CHEMOTHERAPY FOR RELAPSED CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA

Relapse of childhood acute lymphoblastic leukemia (ALL) requires a sec ond round of chemotherapy to achieve remission, and, in face of lack o f donors for bone marrow transplant, remains the only therapeutic opti on for the majority of affected children. Prior to chemotherapy, the d iagnosis of relapse must be beyond any doubts. Diagnostic procedures h ave to follow the same rules as at the first manifestation of ALL. Rem ission rates as well as long-term results are dependent on time and si te of recurrence. The prognosis is dismal for children who have early relapses, in particular in bone marrow (BM) while still receiving firs t-line therapy. In contrast, about 50% of children with late BM relaps es can be cured with intensive chemo-therapy. A second course of preve ntive treatment to the central nervous system (CNS) is mandatory even if the CNS is not apparently involved. The prognosis for children with BM relapse is better if extramedullary sites are concomitantly involv ed. Extramedullary relapse requires systemic therapy supplemented by l ocal treatment to the involved site. For children with CNS relapse, ra diation therapy still appears inevitable, and adverse late sequelae wi ll have to be accepted, considering the possible cure rate of about 40 %. Treatment results in boys with late testicular relapse are in the s ame range as for newly diagnosed ALL. Current treatment cannot retain fertility, but endocrine function can be preserved in the majority of patients. About one-third of children with relapsed ALL can be cured w ith chemotherapy. Particular problems remain the treatment for early B M relapse and relapse of T-cell ALL. In both conditions, drug resistan ce cannot be overcome by currently available treatment options. The se arch for novel approaches will constitute a formidable challenge well into the next millenium.