Prostate cancer: Jonathan Yamzon on MRI/ultrasound fusion biopsy
March 20, 2015 | by Valerie Zapanta
Standard prostate biopsies haven't changed significantly in the past 30 years – nor have the problems inherent with them. Regular biopsies have an expected error rate: Tumors may potentially be undersampled and, 30 percent of the time, men who undergo a radical prostatectomy are found to have more aggressive tumors than expected based on the initial biopsy.
Here, Jonathan Yamzon, M.D., assistant clinical professor in the Division of Urology and Urologic Oncology, explains some of the pitfalls of prostate biopsies, as well as the potential benefits of a magnetic resonance imaging (MRI)/ultrasound fusion biopsy.
What happens during a prostate biopsy?
In a standard prostate biopsy, an ultrasound probe is placed into the rectum to visualize the prostate. Local anesthesia is applied, and biopsy samples are taken systematically across the prostate, with the minimum standard being 12 cores.
A pathologist evaluates the tissue samples, assesses the aggressiveness of the cancer and gives the individual samples a Gleason score ranging from 3 to 5.
The sum of the Gleason scores is achieved by combining the two most prevalent scores seen in the tissue, ranging from 6 (least abnormal and aggressive) to 10 (most abnormal and aggressive). For example, if the reported Gleason is 3+4=7, a pathologist assigned a 3 to the most prevalent grade, followed by a 4, the second most-prevalent grade. The sum totals up to a Gleason score of 7.
Physicians use the Gleason score, among other clinical variables, to assess the aggressiveness of the cancer and recommend follow-up treatment.
What is the controversy around prostate biopsies?
Every prostate biopsy incurs a risk for infection, estimated from 1 to 6 percent. The majority of prostate biopsies are performed because of elevated PSA (prostate-specific antigen) tests and abnormal digital rectal exams. Although a rise in one’s PSA levels may not always be caused by cancer, and 70 percent of the time the biopsies come back negative, the use of PSA tests in screening has been shown to reduce prostate cancer death rates by up to 29 percent.
Despite this, a federal panel (which included doctors who do not treat prostate cancer) suggested that PSA blood tests may do more harm than good because suspicious results put many men through testing that has risks. Some members of the urological community disagree with this recommendation.
With City of Hope recently acquiring the technology and device to provide MRI/ultrasound fusion biopsies, could you explain how the technology works, and how it improves the current biopsy process?
Prior to the biopsy, the patient undergoes an MRI examination known as a multiparametric MRI of the prostate. This special MRI examination is dedicated solely to evaluating the prostate for potential tumors. Areas within the prostate that may represent a tumor are demarcated and may serve as a guide during the actual biopsy. The MRI is analyzed by a specially trained radiologist with special software that will create a 3-dimensional reconstruction of the prostate. The reconstructed images highlight the areas within the prostate suspicious of a tumor.
Then, at the time of the biopsy, the ultrasound is used to visualize the prostate in the usual manner, but the MRI images that highlight the tumor can be superimposed over the ultrasound in real time.
This is beneficial to urologists, because they can perform targeted biopsies on areas most suspicious of a tumor, potentially increasing the yield and reducing the rate of missed lesions. For both patients and physicians, this technology may increase the accuracy of prostate biopsies, reduce the number of biopsies needed and potentially reduce the risks of infection.
At this time, not every prostate patient will undergo this type of biopsy because the data is still maturing regarding its effectiveness. But early data suggests it can be very useful in diagnosis, surveillance, treatment and staging.
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