A very high percentage of blasts positive for CD40 is indicative of a specific decrease of late relapse. The percentage of BCP-ALL cells positive for CD40 surface expression as assessed by flow cytometry was found to be significantly different in patients with late relapse (> 730 days after diagnosis) compared with those remaining in remission (P = .013) with no difference for patients with early relapse (A). In a landmark analysis excluding any patient who is not alive without relapse at 2 years after study entry, high CD40 expression at diagnosis is associated with significantly better relapse-free survival (B). Even in the smaller, clinically defined subgroups of low-risk (LR; C) and high-risk (HR; D) patients, high CD40 expression remains a strong prognostic marker when focusing on late relapse. In the box plot diagrams the boxes represent the interquartile range with the line in the middle indicating the 50th percentile. The error bars, or whiskers, represent the highest and lowest values that are not outliers or extreme values.