DETECTABLE MOLECULAR RESIDUAL DISEASE AT THE BEGINNING OF MAINTENANCETHERAPY INDICATES POOR OUTCOME IN CHILDREN WITH T-CELL ACUTE LYMPHOBLASTIC-LEUKEMIA

The aims of this study were twofold: (1) to assess the marrow of patie nts with T-lineage acute lymphoblastic leukemia (T-ALL) for the presen ce of molecular residual disease (MRD) at different times after diagno sis and determine its value as a prognostic indicator; and (2) to comp are the sensitivity, rapidity, and reliability of two methods for rout ine clinical detection of rearranged T-cell receptor (TCR). Marrow asp irates from 23 patients with T-ALL diagnosed consecutively from 1982 t o 1994 at the Division of Pediatric Hematology and Oncology, Universit y of Catania, Italy, were obtained at diagnosis, at the end of inducti on therapy (6 to 7 weeks after diagnosis), at consolidation and/or rei nforced reinduction (12 to 15 weeks after diagnosis), at the beginning of maintenance therapy (34 to 40 weeks after diagnosis), and at the e nd of therapy (96 to 104 weeks after diagnosis). DNA from the patients ' marrow was screened using the polymerase chain reaction (PCR) for th e four most common LCR 6 rearrangements in T-ALL (V delta 1J delta 1, V delta 2J delta 1, V delta 3J delta 1, and D delta 2J delta 1) and, w hen negative, further tested for the presence of other possible TCR de lta and TCR gamma rearrangements. After identification of junctional r earrangements involving V, D, and J segments by DNA sequencing, clone- specific oligonucleotide probes 5' end-labeled either with fluorescein or with [gamma-P-32]-ATP were used for heminested PCR or dot hybridiz ation of PCR products of marrows from patients in clinical remission. For 17 patients with samples that were informative at the molecular le vel, the estimated relapse-free survival (RFS) at 5 years was 48.6% (/-12%). The sensitivity and specificity for detection of MRD relating to the outcome were 100% and 88.9% for the heminested fluorescence PCR and 71.4% and 88.9% for Southern/dot blot hybridization, respectively . Predictive negative and positive values were 100% and 90.7% for hemi nested fluorescence PCR, respectively. The probability of RFS based on evidence of MRD as detected by heminested fluorescence PCR at the tim e of initiation of maintenance therapy was 100% and 0% for MRD-negativ e and MRD-positive patients, respectively. Thus, the presence of MRD a t the beginning of maintenance therapy is a strong predictor of poor o utcome, and the molecular detection of WIRD at that time might represe nt the basis for a therapeutic decision about such patients. By contra st, the absence of MRD at any time after initiation of treatment stron gly correlates with a favorable outcome. The heminested fluorescence P CR appears to be more accurate and more rapid than other previously us ed methods for the detection of residual leukemia. (C) 1997 by The Ame rican Society of Hematology.