Second central nervous system prophylaxis in children with acute lymphoblastic leukemia who relapse after elective cessation of therapy.

A treatment plan to achieve better disease control in patients with acute lymphoblastic leukemia (ALL) who relapse after elective cessation of therapy was assessed. The principal modifications were (1) a second preventive treatment of the central nervous system (CNS) at relapse and every six weeks throughout therapy, using intrathecal methotrexate with cytosine arabinoside, and (2) a four-week course of systemic chemotherapy given immediately before therapy was stopped a second time. Twenty-four patients were studied. There have been no meningeal relapses, in contrast to seven among 16 similar patients who were retreated without CNS prophylaxis. Although the median length of second hematologic remission was not significantly different from the outcome in the comparison group, a much higher proportion of patients (eight of 24 versus zero of 17) remain in prolonged reinduced complete remission (48-79 months). Children whose first relapse occurred later than six months after cessation of therapy had significantly longer subsequent remissions. These end results establish the value of intrathecal CNS prophylaxis in relapsed ALL and suggest that a late intensive phase of therapy will extend remissions in a substantial proportion of patients.