The Impact of Early Molecular Response in Event Free Survival in Patients with Chronic Myeloid Leukemia Treated with Imatinib

Background

Monitoring response to TKI therapy is one of the key management strategies of chronic myeloid leukemia (CML). Early molecular response to first-line TKI therapy is emerging as an effective prognostic factor indicator of long-term durable response and survival.

Objectives

We conducted a study to evaluate the importance of the early molecular response (EMR) at 3, 6 and 12 months (mo), and 3-year event free survival (EFS).

Methods

This is a retrospective study in a cohort of pts with chronic myeloid leukemia chronic phase (CP) enrolled in 14 Hematology centers in South Brazil. All pts received imatinib 400mg as first or second-line therapy. Patient evaluation and response criteria followed the ELN recommendations. EFS was measured from the start of imatinib to the date of any of the following events while on therapy: death from any cause, loss of complete hematologic response, loss of complete cytogenetic response, discontinuation of therapy for toxicity or lack of efficacy, or progression to accelerated phase or blastic phase.

Results

We analyzed data from 517 pts with CML-CP diagnosed since 1990. After a median observation time of 46 months, 5-year overall survival (OS) was 86% and 5-year event-free-survival was 53%. At 3 mo, EFS was 72,5% for 46 pts with BCR-ABL^IS ≤10% compared to 58% for 14 pts with BCR-ABL^IS >10% (p<0,07). Similarly, when EMR was analysed at 6 mo, the EFS was 81% for 75 pts with BCR-ABL^IS ≤1%, while 31% of EFS was achieved for 38 pts with BCR-ABL^IS >1% (p<0,001). At 12 mo, the 3-year EFS was 86% for 65 pts with with BCR-ABL^IS ≤0,1% compared to 54% for pts with BCR-ABL^IS>0,1% (p<0,001).

Conclusions

A significant proportion of pts achieve ERM after 3,6 and 12 mo of imatinib therapy with better 3-year EFS. ERM may could identify those pts more likely to have a favorable outcome.