The results of the PROMIS study show that using an MRI scan to decide which men need a prostate biopsy could help a quarter of men safely avoid the painful procedure. These results were presented at the American Society of Clinical Oncology annual meeting yesterday.
The usual way of diagnosing prostate cancer in the UK involves having a blood test (called PSA) and a digital rectal examination. If either of these suggest there might be prostate cancer, or if there are other factors that put the man at high risk of prostate cancer, men are then offered a transrectal-ultrasound (TRUS) biopsy.
The current standard for diagnosing prostate cancer is not ideal. Raised PSA levels can indicate prostate cancer, but other prostate conditions also cause higher PSA levels, so having a high PSA does not necessarily mean that a man has prostate cancer. TRUS biopsies are also not a very good diagnostic tool. Prior to PROMIS, we estimated that TRUS-biopsies might miss clinically important tumours in around 30-50% of cases. On the other hand, if one of the needles happens to take a sample from a clinically unimportant tumour, it can lead to unnecessary anxiety and over-treatment (with associated side-effects of treatment, including incontinence and impotence). TRUS-biopsies can have side-effects, including infections (some life-threatening), pain, urinary problems and bleeding.
PROMIS tested whether a MP-MRI (multi-parametric magnetic resonance imaging) scan before biopsy could identify men who might safely avoid a biopsy. PROMIS compared the accuracy of both MP-MRI and TRUS-biopsy against another, more accurate but more invasive type of biopsy, called Template Prostate Mapping (TPM) biopsy.
Between May 2012 and December 2015, 740 men volunteered for the trial of whom 576 had all three tests – ie. a MP-MRI scan, followed (under general anaesthetic) by a combined TPM-biopsy and TRUS-biopsy. Patients and clinicians were not aware of the results of the other tests until all tests had been completed.
PROMIS found that a MP-MRI scan before biopsy would allow at least one in four men to safely avoid a biopsy. This was because the chance that men with a negative MP-MRI had important prostate cancer was very low. We also found that TRUS-biopsies missed about half of important cancers that needed treatment. PROMIS showed that MP-MRI was much more accurate, identifying more than 90% of patients who had important cancers.
Around 150,000 men in the UK have TRUS-biopsies each year, so these results are likely to have a big impact. If the approach recommended by PROMIS is taken up across the UK, around 40,000 men each year could avoid having biopsies and their associated side-effects. Internationally, the impact of this study could be huge, as there are around 1 million TRUS biopsies carried out in Europe, and another 1 million in the USA, each year. In order for this change to take place safely, work needs to be done to make sure the quality of the MP-MRI scans is high enough, and radiologists reading those scans have been properly trained to spot prostate cancer.
PROMIS was coordinated by the MRC Clinical Trials Unit at UCL, and took place in 11 hospitals in the UK. PROMIS was funded by the NIHR Health Technology Assessment programme (project number 09/22/67) and will be published in full in Health Technology Assessment. The views and opinions expressed therein and in any media associated with this study are those of the authors and do not necessarily reflect those of the HTA programme, NIHR, NHS or the Department of Health.