Background: In childhood acute lymphoblastic leukemia (ALL), the relationship between lymphoblast L1/L2 morphology and prognosis is controversial. According to some studies L2 morphology is associated with poor prognosis, whereas in others the association disappears after adjustment for other known risk factors.
Procedure: We investigated the prognostic importance of lymphoblast L1/L2 morphology in childhood ALL treated with current Nordic ALL protocols in Finland. From the routine bone marrow (BM) aspirate and biopsy slides of 251 children with ALL diagnosed in 1990-1995, the blast cell morphology and early treatment responses were assessed blindly in a central review, using French-American-British (FAB) criteria with the Children's Cancer Group (CCG) modification.
Results: L1 morphology (>90% L1) was found in 197 (80%) children and L2 (>/=10% L2) in 49 (20%). Early treatment response was poorer in L2 than in L1: >5% blasts in the marrow on day 15 were seen in 27% of L2 as opposed to 12% of L1 (P = 0.048). The 6-year event-free survival (EFS) in the study population was 75%, 76% in L1 and 70% in L2 (P = 0.34). In the group with white blood cell count (WBC) below 50 x 10(9)/liter at diagnosis, the L2 morphology was associated with inferior survival: 6-year EFS 74% in L2 and 84% in L1 (P = 0.07), with 6-year overall survival (OS) 81% vs. 91% (P = 0.035), respectively. L2 morphology was not associated with any other adverse prognostic factor analyzed.
Conclusions: With the intensive Nordic ALL protocols, lymphoblast L2 morphology is an independent poor prognostic factor, influencing both the early response to treatment and, in the low-WBC group, the ultimate outcome, and should be reemphasized in risk categorization of childhood ALL.
Copyright 1999 Wiley-Liss, Inc.