Statistical evaluation
Statistical analyses were performed via S-PLUS Professional and R
statistics v.1 (MathSoft, Seattle, WA, USA). The descriptive
characteristics of the variables are summarized by mean, median,
frequency and percentage. Kaplan-Meier survival analyses and log rank
test were done to estimate BCR-free rates of all classifications and
compare them. The accuracy of the four prognostic models for prediction
of BCR was quantified according to Harrell’s concordance index11,12. Harrell’s concordance index provides the
probability that, in a randomly selected pair of patients in which one
patient experiences the event (BCR) before the other, the patient who
experiences the event had the worse predicted outcome according to the
predictive model. In accuracy analyses, a value of 100% indicates
perfect prediction versus 50% being equivalent to a toss of a coin. In
our study, the accuracy value of four prognostic models were calculated
according to Harrell’s concordance index. 0.05 was considered as the
significance threshold for p-value.