1094PUse of droplet digital polymerase chain reaction for detecting minimal residual disease: A prospective, multi-institutional study

Abstract Background Droplet digital polymerase chain reaction (ddPCR) is an exact method of measurement in cancer research. The aim of this prospective study was to evaluate minimal residual disease (MRD) using ddPCR in patients with chronic myeloid leukemia (CML). We also evaluated treatment outcome depending on BCR/ABL1 transcript level using ddPCR. Methods Between May 2013 and November 2014, CML patients treated with nilotinib as the first-line therapy were enrolled. BCR/ABL1 transcripts levels were evaluated using ddPCR at the first time of complete molecular response (CMR). CMR was verified by quantitative real-time polymerase chain reaction. Results We enrolled 15 patients from 7 institutions. The treatment period and median follow-up period were 45 months (range, 37–55 months) and 47 months (range, 39–61 months), respectively. The median value of BCR/ABL1 measured by ddPCR was 3.6 copies/20 μl (range, 1.2–6.8 copies/20 μl). Patients with a high level of BCR/ABL1 transcript had a greater tendency to lose the CMR during the follow-up period (0/10 (0%) for low levels vs. 2/5 (40%) for high levels, P = 0.095). In addition, patients with a low level of BCR/ABL1 transcript showed a longer duration of CMR than those with a high level (rate of sustained CMR at 2 years: 100% for low levels vs. 37.5% for high levels, P = 0.032). Conclusions We found that ddPCR is a sensitive method for detecting MRD and that MRD could affect the duration of the treatment response. Legal entity responsible for the study The authors. Funding Novartis Pharmaceuticals Corporation. Disclosure All authors have declared no conflicts of interest.