‘Fast’ MRI shows potential as prostate cancer screening method
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MRI improved detection of clinically significant prostate cancer without increasing overdiagnosis compared with PSA testing, according to a prospective, population-based, blinded cohort study published in JAMA Oncology.
The IP1-PROSTAGRAM study also showed ultrasonography did not improve prostate cancer detection in the general population compared with PSA testing alone.
“The PSA threshold was set at 3 ng/mL or greater to denote a screen-positive result in line with previous screening trials,” David Eldred-Evans, MBBS, MRCS, senior clinical research fellow at Imperial Prostate, Imperial College London, told Healio. “Our findings reemphasize that when interpreting PSA, it is not a dichotomous test, and it is more useful as a continuous variable reflecting a continuum of prostate cancer risk. In IP1-PROSTAGRAM, significant prostate cancer was identified by MRI in men with PSA as low as 0.69 ng/mL.”
Eldred-Evans and colleagues evaluated whether a short, noncontrast MRI protocol — which has an acquisition time of about 15 minutes — or transrectal ultrasonography using an ultrafast scanner (Aixplorer, SuperSonic Imagine) could overcome some of the limitations of PSA testing, which can lead to under- and overdiagnosis, they wrote.
Also, identification of a reliable testing method could pave the way for a national prostate cancer screening program, Eldred-Evans told Healio.
“Image-based screening tests have been successfully adopted in other cancers, such as mammograms for breast cancer and CT for lung cancer,” he said. “In prostate cancer, there have been many previous studies evaluating MRI or ultrasound as tests in secondary care for men with a suspicion of prostate cancer; however, no studies have considered this combination of imaging tests for screening. Our aim was to understand whether fast MRI or ultrasound could be the basis for a new method of a screening program for prostate cancer.”
The analysis included 408 men aged 50 to 69 years (38% white, 32.4% Black, 23% Asian) enrolled between October 2018 and May 2019 at seven primary care practices in the U.K. The men had a life expectancy of at least 10 years; no PSA tests or prostate MRI in the previous 2 years; no urinary infection or prostatitis in the previous 6 months; and no history of prostate biopsy, prostate cancer or any contraindication to MRI.
The men underwent prostate cancer screening with a PSA test, MRI and ultrasonography and, if any results appeared positive on a 5-point scale, they underwent a systematic 12-core biopsy. Men with positive MRI or ultrasound results also underwent additional image fusion-targeted biopsy.
The proportion of men with positive MRI or ultrasonography (defined as a score of 3-5 or 4-5) or PSA test (defined as 3 ng/mL) served as the study’s main outcome.
When using the 3-to-5 score threshold, results showed the proportion of men with positive results appeared higher with MRI (17.7%; 95% CI, 14.3-21.8) and ultrasonography (23.7%; 95% CI, 19.8-28.1) than with PSA testing (9.9%; 95% CI, 7.3-13.2; P < .001 for both).
Using the 4-to-5 score threshold, 10.6% (95% CI, 7.9-14) of men had positive MRI and 12.8% (95% CI, 9.9-16.5) had positive ultrasonography, which was not significantly different than the 9.9% of men positive per PSA testing.
Combined targeted and systematic biopsy identified 37 prostate cancers, 17 of which were clinically significant.
Overall, PSA testing detected seven of the clinically significant cancers, whereas an MRI detected 11 (4-5 threshold) to 14 (3-5 threshold), and ultrasonography detected four (4-5 threshold) to nine (3-5 threshold).
Of the 20 clinically insignificant prostate cancers detected on biopsy, PSA testing detected six, MRI detected five (4-5 threshold) to seven (3-5 threshold), and ultrasonography detected seven (4-5 threshold) to 13 (3-5 threshold).
These data suggest MRI testing detected two times as many significant cancers as PSA testing alone. Moreover, using the 4-to-5 threshold for MRI may improve the detection of clinically significant prostate cancer without leading to unnecessary biopsy or overdiagnosis, according to the researchers.
“A fast MRI appears to have favorable performance characteristics as a new screening test for prostate cancer,” Eldred-Evans told Healio. “This finding needs further evaluation in subsequent studies.
“The ultrasound did not perform as well as in previous secondary care populations,” Eldred-Evans added. “[This is possibly because] we did not include contrast in the scanning protocol to keep the test noninvasive and/or the significant cancers being detected were low volume. Meanwhile, a fast MRI scan ... was able to identify a high number of aggressive cancers without increasing the number of men needing a biopsy compared with PSA.”
This study suggests MRI “will play an important role” in reducing the morbidity and mortality of prostate cancer, according to an editorial accompanying the study by Susanna I. Lee, MD, PhD, chief of women’s imaging , and Aileen O’Shea, MbBCh, BAO, clinical fellow in radiology, both of Massachusetts General Hospital.
“Their findings clearly point to prostate MRI as a promising screening test,” they wrote. “Future trials should be designed to include MRI in the prostate cancer screening strategy with image acquisition and interpretation protocols that are widely accessible, well-tolerated and readily generalizable.
“In the long run, if successful, prostate MRI will be able to join mammography and low-dose CT of the thorax as an imaging screening test that saves lives and improves the general health of the population,” they added.
References:
Eldred-Evans D, et al. JAMA Oncol. 2021;doi:10.1001/jamaoncol.2020.7456.
Lee SI and O’Shea A. JAMA Oncol. 2021;doi:10.1001/jamaoncol.2020.7294.
For more information:
David Eldred-Evans, MBBS, MRCS, can be reached at Imperial College London, 5L01 Charing Cross Hospital, Fifth Floor, London W6 8RP, United Kingdom; email: d.eldred-evans@imperial.ac.uk.
Editor’s Note: On Feb. 15, we corrected the infographic with this article to accurately reflect the number of clinically significant cancers detected by PSA testing. The Editors regret this error.
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Eldred-Evans D, et al. JAMA Oncol. 2021;doi:10.1001/jamaoncol.2020.7456.
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