MRI Improves Prostate Cancer Diagnosis
A trial by the Medical Research Council (MRC) Clinical Trials Unit at UCL has shown that over a quarter of men with a clinical suspicion of prostate cancer could avoid a transrectal ultrasound (TRUS) guided biopsy if they undergo a multi-parametric MRI (MP-MRI) scan first.
The Prostate MRI Imaging Study (PROMIS) also showed that the detection of aggressive cancers can be almost doubled by carrying out an MP-MRI, followed by a biopsy. This is because if the scan is suspicious, the MP-MRI can give information about where the cancer is and its size.
Early prostate cancer produces no specific symptoms so men have a blood test called PSA (Prostate Specific Antigen). PSA is not specific to cancer, so if it is high, men currently undergo TRUS biopsies, whereby an ultrasound probe is inserted into the rectum and used to guide the biopsy needle into the prostate to take 10-12 small samples of tissue from the prostate. Of the approximate 100,000 men every year in the UK who have these biopsies, around 66% (66,000 men) are found to have no cancer or no life-threatening cancer.
TRUS biopsies are a relatively invasive procedure that can sometimes lead to side effects such as pain, bleeding, erectile dysfunction and infection. They can also be inaccurate because they only sample some areas of the prostate. TRUS biopsies are also taken in a random manner, so can pick up low-risk types of cancer that may never progress and spread. These men are then often treated unnecessarily.
The PROMIS study, published in The Lancet, assessed the ability of MP-MRI to identify men who might safely avoid a biopsy. If the MP-MRI result was negative, doctors could then decide whether they should just monitor the patient’s PSA or discharge him altogether. If the MP-MRI result was positive, it might also be helpful in performing a better TRUS biopsy as the biopsy needles could be directed to areas of suspicion in the prostate.
PROMIS also found out how accurate MP-MRI was in comparison to TRUS biopsies at detecting important cancers. While it was already known that TRUS biopsies can miss clinically important tumours, the PROMIS study showed the extent to which this occurs.
The study, which involved 11 NHS hospitals, looked at 576 men with suspected prostate cancer. They were given an MP-MRI scan followed by two types of biopsy. The first of these was a template prostate mapping (TPM) biopsy, which was used as a control to compare the accuracy of the MP-MRI and standard biopsy against. This was followed by a TRUS biopsy.
The MP-MRI scans detected 93% of clinically important cancers. The TRUS biopsies only identified 48% of clinically important cancers. Nine out of 10 men (89%) who had a negative MP-MRI scan, had either no cancer or a harmless cancer.
Dr Hashim Ahmed from University College London Hospitals NHS Foundation Trust (UCLH) and one of the lead investigators on the study, said: “The results of this study show clearly that having an MRI scan, followed by a TRUS biopsy if the scan is positive, can dramatically improve the diagnosis of prostate cancer. What’s more, combining MRI with biopsy could improve the detection of aggressive prostate cancers, reducing the need for repeat biopsies.
“It could also allow around a quarter of men with negative MRI scans to safely avoid having an immediate biopsy and the sometimes unpleasant side-effects these can cause.”
During the study, 44 men suffered a serious complication as a direct result of the biopsies. These included eight cases of sepsis and 58 cases of urinary retention.
Dr Neha Issar-Brown, Programme Manager at the Medical Research Council, said: “The current standard of care for men with high PSA requires them to undergo a relatively invasive procedure, which may not only be unnecessary but also, in some cases, inaccurate. The PROMIS results demonstrate that it is now possible to address these issues, making diagnoses for this otherwise difficult to detect cancer, more specific and reliable. Not only will this enable 1 in 4 men to avoid the stress of a potentially unnecessary procedure and its side effects but also the emotional toll of a misdiagnosis.
“We also need more information about overall cost-effectiveness of this approach and work to ensure there are enough MRI scanners and appropriately trained urologists and radiologists to implement this approach more widely in the NHS.”
Ahmed, H. U., Bosaily, A. E., Brown, L. C., Gabe, R., Kaplan, R., Parmar, M. K., . . . Emberton, M. (2017). Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study. The Lancet. doi:10.1016/s0140-6736(16)32401-1
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