Background: Obtaining a major (Philadelphia chromosome [Ph] of < 35%) or a complete cytogenetic response (Ph of 0%) has been associated with excellent long-term survival. Cytogenetic response may continue to improve with therapy. Because early allogeneic stem cell transplantation (SCT) may be associated with a better outcome, early parameters predicting for subsequent cytogenetic responses would optimize the treatment decision-making.

Methods: The current study was performed to analyze whether early cytogenetic responses may be predictive of later major or complete cytogenetic responses to imatinib mesylate therapy in patients with Ph-positive chronic myelogenous leukemia (CML).

Results: Two hundred sixty-one patients with Ph-positive, chronic-phase CML after failure with interferon therapy who were treated with imatinib mesylate therapy were analyzed. A persistence of 100% Ph-positive cells after > or = 6 months of imatinib mesylate therapy was associated with a major cytogenetic response rate of 9-13% and a complete cytogenetic response rate of 0-4%. However, a minor cytogenetic response after 3-12 months of therapy still was associated with high rates of major (68-83%) or complete (35-54%) cytogenetic response rates.

Conclusions: Patients with Ph-positive, chronic-phase CML who have persistent 100% Ph-positive disease after > or = 6 months of imatinib mesylate therapy may be offered allogeneic SCT or considered for alternative investigational therapies.