An experimental biomarker test more accurately detects prostate cancer than any other screening method currently in use, report researchers at the University of Michigan Comprehensive Cancer Center.
The team developed the test based on their recent finding that gene fusions, pieces of chromosomes that trade places with each other causing two genes to stick together, are common in prostate cancer. They found that by overriding molecular switches that turn off excess growth, the gene fusions may be the causative factor in some forms of the disease.
In the current study, the investigators built upon the PCA3 test by screening for six additional biomarkers including the TMPRSS2:ERG fusion molecule as well as some molecules generally overexpressed in prostate cancer and some which are overexpressed in specific cancer subtypes.
The scientists collected urine samples from 234 men with rising PSA levels before they underwent prostate biopsy. Among this group, biopsy results confirmed a diagnosis of prostate cancer in 138 patients; 96 patients were cancer free.
Correlating the urine biomarker test results with the biopsy data, researchers found that, in combination, four of the seven biomarkers were significant predictors of prostate cancer: GOLPH2, which is generally overexpressed in prostate cancer; SPINK1, overexpressed in a subset of these cancers; the PCA3 transcript expression; and TMPRSS2:ERG fusion status. Of the seven markers, only PCA3 had been previously reported as a diagnostic biomarker, according to the investigators.
When tested as individual biomarkers, GOLPH2, PCA3, and SPINK1 each outperformed PSA, which had identified all of the men in the study as potentially positive for prostate cancer. Screening for the presence of the four different RNA molecules accurately identified 80% of patients who had prostate cancer and was 61% effective in ruling out the disease in other study participants. This is more accurate than the PSA blood test and the newer PCA3 test, the research team reports.
The study is published in the February 1 issue of Cancer Research.