Results from the Korean Imatinib Discontinuation Study (KIDS): Updated Data with 15-Month Median Follow up

• Published in: Blood 2014-12, Vol.124 (21), p.3155-3155
• Main Authors: OH, Yunjeong, Choi, Soo Young, Lee, Sung-Eun, Kim, Soo-Hyun, Kim, Hyeoung-Joon, Kim, Yeo-Kyeoung, Park, Joon Seong, Jeong, Seong Hyun, Kim, Sung-Hyun, Zang, Dae Young, Oh, Sukjoong, Koo, Dong Hoe, Kim, Hawk, Do, Young Rok, Kwak, Jae-Yong, Kim, Jeong-A, Mun, Yeung-Chul, Lee, Won Sik, Jang, Myung Hee, Park, Jinny, Shin, Ho-Jin, Kim, Dong-Wook
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V124.21.3155.3155

▪ Background Approximately 50% of CP CML patients achieve undetectable molecular residual disease (UMRD) at 6-7 years of first-line imatinib (IM) therapy. Although imatinib therapy is effective in chronic myeloid leukemia (CML) patients and a substantial portion of patients achieve UMRD with prolonged IM therapy, up to 10^7 leukemic cells can still be present in the absence of detectable BCR-ABL1 in RQ-PCR assay due to the sensitivity limit of current RQ-PCR technology. The recent several reports to assess whether IM can be discontinued in CML patients have shown that IM discontinuation can be employed based on clinical study in patients who had enough IM therapy and UMRD durations prior to IM discontinuation. In our previous report, the 12-month probability of sustained UMRD of 48 patients was 80.8% (78.4% in 37 patients with at least 12 months follow-up), a higher rate than that reported by the ‘STIM’ (Stop Imatinib) trial. To identify predictors for safer, successful IM discontinuation and to explore additional contributing factors for sustained molecular responses (MRs), this multicenter prospective Korean Imatinib Discontinuation Study (KIDS) is on-going. Methods Patients who were treated with IM for more than 3 years and whose BCR-ABL1 was undetectable in RQ-PCR for at least 2 years were enrolled in this study. After discontinuation, molecular response was monitored using RQ-PCR assay every month up to 6 month follow-up, every 2 months up to 12 month follow-up, and every 3 months thereafter. In case of relapse, defined as loss of MMR on 2 consecutive assessments, IM therapy was re-introduced and molecular response after resumption was observed every month using RQ-PCR. Our primary objectives were to evaluate the probability of persistent UMRD at 12 month follow-up after discontinuation, and to measure the duration of persistent UMRD after discontinuation. The secondary objective was to evaluate the probability of major molecular response (MMR) loss and the time taken to lose MMR after discontinuation. Results Of the 148 patients who were screened for KIDS, 30 patients have failed because of positive result of RQ-PCR tested in the central laboratory (N= 21, 70%), failure to meet inclusion criteria (N=7, 23%) and informed consents withdrawal (N=2, 7%). As of data cut-off date of 2 July 2014, a total of 115 patients (66 females, 49 males) who were diagnosed between 20 Mar 1996 and 12 Jul 2012 were enrolled on KIDS, with a median age of 44 years (range,