Description

Background and study aims:

The aim of this study is to improve the way prostate cancer is diagnosed by looking at two different types of MRI scans and two different types of prostate biopsy (tissue samples). A large study such as this is required to help the NHS decide how to diagnose prostate cancer in the future. If a person is suspected of having prostate cancer, then they are referred by their GP. At the hospital clinic, the participant will then have an MRI scan. If this scan shows that cancer might be present, then the doctor will usually suggest that the patient has a biopsy. There are two ways of doing a prostate MRI. One takes 30-40 minutes and requires a contrast injection called gadolinium (like a dye). This is called long MRI and is most commonly used in the NHS. Gadolinium is safe as it rarely causes any bad reaction but using it means that the scan takes more time. Another type of MRI takes 15-20 minutes and does not use gadolinium contrast. This is called a short MRI. Many studies over the last 5 years have shown that the long and short MRIs are similar in their accuracy in diagnosing important prostate cancer. These studies have not been of high quality or large enough to change NHS practice. Patients with suspicious areas on the MRI are usually advised to have a prostate biopsy. This involves taking tissue samples using a needle. The samples are then looked at under the microscope by a pathologist to see if cancer cells are present. There are two ways of doing a prostate biopsy. One is where the person doing the biopsy decides where to put the biopsy needle by looking at the MRI scans that have been already taken on a computer screen. The needle is guided to the prostate using live ultrasound scans that are shown on a different screen near the patient. The biopsy operator makes a judgement about where to place the biopsy needles. This is called visual registration. Tissue samples from other areas of the prostate that look normal on the MRI scans are also taken to ensure cancer is not missed. The other type of biopsy is called image fusion. During image fusion biopsy, the biopsy operator uses the MRI scans that have been taken beforehand but laid on top of the live ultrasound images during the biopsy. This uses software and takes a few minutes longer to perform. Once the MRI images and ultrasound images are 'fused', the actual biopsies are taken as normal. Studies over the last 5 years have shown mixed results. Some have shown that image fusion biopsy is no better than visual registration biopsy, whilst a few have shown it might make a difference in improving cancer detection. As a result, it is not known for certain which way is better. A large study is needed to show whether the investigators need to do image fusion or not, in order for the NHS to decide whether or not to use it in all hospitals doing prostate biopsies.