Late marrow recurrences in childhood acute lymphoblastic leukaemia.

Thirty children with acute lymphoblastic leukemia had a recurrence in the bone marrow after treatment was stopped electively. A second haematological remission was achieved in 27 (90%), and the median duration of remission was shortest (six months) in those relapsing within six months of stopping treatment. Four of six children relapsing over one year after stopping treatment remained in second haematological remission. Leukaemic infiltration of the central nervous system developed in four patients remaining in marrow remission. It is concluded that conventional chemotherapy is unlikely to be effective in children with acute lymphoblastic leukaemia who relapse soon after stopping treatment, that "reprophylaxis" of the central nervous system probably with long-term intrathecal chemotherapy is essential, and that some patients relapsing after prolonged unmaintained remission may achieve long-term leukaemia-free survival.