Prostate biopsies are dangerous. They can cause bleeding and infection. Occasionally they can cause a fatal infection called sepsis. The other problem with prostate biopsies are that they're not all that accurate. Depending on what study you look at, prostate biopsies miss 25-50% of cancers. So, is there a way to decrease the use of biopsies in a safe and scientific manner?
There are several different ways to perform a prostate biopsy. The most accurate way is the trans rectal ultrasound guided biopsy, or TRUS biopsy. But biopsies are not the only way to spot a prostate cancer. For the last few years, special magnetic resonance imaging (MRI) machines have been developed that can detect prostate cancer without a biopsy. Recently researchers published the results of a trial designed to determine how accurate these MRI scans are compared to TRUS biopsies.
To do the study, they enlisted 576 men who had elevated PSA tests up to 15 ng/mL. They did TRUS biopsies and MRI scans in each man. The MRI scans were able to detect 93% of the clinically significant cancers. So, what's a "clinically significant" prostate cancer? Some prostate cancers are so slow growing and have such a low malignancy level that they're referred to as being clinically insignificant. That means they're not likely to ever cause any problems. Clinically significant cancers is the term used for prostate cancers that are likely to cause a significant level of disease. These are the ones that you need to take seriously. TRUS biopsies were only able to detect 43% of the clinically significant cancers. That sounds like the MRI is a much better way to go. But there's more to this story.
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Although the MRI scans were better at detecting clinically significant cancers, they were also 55% more likely to give a false positive. That means that when the results of the scan looked like a cancer, it was wrong 55% of the time compared to the TRUS biopsy. So, neither one of these tests is perfect. But combining them can be helpful.
The authors concluded that by using MRI to initially screen men before they go to a TRUS biopsy would allow 27% of them — those who were negative on the scan — to avoid a biopsy. And that's a good thing because in the study 6% of the men who went through the biopsy had a serious adverse event. Eight of them developed sepsis.
Additionally, according to the authors, if TRUS biopsies were done only when the MRI scans were positive, "up to 18% more cases of clinically significant cancer might be detected compared with the standard pathway of TRUS-biopsy for everyone. MRI scans used as a triage [screening] test before first prostate biopsy, could reduce unnecessary biopsies by a quarter." So, if you have been told by your doctor that you need a prostate biopsy, the smart thing to do is to get an MRI of your prostate first. If it's positive for cancer, then go ahead with the biopsy. If it's not positive, the odds that you have cancer is so low that a biopsy is not needed. And you just saved yourself some significant aggravation and risk.
Yours for better health,
Frank Shallenberger, MD
Ahmed HU, El-Shater Bosaily A, et al. Diagnostic accuracy of multi-parametric MRI and TRUS biopsy in prostate cancer (PROMIS): a paired validating confirmatory study. Lancet. 2017 Feb 25;389(10071):815-822.