UICC World Cancer Congress 2006

Objective: ETV6/RUNX1 fusion in acute lymphoblastic leukemia (ALL) results from a cryptic translocation between chromosomes #12 and #21. The t(12;21)(p13;q22) is reported to be the most common rearrangement reported in childhood B lineage ALL . Since the presence of the t(12;21) cannot easily be identified by conventional chromosome analysis, other methods like RT-PCR and fluoresence in situ hybridization (FISH) have been used to identify the presence of this rearrangement.

Methods: At Roswell Park Cancer Institute, from 2001 to 2005, we studied the bone marrow/peripheral blood cells from 32 pediatric patients with B lineage ALL for the presence of the ETV6/RUNX1 fusion gene by interphase FISH at initial diagnosis. Conventional cytogenetics (CC) was also performed.

Results:Fourteen of 32 patients (46%) were found to be positive for the ETV6/RUNX1 fusion by FISH using a commercially available probe set. Nine of these patients were male and 5 were female. The median age was 3 years (range 1-15 years). Native RUNX1 was found to be deleted in six patients (43%). CC was successful in 9 patients. Abnormal karyotypes were observed in 3/9 patients. Abnormalities included structural (2/3) and numerical (hyperdiploidy in 1/3). Two patients had Down Syndrome. While the significance of these additional abnormalities is yet to be determined, they might represent genetic alterations influencing the course of the disease or they may be a possible "second hit" necessary for disease transformation.