The impact of intraductal carcinoma of the prostate on the grade group system.

Abstract

34 Background: The 2014 International Society of Urological Pathology (ISUP) and WHO 2016 classifications proposed a new grade group system for prostate cancer. Intraductal carcinoma of the prostate (IDC-P) is newly recognized on them and is reported to be strongly associated with high-grade and high-volume invasive prostate cancer. Although the presence of the IDC-P influences biochemical failure in radical prostatectomy patients, no data are available regarding the significance of IDC-P in integrating to the classification grade group system. The aim of this study is to enhance the utility of grade group system integrating into the presence of IDC-P. Methods: We retrospectively evaluated 1019 patients with prostate cancer who underwent radical prostatectomy without neoadjuvant or adjuvant therapy at the hospitals that the authors were affiliated with between 2005 and 2013. Data on age, PSA level at diagnosis, clinical T stage (cT), pathological T stage (pT), presence of Gleason pattern 5 (GP5), presence of IDC-P, and surgical margin status were analyzed to predict PSA recurrence after prostatectomy. Results: The median patient age was 67 (range, 45–80) years. The median initial PSA was 6.8 ng/ml (range, 0.4–82 ng/ml). The median follow-up period was 82 (range, 0.7–148) months. IDC-P was detected in 157 patients (15.4%). Among these patients, IDC-P positive rate increased correlated with upgrading. The grade group were as follows: Group 1 without IDC-P, 16.0% (n=163); Group 2 without IDC-P, 46.1% (n=470); Group 3 without IDC-P, 15.7% (n=160); Group 4 without IDC-P, 2.6% (n=27); and Group 5 without IDC-P, 4.1% (n=42); Group 2 with IDC-P, 2.9% (n=29); Group 345 with IDC-P, 12.6% [n=128; Group 3 (n=60); Group 4 (n=13); Group 5 (n=55)] Group 3, 4, and 5 with IDC-P showed a significantly worse prognosis than any other groups without IDC-P and Group 2 with IDC-P (p<.0001). In a multivariate analysis, integrating IDC-P into ISUP Grade, PSA level at diagnosis, and surgical margin status significantly predicted the prognosis (P < .0001). Conclusions: Integrating the presence of IDC-P into the grade group system will improve the accuracy of patients’ outcome prediction.