Nodal and periprostatic imaging in localized prostate cancer management

Abstract

The local lymph nodes status is a major prognostic factor in prostate cancer (PCa). Robot-assisted sentinel node biopsy (SNB) is a minimal invasive technique with the advantage of histopathologic examination and confirmation of metastatic nodal disease resulting in a more accurate staging, avoiding the toxicity of extended pelvic lymph node dissection (ePLND). Based on our results, in PCa patients treated with external beam radiotherapy, SNB is an accurate selection tool for the addition of pelvic radiation therapy and androgen derivation therapy only in histologically node positive patients treated with low complication rates and better than nomogram-expected biochemical recurrence outcomes. In addition we demonstrated that in patients treated with robot-assisted radical prostatectomy (RARP), SNB combined with ePLND improves the biochemical recurrence free rate (BCR) compared to ePLND only. Moreover, BCR outcome was better than the prediction of MSKCC nomogram. We preformed also the first external validation of Winter nomogram, which is a SN based nomogram, demonstrating high accuracy for the prediction of lymph node invasion which was comparable to the predictions of MSKCC and Briganti nomograms. However, further research and randomized studies to assess the effect of SNB on lymph node detection rate and the relationship between SNB and BCR are warranted. Local staging with multiparametric (mp)-Magnetic Resonance Imaging (MRI) has become widely available and provides new diagnostic means to assess the local extent of prostate tumours. In our cohort we demonstrated high sensitivity (85%) and specificity (95%) of MRI for the detection of seminal vesicle invasion which was significantly improved with the radiologist’s expertise. Moreover we demonstrated that MRI is useful for classifying PCa patients treated with RARP in benign prostate hyperplasia (BPH) patterns which were found to be associated with preoperative lower urinary tract symptoms. The later were significantly improved after the prostatectomy. Moreover we observed that periprostatic fascia thickness determined in MR images combined with intraoperative fascia preservation score were correlated to post-prostatectomy erectile function outcome. The MRI analysis indicated a large anatomical heterogeneity in FT between patients, as was the case in histologic evaluation of the fascia. Finally we developed a model for predicting incontinence after prostatectomy based on the observations that more extensive fascia preservation as well as longer membranous urethral length and shorter inner levator distance independently predict improved continence recovery. These results are a step closer to provide a more personalized approach in counselling a patient who consider RARP as treatment for prostate cancer.