Timo Soeterik

91 Nerve Sparing and Risk of Positive Margins Evaluation of Predictors for Positive Surgical Margins The results of the multivariable analysis predicting positive margins are presented in Table 2. Model 1 included solely complete cases. Additional analysis was done after accounting for missing data using multiple imputation (model 2). Overall, model 2 resulted in more precise estimation of coefficients, with narrower 95% confidence intervals compared with the complete case analysis (model 1). In both models, nerve sparing was associated with significantly higher odds of ipsilateral positive margins. Other covariates found to be significant predictors for positive margins in models 1 and 2 were PSAD, highest ipsilateral biopsy ISUP grade 2 and higher, percentage of positive cores on systematic biopsy and presence of EPE on preoperative mpMRI (Table 2). TABLE 2. Multivariable logistic regression analysis predicting positive surgical margins Model 1 a ( N = 3325) OR (95% CI) p Model 2 b ( N = 5148) OR (95% CI) p Age 0.98 (0.96 – 1.0) 0.038 0.98 (0.97 – 1.00) 0.105 PSAD 2.72 (1.57 – 4.72) <0.001 3.64 (2.36 – 5.90) <0.001 ISUP grade Benign 1 2 3 4 5 Referent 1.15 (0.79 – 1.68) 1.48 (0.97 – 2.27) 1.65 (0.99 – 2.73) 2.09 (1.20 – 3.66) 5.56 (2.90 – 10.63) 0.4675 0.0687 0.053 0.0097 <0.001 Referent 1.24 (0.93 – 1.81) 1.58 (1.13 – 2.53) 1.62 (1.13 – 2.69) 2.11 (1.39 – 3.59) 4.43 (3.17 – 10.12) 0.204 0.015 0.037 0.002 <0.001 DRE T1 T2 T3 Referent 1.33 (0.99 – 1.79) 1.45 (0.81 – 2.60) 0.0618 0.2143 Referent 1.21 (0.93 – 1.62) 1.66 (0.93 – 3.01) 0.173 0.075 MRI stage Organ-confined EPE Referent 1.48 (1.05 – 2.07) 0.024 Referent 1.42 (1.03 – 1.91) 0.031 % Positive cores 3.50 (2.23 – 5.49) <0.001 3.82 (2.50 – 5.86) <0.001 Nerve sparing Non-nerve sparing Nerve sparing Referent 1.53 (1.15 – 2.03) <0.001 Referent 1.42 (1.14 – 1.82) 0.005 a Model 1: complete case analysis. b Model 2: imputed case analysis using multiple imputations. * The analysis also included the covariates: hospital (N=4) and surgeon (N=14), ORs are not shown. Abbreviations: PSAD = prostate-specific antigen density, DRE = digital rectal examination, EPE = extraprostatic extension. 5