Long-term control of central nervous system leukaemia.

Seventy-four children with acute lymphoblastic leukaemia had one or more episodes of central nervous system (CNS) leukaemia. 5 children had CNS involvement at diagnosis; 4 survived for less than one year. In 35 children who had not had a previous bone marrow relapse on treatment and who received combination chemotherapy, the median duration of haematological remission from the time of first CNS relapse was almost 3 years. 5 children received full dose (2400 rads) craniospinal irradiation after their first CNS relapse; 4 have remained in CNS and haematological remission for 2 1/2 years or more. 18 children who had a CNS relapse after irradiation received 4-weekly intrathecal methotrexate; in 8 children this was given via an intraventricular reservoir. The median duration of CNS remission in children receiving intrathecal methotrexate was 2 years. Systemic and intrathecal treatment was stopped in 7 children after 2 1/2 years in continuous remission and in 2 children after 2 years. 4 of these 9 children remain in remission at intervals from 41 to 69 weeks off treatment but one is severely retarded. These results show that CNS disease is compatible with prolonged survival, but illustrate the difficulties of eradicating established CNS leukaemia.