[Pathological findings of visible and non-visible tumors on multiparametric magnetic resonance imaging (MRI) prior to radical prostatectomy].

INTRODUCTION: As urologists are questioned about the overtreatment of localized prostate cancer, multiparametric MRI can diagnose significant prostate cancer thanks to targeted biopsies. However, some tumors cannot be detected by MRI. What are the pathological characteristics of those tumors?

MATERIALS AND METHODS: We have selected 144 consecutive patients treated with radical prostatectomy for clinically localized prostate cancer diagnosed on systematic and targeted biopsies (Koelis® ) according to multiparametric MRI findings. On MRI, each suspicious area was graded according to the PI-RADS score v1.0. On radical prostatectomy specimen, tumor foci with a Gleason score greater than 3+3 and/or a tumor volume greater than 0,5cm3 were considered significant. The grade-four tumoral volume was calculated by multiplying the tumoral volume by grade 4 tumoral percentage.

RESULTS: Two hundred and seventy seven tumors were identified. A hundred and thirty nine were non-visible on MRI. They had a significantly lower volume (0.15cm3 versus 1.45cm3 , P<0.0001) and a Gleason score significantly lower (P<0.0001) than apparent tumors. 17.3% of non-apparent tumors were significant. Moreover, the grade-four tumoral volume of significant non-apparent tumors was significantly lower than that of significant apparent tumors (0.11cm3 versus 0.66cm3 , P<0.0001).

CONCLUSION: Non-apparent prostate tumors on multiparametric MRI have a Gleason score, a tumor volume - and consequently - a grade 4 tumor volume significantly lower than apparent tumors.

LEVEL OF PROOF: 4.