MADRID — Screening for prostate cancer using MRI and a lower prostate-specific antigen (PSA) threshold could result in fewer men needing biopsies with no compromise to cancer detection rates, a pilot study suggests.
"These are promising results," said Anna Grenabo Bergdahl, MD, from the University of Göteborg in Sweden. "Now a full-scale trial is needed to validate them."
"These results may contribute to a paradigm shift in the screening and diagnosis of prostate cancer," Dr Bergdahl said here at the European Association of Urology 30th Annual Congress.
The pilot study, nested in a randomized screening trial, involved 124 men (mean age, 69.5 years) with a PSA level of at least 1.8 ng/mL. All men underwent a screening MRI.
Biopsies were performed in all men with PSA levels of 3.0 ng/mL or higher, and in those with PSA levels from 1.8 to 2.99 ng/mL if a suspicious lesion was detected on MRI.
All men underwent a standard 10-core systematic biopsy performed by a clinician blinded to the MRI results. For men with suspicious lesions on MRI, this was followed by three additional MRI-targeted biopsies.
For men with PSA levels of at least 3.0 ng/mL, the detection rate of significant cancers was 5.2% with systematic biopsy alone; this dropped slightly, to 3.6%, when targeted biopsy was used. However, when the PSA threshold was lowered to 1.8 ng/mL, the detection rate of significant cancers increased to 5.9% with targeted biopsy.
"Significant cancers were missed with all three screening strategies, but a PSA cutoff of 1.8 ng/mL plus MRI-targeted biopsy missed the fewest," Dr Bergdahl reported.
Of course, the detection of significant cancers must be balanced against the detection of insignificant cancers.
With the 3.0 ng/mL PSA threshold, the rate of insignificant cancer detection was 1.2% with systematic biopsy, which dropped to 0.3% with targeted biopsy. With the 1.8 ng/mL PSA threshold, the rate with targeted biopsy increased only slightly, to 1.1%.
"We're not at the point where we can get rid of the systematic biopsy yet, because when MRI was added to exempt men from biopsy, sensitivity decreased a little bit and we missed a couple of significant cancers. It's too early to say why they weren't visible on MRI," Dr Bergdahl explained.
However, "MRI will definitely have a role in the future," she said. "Some of the men in the study had their PSA raised for years and had repeatedly negative systematic biopsies. Then we did an MRI and found a fairly large interior tumor."
A combination of all three approaches might be a useful strategy in the future. "I think we will have some kind of biomarker. I don't know if PSA is the one, but probably it is. Then we will have to choose some kind of cutoff for indicating an MRI. If the MRI is positive, we might want to do both a targeted and a systematic biopsy in those few patients," she explained.
The pilot study has given rise to a Göteborg trial that is randomizing 40,000 men to each of the three approaches.
Fewer but Better Biopsies
"MRI followed by MRI-targeted biopsy will result in fewer but better biopsies," said Fouad Aoun, MD, from the Jules Bordet Institute in Brussels, who was not involved in the study.
Such an approach "results in increased cancer detection per biopsy core, better detection of high-grade and clinically significant cancers, and improved clinicopathological correlation," he told Medscape Medical News.
Dr Aoun, who was involved in a similar study of men with suspected prostate cancer (Biomed Res Int. 2015;2015:571708), said that the Göteborg results "highlight a new concept to revisit PSA screening strategies and add to what we know about MRI."
However, he urged caution in translating the results to a population-based setting.
"The authors reported outcomes from the Göteborg randomized screening arm of the European Randomized trial of Screening for Prostate Cancer (ERSPC). The cumulative incidence of prostate cancer in this trial is higher than that reported at other ERSPC sites or from other screening trials, even those with high-intensity strategies of screening. The high percentage of previously screened and previously biopsied patients makes the findings difficult to generalize to biopsy-naïve patients," he explained.
Other issues need to be addressed, including determining which lesions should be targeted, said Dr Aoun. "We think that genetics will play an important role in understanding the biological behavior of these foci, and may be incorporated in future screening strategies."
If an MRI-based screening strategy is implemented on a large scale, education and training of physicians and radiologists will be needed, he added.
"The time-consuming nature of the procedure could limit its widespread acceptance. Results from the full-sized trial will better inform our understanding of these problems, especially if it demonstrates a positive impact on prostate-cancer-specific survival and on overall survival."
Dr Bergdahl and Dr Aoun have disclosed no relevant financial relationships.
European Association of Urology (EAU) 30th Annual Congress: Abstract 760. Presented March 23, 2015.
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Cite this: Spare the Needle, Save the Prostate - Medscape - Mar 25, 2015.