Collision tumors revealed by prospectively assessing subtype-defining molecular alterations in 904 individual prostate cancer foci.
Academic Article
Overview
abstract
BACKGROUND: Prostate cancer is multifocal with distinct molecular subtypes. The utility of genomic subtyping has been challenged due to inter- and intra-focal heterogeneity. We sought to characterize the subtype-defining molecular alterations of primary prostate cancer across all tumor foci within radical prostatectomy (RP) specimens and determine the prevalence of collision tumors. METHODS: From the Early Detection Research Network cohort, we identified 333 prospectively collected RPs from 2010 to 2014 and assessed ERG, SPINK1, PTEN, and SPOP molecular status. We utilized dual ERG/SPINK1 immunohistochemistry, fluorescence in situ hybridization to confirm ERG rearrangements and characterize PTEN deletion, and high-resolution melting curve analysis and Sanger sequencing to determine SPOP mutation status. Analysis of biochemical recurrence-free of patients with collision tumors was conducted using Kaplan-Meier method. RESULTS: Based on index focus alone, ERG, SPINK1, PTEN, and SPOP alterations were identified in 47.5%, 10.8%, 14.3%, and 5.1% of RP specimens, respectively. In 233 multifocal RPs with ERG/SPINK1 status in all foci, 139 (59.7%) had discordant molecular alterations between foci. Collision tumors, as defined by discrepant ERG/SPINK1 status within a single focus, were identified in 29 (9.4%) RP specimens. CONCLUSION: Interfocal molecular heterogeneity was identified in ~60% of multifocal RP specimens and collision tumors were present in ~10%. We present this phenomenon as a model for the intra-focal heterogeneity observed in previous studies and propose future genomic studies screen for collision tumors to better characterize molecular heterogeneity.
