In-Depth Comparison of Genetic Variants Demonstrates a Close Relationship Between Invasive and Intraductal Components of Prostate Cancer.

Intraductal carcinoma (IDC) of the prostate is often associated with concurrent high-grade invasive prostate cancer (PCa) and poor clinical outcomes. In this context, IDC is thought to represent the retrograde spread of invasive prostatic adenocarcinoma into the acini and ducts. Prior studies have demonstrated a concordance of PTEN loss and genomic instability between the IDC and high-grade invasive components of PCa, but larger genomic association studies to solidify our understanding of the relationship between these 2 lesions are lacking. Here, we evaluate the genomic relationship between duct-confined (high-grade prostatic intraepithelial neoplasia and IDC) and invasive components of high-grade PCa using genetic variants generated by whole exome sequencing. High-grade prostatic intraepithelial neoplasia and IDC were laser-microdissected, and PCa and nonneoplastic tissue was manually dissected from 12 radical prostatectomies. A targeted next-generation sequencing panel was used to identify disease-relevant variants. Additionally, the degree of overlap between adjacent lesions was determined by comparing exome-wide variants detected using whole exome sequencing data. Our results demonstrate that IDC and invasive high-grade PCa components show common genetic variants and copy number alterations. Hierarchical clustering of genome-wide variants suggests that in these tumors, IDC is more closely related to the high-grade invasive components of the tumor compared with high-grade prostatic intraepithelial neoplasia. In conclusion, this study reinforces the concept that, in the context of high-grade PCa, IDC likely represents a late event associated with tumor progression.