- Biopsies sometimes give wrong diagnosis to men with no cancer or harmless forms of prostate cancer.
- Biopsies can also cause side effects like bleeding, pain and serious infections.
- New study states that MRI picks up 93% of aggressive cancers accurately, compared with 48% for a biopsy.
Men with suspected prostate cancer could avoid unnecessary and invasive biopsies and instead could be given an MRI scan.
This could help improve diagnosis and avoid the dangerous effects of biopsy especially in those who do not have aggressive cancers.
‘Magnetic resonance imaging is twice as likely as biopsy to spot prostate cancer.’
The study estimates that MRI could help one in four (27%) men avoid an unnecessary biopsy and reduce the number of men who are over-diagnosed - diagnosed with a cancer that does not go on to cause any harm during their lifetime - by 5%
Men undergo prostate biopsy if they suspect prostate cancer, experience symptoms or have a prostate specific antigen (PSA) test showing high levels of the PSA protein in their blood.
But PSA test is not always accurate and most men have to undergo biopsies for confirmation.
Each year, in the UK over 100,000 prostate biopsies are carried out and in Europe one million are conducted.
"Prostate cancer has aggressive and harmless forms. Our current biopsy test can be inaccurate because the tissue samples are taken at random. This means it cannot confirm whether a cancer is aggressive or not and can miss aggressive cancers that are actually there." lead author, Dr Hashim Ahmed, UCL, UK.
"Because of this some men with no cancer or harmless cancers are sometimes given the wrong diagnosis and are then treated even though this offers no survival benefit and can often cause side effects. On top of these errors in diagnosis, the current biopsy test can cause side effects such as bleeding, pain and serious infections." Ahmed added.
Testing Accuracy of MP-MRI Scan
Multi-parametric MRI (MP-MRI)scans helps differentiate between aggressive and harmless cancers by providing information about the cancer's size, how densely packed its cells are and how well connected to the bloodstream.
For the study, 576 men with suspected prostate cancer were given an MP-MRI scan followed by two types of biopsy in 11 NHS hospitals.
First, they underwent a template prostate mapping (TPM) biopsy, which was used as a control to compare the accuracy of the MP-MRI and standard biopsy against.
The second biopsy was the standard transrectal ultrasound-guided (TRUS) biopsy - the most commonly used biopsy for diagnosing prostate cancer.
The TPM biopsy found that less than half of the men in the study, about 40%, had aggressive cancer.
The MP-MRI scan accurately diagnosed almost all of the aggressive cancers at 93%, whereas the TRUS biopsy correctly diagnosed only half at 48%.
In men who had a negative MP-MRI scan, nine out of 10 (89%) had either no cancer or a harmless cancer.
In those who do not need immediate biopsies and have harmless cancers, MP-MRI could be used before TRUS biopsy to reduce over-diagnosis of aggressive cancers. This group could instead continue to be monitored by their doctors.
Those thought to have aggressive cancers could have TRUS biopsy to confirm their MP-MRI scan result. This would help in improving detection of aggressive cancers.
"Our results show that MP-MRI should be used before biopsy. Our study found that using the two tests could reduce over-diagnosis of harmless cancers by 5%, prevent one in four men having an unnecessary biopsy, and improve the detection of aggressive cancers from 48% to 93%," said Dr Hashim Ahmed.
"While combining the two tests gives better results than biopsy alone, this is still not 100% accurate so it would be important that men would still be monitored after their MP-MRI scan. Biopsies will still be needed if an MP-MRI scan shows suspected cancer too, but the scan could help to guide the biopsy so that fewer and better biopsies are taken." Ahmed added.
During the study, biopsies resulted in 44 serious adverse events, with eight cases of sepsis caused by a urinary tract infection and 58 cases of urinary retention.
More research is needed into the cost-effectiveness of this approach, how it affects hospital capacity and ensuring there are enough radiologists to conduct the MP-MRI in the NHS.
The study is published in The Lancet
- Hashim Ahmed et al. Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study. The Lancet ; (2017)