Ductal Adenocarcinoma of the Prostate Gland Treated With Radical Prostatectomy or Radiation Therapy: A Single Institutional Retrospective Review With Long-Term Follow-Up

Abstract

Ductal adenocarcinoma is a rare variant of prostate cancer considered to be more aggressive than pure acinar adenocarcinoma which often presents at advanced clinical stages in elderly men with urinary symptoms. To better elucidate the behavior of this subtype, we investigated the clinical outcomes of patients who were managed with curative intent. We retrospectively evaluated 31 patients with histologically-confirmed, non-metastatic ductal adenocarcinoma of the prostate who were treated with radical prostatectomy (RP) or radiation therapy (RT) at our institution from 2002-2014. Pathology was required to demonstrate ductal adenocarcinoma in either a pure form or intermixed with acinar elements. Median follow-up was 64.9 months (range: 20.5-174.5 months). 29% of patients presented with significant urinary symptoms including 5 with gross painless hematuria. Median age was 66 (range: 53-80 years) and median pre-treatment PSA was 6.7 (range: 2.3-15.2). Palpable nodularity consistent with cT2 disease was noted in 15 patients; another 15 exhibited clinical T1c exams. Of the cohort, 25 patients underwent RP and 6 patients underwent RT (including 3 patients who received androgen deprivation therapy for at least 6 months). Overall, 15 patients developed biochemical and/or clinical progression and 2 patients died (both from metastatic disease). The RP group accounted for all but one incidences of progression and both deaths. The 5-year/10-year progression-free probability (PFP), prostate-cancer-specific survival (PCSS), and overall survival (OS) rates were 56%/49%, 100%/86%, and 100%/86%. In the RP group, surgical pathology revealed pure ductal type in 7 (28%) patients and mixed ductal/acinar type in 18 (72%) patients. Twelve (48%) patients had pathological tumor classification of pT3a or higher, 11 patients (44%) had post-surgical Gleason score of 8 or higher, and 10 patients (40%) had positive margins. No statistically significant differences were observed between pure type and mixed type in terms of PFS, PCSS, or OS. There was a trend towards pure ductal type presenting in older patients (p=0.07), but no other significant demographic or pathologic differences were found. In the RT group, a high proportion (66%) of patients exhibited pure type, likely secondary to the limitations of biopsy sampling. Notably, the two patients who underwent RP and died from metastatic disease had pure type, pT3b, Gleason 9-10, positive margins, and perineural invasion. In one of the largest single-institution retrospective series of the modern era investigating ductal adenocarcinoma of the prostate treated with curative intent, our data suggest a favorable prognosis comparable to that of pure acinar adenocarcinoma. Although the degree of ductal involvement (pure versus mixed) on pathology was not predictive of outcomes, it may be associated with differences in patient characteristics, especially age.