric oncology departments compared with adult hematology departments. However, some of these comparisons have been hampered by either biased risk-group stratification (adult protocols considering young adults as lower risk and pediatric protocols considering the same age-group as high-risk), or a markedly higher treatment-related mortality for the adult treatment. During the 1990s in Sweden, adolescents with ALL were treated in a pediatric oncology unit or in an adult haematological unit, depending on the initial referral. For both groups there were well established national (and for children Nordic) treatment protocols designed by the Swedish Adult ALL Group and the Nordic Society of Pediatric Haematology and Oncology (NOPHO), but with different treatment strategies. In the NOPHO protocol, the teenagers were excluded from the lowest risk-group, but were only treated as high-risk if additional risk-factors were present, whereas age was not a risk-factor in the adult protocol.

The clinical characteristics, treatment and outcome for patients with ALL aged 10–40 years treated either according to the NOPHO protocol NOPHO ALL-92 (1992–2000), or the Swedish Adult ALL Group protocol 1994–2000, were reviewed. The impact of these treatment protocols on remission rate and survival was analysed. In total, 243 patients with B-precursor and T-cell ALL were treated according to the protocols. There was a significant difference in remission rate between the pediatric protocol (99%, n=144) and the adult protocol (90%, n=99) (p<0,01). Furthermore, the event-free survival (EFS) was superior for patients treated according the pediatric protocol compared to patients treated according to the adult protocol (p<0.01). Both protocols included response to induction treatment in the treatment stratification, but the difference in outcome was significant also when only pre-treatment risk-criteria, not including initial treatment response, were considered. Patients aged 15–25 had a superior outcome compared to patients aged 26–40 within the adult protocol group (p=0.01). Both protocols had treatment related mortality rates well below 5%. Treatment protocol was identified as an independent risk-factor in multiple regression analyses and was the only independent predictor of outcome in the 15–20 year age group. The results indicate that adolescents may benefit from treatment according to the pediatric protocol. Future trials are called for to determine whether young adults could benefit from similar treatment.