Fig. 2

Identification of optimal cut-off values for the various clinical characteristics using X-tile software analysis. Year of diagnosis: (a) best cut-off value for the year of diagnosis and (b) survival curves for different years of diagnosis. Age: (c) best cut-off value for age and (d) survival curves for different ages. Tumor size: (e) best cut-off value for tumor size and (f) survival curves for different tumor sizes. Based on overall survival, the optimal minimum and maximum cut-off values for the year of diagnosis are 2001 and 2005, respectively, while those for age at diagnosis and tumor sizes are 57 and 73 years and 59 and 176 mm, respectively