Biopsy proven Gleason score is essential to decide treatment modalities for prostate cancer, either surgical (radical prostatectomy) or non-surgical (active surveillance, watchful waiting, radiation therapy and hormone therapy). Several studies indicated that biopsy proven Gleason score may underestimate Gleason score at radical prostatectomy, hence we aimed to calculate the minimum length of biopsy cores needed to have Gleason score agreement. We evaluated 115 prostate cancer patients who underwent multiparametric magnetic resonance/transperineal ultrasonography fusion biopsy and subsequently, radical prostatectomy. Biopsy proven Gleason score was consistent with Gleason score at subsequent radical prostatectomy in 82.6% of patients, while in 17.4% of patients, Gleason score was higher at radical prostatectomy. Gleason score agreement showed a strong direct association with a ratio > 0.05 between the total volume of biopsies performed in tumor area and the volume of the corresponding tumor at radical prostatectomy. A significant association was also found with a ratio ≥ 0.0034 between the tumor volume in the biopsy and the volume of the corresponding tumor at radical prostatectomy and with a ratio ≥ 0.086 between the tumor volume in the biopsy and the total volume of biopsies performed in the tumor area. These results could be exploited to calculate the minimum length of biopsy cores needed to have a correct Gleason score estimation and therefore be used in fusion targeted biopsies with volume adjustments.
