Statistical analysis
Continuous data are presented as mean ± standard deviation or median [range], and categorical variables are given as counts and percentages. Survival rates were calculated using the Kaplan–Meier method. Statistical analyses were performed using the Stat-View Statistical Software Package 5.0 (SAS Institute, Inc., Cary, NC, USA), NCSS 2001 (Number Cruncher Statistical System, Kaysville, Utah).