Abstract 774: Detection of intraductal carcinoma of the prostate (IDCP) cases focusing on high-grade prostatic intraepithelial neoplasia (PIN) findings regarding invasive carcinoma of the prostate
Authors: Watanabe Ryuta , Arai Osuke , Onishi Tomoya , Kakuda Toshio , Noda Terutaka , Nishimura Kenichi , Fukumoto Tetsuya , Miura Noriyoshi , Kurata Mie , Miyauchi Yuki , Kitazawa Riko , Haffner Michael C. , Kikugawa Tadahiko , Saika Takashi 
Published: April 2023

Background: Intraductal carcinoma of the prostate (IDCP) is a pathological pattern that involves atypical cells proliferating within the normal gland where basal cells are preserved. These exhibit cribriform morphology, a finding associated with poor prognosis. In addition to the TMPRSS2-ERG fusion gene, TP53, RB1, and PTEN deletions and HRR gene mutations, such as a BRCA mutations, are frequently detected in patients with IDCP. The National Comprehensive Cancer Network (NCCN) guidelines suggest that early genetic testing should be considered. However, IDCP recognition is notably low, and diagnosis requires skill.

Methods: Among 1026 cases who underwent total prostatectomy for prostate cancer at our hospital between 2011 and 2021, we selected 98 cases with "prostate cancer with high-grade prostatic intraepithelial neoplasia (PIN) in the background" by referring to the pathology reports. Twelve cases which were considered suggestive of IDCP were reviewed by three pathologists to determine the presence of IDCP. Additionally a gene test of prostatectomy specimens was submitted for the relevant cases to determine the presence or absence of HRR gene mutations.

Results: Five of the twelve cases were determined to be IDCP positive. Characteristics of the five cases are shown in the table. Pathology genetic testing identified HRR-related genetic abnormalities, including BRCA mutations.

Conclusions: We were able to establish IDCP cases from past high-grade PIN cases. As a number of HRR gene mutations of unknown pathological significance were detected, IDCP cases could be retrieved from past cases and genetic abnormalities could be identified efficiently. The findings of the study provide a possible approach to diagnose prostate cancer cases with genetic mutations at an early stage. I am also currently working on a Visium for IDCP, and will present the results of that analysis on the day.

Case 1 Case 2 Case 3 Case 4 Case 5 Age 61 73 80 69 75 iPSA (ng/ml) 31.5 5.5 88.02 7.2 4.67 Gleason Score 4+5 4+4 4+3 4+3 4+3 TNM pT2bN0M0 pT2bN0M0 pT3aN0M0 pT2aN0M0 pT2aN0M0 Follw up periods 28 months 37 months 22 months 45 months 42 months Recurrence None None Death by other causes None 27 months → RT Gene abnormality TOE1, FANCC, CHEK2 RECQL, TOE1, USH2A, PRPF3 APC, POLE, TOE1, ATR, PMS2 RET, BRCA2, TP53 BLM, POLE, BRCA1

Citation Format: Ryuta Watanabe, Osuke Arai, Tomoya Onishi, Toshio Kakuda, Terutaka Noda, Kenichi Nishimura, Tetsuya Fukumoto, Noriyoshi Miura, Mie Kurata, Yuki Miyauchi, Riko Kitazawa, Michael C. Haffner, Tadahiko Kikugawa, Takashi Saika. Detection of intraductal carcinoma of the prostate (IDCP) cases focusing on high-grade prostatic intraepithelial neoplasia (PIN) findings regarding invasive carcinoma of the prostate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 774.