Urine Assay for Prostate Cancer Advances
SAN DIEGO—A commercial assay may prove to be valuable for determining which men with elevated prostate-specific antigen (PSA) levels or an abnormal digital rectal exam (DRE) are likely to have prostate cancer and hence should undergo biopsy.
PSA testing or a DRE alone has a low specificity for prostate cancer, so a team has developed a urine-based assay that detects methylated cancer-specific enzymes to complement the other tests.
In a study presented at the College of American Pathologists' annual meeting, the team tested the assay on 103 men who had already been diagnosed with cancer and 77 who had not. The assay had a 60% sensitivity and an 81% specificity for prostate cancer.
“Trials are under way to verify the assay's performance and to establish final cutoff values for negative and positive test results,” said lead investigator Jonathan Baden, MSc, senior scientist for research and development at Veridex, the company developing the assay. “We have plans to submit these product data for FDA approval in the near future.”
Another researcher with an interest in screening for methylated cancer markers expressed confidence in the potential value of the assay.
“Future work should attempt to improve on the overall sensitivity and specificity of the system. Use of other urine methylation biomarkers and/or incorporation of serum methylation biomarkers may improve the assay's performance,” said Jinesh Shah, MD, assistant clinical professor of radiation oncology at Columbia University in New York City.
“Overall, this work may ultimately better define which patients, based on screening results, should have a prostate biopsy to determine if cancer is present.”
The assay involves polymerase chain reaction detection of three methylated molecules that are highly specific indicators of prostate cancer. Mr. Baden and his co-investigators tested the assay at nine clinical sites, evaluating 180 patients who had PSA levels of 2-10 ng/mL.
The use of the three markers together yielded a sensitivity of 60%, a specificity of 81%, a positive predictive value of 100%, and a negative predictive value of 78.7%. Furthermore, the assay had a statistically higher accuracy at each of the clinical sites than the use of a standard nomogram that incorporates the patient's age and the combination of PSA testing and DRE.