Time course of the sequential triangular test for statistical analysis of the PFS until statistical significance in April 1999. Z is the log-rank statistic and indicates the deviation of the observed number from the expected number of events in the IFN-α group under the null hypothesis of no difference. V is the variance of Z and is approximately equal to a quarter of the observed number of events in both groups. The sample path crossed the upper line; thus, a significant advantage of ASCT could be detected. At the time of the final analysis, the value for Z was 26.6, and the value for V was 32.9.