Sudden blast crisis in patients with Philadelphia chromosome-positive chronic myeloid leukemia who achieved complete cytogenetic remission after imatinib therapy

BACKGROUND. Most patients with Philadelphia chromosome (Ph)-positive chronic myeloid leukemia (CML) in chronic phase (CP) who receive treatment with imatinib achieve complete cytogenetic remission (CCR), which is correlated tightly with long-term progression-free survival. In these patients, the occurrence of blastic crisis (BC) is rare, and its clinical biologic characteristics are not well known. METHODS. Among 164 patients who received imatinib and were followed for a median of 35 months, I I patients (6.7%) developed a BC; this was sudden (i.e., it occurred within 3 months of a documented CCR) in 6 patients (54.5%). Those patients were analyzed with respect to their clinical and biologic features and were compared with previous reports. RESULTS. At the time of diagnosis, there were 3 low-risk patients and 3 intermediate-risk patients; 4 patients had received pretreatment with interferon, and 2 patients received only imatimb. The median CP was 18 months, and the median duration of imatimb therapy was 7 months. The median time to CCR was 3 months, and the median time from CCR to BC was 4 months. BC phenotype was lymphoid in 2 patients, myeloid,in 3 patients (including 2 patients who had extramedullary localization), and biclonal in I patient. Karyotype evolution was detected in 4 patients, whereas a Ph-positive/Ph-negative mosaicism was evident in all 6 patients. One patient presented an M351T mutation. The overall median survival was 3 months. CONCLUSIONS. Sudden BC generally is an uncommon phenomenon that may be relatively frequent in patients with CIVIL who receive imatinib. Clinical and biologic features also seem to characterize this peculiar type of abrupt disease evolution, which intervenes in patients' response to this drug. Close monitoring of disease markers and full disease eradication are warranted.