Multiparametric magnetic resonance imaging (MRI) and MRI-guided prostate biopsy are emerging as useful applications in the detection of prostate cancer. Transrectal ultrasound (TRUS) biopsy, the current traditional method of diagnosis prostate cancer, can result in sampling errors that lead to delayed diagnosis or misclassification of cancers. In a first-of-its-kind trial, TRUS biopsy and MRI-guided prostate biopsy were compared to see which can best detect prostate cancers and help to triage prostate cancer patients.
MRI-guided prostate biopsy outperforms TRUS biopsy
Researchers compared MRI-guided prostate biopsy with TRUS biopsy in a study of 223 men who had never before received either type of biopsy. Mean age of the mean was 63 years and mean prostate specific antigen (PSA) level was 5.3, which would be considered slightly elevated. Results of the study were published July 2014 in European Urology.
Multiparametric MRI was performed in each patient and exams were scored according to the Prostate Imaging Reporting and Data System (PI-RADS), which grades potentially cancerous lesions detected by MRI on a scale of 1 (low risk) to 5 (high risk). There were 143 men who received a PI-RADS grade of 3 or higher. This group received MRI-guided prostate biopsy immediately followed by TRUS biopsy. Men with a PI-RADS grade of 2 or lower received TRUS biopsy only.
By limiting biopsy to men with PI-RADS grades of 3 or higher, researchers determined that multiparametric MRI could reduce the need for biopsy by about one-half. Replacing TRUS biopsy with MRI-guided biopsy could:
- Reduce the number of biopsies by 36 percent.
- Reduce number of cores taken by 84 percent.
- Reduce detection of low-risk cancer by 87 percent.
- Increase detection of intermediate- and high-risk cancer by 18 percent.
“The results of this diagnostic study support apparent patient benefits,” wrote researchers, from the Wesley Hospital in Brisbane, Australia and the Radboud University Medical Center in Nijmegen, the Netherlands. “Most importantly, when using the multiparametric MRI and MRI-guided biopsy pathway instead of TRUS biopsy, the number of men diagnosed with low-risk prostate cancer will be reduced, and at the same time, the number of men diagnosed with intermediate- or high-risk prostate cancer will be increased.”
The need for an alternative prostate cancer detection method
While TRUS has been for a long time, and still is, a valuable diagnostic tool in the fight against prostate cancer, it has its downfalls. Due to its inability to differentiate between high-grade and low-grade prostate cancers, it can result in misclassification of cancers that can lead to radical treatments when they aren’t necessary and result in delayed diagnosis of prostate cancers requiring treatment. Many low-grade cancers would take too long to grow to cause significant harm, but without accurate information, men can be tempted to receive radical treatment that has potential to affect their quality of life.
Additionally, the number of core sample taken during TRUS (generally 8-14) when compared to the number taken during MRI-guided biopsy (generally 2-4), pose an increased risk. Biopsy needles can cause infection or bleeding, as well as other conditions, and it is important to limit that risk.
While PSA screening and subsequent TRUS biopsy have been associated with a reduction in prostate cancer mortality, researchers note that “However, this benefit is associated with the diagnosis of many indolent tumors, for which radical treatment leads to an adverse impact on quality of life without altering survival.”
Multiparametric MRI and MRI-guided prostate biopsy are emerging as a viable alternative to TRUS biopsy. As more research explores multiparametric MRI and MRI-guided prostate biopsy, additional benefits may be realized.