Table 4.
Extended Multivariate Cox Model Analysis
| Variable | Effect | HR (95% CI) | Median P | |
|---|---|---|---|---|
| Age | 0.84 | 2.31 | (1.65,3.25) | <.001 |
| HV | 0.67 | 1.95 | (1.28, 2.97) | .006 |
| SUVpeak | 0.97 | 2.63 | (1.52, 4.56) | .001 |
| TBmax | −0.75 | 0.47 | (0.28, 0.80) | .010 |
| HIST CoVa | 1.29 | 3.65 | (1.72, 7.73) | .001 |
| HIST QCOD | −0.59 | 0.55 | (0.36, 0.86) | .015 |
| HIST Kurtosis | −0.55 | 0.58 | (0.34, 0.98) | .048 |
| GLRLM Long runs emphasis | −1.26 | 0.28 | (0.14, 0.58) | .001 |
| GLSZM Zone size entropy | 0.74 | 2.10 | (1.18, 3.71) | 0.020 |
| GLSZM Low gray-level zone emphasis | 0.41 | 1.51 | (0.94, 2.45) | 0.110 |
Extended multivariate Cox model obtained by selecting additional variables (conventional or radiomic) to the base model, showing predictor effects, associated hazard ratio (HR) with associated 95% confidence interval (CI), and bootstrap median P-values obtained from 1,000 bootstrap resamples. Nine of the 10 variables are significant at the 5% level; P-values in bold indicate significance after Bonferroni correction. This model has a concordance index of 0.774. The likelihood ratio test confirmed the significant contribution (P = .010) of the additional set of radiomic variables.
HIST CoV, HIST QCOD, and HIST Kurtosis, respectively refer to the coefficient of variation (CoV), quartile coefficient of dispersion (QCOD), and kurtosis of the histogram of discretized uptake values; these 3 features evaluate various aspects of discretized uptake distribution variability. GLRLM long runs emphasize discretized images with long-run lengths (ie, sequences of voxels with the same discretized intensity). GLSZM zone size entropy evaluates entropy (or uniformity) in the distribution of groups of connected voxels with the same discretized intensity. GLSZM low gray-level zone emphasis highlights discretized images containing more low-intensity regions.