Statistical analysis
All continuous data were expressed as means ± standard deviation,
medians (quartile: 25-75%), or numbers (expressed as percentage, %).
The comparison between groups was analyzed using univariate (unpaired
Student’s t -test and Fisher’s exact test) and multivariate
analyses with a Cox hazard model. A p -value of < 0.05
was considered statistically significant. Recurrence curves were plotted
using the Kaplan-Meier method. All statistical analyses were performed
with R commander, which is a graphical user interface for R (Saitama
Medical Center, Jichi Medical University, Saitama, Japan).