Assessment of residual disease in acute leukemia by means of polymerase chain reaction.

Along a 5-year period in a single institution, specific molecular markers were prospectively looked for in consecutive patients with acute leukemia, by means of polymerase chain reaction (PCR): In patients with acute lymphoblastic leukemia (ALL), the BCR/ABL and TEL-AML1 fusion transcripts as well as clonotypic immunoglobulin gene rearrangements were investigated, whereas in patients with acute myelogenous leukemia (AML) the PML-RAR alpha, AML1-ETO and CBF beta-MYH11 fusion proteins were assessed. Specific molecular markers were identified in 15/75 patients: Four with ALL (three with clonotypic IgG rearrangements and one with BCR/ABL) and 11 with AML (nine with the PML/RAR alpha fusion protein--M3 AML-, and two with the AML1/ETO fusion protein--M2 AML-). During follow-up periods ranging from 1 to 60 months, seven patients cleared the residual disease assessed by PCR (RD-PCR), whereas eight patients had either persistence of RD-PCR or a molecular relapse. For patients without or with RD-PCR, the 30-month survival (SV) was 86% and 14%, respectively, whereas median SV was > 60 and two months, also respectively (p < 0.01). Six of eight patients with detectable RD-PCR died, all of them within three months after the detection of the RD-PCR, whereas two of the patients that relapsed were rescued with treatment and entered a second molecular remission. Two of the three molecular relapses were detected without an overt morphological relapse. It is concluded that PCR is a valuable method for assessing residual disease and that early diagnosis of relapses may lead into effective salvage treatment in some instances.