Event-free Kaplan-Meier curves. Survival was evaluated using Kaplan-Meier analysis. Events included disease progression, large-cell transformation, and death. There were 10 events, including 7 deaths, 1 large-cell transformation after biopsy, and 3 patients who progressed despite systemic treatments. The log-rank test was used to determine significance of differences between survival curves. Event-free survival is shown (A) by clinical stage (P < .001); (B) by hierarchical cluster, using a 3-cluster partition (P = .028); and (C) by hierarchical cluster, using a 2-cluster partition (P = .02).