Liquid Biopsy Could Help Identify Aggressive Prostate Cancers, Study Says

A non-invasive test that examines microRNAs — small RNA molecules — in urine may be used to identify aggressive prostate cancers with great accuracy, potentially avoiding unnecessary treatments for slow-growing cancers, a study suggests.

The study, “Temporal stability and prognostic biomarker potential of the prostate cancer urine transcriptome,” was published in the Journal of the National Cancer Institute. 

Prostate cancer is usually easy to diagnose, but it can be difficult to distinguish between aggressive tumors that pose a serious threat to health and slow-growing tumors that probably won’t ever cause problems, even if left untreated.

Unnecessary treatments can be a burden to the individual and the healthcare system, but not getting sufficient treatment can be deadly — and about a quarter of people diagnosed with prostate cancer will fall into one of those two categories.

The current gold standard for diagnosing and assessing risk in prostate cancer is a biopsy — inserting a needle into the prostate and taking cells for examination. This is invasive, and carries risks such as infections. Blood tests are less invasive, but are also less accurate.

Yet the prostate naturally sheds substances into the urine — might a urine test be able to stratify prostate cancer risk, both accurately and non-invasively?

“We developed a three-stage experimental strategy that would maximize statistical and data science considerations to give us the best chance of finding a biomarker to predict prostate cancer aggressiveness,” Paul Boutros, PhD, a co-author of the study and professor at UCLA, said in a press release.

Boutros and colleagues specifically looked at microRNAs — tiny bits of RNA encoded in the genome but not translated into proteins — that were detectable in prostate cancer patients’ urine.

They first figured out which microRNAs they could detect in a small group of 10 patients. They then  used this to inform studies in a larger group of 99 patients. These results were used to develop a panel of seven microRNAs with predictive value, which was tested in another 40 patients.

The microRNAs included in the panel are: miR-3195, let-7b-5p, miR-144-3p, miR-451a, miR-148a-3p, miR-512-5p, and miR-431-5p.

The researchers evaluated participants for at least three years, which allowed investigators to account for variability in RNA levels within an individual.

“Being able to go beyond just a snapshot in time is critical because you are able to focus in on the trends that are associated with the cancer, which is really the most important thing to distinguish in order to develop an accurate biomarker,” Boutros said.

The panel that was developed was able to accurately identify 80% of aggressive cancers in the test cohort. This is a promising start, though the researchers wrote in their paper that “further validation of urine miRNA biomarkers in large tightly defined patient populations is required to improve risk stratification protocols for prostate cancer.”