A proposal for integrating intraductal carcinoma of the prostate into pathological T substaging

The present study aims primarily to determine how incorporation of intraductal carcinoma of the prostate (IDCP) detected in radical prostatectomy (RP) specimens into pathological T (pT) impacts patient outcomes. The study included 1190 patients who had undergone RP at Mie University Hospital (Tsu, Mie, Japan) from 2015-2023 (n=470) and at the University of Rochester Medical Center (Rochester, NY, USA) from 2010-2011 (n=720). The risks of biochemical recurrence (BCR) were compared in RP patients with or without IDCP according to pT stage (ie, pT2/IDCP+, pT2/IDCP-, pT3a/IDCP+, pT3a/IDCP-, pT3b/IDCP+, pT3b/IDCP-). The prognosis of the pT2/IDCP- group was significantly better than that of the other groups (P < 0.001). Meanwhile, there was no statistically significant difference in BCR between pT2/IDCP+ and pT3a/IDCP- (P = 0.548). In pT3b patients, IDCP had no additional prognostic impact. IDCP in pT2 and pT3a cases was strongly associated with the risk of BCR. In addition, the prognosis for pT2/IDCP+ vs. pT3a/IDCP- or pT3b/IDCP- vs. pT3b/IDCP+ was comparable. These findings indicate that IDCP may confer a BCR risk comparable to that of extraprostatic extension in pT2 cases, but its prognostic impact appears limited in pT3b disease.