Cancer Biomarker Complements Prostate Test

A DNA-based biomarker blood test could supplement the prostate-specific antigen (PSA) test currently offered to screen men for prostate cancer.

A highly specific circulating biomarker like the Glutathione S-transferase P (GSTP1) enzyme would complement the PSA test and could greatly improve the accuracy of prostate cancer detection before recommending patients for an invasive biopsy.

A cross-disciplinary collaborative effort was conducted under the auspices of the University of Cincinnati (UC; Cincinnati, OH, USA) to perform a meta-analysis on data related to DNA methylation in bodily fluids. More than 2,000 human biologic samples from 1,635 prostate cancer cases and 573 controls were analyzed for the current study, including whole blood, plasma, urine, ejaculates, and other secretions. The data was collected from 22 studies in US and Europe performed between 2000 and 2009.

Alterations of the DNA methylation process are commonly associated with cancerous tumor growth and changes can be detected in bodily fluids. GSTP1 DNA methylation is particularly associated with prostate cancer and can be detected in the bloodstream using high throughput standardized molecular biology techniques. The scientists determined that GSTP1 was a statistically significant biomarker for prostate cancer and could increase the specificity of prostate cancer diagnosis by up to 70% as compared to using the PSA test alone.

Tianying Wu, MD, PhD, a molecular epidemiologist at UC, said, "The PSA test is highly sensitive, but it cannot differentiate between prostate cancer and benign prostatic conditions such as benign prostatic hyperplasia, leading many men to have unnecessary biopsies. Measuring GSTPI in plasma or urine is an easy and noninvasive test. This biomarker will give physicians reassurance regards to whether to conduct biopsies in selected patients." The DNA methylation test in whole blood samples is less sensitive to prostate cancer stages than the same test done in plasma, serum, or urine. The study was published online on June 7, 2011, in the British Journal of Cancer.

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