The identification of prostate cancer (PCa) patients at high risk for extra-prostatic extension (EPE) is paramount for both treatment planning and patient prognosis [1], [2], [3]. The decision whether to perform nerve-sparing surgery (NSS) and the grade of preservation of neurovascular bundles is strictly related to the risk of positive surgical margins (PSMs). This risk is significantly elevated in cases where the disease extends beyond the prostate capsule [3,4]. In this context, the greatest challenge for urologists is balancing the oncological risk of EPE and PSMs, with the functional benefit of performing a nerve-sparing radical prostatectomy. The risk stratification of EPE at final pathological examination has been historically estimated using tools based on clinical and biopsy parameters such as the Partin tables and the Memorial Sloan Kettering Cancer Center (MSKCC) nomogram [5,6]. Recently, with the widespread of multiparametric magnetic resonance imaging (mpMRI), several mpMRI-based models have been developed to improve the accuracy in the prediction of EPE [7], [8], [9], [10]. However, the low sensitivity and positive predictive value of mpMRI for local staging of PCa, as well as the heterogeneous results shown in external validation cohorts, have limited their use in clinical practice [11], [12], [13], [14].

Microultrasound (microUS) is a high-resolution US-based imaging modality operating at higher frequencies (29 MHz) than conventional US system (6–8 MHz). This imaging tool allows a direct visualization of the alterations suspicious for PCa with a similar accuracy to mpMRI in the detection of clinically significant (cs)PCa [15], [16], [17], [18]. Moreover, microUS offers the opportunity of performing a real-time assessment of both the prostatic capsule and surrounding tissues with potential benefits in local staging [19].

The aim of this study is to develop an easy-to-apply microUS-based nomogram for the prediction of EPE in PCa patients undergoing Robot Assisted Radical Prostatectomy (RARP), thus guiding the plane of dissection and the grade of nerve-sparing.