Cytogenetic response to imatinib treatment in Southern Brazilian patients with chronic myelogenous leukemia and variant Philadelphia chromosome.

Variant Philadelphia (Ph) chromosome can be observed in 5-10 % of chronic myelogenous leukemia (CML) patients. However, there are only a few studies which have analyzed the prognostic implications of these complex translocations in CML patients after the advent of imatinib mesylate and the results found are conflicting. We investigated the clinical features and cytogenetic response of Brazilian chronic phase (CP) CML patients with variant Ph treated with imatinib mesylate. Among 93 CP CML patients, eight (8.6 %) exhibited complex translocations, involving one (n = 6), two (n = 1), or three (n = 1) additional chromosomes. At 6, 12, and 18 months, a complete cytogenetic response was observed in 100 % of variant Ph patients, respectively. No significant difference was found between variant Ph and standard translocation patients regarding the response to IM treatment at 6, 12, and 18 months. Likewise, there was no statistically significant difference between the two groups concerning the overall survival, failure-free survival, progression-free survival, and event-free survival. The results obtained in our study, despite our sample size, suggest, in agreement to other data found in the literature, that the presence of variant Philadelphia chromosome does not bestow a prognostic disadvantage when compared to the group with classic Ph. This observation does not suggest the need to adjust the treatment protocol due to the presence of variant Ph. However, further studies with larger sample sizes and evaluating both the cytogenetic and molecular response to IM treatment should be conducted to confirm our findings.