Use of dual-color interphase FISH for the detection of inv(16) in acute myeloid leukemia at diagnosis, relapse and during follow-up: a study of 23 patients

The value of dual-color fluorescence in situ hybridization (FISH) for the d etection of inv(16), using two contigs of cosmid probes mapping on both sid es of the chromosome 16p breakpoint region, was evaluated in 23 acute myelo id leukemias (AML) in different phases of the disease. At diagnosis interph ase FISH detected inv(16) in 19/19 (100%) cases with conventional cytogenet ics (CC) evident aberration and excluded the rearrangement in two patients with CC suspected inv(16). Moreover, it also identified an associated del(1 6p) in two patients. At relapse, it revealed the inv(16) in 8/8 (100%) stud ied cases. These results were concordant with those of reverse transcriptas e-polymerase chain reaction (RT-PCR). From 13 patients who obtained at leas t one complete remission (CR), 31 follow-up samples were analyzed using int erphase FISH. Twenty-nine specimens scored negative for inv(16) and two wer e positive. RT-PCP detected CBF beta/MYH11 transcripts in four of the nine CR samples analyzed, being more sensitive than interphase FISH. Eight of th e 13 patients relapsed at a median time of 6.5 months (range 1-15) from the last negative FISH analysis. Of the two patients with positive FISH in CR, one relapsed soon after. At diagnosis and relapse, interphase-FISH proved to be an effective technique for detecting inv(16) appearing more sensitive than CC. Prospective studies with more frequent controls and possibly addi tional FISH probes are needed to assess the value of interphase FISH for mi nimal residual disease (MRD) and relapse prediction.