Outcomes of men with ductal prostate cancer undergoing definitive therapy for localized disease.

350 Background: Ductal prostate adenocarcinoma (DAC) is an aggressive variant of prostate cancer (PC). We aimed to assess the outcomes of men with localized DAC undergoing radical prostatectomy (RP) or external beam radiotherapy (RTx) compared to acinar adenocarcinoma of the prostate (PAC) and investigate any difference between these treatment modalities. Methods: All patients presenting to our institution with localized DAC from January 2005 - November 2018 were compared to a pooled cohort of patients from 3 tertiary referral centers who underwent RP for Gleason 8 PC and a cohort of high risk PC patients who underwent RTx for PAC. Patient, tumor characteristics and outcome data were analyzed. Results: 257 men with DAC were identified and compared to 803 with PAC. 203 men with DAC and 729 men with PAC underwent RP while 54 men with DAC and 74 men with PAC underwent RTx. Men with DAC were older (65 vs 63 years and 70.5 vs 66 years) and had higher cT3/T4 stage (43% vs 2.8% and 44.5% vs 31.1%) in both groups, respectively (all p <0.05). The median follow-up for men undergoing RP was 34 (range 0.9 to 177) months and 73.4 (range 0.6 – 224.2) months for men having RTx. Presence of DAC was an independent risk factor for metastases (HR 2.5 (95% CI 1.4- 4.8); p<0.01) and death (HR 2.3 (95% CI 1.1 – 4.7); p=0.02) following RP. The 3- year overall survival (OS) rates for DAC and PAC in men undergoing RP were 93.3% vs 99.3% (p<0.01). On adjusting for Gleason score, clinical T stage, PSA and age, DAC was also an independent risk factor for death (HR 6.1 (95% CI 1.7-22.2); p<0.01) in men undergoing RTx with 5-year OS rates of 100% and 81.6% for DAC and PAC, respectively. There was no difference in the OS of men with DAC between RP and RTx. Conclusions: Men undergoing RP or RTx for localized DAC had worse outcomes compared to PAC, but no survival difference was seen between these treatment modalities. DAC behaves clinically differently than PAC. Further evaluation of the underlying biology and potential for specific targeted multimodality therapies in DAC is needed.