A cup and no needle? New urine test for cancer
Rather than use blood, researchers have developed a new urine test that can screen men for prostate cancer, identifying those with high risks and even the cancer's aggressiveness.
Currently, blood tests for prostate cancer measures elevated levels of a protein called serum prostate-specific antigen (PSA). However, serum PSA levels elevate for many reasons unrelated to cancer.
This of course means there're lots of misdiagnoses and about 1 million biopsies a year, some completely unnecessary.
So a team led by Arul Chinnaiyan from the University of Michigan Medical School, Ann Arbor, looked for another way... genetic markers present in urine:
- First, there is a genetic change specific to prostate cancer: a 'fusion' of 2 genes called TMPRSS2 and ERG. Previous studies showed how TMPRSS2-ERG fusions are present in 50% of PSA-screened men with prostate cancer.
- Also, a portion of RNA called prostate specific antigen 3 (PCA3) is seen in unusually high levels in more than 95% of prostate cancer.
They found that men with high levels of TMPRSS2-ERG along with PCA3 likely have prostate cancer. The combination was more predictive than either marker alone.
Every year, Science News reports, hundreds of thousands of men getting a physical examination find themselves in a gray zone, showing signs of prostate cancer on the blood test. For these men, the new tool could help guide their decision to undergo invasive (needle) biopsies.
To test the new test's accuracy:
- The researchers screened over 1,000 men with the new urine test.
- Then they were separated into different categories of cancer risk: lowest, intermediate, highest.
- Subsequent biopsies resulted in cancer diagnoses in 21%, 43%, and 69% of the men in those respective groups.
Higher urine test scores also correlated with the aggressiveness of the cancer – something that biopsies can't do reliably. In the low-risk group, only 7% had aggressive cancer, compared with 40% of the men classified as high-risk.
"You can have low PSA and have cancer, or high PSA and not have cancer," says study researcher Michigan’s Scott Tomlins. This new urine test, however, can be used "to stratify men into saying, 'You have a high chance of having cancer, and you should get a biopsy now, or if you are in a lower risk group you have a much lower risk of cancer and perhaps you could delay the biopsy,'" he adds.
According to Nature News, the results pave the way for Gen-Probe, the molecular diagnostic company based in San Diego that has licensed the test, to seek approval from the US Food and Drug Administration.
BUT, urine-based tests aren't likely to replace the PSA test any time soon. According to Chinnaiyan: "the bar will be pretty high when attempting to replace a test physicians have used for so long."
The findings were published today in Science Translational Medicine.
Image by insanephotos via Flickr
This post was originally published on Smartplanet.com