A drug activated by laser light which successfully destroys early prostate cancer while avoiding surgery side effects has been labelled a "huge leap" forward.
Trial results reflected favourably on the new technique, called vascular-targeted photodynamic therapy (VTP), in comparison to standard prostate cancer care.
Of 196 men who underwent the treatment, about half showed no signs of the disease two years later.
VTP, which involves injecting a light-sensitive drug into the bloodstream, "switches" the drug on via laser pulses fired through optical fibres inserted into the prostate.
Results for VTP were significantly better compared with those where men received standard care, with only 13.5% showing no later signs of the disease.
Further results showed that as VTP only targets prostate tumours, it does not cause the long-term problems of impotence and urinary incontinence often associated with "radical" surgery or radiotherapy.
Lead investigator Professor Mark Emberton described the results as "excellent news" for men with early localised prostate cancer.
"This is truly a huge leap forward for prostate cancer treatment, which has previously lagged decades behind other solid cancers such as breast cancer," he said.
Professor Emberton added: "In 1975, almost everyone with breast cancer was given a radical mastectomy, but since then treatments have steady improved and we now rarely need to remove the whole breast.
"In prostate cancer, we are still commonly removing or irradiating the whole prostate, so the success of this new tissue-preserving treatment is welcome news indeed."
Currently, men with low-risk localised prostate cancer are put under "active surveillance", which means monitoring the disease but providing no treatment unless it becomes more severe.
In the trial, consisting of 413 men, participants were randomly assigned either to VTP or active surveillance.
Only 6% of the VTP group later needed radical treatment, compared with 30% of active surveillance patients.
VTP treatment also doubled the average time of cancer progression from 14 months to 28 months.
Professor Emberton said: "We can now pinpoint prostate cancers using MRI (magnetic resonance imaging) scans and targeted biopsies, allowing a much more targeted approach to diagnosis and treatment.
"This means we could accurately identify men who would benefit from VTP and deliver treatment more precisely to the tumour.
"With such an approach, we should be able to achieve a significantly higher remission rate than in the trial and send nearly all low-risk localised prostate cancers into remission."
He added that researchers hope VTP will also be effective against other forms of cancer.