Central nervous system disease in childhood acute lymphoblastic leukemia: prognostic factors and results of treatment.

In the five Nordic countries, 808 children 1 to 15 years of age (428 boys, 380 girls) were diagnosed with non-B acute lymphoblastic leukemia (ALL) from July 1981 through June 1986. Complete remission was achieved in 770 children (95%). Central nervous system (CNS) involvement at diagnosis was noticed in 34 children, of whom 26 achieved remission. Of these 26 patients 11 subsequently relapsed, 5 in the central nervous system. An interim analysis in January 1990 (observation time 3 1/2 to 8 1/2 years) revealed that isolated CNS relapse had occurred in 70 children (9.0%). Of these 70 patients, 12 out of 142 children (8.5%) had initially received irradiation and 58 out of 628 children (9.2%) only chemotherapy as CNS-prophylaxis. There was a significant higher risk for boys (12%) than for girls (6%) to relapse in the CNS compartment. Unfavorable prognostic factors for survival after isolated CNS relapse were short duration of first remission and male sex. In high-risk patients after an isolated CNS relapse, there was no difference in prognosis related to treatment with or without irradiation as initial CNS prophylaxis.