Tiny bubbles of fat in urine hold molecules that could predict whether prostate cancer is aggressive, according to research published in the British Journal of Cancer today (Wednesday).
Molecules called RNA that are carried directly from the tumour out of the body in fatty capsules - called exosomes - can be used to figure out which genes are turned on and off in an individual's cancer.
Exosomes are found in urine from people with and without cancer, but seem to be excreted in large quantities by some cancer cells.
For the first time, scientists have discovered that tumour-derived genetic information inside urinary exosomes can be used for tumour detection and biomarker discovery.
This information could help doctors decide which prostate cancers are aggressive and require rapid treatment. Many cases do not progress and can be left untreated.
Invasive treatment can leave men with long-term side effects, including incontinence and impotence, so distinguishing between the aggressive and dormant tumours is one of the biggest challenges for researchers in the field.
Up until now, researchers have used levels of proteins, like prostate specific antigen (PSA), produced by cancer cells to try to spot the aggressive tumours.
This new approach analyses RNA - which is involved in the production of proteins like PSA - to take a step further back and find out which genes have gone wrong inside the cancer. Different genes are switched on and off in aggressive and dormant prostate cancers.
Dr Jonas Nilsson, lead author based at the VU University Medical Centre in Amsterdam, said: "We hope that this innovative approach to studying prostate cancer will reveal new biomarkers for aggressive tumours.
"Tumour-derived RNA is preserved in these capsules and gives us an insight into the genetics of an individual's tumour."
Prostate cancer is the most common cancer in men in the UK, with around 34,000 new cases diagnosed each year. Around 10,000 men die from the disease each year in the UK.
Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "This technique is a fresh view on an old problem and could really help scientists find that elusive biomarker.
"It's still unclear what the best treatment approach is for early prostate cancer, so it's important we find answers to this as soon as possible.
"Distinguishing the aggressive tumours that must be treated from those that don't need treatment will go a long way towards resolving this issue."