Achieving a Major Molecular Response at the Time of a Complete Cytogenetic Response (CCgR) Predicts a Better Duration of CCgR in Imatinib-Treated Chronic Myeloid Leukemia Patients

Purpose: Most patients with chronic-phase chronic myeloid leukemia (CML) who receive imatinib achieve a complete cytogenetic remission (CCgR) and low levels of BCR-ABL transcripts. CCgR is durable in the majority of patients but relapse occurs in a subset. Experimental Design: To determine the potential of quantitative reverse transcription-PCR of BCR-ABL to predict cytogenetic relapse, we serially monitored residual disease in 97 CML patients with an imatinib-induced CCgR. Patients with late chronic phase CML after IFN-α failure were treated with imatinib (400 mg daily). Results: During the imatinib median follow-up time of 36 months (range, 12-54 months), disease monitoring occurred by cytogenetics and quantitative PCR. Twenty percent of patients experienced cytogenetic relapse at a median of 18 months after CCgR and a median of 24 months after starting imatinib. None of the possible prognostic factors studied in univariate and multivariate analyses seemed to predict for loss of cytogenetic response but the reduction of BCR-ABL transcript levels at the time of CCgR is an important prognostic factor. Conclusions: In our study, we showed not only that achieving a major molecular remission at 12 months is predictive of a durable cytogenetic remission but also that patients who achieved a major molecular remission (expressed both as the BCR-ABL/β2 microglobulin ratio % P