Short MRI protocol promising for community-based prostate cancer screening
medwireNews: Biparametric magnetic resonance imaging (MRI) identifies more clinically significant prostate cancers than prostate-specific antigen (PSA) screening without increasing the rate of overdiagnosis or need for biopsies, suggest the IP1-PROSTAGRAM results.
These findings indicate that “short, noncontrast MRI may have favorable performance characteristics as a community-based screening test,” say the study investigators.
In the blinded study, 403 men between the ages of 50 and 69 years underwent a serum PSA test, biparametric, noncontrast MRI (T2 weighted and diffusion), and ultrasonography (B-mode and shear wave elastography) at one of seven UK-based primary care practices and two imaging centers. A systematic 12-core biopsy was performed for individuals with a positive result on any of the tests, while those with a positive MRI or ultrasonography also had an image-fusion targeted biopsy.
When a threshold of 4 points on a 5-point scale of suspicion was applied to the MRI and ultrasonography strategies, there was no significant difference in the proportion of patients who had a positive MRI or ultrasonography result compared with those who had a positive PSA test (≥3 ng/mL), at 10.6 and 12.8 versus 9.9%, respectively.
However, MRI identified more clinically significant cancers, defined by a Gleason score of 3+4 or higher, than ultrasonography and PSA testing, at 11 versus four and seven cases, respectively.
Of note, this greater detection of clinically significant cancers did not come at the cost of increased overdiagnosis since the three screening tools identified a similar number of clinically insignificant cancers, with five, seven, and six detected by MRI, ultrasonography, and PSA, respectively, in addition to 22, 35, and 23 benign tumors.
The researchers also tested a lower threshold for suspicion on MRI and ultrasonography, whereby patients scoring between 3 and 5 points were encouraged to have a biopsy.
This strategy resulted in significantly more patients being recommended for biopsies based on results from MRI and ultrasonography than PSA (17.7 and 23.7 vs 9.9%). Once again MRI identified more clinically significant cancers than ultrasonography and PSA testing (14 vs nine and seven, respectively). Additionally, MRI, ultrasonography, and PSA testing identified seven, 13, and six clinically insignificant cancers, respectively, and 44, 63, and 23 benign cancers.
Of the nine adverse events reported during the course of the study, three were associated with MRI, five with ultrasonography, and one with PSA testing; the most common event was procedure-related pain or anxiety. But none of these adverse events were serious, say David Eldred-Evans (Imperial College London, UK) and colleagues.
Writing in JAMA Oncology, the investigators say that “an MRI score of 4 or 5 may provide a better balance between the potential benefits and harms of screening,” while “ultrasonography, at either score threshold, would not provide an improved trade-off in performance compared with PSA testing.”
The authors of an accompanying commentary say “that with either threshold, adding [biparametric] MRI to serum PSA testing for screening will likely increase rates of both clinically significant and insignificant cancers diagnosed.”
But Susanna Lee and Aileen O’Shea, both from the Massachusetts General Hospital in Boston, USA, believe that “[t]he IP1-PROSTAGRAM study lays the groundwork for future trials to examine the role of imaging in population-based prostate cancer screening.”
The study results “clearly point to prostate MRI as a promising screening test,” they continue. “Future trials should be designed to include MRI in the prostate cancer screening strategy with image acquisition and interruption protocols that are widely accessible, well tolerated, and readily generalizable.”
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