Follow-up Study on Chronic Myeloid Leukemia Patients Achieving Treatment-free Remission

• Primary goal: To evaluate the feasibility, safety and clinical consequences of TKI discontinuation in chronic phase CML(CP-CML) patients with deep treatment response and good medical compliance in Taiwan

• Molecular response monitoring:

• After discontinuation of TKI therapy, participants will receive monthly molecular monitoring of BCR-ABL transcript levels by real-time quantitative polymerase chain reaction (RT-qPCR) for one year, every two months for the second year and every three months thereafter.
• If loss of major molecular response (MMR) (BCR-ABL transcript level ⩽ 0.1% IS) is detected at any time point post TKI discontinuation, the participant should receive repeated testing within two weeks. If loss of MMR is confirmed, TKI should be resumed within four weeks
• RT-qPCR of BCR-ABL would be ordered every four weeks until MR4 (BCR-ABL transcript level ⩽ 0.01% IS) is re-established, and then every 12 weeks indefinitely.
• For patients who fails to achieve MMR again within three months after TKI is re-initiated, BCR-ABL kinase domain mutation testing would be performed

Inclusion criteria

• The participant should be an adult (age ⩾20 years) with CP-CML.
• The BCR-ABL fusion should be in the form of either e13a2 or e14a2 (p210)
• The participant should not have documented resistance to a 2nd-generation TKI (Nilotinib or Dasatinib)
• The participant should have received ≥ 5 years of consecutive treatment with imatinib, or ≥ 4 years of consecutive treatment with a 2nd-generation TKI (Nilotinib or Dasatinib)
• The participant should have achieved MR4.5 (BCR-ABL ⩽0.0032% IS) or undetectable disease in the peripheral blood or bone marrow, for ≥ 2 years, which is documented on ≥ 4 separate tests performed ≥ 3 months apart.
• Access to a reliable qPCR-based BCR-ABL test with a sensitivity of detecting of at least MR4.5.

Exclusion criteria

• After evaluation, the participant is deemed to be ineligible by the investigator of this study.
• The participant has no intention to be recruited into this study.