Ductal adenocarcinoma of the prostate: An unusual entity with atypical behaviour

Abstract

Purpose: Ductal adenocarcinoma of the prostate is a rare and unusual variant of prostate cancer. This case series of 27 patients is the first to report the outcome of pure and mixed ductal adenocarcinoma treated with external beam radiotherapy in Australia. Methods and Materials: A retrospective review was performed of pure and mixed ductal adenocarcinoma of the prostate seen at the Departments of Radiation Oncology of the Sydney Cancer Centre, Royal Prince Alfred Hospital and Northern Sydney Cancer Centre, Royal North Shore Hospital, between 2000 and 2015. Results: Twenty-seven patients were treated with definitive radiotherapy with radical intent between 2000 and 2015, 11 patients (40.7%) with pure ductal adenocarcinoma, and 16 (59.3%) with mixed ductal-acinar adenocarcinoma. The median age was 75 years. Haematuria was the presenting complaint in 9 patients (33%), 10 patients (37%) presented with lower urinary tract symptoms and 9 patients (33%) were asymptomatic at the time of diagnosis. The median initial serum PSA level was 9.6 ng/mL (range 0.18-25). The Gleason Score ranged from 7 to 10. Patients were treated with external beam radiation treatment (EBRT) with doses ranging from 70-84 Gy in conventional 2 Gy per fraction. One patient underwent HDR brachytherapy and one had hypofractionated EBRT (60 Gy in 20 fractions). Lymph nodes were treated in 15 patients to a dose of 60 Gy in 40 fractions. Androgen deprivation therapy was used in 21 patients, for a median duration of 7 months. Median follow-up was 38 months. Four patients (14.8%) experienced biochemical recurrence with a median time to recurrence of 32.5 months. In those with pure ductal adenocarcinoma, four failed locally (three of whom did not meet the Phoenix definition of failure).1 All of these patients received less than 80 Gy or did not receive HDR brachytherapy. Three patients (11.1%) developed metastatic disease, two of whom had CT detected (and biopsy proven) lung metastases. One patient had bone metastases. All three metastases occurred with a PSA level of <3 ng/mL. One patient subsequently died of their ductal prostate adenocarcinoma. Conclusion: This series demonstrates the atypical clinical presentation of this entity (haematuria, urethral mass) as well as its propensity to metastasize to unusual sites.2 Local failure or metastases occur at low absolute PSA values, and may be in the absence of symptoms. We recommend regular CT examinations as part of follow- up for patients with a significant component of ductal adenocarcinoma.