Prostate cancer is the commonest cancer in men. Current treatments include surgery to remove the whole prostate or radiotherapy of the whole prostate. These radical treatments can treat the cancer effectively but often cause unwanted side effects. Meanwhile widespread screening with prostate-specific antigen has led to an increased diagnosis of localised prostate cancer; at the same time, widespread use of abdominal imaging has led to increased detection of renal masses. In response to demand for improved outcomes with reduced side effects, focal therapy has emerged as an important procedure...