In men with elevated prostate specific antigen (PSA), an investigational urine test can detect and stratify prostate cancer, researchers reported.
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The test is based on the detection of a gene fusion that is specific to prostate cancer, combined with another marker, according to Arul Chinnaiyan, MD, PhD, of the University of Michigan Medical School in Ann Arbor, and colleagues.
Stratifying patients by the combined marker identified groups with markedly different risks of cancer, high-grade cancer, and clinically significant cancer on biopsy, Chinnaiyan and colleagues reported online in Science Translational Medicine.
The noninvasive test could allow some men with elevated PSA to avoid a needle biopsy, the researchers noted.
“Many more men have elevated PSA than actually have cancer but it can be difficult to determine this without biopsy,” Chinnaiyan said in a statement. “The hope is that this test could be an intermediate step before getting a biopsy.”
The fusion at the heart of the test involves the genes transmembrane protease, serine 2 (TMPRSS2), and v-ets erythroblastosis virus E26 oncogene homolog (avian) (ERG).
The fusion appears in about half of all prostate cancers, Chinnaiyan and colleagues noted, but when it appears it is almost 100% specific for malignancy.
In a series of experiments, the researchers showed that the fusion gene was associated with indicators of clinically significant cancer at biopsy and prostatectomy.
The indicators included tumor size, high Gleason score at prostatectomy, and upgrading of Gleason grade at prostatectomy, they reported.
But because the fusion gene is not universally present, the researchers created a model that combined it and the prostate cancer antigen 3 (PCA3) gene.
In 1,065 men who underwent biopsy, the researchers used the model to stratify men into three groups – lowest, intermediate, and highest levels of the combined genes.
They found that the groups had distinctly different patterns of risk. Specifically:
- 363, 346, and 356 men were in the lowest, intermediate, and highest score groups, respectively – or 34%, 32% and 33%.
- Biopsy resulted in a cancer diagnosis in 21%, 43%, and 69% of men in the lowest, intermediate, and highest groups, respectively. The difference between the low and high groups was significant at P<0.001.
- 7%, 20%, and 40% of men in the lowest, intermediate, and highest groups were diagnosed with cancer that had a Gleason score of greater than 6. The difference between the low and high groups was again significant at P<0.001.
- Of the 966 men with enough information to determine the Epstein criteria for significance of cancer on biopsy, 15%, 33%, and 61% of men in the three groups, respectively, had Epstein-criteria-defined significant cancer.
The researchers cautioned that the test remains investigational. As well, they noted, most of the men studied so far have been Caucasian, so that additional study is needed to see if the results apply more broadly.