The grading of intraductal carcinoma of the prostate (IDC-P) associated with conventional prostatic adenocarcinoma (CPA) remains controversial, particularly regarding whether IDC-P exhibiting a solid nest pattern is prognostically equivalent to Gleason grade 5 CPA. We retrospectively analyzed consecutive radical prostatectomy patients with grade 5 CPA as a primary, secondary, or tertiary pattern, as well as cribriform IDC-P, while excluding cases exhibiting comedonecrosis within IDC-P. We then compared clinicopathologic features and long-term oncologic outcomes between those with (n=28 [24.3%]) and without (n=87 [75.7%]) solid-pattern IDC-P. Solid IDC-P cases were significantly associated with a higher incidence of lymph node metastasis, larger estimated tumor volume, and more frequent administration of adjuvant therapy immediately after prostatectomy. No significant differences were observed in preoperative prostate-specific antigen, Grade Group, pT stage, or surgical margin status between the 2 groups. Univariate analysis revealed significantly worse biochemical recurrence-free survival ( P =0.010) and cancer-specific survival ( P =0.003) in patients with solid IDC-P. In multivariable Cox regression analyses, solid IDC-P remained significantly predictive of postoperative recurrence when adjusting for prognostic factors, including Grade Group (hazard ratio 1.902, P =0.039) or the percentage of pattern 5 (hazard ratio 1.986, P =0.028). Solid-pattern IDC-P was thus found to represent an independent adverse prognostic indicator in men undergoing radical prostatectomy, further suggesting that the clinical impact of solid IDC-P versus Gleason grade 5 CPA (or cribriform IDC-P) was not comparable. It might therefore be inadequate to simply translate solid IDC-P as a grade 5 pattern.
Keywords: conventional prostatic adenocarcinoma; intraductal carcinoma of the prostate; prognosis; radical prostatectomy; solid nest pattern.
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