Comparison of Response Over 6 Years Between Patients with Chronic Myeloid Leukemia Who Received Imatinib as Initial Therapy and Those Who Received Imatinib as Secondary Therapy.

To compare responses in a single center over 6 years between patients with Philadelphia-positive chronic myeloid leukemia (CML) who received imatinib as initial therapy and those who received imatinib as secondary therapy.

We reviewed 171 cases of patients with Philadelphia chromosome (Ph)-positive CML who received imatinib for 72 months: 73 patients in an initial therapy group (time from diagnosis of CML less than 6 months) and 98 patients in a secondary therapy group (time from diagnosis of CML greater than 6 months).

Cumulative rates of complete cytogenetic response (CCyR) at 6, 12, and 36 months after imatinib treatment in the initial therapy group and secondary therapy group were 75%, 89% and 96%, and 48%, 77% and 84%, respectively (P=0.0002). The median time to CCyR in initial and secondary therapy groups was 6 months (95%CI, 3.3–8.3) and 9 months (95%CI, 6.4–11.6), respectively (P=0.0002). Cumulative rates of major molecular response (MMoR) at 9, 12 and 18 months after imatinib treatment in initial therapy and secondary therapy groups were 26%, 42% and 49%, and 16%, 25% and 36%, respectively (P=0.048). The median time to MMoR in initial and secondary therapy groups was 19 months (95%CI, 11.7–26.3) and 36 months (95%CI, 19.7–52.4), respectively (P=0.048). Estimated rates of freedom from progression to accelerated phase (AP) and blastic phase (BP) in initial and secondary therapy groups were 99% and 89%, respectively (P=0.08). Estimated 6-year progression-free survival (PFS) rates in cases with CCyR and without CCyR were 93% and 62%, respectively (P=0.0012). Estimated 6-year event-free survival (EFS) rates in initial and secondary therapy groups were 96% and 68%, respectively (P=0.04). The event was defined as progression to accelerated AP and BP, loss of CCyR or CHR.

The time to CCyR and MMoR in the initial therapy group was significantly shorter than that in the secondary therapy group. There was no difference in PFS rates between the two groups in the 72-month long-term follow-up. The EFS rates indicated that patients receiving imatinib as initial therapy achieved more stable remissions than those receiving it as secondary therapy.

No relevant conflicts of interest to declare.