Objective: Based on unfavorable oncological and functional outcomes of non-organ-confined (NOC) prostate cancer (PCa), defined as ≥ pT3, pN1 or both, we aimed to develop a NOC prediction tool based on multiparametric MRI-guided targeted fusion biopsy (TBx).
Materials and methods: Analyses were restricted to 594 patients with simultaneous PCa detection at systematic biopsy (SBx), TBx and subsequent radical prostatectomy (RP) at our institution. Development (n = 396; cohort 1) and validation cohorts (n = 198; cohort 2) were used to develop and validate the NOC nomogram. A head-to-head comparison was performed between stand-alone TBx model and combined TBx/SBx model. Second validation was performed in patients with positive TBx, but negative SBx (n = 193; cohort 3).
Results: The most parsimonious TBx model included three independent predictors of NOC: pretreatment PSA (OR 1.05 95% CI: 1.01-1.08), highest TBx-detected Gleason pattern (3 + 3 [REF] vs. ≥ 4 + 5; OR 9.3 95% CI 3.8-22) and presence of TBx-detected perineural invasion (OR 2.2 95% CI: 1.3-3.6). The combined TBx/SBx model had the same predictors. For the stand-alone TBx and combined TBx/SBx model, external validation yielded accuracy of 76.5% (95% CI: 69.3-83.1) and 76.6% (95% CI: 69.4-83.6) within cohort 2. The external validation of the stand-alone TBx model yielded 72.4% (95% CI: 65.0-79.6) accuracy within cohort 3.
Conclusion: Our stand-alone TBx-based nomogram can identify PCa patients at the risk of NOC, using three simple variables, with the similar accuracy as the TBx/SBx-based model. It is non-inferior to combined TBx/SBx-based model and performs with sufficient accuracy in specific patients with positive TBx, but negative SBx.
Keywords: Extracapsular extension; Nomogram; Perineural invasion; Targeted biopsy; mpMRI.