The impact of intraductal carcinoma of the prostate on the site and timing of recurrence and cancer-specific survival

Background: To investigate the effect of intraductal carcinoma of the prostate (IDC-P) in radical prostatectomy (RP) specimens in the context of the site of recurrence, time to recurrence, and cancer-specific survival in two academic cohorts of locally, regionally, or distantly recurrent prostate cancer.

Methods: Our cohort included men enrolled into two academic tissue repositories from 1993 to 2011, who were treated with first-line RP who later experienced local recurrence, regional recurrence, or distant metastasis (together termed clinical recurrence, CR). RP material was reviewed to identify IDC-P and to update grading to current standards. The primary endpoint was the initial location of CR. Secondary endpoints included time to CR and cancer-specific survival. Pearson's chi-square, Welch's t-test, Mann-Whitney U test and Fisher's exact test were performed for univariate analyses. Multinomial logistic regression was used for multivariate analyses. Cancer-specific survival was analyzed with the generalized Wilcoxon test and Cox regression.

Results: Eighty-five patients with CR were included in the analysis. IDC-P was present in 78.5% of patients from Center 1 and 70.0% from Center 2 (P = 0.547). IDC-P was independently associated with distant metastasis at initial CR (multivariate odds ratio = 6.27, P = 0.015). IDC-P status did not affect time to recurrence; median survival without recurrence was at 53 months for IDC-P(+) and at 50 months for IDC-P(-) (P = 0.441). Distant metastases at the initial CR event had a 36% reduction of cancer-specific survival compared to local recurrences (P = 0.007). Additionally, prostatic-bed radiotherapy (adjuvant or salvage for biochemical recurrence before distant metastasis) was associated with a 25% reduction in cancer-specific mortality compared to no radiotherapy (P = 0.023). Similar reduction in cancer-specific mortality was observed in the subgroup of patients with distant metastasis and IDC-P when treated with radiotherapy (29%, P = 0.050).

Conclusions: In our cohort, presence of IDC-P was an independent factor for distant metastasis at initial CR, but did not have a significant impact on time to CR. Furthermore, metastatic patients showed statistically reduced cancer-specific mortality when treated with radiotherapy. This reduction in cancer-specific mortality was also identified in patients with IDC-P. Future large scale validation studies should take into account the presence of IDC-P and confirm its impact on disease progression.