Population-based study of the incidence and survival for intraductal carcinoma of the prostate.

PURPOSE: The degree to which intraductal carcinoma of the prostate (IDC-P) affects clinical course remains poorly understood owing to small sample sizes from single-center studies. We sought to determine prognostic factors and outcomes associated with IDC-P in radical prostatectomy (RP) specimens.

MATERIALS AND METHODS: This is a retrospective study of RP during 2004 to 2013 using Surveillance, Epidemiology, and End Results to compare IDC-P with non-IDC-P. The effect of IDC-P on overall and disease-specific survival was assessed using Cox regression with a median follow-up of 4.8 years (interquartile range [IQR]: 2.6-7.0y; P = 0.01). Median prostate-specific antigen at diagnosis in IDC-P vs. non-IDC-P was similar (P = 0.23) at 6.2 (IQR: 4.6-13.0) vs. 6.1ng/ml (IQR: 4.6-9.8).

RESULTS: We identified 159,777 RP from 2004 to 2013, and 242 (0.002%) had IDC-P pathologic features. IDC-P was associated with a greater likelihood of extraprostatic stage, pT3/T4, 45.9% vs. 21.6% (P<0.001), higher grade, GS≥ 7, 79.3% vs. 62.7% (P<0.001), lymph node metastases, 5.8% vs. 2.4% (P<0.001), and positive surgical margins, 25.6% vs. 19.5% (P = 0.02). IDC-P was associated with a 3-fold increase in prostate cancer-specific mortality relative to non-IDC-P (hazard ratio = 3.0, 95% CI: 1.5-5.7; P<0.01). Limitations include retrospective design and potential underreporting of IDC-P that leads to underestimation of the true effect size.

CONCLUSIONS: The significance of IDC-P features has been recently recognized by the World Health Organization and it is associated with high-grade, extraprostatic features, and worse prostate cancer-specific mortality. Understanding its prognostic significance better guides adjuvant therapies and clinical trials.