Combining two methods of prostate biopsy — using one guided by magnetic resonance imaging (MRI) along with conventional ultrasound-guided biopsy — results in a more accurate detection of clinically significant prostate cancers than either method alone, a study shows.
The researchers hope this combined method will improve clinicians’ current confidence levels in prostate cancer diagnosis and aid in the subsequent selection of appropriate treatment.
The study, “MRI-Targeted, Systematic, and Combined Biopsy for Prostate Cancer Diagnosis,” was published in the New England Journal of Medicine.
A prostate cancer diagnosis requires collecting small amounts of prostate tissue for analysis. Transrectal ultrasound-guided (TRUS) 12-core prostate biopsy — which involves the collection of 12 samples of tissue in different sections of the prostate — is the standard method for the initial diagnosis and grading of prostate cancer.
However, this method has a low sensitivity, meaning that it results in prostate cancer misclassification. This diagnostic uncertainty has contributed to both undertreatment in men with aggressive disease and overtreatment in men with low-risk disease.
Previous studies have shown that MRI-guided biopsy is superior to the standard technique in detecting medium-to-high risk prostate cancer. However, whether standard biopsy should be entirely omitted, or if the two methods should be combined, remains unclear.
A team of researchers now sought to identify the most effective method for prostate cancer diagnosis. They evaluated cancer classifications and the diagnostic accuracy of standard, MRI-guided, or combined prostate biopsies in 2,103 men with MRI-visible lesions. During the procedure, all patients underwent two biopsies — an MRI-guided one followed by a standard one.
Supported by the National Institutes of Health and the Center for Cancer Research of the National Cancer Institute, the study first compared the prostate cancer classification results of each biopsy method, specifically standard, MRI-guided, and combined. Then, to assess their predictive value, data from each method were compared with that of whole prostate analysis in men who later underwent surgical prostate removal.
The patients’ mean age was 63.3 years, and most of them were Caucasian (78.6%); most also had undergone at least one prior biopsy (79.3%).
The results showed that cancer was diagnosed in 52.5% of men by standard biopsy, in 51.5% through an MRI-guided one, and in 62.4% using the combined method. A total of 404 men subsequently underwent prostate removal.
The use of the MRI-guided technique alone led to significantly more diagnoses of medium-to-high-risk cancers and less of very low-risk cancers than standard biopsy. However, using an MRI-guided strategy alone still missed 8.8% of clinically significant cancers, the researchers noted.
Combined biopsy resulted in a nearly 10% increase in cancer diagnoses and in upgrades to a higher risk classification in 458 men (21.8%), compared with either method alone. It also was associated with the lowest rate of clinically significant upgrading (3.5%) in cancer classification between biopsy and whole prostate analysis after surgery.
The highest rates of clinically significant upgrading were found with standard biopsy (16.8%), followed by those using the MRI-guided method (8.7%).
“In this study, we found that combined biopsy leads to an increase in the number of cancer diagnoses and improves the likelihood that the biopsy findings are predictive of the true … nature of the patient’s disease,” the researchers said.
Moreover, men whose cancer was classified as low-risk with the combined method had a small chance of having medium-to-high-risk disease. The team emphasized this finding as support that using both methods may “reduce the risks of both overtreatment and undertreatment out of fear of misdiagnosis.”
“Potentially, these data may usher in a new era of increased confidence in the selection of prostate cancer treatment on the basis of biopsy results,” the researchers said.
The team also noted that future studies are needed to determine those situations in which prostate cancer patients may undergo MRI-guided biopsy alone.
This study was part of a larger clinical trial (NCT00102544) evaluating an electromagnetic tracking device for MRI-guided biopsies.
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