The study was the first to use an experimental treatment known as HIFU (high-intensity focused ultrasound) to treat areas of cancer which are only a few millimetres in size, a technique known as focal therapy.
Focal therapy is similar in principle to the "lumpectomy" operation commonly used as an alternative to a full mastectomy in breast cancer.
One year after treatment none of the 41 men in the trial had incontinence, and just one in 10 suffered from impotence – both common side-effects of conventional treatment. The majority (95%) were also cancer-free after a year.
Researchers concluded that "focal therapy of individual prostate cancer lesions, whether multifocal or unifocal, leads to a low rate of genitourinary side-effects and an encouraging rate of early absence of clinically significant prostate cancer".
The results of the phase 1 study, funded by the Medical Research Council and conducted by researchers at University College London, are published in the journal Lancet Oncology.