Delaying treatment for localised prostate cancer does not increase the risk of death, new research suggests.

According to a new study, active monitoring of the disease has the same high survival rates after 15 years as radiotherapy or surgery.

Men on active monitoring – which involves regular tests to check on the cancer – were more likely to see it progress or spread than those receiving radiotherapy or surgery.

However, this did not reduce their likelihood of survival, the study suggests.

The trial also found the negative impacts of radiotherapy and surgery on urinary and sexual function persist much longer than previously thought – for up to 12 years.

Researchers suggest the findings show treatment decisions following diagnosis for low and intermediate risk localised prostate cancer – cancer inside the prostate that has not spread to other parts of the body – do not need to be rushed.

The latest findings from the ProtecT trial, led by the Universities of Oxford and Bristol, were presented at the European Association of Urology (EAU) Congress in Milan and published in the New England Journal of Medicine.

Lead investigator Professor Freddie Hamdy from the University of Oxford said: “It’s clear that, unlike many other cancers, a diagnosis of prostate cancer should not be a cause for panic or rushed decision making.

“Patients and clinicians can and should take their time to weigh up the benefits and possible harms of different treatments in the knowledge that this will not adversely affect their survival.”

The trial, the first to fully evaluate three major treatment options – active monitoring, surgery (radical prostatectomy) and radiotherapy with hormones for men with localised prostate cancer, was conducted in nine UK centres.

Between 1999 and 2009, 1,643 men aged 50-69, who were diagnosed with localised prostate cancer were put into one of the three treatment groups.

They were followed for an average of 15 years, to measure death rates, cancer progression and spread, and the impact of treatments on quality of life.

The study found that around 97% of the men diagnosed with prostate cancer survived 15 years after diagnosis, irrespective of which treatment they received.

After 15 years around a quarter of those on active monitoring had still not had any invasive treatment.

Men from all three groups reported similar overall quality of life.

The negative effects of surgery or radiotherapy on urinary, bowel and sexual function were found to persist much longer than previously thought.

Research published in 2016 found that, after 10 years follow up, men whose cancer was being actively monitored were twice as likely to see it progress or metastasise than those in the other groups.

While the assumption had been this might lead to a lower survival rate for men on active monitoring over a longer time period, the results from the 15-year follow up show this is not the case.

Prof Hamdy said: “This is very good news.

“Most men with localised prostate cancer are likely to live for a long time, whether or not they receive invasive treatment and whether or not their disease has spread, so a quick decision for treatment is not necessary and could cause harm.

“It’s also now clear that a small group of men with aggressive disease are unable to benefit from any of the current treatments, however early these are given.

“We need to both improve our ability to identify these cases and our ability to treat them.”

Co-investigator Professor Jenny Donovan, from the University of Bristol, said: “Now men diagnosed with localised prostate cancer can use their own values and priorities when making the difficult decisions about which treatment to choose.”

Researchers say the new trial also highlighted flaws in current methods to predict which prostate cancers are likely to grow quickly and spread.

Initially, all those involved in the trial were diagnosed with localised cancer and 77% of them were deemed low risk.

Reassessment using more modern methods showed that a far greater number would now be considered intermediate-risk – and in around 30% of men, the disease had already spread beyond the prostate.

This means the men in the study had higher grade and stage disease than was thought initially.

Some of the men who subsequently died of their prostate cancer had been assessed as low risk at diagnosis, which the researchers say is an issue of concern.

Professor Peter Albers, chair of the EAU’s Scientific Congress Office and a urologist at Dusseldorf University, said it was “clear” that not enough is known about the biology of the disease to determine which cancers will be the most aggressive, and more research is urgently needed.