Image: The photomicrograph shows the appearance of a low grade carcinoma of the prostate that can be difficult to recognize as malignancy, particularly in small needle biopsies (Photo courtesy of the University of Washington).
Two independent trials have now validated the performance of an epigenetic test that could provide physicians with a better tool to help eliminate unnecessary repeat prostate biopsies.
Patients with a negative biopsy have been evaluated with an epigenetic test to identify those at low risk for harboring cancer missed through biopsy sampling error who could forego an unnecessary repeat biopsy.
Scientists at the James Buchanan Brady Urological Institute (Baltimore, MD, USA) working with colleagues from other institutes, evaluated the archived, cancer negative prostate biopsy core tissue samples of 350 subjects from a total of five urological centers in the USA. All subjects underwent repeat biopsy within 24 months with a negative (controls) or positive (cases) histopathological result. Centralized blinded pathology evaluation of the two biopsy series was performed in all available samples from each site.
Formalin fixed, paraffin embedded tissue cores were epigenetically profiled based on three genes: glutathione S-transferase pi (GSTP1), adenomatous polyposis coli (APC) and Ras association (RalGDS/AF-6) domain family 1 (RASSF1). GSTP1 methylation is a specific biomarker for prostate cancer and this gene is methylated in up to 90% of prostate cancer cases. Additionally, APC and RASSF1 are important field effect markers and increase the diagnostic sensitivity of the assay. Epigenetic analysis was performed in random, blinded fashion using a multiplex methylation specific polymerase chain reaction (MDxHealth; Irvine, CA, USA).
After correcting for age, prostate specific antigen (PSA), digital rectal exam, histopathological characteristics of the first biopsy, and race, this epigenetic test proved to be the most significant, independent, and strongest predictor of patient outcome with an odds ratio of 2.69 as well as the most valuable diagnostic aid of all evaluated risk factors. Alan W. Partin, MD, PhD, the lead author of the study said, “This epigenetic assay is a significant, independent predictor and has been shown to be the most valuable diagnostic aid of all evaluated risk factors in two independent trials. Negative findings of this assay could be used to reduce concern over unsampled cancer and effectively avoid unnecessary repeat biopsies.” The study was published online on April 18, 2014, in the Journal of Urology.
James Buchanan Brady Urological Institute