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Figure 1. Identification of optimal cutoff values of age of diagnosis (A, B) and tumor size (C, D) via X-tile analysis.
Optimal cutoff values of age were identified as 38, 54, and 66 years based on overall survival. Optimal cutoff values of tumor size were identified as 2.9 cm and 10.0 cm based on overall survival. Histogram and Kaplan-Meier analysis were developed based on sink cutoff values.
Figure 2. Nomograms to predict 3- and 5-year (A) overall survival (B) cancer-specific survival for patients with chordoma.
A vertical line can be drawn between each variable and the points scale to acquire the points of each variable. Predicted survival rate was calculated according to the total points by drawing a vertical line from the Total Points scale to the overall survival or cancer-specific survival scale.
Figure 3. Internal calibration plots of 3-year (A) and 5-year (B) overall survival nomogram calibration curves; 3-year (C) and 5-year (D) cancer-specific survival nomogram calibration curves.
The cohort was divided into five subgroups with the equal sample size for present internal validation. The dashed line represents an excellent match between actual survival outcome (Y-axis) and nomogram prediction (X-axis). Closer distances between dashed line and points indicate higher prediction accuracy.
Table 1: Baseline demographic and clinical characteristics of patients with chordoma
Variables Training cohort Validation cohort
Surgical stage, n, %
Chemotherapy, n, %
No significant differences regarding patient age, gender, primary site, tumor size,
histology, surgical stage, use of surgery, use of chemotherapy and use of radiation
were found between training and validation cohort.
Table 2: Univariate cox regression analysis of cancer-specific survival and Overall survival in the training cohort
Variables Cancer-specific survival