Reemphasis on lymphoblast L2 morphology as a poor prognostic factor in childhood acute lymphoblastic leukemia

Background, in childhood acute lymphoblastic leukemia (ALL), the relationsh ip between lymphoblast L1/L2 morphology and prognosis is controversial. Acc ording to some studies L2 morphology is associated with poor prognosis, whe reas in others the association disappears after adjustment for other known risk factors. Procedure. We investigated the prognostic importance of lymph oblast L1/L2 morphology in childhood ALL treated with current Nordic ALL pr otocols in Finland. From the routine bone marrow (BM) aspirate and biopsy s lides of 251 children with ALL diagnosed in 1990-1995, the blast cell morph ology and early treatment responses were assessed blindly in a central revi ew, using French-American; British (FAB) criteria with the Children's Cance r Group (CCG) modification. Results, L1 morphology (>90% L1] was found in 1 97 (80%) children and L2 (greater than or equal to 10% L2) in 49 (20%). Ear ly 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) b elow 50 x 10(9)/liter at diagnosis, the L2 morphology was associated with i nferior survival: 6-year EFS 74% in L2 and 84% in L1 (P = 0.07), with 6-yea r overall survival (OS) 81% vs. 91% (P = 0.035), respectively. L2 morpholog y was not associated with any other adverse prognostic factor analyzed. Con clusions. With the intensive Nordic ALL protocols, lymphoblast L2 morpholog y is an independent poor prognostic factor, influencing both the early resp onse to treatment and, in the low-WBC group, the ultimate outcome, and shou ld be reemphasized in risk categorization of childhood ALL. Med. Pediatr. O ncol. 33: 388-394, 1999. (C) 1999 Wiley-Liss, Inc.