Cumulative incidence of blast transformation in 73 patients who had been splenectomized within 5 years from diagnosis and in the 462 nonsplenectomized patients. The vertical lines represent 95% CIs. Actuarial data beyond 144 months were not reported because the number of patients remaining in each group was too small. The incidence of blast transformation from the time of splenectomy is also represented in the upper left corner.