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DNA Integrity Assay: A Plasma-Based Screening Tool for the Detection of Prostate Cancer

Authors' Affiliations: ¹ Robert E. Wise Research and Education Institute, Cell and Molecular Biology Laboratory; ² Department of Urology, Lahey Clinic Medical Center, Burlington, Massachusetts; and ³ Applied Research Group, Exact Sciences Corporation, Marlborough, Massachusetts

Requests for reprints: Ian C. Summerhayes, Cell and Molecular Biology Laboratory, Lahey Clinic, 31 Mall Road, Burlington, MA 01805. Phone: 781-744-2990; Fax: 781-744-2984.

Purpose: The aim of this study was to evaluate the utility of the DNA integrity assay (DIA) as a plasma-based screening tool for the detection of prostate cancer.

Experimental Design: Blood samples were collected from patients with biopsy-proven prostate cancer prior to prostatectomy (n = 123) and processed as two-spin plasma preparations. The three control groups included: males <40 years old with no history of cancer (group 1, n = 20); cancer-free postprostatectomy patients (group 2, n = 25), and patients with a negative prostate biopsy (group 3, n = 22). DNA in plasma preparations were isolated, hybrid-captured, and DNA fragments (200 bp, 1.3, 1.8, and 2.4 kb) were multiplexed in real-time PCR. A baseline cutoff was determined for individual fragment lengths to establish a DIA score for each patient sample.

Results: Patients with prostate cancer (86 of 123; 69.9%) were determined to have a positive DIA score of 7. The DIA results from control groups 1, 2, and 3 showed specificities of 90%, 92%, and 68.2%, respectively. Of the patients with negative age-adjusted prostate-specific antigen (PSA) and prostate cancer, 19 of 30 (63%) had a positive DIA score. The area under the receiver operating characteristic curve for DIA was 0.788.

Conclusion: While detecting 69.9% of those with prostate cancer, DIA maintained an overall specificity of 68.2% to 92%, a range favorably comparable to that currently accepted for PSA (60-70%). The variability in specificity between control groups is likely explained by the established 19% to 30% detection of prostate cancer on subsequent biopsies associated with control group 3. DIA detected 63% of the prostate cancers undetected by currently accepted PSA ranges.