Being of the first of its kind, an Australian clinical trial has revealed that a biopsy guided by MRI can considerably improve the diagnosis of life-threatening prostate cancer and reduce the over-diagnosis of non-life-threatening cases, consequently avoiding the sometimes difficult side effects of needless treatment.
Presently, to determine if a patient has prostate cancer, they follow a test that shows whether or not the patient has raised prostate-specific antigen (PSA) levels, a man has to undergo a painful procedure called transrectal ultrasound guided biopsy (TRUSGB) that involves taking up to 30 random needle biopsies of his prostate through the rectum.
Yet with the new MRI-guided system, doctors first perform an MRI scan and get a better understanding of where a tumor might be located in the prostate and what course of action best to take.
Then, if the scan points out a need for it, they take two needle samples of that area, sparing the need for several biopsies.
The new system employs a technique called multi-parametric magnetic resonance imaging (mpMRI).
"This is a significant improvement in terms of accuracy and in reducing discomfort for patients and spares many men the burden of multiple prostate biopsies. This latest mpMRI imaging technique will reduce over-treatment of men with non-life-threatening prostate cancer, avoiding the possible side-effects of treatment," said Urologist Dr. Les Thompson, who led the 2-year clinical trial at Brisbane's Wesley Hospital.
Thompson and his colleagues report, in the journal European Urology, how the trial showed that use of mpMRI:
-Halved (reduced by 51%) the number of men needing prostate biopsies
-Showed a 92% sensitivity in diagnosing life-threatening disease (compared with the current leading method TRUSGB, which has only a 70% sensitivity in diagnosing life-threatening prostate cancer)
-Cut the problem of over-diagnosis of non-life-threatening prostate cancer by around 90%.
The trial had registered 223 patients with raised PSA levels. All of the patients underwent both diagnostic procedures: the standard TRUSGB, and the new method where an mpMRI scan is performed first, and then only those patients whose MRI image points to high-risk prostate cancer undergo MRI-guided biopsy.
Co-investigator Dr. Rob Parkinson, a specialist radiologist at the hospital, notes that mpMRI uses three parameters when scanning the prostate.
"Diffusion-weighted imaging, one of these three parameters, assesses movement of water molecules within tissues. An imaging map is mathematically generated from this information, and prostate cancer is evident as a dark area."
“In TRUSGB, which utilizes ultrasound to help guide biopsy sampling, the core samples are random and taken from all areas of the prostate, but, when biopsies are done following a prostate mpMRI you know where the tumour is located and thus where to direct the biopsy needle," he added.
One of the issues that is certain to be raised in deciding how to proceed with the new system as a diagnostic tool is the higher costs linked with MRI.
According to a report in The Austrailian news channel, Thompson says he is working to get it listed as a medicare item like mammograms for breast screening.
He vehemently advocates that the cost is small when compared to the social and emotional costs of misdiagnoses that occur with the current method.
According to the American Cancer Society, prostate cancer occurs mainly in older men, approximately 6 in 10 cases are diagnosed in men aged 65 and over. Around 1 man in 7 will be diagnosed with prostate cancer during his lifetime.
