Reduced sensitivity of multiparametric MRI for clinically significant prostate cancer in men under the age of 50.

Introduction: Three percent of all new diagnosed prostate cancer (PC) patients arc under the age of 50. Multiparametric MRI (mpMRI) is considered as increasingly powerful tool for decision-making in diagnosis of PC and in some active surveillance protocols. Since prostate architecture changes with age, we evaluated the sensitivity of mpMRI to detect clinically significant PC in patients under the age of 50 compared to pair-matched older patients. Methods: Data from a prospective collected and ethics approved database were retrospectively analyzed. We reviewed 1,395 records of PC patients from the years 2012-2017, identifying those under the age of 50 who had radical prostatectomy as primary treatment, a pre-operative mpMRI, a full clinical data set and who had clinically significant cancer (N=51). Tumor size and International Society of Urological Pathology (ISUP) score pair-matching was performed for patients older than 55 years. Clinically significant cancer was defined as ISUP >2 or ISUP 2 with >5% Gleason 4. The sensitivity to detect clinically significant cancer with mpMRI was calculated using pre-operative Prostate Imaging Reporting and Data System (PI-RADS) score and whole-gland final pathology. Results: The median patient age in the young and older groups was 47 and 62, respectively. Both cohorts matched significantly regarding tumor volume (P =0.91) and ISUP score (P=1.0). The median PI-RADS score for the young group was 3, and 4 for the older group. The sensitivity for mpMRI, for PI-RADS 3,4 and 5 was 80.3% (95% CI 66.8%-90.1%) in the young group and 84.3% in the older group (95% CI 71.4% 92.9%), demonstrating no statistically significant difference (P=0.603). Sensitivity of mpMRI for PI-RADS 4,5 was 49.0% (95% CI 34.7%-63.4%) for the young group and 72.5% (95% CI 58.2%-84.1%) for the older group, which differ significantly (P=0.014). Conclusions: mpMRI may have a reduced sensitivity for detecting clinically significant PC in patients under the age of 50 for PI-RADS score 4,5 lesions. Many significant PC lesions were reported as PI-RADS 3 under the age of 50. We recommend that increased significance is placed on PI-RADS 3 lesions found in patients under the age of 50.