Effect of isolated central nervous system leukaemia on bone marrow remission and survival in childhood acute lymphoblastic leukaemia. A report for Children's Cancer Study Group.

The Children's Cancer Study Group investigated the relative efficacies of four treatments directed at the central nervous system (CNS) and other sanctuary areas in 724 children with acute lymphoblastic leukaemia (ALL). The results show that CNS relapse rates are lower in patients receiving effective treatment before CNS symptoms arise, but the bone marrow relapse rate was not significantly affected by prophylactic therapy. In patients with an initial white blood count of 50000/microliter or more, multiple CNS relapses resulted in a lower survival rate. The data from the group receiving the least effective CNS prophylaxis indicate that CNS leukaemia is not necessarily followed by bone marrow relapse and death. These observations suggest that reseeding of the bone marrow by leukaemic cells from the CNS is not a major factor in the evolution of ALL. CNS prophylaxis is of value in averting the CNS complications of ALL and those associated with its therapy, but the improved survival in childhood ALL during the past decade is probably not due to the successful prevention of CNS leukaemia. Improvements in survival are probably the result of more effective systemic chemotherapy and better general management.