3292 - Radiotherapy vs. Radical Prostatectomy in Patients with Intraductal Carcinoma of the Prostate

T. Stamey¹, K. Armel¹, S. Chen², M. Navaid³, M. C. Larkins¹, A. Bhatt¹, and A. W. Ju⁴; ¹Brody School of Medicine, East Carolina University, Greenville, NC, ²Department of Pathology and Laboratory Medicine, Brody School of Medicine at East Carolina University, Greenville, NC, ³ECU Health Division of Hematology/Oncology Department of Internal Medicine, Greenville, NC, ⁴Department of Radiation Oncology, Brody School of Medicine, East Carolina University, Greenville, NC

Purpose/Objective(s): Intraductal carcinoma of the prostate (IDC-P) is considered both a distinct entity (found alone in ~3% of prostate biopsies) and negative prognostic factor of prostatic cancer (identified in ~20% of all patients with prostate cancer). Current National Comprehensive Cancer Network® (NCCN®) guidelines for all patients with prostate cancer recommend either radiotherapy (RT) or radical prostatectomy (RP) as initial treatment in the context of patient risk and life expectancy. Given the mortality and rarity of this disease, we analyzed treatment trends of patients diagnosed with IDC-P in the US. Materials/

Methods: A retrospective cohort study utilizing the Surveillance, Epidemiology, and End Results (SEER) database sponsored by the National Cancer Institute (NCI) was conducted for patients with a diagnosis of IDC-P between 2000 and 2018. Univariate and multivariate survival analyses were performed using 95% confidence intervals [CI] and a p-value < 0.05 indicating significance.
Results: 423 patients with complete survival, staging, and treatment information were identified. 32% received only RT (10% underwent brachytherapy and 90% received external beam RT (EBRT)), 56% underwent RP, and 8% received both. On multivariate Cox regression analysis, RP improved OS compared to RT (p<0.001). Stratifying by stage, patients with local IDC-P treated with RT only had decreased five-year overall survival (5y OS) compared to those that underwent RP only (72% vs 98%; p<0.001); this did not hold for patients with regional disease (p=0.790). This trend remained true upon comparison of patients either <65 years or =65 years at diagnosis (see Table 1). 5y OS for patients that underwent RP solely was non-inferior to patients that received adjuvant RT after RP in those with either local or regional disease (p=0.513 and 0.491, respectively). No difference was seen in 5y OS regarding modality of RT for patients with local or regional disease (p=0.194 and 0.285, respectively). Proportional analysis of treatment stratified by race revealed White patients were more likely than Asian (7% of cohort) or Black (11% of cohort) patients to receive RP with adjuvant RT, while Black patients were most likely to undergo RP alone (Likelihood Ratio=12.4; p=0.054).
Conclusion: This analysis found RP for IDC-P to offer survival benefit compared to RT and was non-inferior to RP with adjuvant EBRT for patients with local disease; this trend remained true among patients either <65 years or =65 years at diagnosis. No difference in survival was seen between EBRT or brachytherapy among patients treated with RT only. Differences in rates of RP and RT may exist with respect to race. Further investigation of regional differences and the impact of chemotherapy on outcomes for patients with ICD-P is warranted.

Abstract 3292 – Table 1

Stage	Age at Diagnosis	Five-year Overall Survival (Radiotherapy (RT) vs Radical Prostatectomy (RP))	p-value
Local	<65 years	57% vs 99%	<0.001
	=65 years	76% vs 97%	<0.001
Regional	<65 years	100% vs 84%	0.645
	=65 years	88% vs 100%	0.597