Monitoring patients in complete cytogenetic remission after treatment of CML in chronic phase with imatinib: patterns of residual leukaemia and prognostic factors for cytogenetic relapse

We monitored BCR-ABL transcript levels by quantitative real-time PCR in 103 patients treated with imatinib for chronic myeloid leukaemia in chronic phase for a median of 30.3 months ( range 5.5 - 49.9) after they achieved complete cytogenetic remission (CCyR). The patients could be divided into three groups: ( 1) in 32 patients transcript levels continued to decline during the period of observation ( nadir BCR - ABL/ABL ratio 0.015%); in five of these patients BCR - ABL transcripts became undetectable on repeated testing, ( 2) in 42 patients the transcript levels reached a plateau and ( 3) in 26 patients transcript numbers increased and the initial CCyR was lost. Three patients were not evaluable. Patients who remained in CCyR for at least 24 months appeared to have a low risk of subsequent cytogenetic relapse. We conclude that the pattern of 'residual' disease after achieving CCyR on imatinib is variable: some patients in CCyR show a progressive reduction in the level of residual disease, some reach a plateau where transcript numbers are relatively stable and others relapse with Ph-positive metaphases.