Complete cytogenetic and molecular responses to interferon-α-based therapy for chronic myelogenous leukemia are associated with excellent long-term prognosis

BACKGROUND. Little is known regarding long-term prognosis among patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML) who achieve a complete cytogenetic response (0% Ph-positive cells) after treatment with interferon-α. METHODS. The authors analyzed 512 patients with Ph-positive, early chronic-phase CML who were treated with interferon-based therapies between 1981-1995 for the incidence and durability of complete cytogenetic response, and in relation to long-term prognosis. RESULTS. One hundred forty patients (27%) achieved a complete cytogenetic response. Their 10-year survival rate was 78%. At the time of last follow-up, 44 patients (31%, 9% of the total) were alive, 21 in first and 23 in second durable complete cytogenetic response (median, 127 months; range, 88-191 months); 39 patients had not received any therapy for a median of 50 months (range, 11-139 months). Analysis by reverse transcriptase-polymerase chain reaction in 78 patients during complete cytogenetic response showed 46 who had achieved at least 1 complete molecular response. Five of these 78 patients had died by the time of last follow-up, but only 2 had died of disease-specific causes. Recurrence rates were significantly lower and cytogenetic response durations were significantly longer among patients who achieved at least one complete molecular response. CONCLUSIONS. Achieving a complete cytogenetic or molecular response after therapy with interferon-α appears to be associated with excellent long-term prognosis. Approximately 10% of patients reportedly can achieve durable complete cytogenetic response, with or without continuation of interferon. This finding emphasizes the potential of long-term event-free survival in CML patients outside the context of allogeneic stem cell transplantation, which may be improved with new therapies such as imatinib mesylate.