Long-term follow-up results of Chronic myeloid leukemia by RQ-PCR monitoring of BCR-ABL transcripts in imatinib era -a single institutional experience

Background: Chronic myeloid leukemia (CML) is a myeloproliferative disorder associated with the Philadelphia chromosome and peripheral leukocytosis which prior to the imatinib era, eventually led to acute leukemia within 3-5 years. According to current treatment guidelines, the monitoring of molecular response by RQ-PCR has been considered an important part of management of patients on tyrosine kinase inhibitor (TKI) therapy. Patients and Methods: This retrospective study aimed to evaluate the characteristics and treatment outcomes of CML patients treated at our institution from July 2004 until February 2012. The molecular response was monitored by RQ-PCR, and the impact of early molecular response on overall survival (OS) and event free survival (EFS) was also analyzed. Results: A total of 50 patient records were reviewed. The mean age was 43.5 years. Forty patients (80%) were diagnosed as CML in CP, while 4 (8%) were in AP and 6 (12 %) in BC. Patients with CML in CP had significantly longer mean survival of 109.4 months, compared with 58.5 months in AP and 48.9 months in BC groups (p=0.001). There was no significant OS benefit associated with MMR at 12 months (p=0.86) and 18 months (p=0.69). Early reduction of more than 10% of BCR-ABL transcripts at 3 months was related to high probability of achieving MMR at 12 and 18-month landmarks. In addition, MMR at 18 months and 10% or greater BCR-ABL reduction at 3 months were significantly associated with durable EFS (p=0.011 and p=0.015 respectively). Conclusions: The current analysis in our cohort of patients from Taiwan confirmed the efficacy and safety of imatinib therapy seen in larger randomized trials in CML patients. Early achievement of molecular response improved durable EFS, but not OS.