Analysis of Cell-free DNA (cfDNA) in Men With Elevated PSA Levels

Overview

This is a multi-centre prospective study in which blood samples will be taken from 1500 male patients aged between 21-80 scheduled for prostate biopsy. Analysis of cell-free cancer DNA extracted from these samples will be undertaken to determine whether copy number instability scores derived from the cfDNA correlates with PSA screening levels and prostate biopsy results (i.e. Gleason score) in these patients.

The prostate is the most common site of cancer in men with 240,000 new cases diagnosed annually in the United States with approximately 28,000 yearly deaths. Prostate screening typically relies on digital rectal exam (DRE) and prostate specific antigen (PSA) levels. Limitations of the PSA test include its low sensitivity and low specificity and its inability to distinguish between low-grade and high-grade lesions. Recent screening trials suggest that PSA-based screening programs result in small or no reduction in mortality, and have significant treatment-related adverse events (AEs). Better serum/plasma biomarkers are needed to supplement the PSA test in the diagnosis and management of a disease with a multiplicity of presentations and clinical outcomes. Cancer-derived DNA present in peripheral blood (referred to as cell-free DNA or cfDNA) was first reported in 1948, but research into this area remained in a dormant state for over 50 years. Over the last ten years however, the development of Next Generation Sequencing (NGS) using massive parallel arrays has allowed researchers to create a database robust enough to distinguish normal genomic from non-diploid cfDNA. In 2008, fetal trisomy of chromosome 21 was detected by analyzing cfDNA in maternal blood. Since then, the method has been validated for trisomy 13, 18, and 21 as a clinical laboratory procedure with remarkable accuracy \>99%. Recently, cancer derived cfDNA has been demonstrated to recapitulate genomic tumor DNA. Current clinical acceptance of the utility of cfDNA in cancer diagnosis has been demonstrated in multiple abstracts at the 2014 and 2015 ASCO meetings in Chicago. In a recent publication in Clinical Chemistry, researchers at Vanderbilt University, Gottingen, Germany, and at the University of Toronto, Canada, analyzed cfDNA in the bloodstream from healthy controls as compared to those with clinically diagnosed prostate cancer. The results of this study demonstrated that it is possible to distinguish prostate cancer from healthy controls without prior knowledge of the genetic signature of the tumors and with over three times the sensitivity of the FDA-approved blood test for prostate cancer (i.e., prostate-specific antigen (PSA)). The study examined serum from more than 200 subjects with prostate cancer and more than 200 controls. The comparative data included PSA levels and prostate tissue biopsy grading (referred to as the Gleason score). The technique distinguished prostate cancer from normal controls with 84% accuracy and cancer from benign hyperplasia and prostatitis with an accuracy of 91%. Because the method quantifies the inherent chromosomal instability of cancer and can be followed as a function of time (without having to do an invasive tissue biopsy), it is called a "liquid biopsy." This multi-centre clinical study will analyze cfDNA from subjects scheduled for prostate biopsy and is designed to validate the results obtained in the above-mentioned retrospective study. If validated, the prostate cfDNA determination test will provide a non-invasive test to aid in the diagnosis of prostate cancer, as well as provide guidance on whether a biopsy should be performed. With regard to the study procedures used, the study subject will undergo routine venipuncture and \~20 millilitres of blood (approximately 2 tablespoons) will be collected. The blood will then be processed by the Sponsor's laboratory and sent to the Sponsor's testing facility in Gottingen, Germany.

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