E2A/HLF fusion cDNAs and the use of RT-PCR for the detection of minimal residual disease in t(17;19)(q22;p13) acute lymphoblastic leukemia.

Three cases of acute lymphoblastic leukemia (ALL) with the rare t(17;19)(q22;p13) translocation were investigated for E2A/HLF fusion genes using reverse transcription coupled with polymerase chain reaction (RT-PCR). The patients had C-ALL, F/17 years (case 1) or pre-B ALL, M/11 years (case 2) and M/13 years (case 3). Case 1 had an event-free survival (EFS) of 42 months. Case 2 was ultimately refractory to treatment. Case 3 presented following EFS of 16 months in morphological remission (1% blasts), but with immunological and cytogenetic evidence of active disease, then relapsed, remitted and relapsed. Type II E2A/HLF fusion cDNA was found at diagnosis (cases 1, 2), at presentation (case 3) and in all samples tested, whether with active disease or in complete remission (CR). Case 3 showed, in addition, type I fusion E2A/HLF cDNA at presentation, through induction therapy when there was evidence of active disease, but not in CR. Cases 1 and 3 had bone marrow transplantation while in CR but with residual disease detectable by RT-PCR. All patients have died of ALL. Two cases (2 and 3) had hypercalcemia with bone lesions. No case had any evidence of disseminated intravascular coagulation. This is the first demonstration of the value of RT-PCR for the detection of minimal residual disease in t(17;19) ALL.