Incremental accuracy of incorporating MDCT pattern into the R-ISS model. (A) PFS and (B) OS. To determine whether MDCT findings of the AS have incremental predictive value over conventional risk factors, receiver operating characteristic curves for 2 logistic regression models were developed: a basic model (age, sex, and R-ISS stage) and a basic + MDCT model (the basic model plus MDCT findings). Differences in the AUCs were compared. Incorporation of MDCT findings into the basic model resulted in no significant increase in the AUC (P = .671), with a change from 0.61 (95% CI: 0.53-0.69) to 0.61 (95% CI: 0.52-0.69) for PFS. No significant increase of NRI (0.09; 95% CI: −0.38 to 0.19; P = .532) and IDI (−0.006; 95% CI: −0.03 to 0.02; P = .624) was achieved. For OS, incorporating MDCT findings into the basic model did not significantly increase the AUC (P = .404), with a change from 0.66 (95% CI: 0.57-0.74) to 0.68 (95% CI: 0.60-0.76). Nevertheless, both NRI (0.37; 95% CI: 0.07-0.66; P = .015) and IDI (0.03; 95% CI: 0.0004-0.06; P = 0.048) exhibited significant incremental prognostic value for MDCT pattern.