Landmark analysis of progression-free survival according to the cytogenetic response at 12 months. A total of 408 patients who were remaining progression free on study treatment at 12 months were categorized according to their degree of cytogenetic response by 12 months. The estimated 6-year PFS rate was 88% in patients with CCyR, 76% for PCyR, 66% for minor CyR, 43% for minimal CyR, and only 25% for patients who had not achieved any cytogenetic response on the first 12 months of imatinib treatment.