MP56-13: The percentage of positive MRI targeted biopsy cores is inversely associated with Gleason score upgrading at radical prostatectomy. The importance of accurate targeted sampling

Armando Stabile, Jeffrey Karnes, Giovanni Motterle, Giorgio Gandaglia, Nicola Fossati, Vito Cucchiara, Francesco Barletta, Simone Scuderi, Daniele Robesti, Enrico Camisassa, Aldo Rizzo, Federico Deho', Andrea Gallina, Sabrina Comana, Alberto Martini, Gabriele Sorce, Paolo Dell'Oglio, Andrea Salonia, Vincenzo Mirone, Francesco Montorsi, Francesco De Cobelli, Alberto Briganti

Introduction: The introduction of mp-MRI has opened the way to MRI-targeted biopsies. However, the optimal biopsy approach to the index lesion (IL) is still unknown. Accurate targeted sampling is key not only for diagnostic purposes but also for accurate cancer grading. We hypothesized that the percentage of positive TBx cores (%TBxC) taken at the IL is related to the rate of upgrading at radical prostatectomy (RP)

Methods: We identified 309 men with positive MRI of the prostate (PI-RADS=3) receiving TBx plus systematic biopsy and a subsequent radical prostatectomy (RP) for clinically localized prostate cancer (PCa) with biopsy Gleason score (GS) = 7 at two referral Centres between 2013 and 2019. All men received at least 3 TBx cores at TBx of the IL. The study outcome was the presence of upgrading at RP, defined as an increase in GS at RP as compared to biopsy (from 6 to 7 or from 7 to 8-10). Multivariable logistic regression models (MVA) were used to assess the relationship between %TBxC (defined as the ratio between the number of positive TBx cores and the total number of TBx cores) and the rate of upgrading after accounting for the following confounders: age, PSA density, clinical stage at DRE, MRI lesion volume, PI-RADS score (3 vs 4 vs 5). Non-parametric loess function was used to graphically explore the effect of %TBxC on the rate of GS upgrading

Results: The median number of TBx cores was 5 (IQR: 4-10). Overall, 23% and 77% of men had GS 6 and 7 at biopsy. Overall 9, 83, and 8% of men had GS 6, 7 and 8 at final pathology and 18% (n=56) of all men experienced upgrading at RP. At MVA the %TBxC was the only independent predictor of upgrading at RP (OR: 0.18; p=0.002) showing a protective effect. Figure 1 shows the relationship between %TBxC and GS upgrading. In men with a %TBxC of 10% the risk of upgrading was 35% while in men with a %TBxC of 90% the risk of upgrading at RP was only 10%.

Conclusions: The overall %TBxC is inversely associated with the risk of GS upgrading at RP and it represents a useful parameter to help stratifying the risk of upgrading at RP. Our data indirectly also supports the importance of accurate biopsy sampling of the IL Source of

Funding: none