Outcome after classification by the COG risk classification algorithm. (A) CCG 1950s/1960s B-precursor ALL event-free survival outcome by COG risk classification algorithm. The P value for the log-rank test was less than .001. Hazard ratios (with low risk being the baseline) were 1.53 for standard risk, 2.73 for high risk, and 8.82 for very high risk. (B) POG ALinC 16 B-precursor ALL event-free survival outcome by COG risk classification algorithm (does not include rapidity of response because those data were not collected for these studies). The P value for the log-rank test was less than .001. Hazard ratios (with the low-risk group being the baseline) were 2.05 for standard risk, 3.34 for high risk, and 15.02 for very high risk.