Exosomes as a Platform for Clinical Diagnostics

Prostate cancer (PCa) affects one in nine men and is the most diagnosed solid tumor cancer among men in the United States. The introduction of the prostate-specific antigen (PSA) biomarker blood test in the late 1980s gave rise to a marked increase in PCa cases. Widespread PSA screening led to the earlier detection of aggressive tumors (screening benefit) and increased detection of indolent tumors (screening risk). Unfortunately, the PSA test is unreliable for detecting high-grade PCa (HGPC), leaving a gap for accurate HGPC diagnoses. In 2012, the US Preventive Services Task Force (USPSTF) recommended against PSA screening due to the limited benefits of broad PSA screening. In 2017, to avoid missing HGPC and potentially increasing PCa mortality, the USPSTF promoted age-specific shared decision PSA testing for men aged 55–69 years.

Several assays, including the ExoDx Prostate (IntelliScore) (EPI) test, were developed to make more informed decisions on which patients could likely defer prostate biopsy and which patients are at higher risk for HGPC and should proceed to biopsy. EPI is a noninvasive urine-based gene expression assay. It does not require a pre-collection digital rectal exam (DRE) nor clinical features to provide a result and helps discriminate benign/low-grade PCa (Grade Group, GG1) from HGPC (>GG2) for men aged ≥50 who are in the PSA “gray zone” (2–10 ng/mL).

Learning Objectives:

1. Discuss exosome basics.
2. Review how exosomes can provide value for clinical diagnostics.
3. Classify how exosomes are being used for prostate cancer early detection.