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1243 Second Imatinib Discontinuation Outcomes in Patients Regaining Durable Deep Molecular Response in the Korean Imatinib Discontinuation Study; KID StudyClinically Relevant Abstract

Program: Oral and Poster Abstracts
Session: 632. Chronic Myeloid Leukemia: Therapy: Poster I
Hematology Disease Topics & Pathways:
Adult, Diseases, CML, Non-Biological, Study Population, Myeloid Malignancies
Saturday, December 5, 2020, 7:00 AM-3:30 PM

Sung-Eun Lee, M.D, Ph.D.1*, Joon Seong Park, MD2*, Young Rok Do, PhD, MD3, Sung-Hyun Kim, MD, PhD4, Dae Young Zang, MD, PhD5*, Sukjoong Oh, MD, PhD6, Jae-Yong Kwak7, Jeong-A Kim8, Yeung-Chul Mun, MD9*, Won Sik Lee, MD, PhD10 and Dong-Wook Kim, MD1,11

1Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea, Republic of (South)
2Ajou University School of Medicine, Suwon, Korea, Republic of (South)
3Dongsan Medical Center, Keimyung University School of Medicine, Daegu, Korea, Republic of (South)
4Dong-A University College of Medicine, Busan, Korea, Republic of (South)
5Hallym University College of Medicine, Anyang, Korea, Republic of (South)
6Kangbuk Samsung Hospital, School of Medicine, Sungkyunkwan University, Seoul, Korea, Republic of (South)
7Chonbuk National University Medical School, Jeonju, Korea, Republic of (South)
8Department of Hematology, St. Vincent Hospital, College of Medicine, The Catholic University of Korea, Suwon, South Korea
9Department of Hematology, Ewha Womans University, Seoul, Korea, Republic of (South)
10Inje University College of Medicine, Inje University Busan Paik Hospital, Busan, Korea, Republic of (South)
11Leukemia Research Institute, The Catholic University of Korea, Seoul, Korea, Republic of (South)

Backgroud: Although multiple trials have shown that stopping tyrosine kinase inhibitor (TKI) treatment can be employed in CP CML patients with sustained deep molecular response (DMR) after enough TKI therapy, they emphasized the need for close monitoring because about 50-70% of patients experienced molecular relapse. However, most patients with molecular recurrence regain their initial molecular level after restarting TKI therapy.

Aims: In this study, we analyzed second imatinib (IM) discontinuation outcomes in patients regaining durable DMR in the Korean multicenter prospective study (Korean Imatinib Discontinuation Study; KID Study)

Methods: CP CML patients who were treated with IM for more than 3 years and maintained DMR for at least 2 years were eligible for the Korean multicenter prospective study and in cases of MMR loss on 2 consecutive assessments, IM treatment was re-introduced. After IM resumption, the molecular response was evaluated every month until re-achievement of MMR and every 3 months thereafter. The second stop was permitted in the patients who were in second DMR for at least 2 years.

Results: Among the patients who maintained a second DMR for at least 2 years after IM resumption, 23 patients entered into a second IM stop. Prior to first discontinuation, the median duration of IM therapy was 73.2 months (range, 38.4-133.2 months) and the duration of sustained UMRD was 38.4 months (range, 24-102 months). After first attempt of IM discontinuation, they relapsed after a median duration of 3.7 months (range, 1.8-20.8 months) and re-achieved UMRD at a median of 5.8 months (range, 1.7-12.1 months) after IM resumption. After sustaining a second DMR for a median of 26.3 months, IM therapy discontinued for a second time.

With a median follow-up of 29.5 months (range, 9-63 months) since second IM stop, 15/23 patients (65%) lost MMR after a median 2.9 months (range, 1.8-30.7 months), which was similar to those of the first IM discontinuation [median 3.7 (range, 1.8-20.8 months)]. The patients who lost MMR were retreated with IM for a median of 24.5 months (range, 1.2-49.7 months); 14 patients re-achieved MMR and one patient was in therapy for 1.2 months.

Conclusion: Our data demonstrated that a second attempt might be possible and the median time to MMR loss after second discontinuation was similar to those of the first discontinuation. Further studies on the predictors to select patients for a trial of second TFR and novel strategies will be warranted.

Disclosures: Kim: ILYANG: Consultancy, Honoraria, Research Funding; Takeda: Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Sun Pharma.: Research Funding.

*signifies non-member of ASH