DETECTION OF MINIMAL RESIDUAL DISEASE IN PATIENTS WITH AML1 ETO-ASSOCIATED ACUTE MYELOID-LEUKEMIA USING A NOVEL QUANTITATIVE REVERSE TRANSCRIPTION-POLYMERASE CHAIN-REACTION ASSAY/

The AML1/ETO fusion transcript can be detected by reverse transcriptio n polymerase chain reaction (RT-PCR) in patients with t(8;21)-associat ed acute myeloid leukemia (AML) in longterm complete remission (CR). Q uantitation of the amount of the fusion transcript during CR may there fore be more predictive of cure or relapse than a simple qualitative a ssessment. Real Time PCR, a fluorometric-based technique, allows simpl e and rapid quantitation of a target sequence during the extension pha se of PCR amplification, in contrast to end-point quantitative methods . Six patients with t(8;21)(q22;q22) AML, who achieved CR were studied by Real Time RT-PCR at different time intervals following diagnosis a nd high-dose cytarabine and anthracycline-based induction therapy. Fiv e patients had a diagnostic bone marrow (BM) sample available for mole cular analysis. Each patient showed greater than or equal to 10(3) cop ies of the AML1/ETO fusion transcript at diagnosis, and each showed a 2- to 4-log decrease in copy number following successful induction che motherapy. This is comparable to the log-fold reduction in leukemic bl asts that is thought to occur in patients successfully cytoreduced int o CR by induction chemotherapy. The sixth patient showed a relatively high copy number immediately following successful remission induction chemotherapy, which continued to increase during early CR and was late r followed by relapse. Real Time RT-PCR appears to offer advantages ov er previously used quantitative RT-PCR methods by providing absolute q uantitation of the target sequence, expanding the dynamic range of qua ntitation to over six orders of magnitude, eliminating the post-PCR pr ocessing, and reducing labor and carryover contamination. These featur es make this an attractive method to prospectively evaluate the progno stic value of AML1/ETO fusion transcript quantitation in a larger pati ent population with t(8;21)(q22;q22) AML in CR.