A traditional mainstay for early detection of prostate cancer, TRUS has been overshadowed in recent years by mpMRI. But TRUS offers some important clinical and cost benefits, and it still has its place, according to Dr. Edouard Trabulsi and colleagues from Thomas Jefferson Univesity in Philadelphia.
Some consider mpMRI superior to TRUS for prostate evaluation because it can identify specific cancer foci, information that's used for guiding biopsies, Trabulsi and colleagues noted. The modality uses higher magnet strength and a combination of sequences to produce the most accurate resolution and lesion detection. And biopsies guided by mpMRI have their benefits, including an increase in the diagnosis of clinically significant cancers.
"Fortunately or unfortunately, MRI is now considered the standard of care," said Dr. Ethan Halpern, who presented the research on behalf of Trabulsi. "If you say, 'Let's do an ultrasound,' people look at you like, 'What, are you from the Stone Age?' "
But mpMRI also has its drawbacks, such as limited access for patients, high cost, a need for multiple patient visits, and variable clinician experience, Halpern told session attendees. In fact, there's no consensus from various professional groups about whether it is the standard of care. And as of yet, no large studies compare enhanced multiparametric transrectal ultrasound to MRI-targeted biopsies, according to Trabulsi's team.
That's why TRUS continues to offer an interesting alternative for the early detection of prostate cancer. It works similarly to mpMRI, using multiple sequences together to visualize and target suspicious lesions for biopsy. It's an option for patients who can't undergo MRI due to claustrophobia, metal implants, or lack of insurance coverage -- and it's less expensive than MRI. It also has clinical benefits, according to Trabulsi's group.
"It appears to give equal performance in diagnosing clinically significant disease, especially in the prostate's peripheral zone," Halpern said.
However, TRUS does have disadvantages, including the following:
- It's not widely available.
- It's operator dependent.
- There's no standardized grading -- although a Prostate Imaging Reporting and Data System (PI-RADS)-type scoring could work.
- It has difficulty with real-time quantification of blood flow.
- It shows poor performance with the transition zone and anterior areas of the prostate.
Despite these limitations, Trabulsi and colleagues believe there's definitely a place for TRUS in the prostate cancer arsenal, Halpern told session attendees.
"There's been tremendous growth and interest in mpMRI, at the risk of hindering research into enhanced ultrasound," he said. "But there's clearly a subset of patients who may benefit from TRUS, and the concept of a PI-RADS-type scoring system is gaining interest. And moving from qualitative to quantitative TRUS parameters should ameliorate concerns about operator variability."
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