The second-generation tyrosine kinase inhibitors (TKIs) dasatinib and nilotinib produce optimal cytogenetic response after 3 months of treatment in themajority of patients with chronic myeloid leukemia (CML) in the chronic phase, a much faster rate than the 12 to 18 months for the peaked response reported with imatinib (Jabbour E, et al. J Clin Oncol. 2011;29:4260-4266). In 2 simultaneous phase 2 trials, 167 patients with newly diagnosed chronic-phase CML were randomized to nilotinib (N = 81) or to dasatinib (N = 86). At 3 months, all 160 evaluable patients demonstrated optimal response (ie, complete hematologic response) with either of the secondgeneration TKIs. By 18 months, 99 of 118 evaluable patients achieved an optimal response. Overall, 155 patients achieved a complete cytogenetic re - sponse (CCyR) after a median followup of 33 months, including 146 who achieved a major molecular response (MMR) and 46 who achieved complete molecular response (CMR). At months 6, 12, and 18, the rates of suboptimal response (ie, less than MMR) were 2%, 1%, and 12%, respectively. The failure response was only demonstrated on month 18, by 5 patients. At each time point, DFS did not differ significantly between patients who achieved CCyR without an MMR or CMR and those who achieved CCyR with an MMR or CMR. These results confirm that secondgeneration TKIs used in the front-line setting are highly efficacious, with the majority of responses (99%) occurring within the first 3 months of therapy. In contrast, the results obtained with imatinib therapy showed that CCyR rates peak around 12 to 18 months. This study shows that the secondgeneration TKIs produce CCyRs at a much faster response rate than with imatinib.
