CHICAGO – Fusing MRI with real-time, three-dimensional ultrasound allows for more targeted prostate biopsies and finds additional cancers, compared with standard systematic biopsies.
"This may lead to fewer total biopsies, improved yield and improved confidence for active surveillance," Dr. Daniel J.A. Margolis said at the annual meeting of the Radiological Society of North America.
Dr. Daniel J.A. Margolis
Direct MRI-guided biopsy is not universally available, leaving most centers to use two-dimensional ultrasound to systematically biopsy 12 areas of the prostate, whether they are all suspicious or not. Not surprising, roughly 30% of systematic core biopsies are false negative, explained radiologist Dr. Margolis of the University of California, Los Angeles.
Researchers at UCLA departments and the medical device company Eigen have been using external-array 3 Tesla MRI scans, including T2-weighted, diffusion-weighted, and dynamic contrast-enhanced images to identify suspicious areas in the prostate. The areas are scored on a 5-point scale by a radiologist based on cancer risk, and the data are used to create a 3-D contoured reconstruction that is fused with real-time, transrectal ultrasound during biopsy.
Early results were promising in the two groups of men most likely to benefit from the new imaging technology – those with a prior negative biopsy and elevated prostate-specific antigen (PSA) levels and those with low-risk prostate cancer under active surveillance. In 47 such men, the biopsy-positivity rate was 33% with MRI-fusion ultrasound vs. 7% for systematic, nontargeted biopsy (Urol. Oncol. 2011;29:334-42).
At the meeting, Dr. Margolis presented data from 57 consecutive men with a previous biopsy, in whom MRI-fusion ultrasound identified 101 suspicious areas. In all, 22 men had 28 positive MRI targets.
Positive biopsies were found in 12 patients on targets only. Nine patients had positive lesions on both MRI-fusion ultrasound and systematic biopsy. In one additional patient, the positive systematic core was changed from Gleason 3+3 to 3+4 disease with the targeted biopsy.
Seven patients had positive biopsies found on systematic biopsy only, although all were Gleason score 3+3, less than 4 mm in size and less than 25% of the core, Dr. Margolis said.
A separate study presented in the same session suggests that fusing MRI with transrectal ultrasound biopsy may also be useful in identifying aggressive tumors in men with no prior prostate biopsy or suspicious digital rectal exam and a PSA of 3-10 ng/mL (mean 8 ng/mL).
The overall cancer detection rate was 52% among 323 (168/323) such men, 73% within MRI targets (144/197) and 19% with sextant biopsy (24/126), reported Dr. François Cornud, a consultant radiologist at René Descartes University, Paris.
Dr. Francois Cornud
In 98 patients with both MRI targeted- and sextant-positive biopsies, targeted biopsies identified significantly more cancers with a Gleason score greater than 6 (44% vs. 25%), with a length in any core of more than 7 mm (50% vs. 25.5%) and with a longer mean length (5.3 mm vs. 0.8 mm).
Interestingly, performance was similar whether the multiparametric MRI data were fused with the real-time ultrasound images visually or by a computerized electromagnetic navigator system.
"Targeted biopsies definitely provide better evaluation of tumor burden and Gleason score," Dr. Cornud said, adding that "a negative MRI prior to biopsy may mean no cancer or indolent cancer and may suggest that in these patients biopsy may be deferred."
Both studies were well received, although one attendee questioned whether the researchers have been able to convince frequently reluctant urologists that targeted biopsies are worth it. Dr. Margolis said his project was actually instigated by an urologist. Dr. Cornud said the majority of his urologists are now requesting an MRI and its findings.
Dr. Margolis reported a research grant from Siemens AG and a coauthor reported conflicts with several pharmaceutical and device firms. Dr. Cornud and his coauthors reported no relevant disclosures.