Quantitative measurement of BCR/abl transcripts using real-time polymerase chain reaction

Background: Quantitative real-time polymerase chain reaction (Q-Rt-PCR) is a new tool in the detection and quantification of the BCR/abl fusion transcripts in chronic myelogenous leukemia (CML). This study investigates its specificity, sensitivity and potential clinical usefulness. Patients and Methods: Parallel analysis of Q-Rt-PCR and the conventional reverse transcription-mediated PCR (RT-PCR) were performed on 567 samples from 481 patients. Treatment response was monitored by Q-Rt-PCR at 6 and 12 months of 61 patients on STI-571 and 103 patients on interferon. Results: The concordance rate between Q-Rt-PCR and RT-PCR was 96.3% (546/567), with 341 positives and 205 negatives. The positive equivalents ranged from 2 × 10^-6 to 1.2 μg of K562 cell RNA. Karyotyping in 372 samples revealed excellent correlation with Q-Rt-PCR measurements (P<0.001). Setting residual BCR/abl <0.01 as an early goal of molecular response, we observed that STI-571 induced a better response than interferon: 49% (20 of 41 patients) versus 35% (15 of 62 patients) at 6 months (P = 0.025) and 52% (32 of 61 patients) versus 34% (35 of 103 patients) at 12 months (P = 0.01), respectively. Conclusions: Q-Rt-PCR provides reliable measurements of BCR/abl fusion transcripts. It is potentially useful in assessing molecular residual disease after therapy.