Introduction
With current treatment, 5-year event-free survival (EFS) rates in acute lymphoblastic leukemia (ALL) ranges between 75% and 80%. Therefore, relapse of ALL is still frequent, with an incidence range similar to that of neuroblastoma. Problems in the management of ALL relapse are the drug resistance of the leukemic cells and the reduced tolerance of patients to a second round of treatment after having already received intensive frontline therapy, resulting in a lower remission rate as well as a higher incidence of relapse and an inferior outcome overall.
Intensified polychemotherapy is essential for induction of a second complete remission (CR). Depending on a variety of prognostic factors, remission may be maintained with chemotherapy with or without cranial irradiation or with intensification of treatment by stem cell transplantation (SCT).
Diagnosis of relapse
The diagnosis of ALL relapse (i.e., the reappearance of leukemic cells in any anatomic compartment following CR) must be unequivocal. he workup includes a careful physical examination as well as investigations of the bone marrow (BM), the cerebrospinal luid (CSF) and, if necessary, biopsies of other involved sites (e.g., the testicles, lymph nodes, or any other organs or tissues).As at initial diagnosis, the leukemic cells have to be characterized morphologically and by immunophenotyping, as well as by cytogenetic and molecular genetic procedures. Only this comprehensive information, together with clinical findings, allows one to classify the leukemic subtype adequately and to assess the prognosis of individual patients.