The happy fact is that most prostate tumors are slow growing and not fatal. Even better, the current state of genomic fingerprinting is such that we can usually forecast how aggressive and lethal any given prostate tumor will be. But in the majority of cases that involve more than one prostate tumor, it is only ever the largest tumor that is typically fingerprinted – the rest slip in under the radar.

It's almost as if prostate cancer is pranking us.

A team of researchers has published data in European Urology that in hindsight seemed obvious: when we perform genomic fingerprinting on only one tumor sample, a smaller yet more aggressive tumor can potentially missed.

"We examined the molecular composition of heterogeneous cancerous tumors in a patient's prostate. We found a lot of genetic differences among these tumors, and concluded that information from a single cancer biopsy is not sufficient to guide treatment decisions," said Hannelore Heemers, PhD, of Cleveland Clinic's Lerner Research Institute Department of Cancer Biology. "Precise treatment is more complicated and the findings demonstrate a weakness in current genetic fingerprinting in prostate cancer."

Heemers led the team that used next-generation sequencing techniques to genotype prostate tumors from four men who underwent radical prostatectomy at Roswell Park. The researchers also drew upon examined public data from the Cancer Genome Atlas to confirm their findings.

"High risk prostate cancers differ genetically among patients, among the different tumors within an individual patient and even within different sections of a single tumor," said James Mohler, MD, chair of the Department of Urology at Roswell Park Cancer Institute in Buffalo. "Clinicians need to be careful about using the information from a gene-based test, because the analysis may not have been performed on the most aggressive portion of a man's prostate cancer."

The study makes the point that the use of genomic analysis to personalize treatment plans is in its infancy and that many more large studies will be needed to develop the appropriate prognostic tools that can be relied on to guide treatment selection and planning for men with prostate cancer.