Currently men with pussy cat cancers are often put through invasive tests and treatment, suffering side effects such as a loss of sex drive and impotence, when in fact the cancer would not have threatened their life. If a reliable test were found to establish how aggressive the tumour was, these men could be spared this treatment.

JG Ballard, the author of Empire of the Sun and Crash, died from prostate cancer last month at the age of 78 after a lengthy battle with the illness.

Prostate cancer is the most common cancer in men in the UK, with around 34,000 new cases diagnosed annually. Around 10,000 men die from the disease each year in the UK.

Researchers have discovered that information contained in the fatty capsules, called exosomes, comes straight from the tumour and contains information about the genetics of the particular cancer.

Different genes are switched on and off in aggressive and dormant prostate cancers.

Until now, medics have used levels of proteins, like prostate specific antigen (PSA), produced by cancer cells to try to spot the aggressive tumours but this is problematic.

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.”

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.”