The influence of the presence of intraductal carcinoma of the prostate on the grade group system's prognostic performance

Background Although the presence of intraductal carcinoma of the prostate (IDC-P) influences biochemical failure in radical prostatectomy patients, no data are available regarding the impact of its integration into the classification grade group system. Thus, the aim of this study was to enhance the utility of the grade group system by integrating the presence of IDC-P. Methods This study was a retrospective evaluation of 1019 patients with prostate cancer who underwent radical prostatectomy between 2005 and 2013 without neoadjuvant or adjuvant therapy. The data on age, prostate-specific antigen (PSA) level at diagnosis, 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 and the median initial PSA level was 6.8 (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, the increase in the positive rate of IDC-P correlated with tumor upgrading. The grade groups (GGs) were as follows: GG1 without IDC-P, 16.0% (n = 163); GG2 without IDC-P, 46.1% (n = 470); GG3 without IDC-P, 15.7% (n = 160); GG4 without IDC-P, 2.6% (n = 27); GG5 without IDC-P, 4.1% (n = 42); any GG with IDC-P, 15.4% [n = 157; GG 2 (n = 29); GG3 (n = 60); GG4 (n = 13); GG5 (n = 55)]. Any grade Group with IDC-P showed significantly worse prognosis than any other group without IDC-P (P < 0.0001). In a multivariate analysis, integration of the IDC-P into the Grade Groups, the PSA level at diagnosis, and the surgical margin status were significant prognostic predictors (P < 0.0001, < 0.0001 and < 0.0001, respectively). Conclusions Integrating the presence of IDC-P into the grade group system will result in more accurate predictions of patient outcome.