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How to Make Active Surveillance Safer
How to Make Active Surveillance Safer
For carefully screened patients, active surveillance can prevent the unnecessary treatment of prostate cancer. However, this approach is not without potential side effects.
Preventing Infections from Prostate Biopsies
According to H. Ballentine Carter, M.D., from Johns Hopkins Medicine, patients on active surveillance need periodic prostate biopsies for disease monitoring, which may lead to infection.
To get a needle into the prostate, the urologist needs to go through the rectum. During the biopsy process, there is a chance that related infections can develop if bacteria in the rectum (such as E. coli) find their way to the prostate and into the bloodstream. To prevent this, urologists administer an antibiotic called a fluoroquinolone (FQ) before and after the procedure.
Fighting FQ Resistance
About one in five men has FQ resistance. This could result in an infection that is difficult to treat. A few years ago, researchers at the James Buchanan Brady Urological Institute began a program to determine whether or not patients have FQ resistance before the biopsy. Using information gathered from simple rectal swab samples, researchers can select the best antibiotic to prevent infection. As part of the Johns Hopkins Medicine Active Surveillance Program, patients have been getting these rectal swabs every six months. This has provided researchers key information on how resistance develops over time.
Jason Cohen, a Johns Hopkins Medicine medical student who has studied these swabs, found that diabetes is a risk factor for FQ resistance. He also identified a substantial number of men with E. coli who are resistant to other antibiotics commonly used to prevent post-biopsy infections. This study, for the first time, evaluated the longitudinal patterns among men with repeat rectal swabs, according to Dr. Carter. Two of three men who harbored resistant organisms maintained this resistance on a follow-up swab six months to a year later. Nine percent of those who had no resistant organisms developed a resistant organism at the second swab.
Multiple biopsies were not associated with increased FQ resistance. Using this information, infectious disease experts have helped develop an approach to repeat prostate biopsies that is safer for men in active surveillance and for those undergoing routine prostate biopsies for an elevated PSA.
Lowering the Risk of Misclassified Cancer
Misclassification can be an issue when relying on a prostate biopsy, which samples only a small fraction of the prostate. If a diagnosis of low-grade prostate cancer is made based on a prostate biopsy and the patient chooses active surveillance, the risk that a higher-grade, more aggressive cancer is present within the prostate can range from 10 percent to 30 percent.
Imaging Technique for Low-Grade Cancers
Researchers are exploring a new technique called multiparametric magnetic resonance imaging (mpMRI), which could lower the risk by helping select which men truly have low-grade cancers. It could also reduce the number of prostate biopsies needed by patients on active surveillance.
By assessing three key parameters, mpMRI can detect prostate cancers that were missed on a prostate biopsy, particularly tumors arising from sites that are not commonly sampled, such as the area near the front of the gland.
Researchers at Johns Hopkins Medicine recently studied a group of patients on active surveillance. The results demonstrated that when mpMRI suggested the absence of prostate cancer in a particular area of the prostate, there was a high probability that cancer would be absent on multiple biopsies taken from these negative mpMRI areas.
Dr. Carter and some imaging experts recently studied 96 men who met the strictest criteria for entering the Johns Hopkins Medicine Active Surveillance Program and had an mpMRI within one year of entering the program. In follow-up biopsies, the researchers found cancer in 8 percent of those without any abnormality on the baseline mpMRI. They found cancer in 41 percent of those who showed an mpMRI abnormality on their baseline scans.
The scientists concluded that men without any mpMRI abnormality have a 65 percent less chance of a positive follow-up prostate biopsy that would have triggered prostate cancer treatment. As a routine process, they are now using mpMRI to help select the most appropriate candidates for active surveillance and reduce the frequency of prostate biopsies.
New technology is also making it possible for the research team to merge the mpMRI with a live ultrasound image. Using this technology during a prostate biopsy enables physicians to target specific areas within the prostate that are abnormal on the mpMRI.
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