MRI plus blood-based test shows promise as prostate cancer screening strategy
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Combining an MRI-targeted biopsy approach with the Stockholm3 blood test for prostate cancer screening reduced overdetection while still identifying significant cancer, according to results of the randomized, population-based STHLM3MRI trial.
The findings, scheduled for presentation during the virtual European Association of Urology Congress and published in The New England Journal of Medicine, address the greatest barrier to the introduction of nationwide screening, according to the researchers.
“Using modern diagnostic methods, we can maintain the benefits of prostate cancer screening, but decrease the downsides — including the important issue of overdetection — substantially,” Tobias Nordström, MD, PhD, associate professor of urology in the department of clinical sciences at Karolinska Institutet at Danderyd Hospital in Stockholm, told Healio.
Although PSA screening has been shown to reduce prostate cancer mortality, it can cause adverse outcomes and lead to overdiagnosis.
To address these challenges, Nordström and colleagues compared a screening strategy using PSA with a blood-based risk prediction algorithm — dubbed the Stockholm3 test — along with systematic biopsies alone or with MRI-targeted biopsies. Researchers described the Stockholm3 test as a risk-prediction model that includes clinical variables, such as age and previous biopsy status, a single-nucleotide-based genetic score and measurements of five protein levels (total PSA, free PSA, hK2, MSMB and MIC-1).
“There is previous knowledge on the value of early detection and that MRI might be of benefit for men coming for prostate cancer workup in daily clinical practices,” Nordström said. “However, there is an important evidence gap regarding well-defined populations of men in prostate cancer screening situations.”
Of the 12,750 men (median age, 61 years; interquartile range, 55-67) invited by mail who enrolled in the trial, 2,293 screened positive to either or both blood tests with a PSA level of at least 3 ng/mL or Stockholm3 score of at least 11%. Researchers randomly assigned that group 2:3 to undergo systemic prostate biopsies or biopsy only after biparametric MRI showed suspicious lesions.
The proportion of men diagnosed with clinically significant prostate cancer (Gleason score 7) served as the primary outcome. Secondary outcomes included the detection of clinically insignificant cancers (Gleason score 6), performed MRIs and biopsy procedures.
Results showed area under the receiver operating characteristic curve for significant cancer in the standard biopsy group was 0.76 (95% CI, 0.72-0.8) for Stockholm3 and 0.6 (95% CI, 0.54-0.65) for PSA.
When researchers increased the Stockholm3 cutoff to 15%, the sensitivity to detect significant cancers remained unchanged while leading to 36% (95% CI, 24-46) fewer MRIs and 8% (95% CI, 2-20) fewer biopsy procedures compared with a PSA of 3 ng/ml or higher in the MRI-targeted biopsy group.
Overall, the approach of using Stockholm3 score plus MRI-targeted biopsies led to 69% (95% CI, 53-80) fewer low-grade cancers and 53% (95% CI, 45-59) fewer biopsy procedures compared with PSA plus systematic biopsies.
In the NEJM report, researchers reported data of 1,532 men who met the PSA cutoff, regardless of Stockholm3 score. Of them, 603 underwent standard biopsy and 929 underwent experimental MRI-targeted biopsy.
Results showed clinically significant cancer in 192 men (21%) in the experimental biopsy group and 106 men (18%) in the standard biopsy group (difference, 3 percentage points; 95% CI, –1 to 7). These data indicate the experimental biopsy method was noninferior to the standard biopsy approach because the lower boundary of the CI was higher than –4, with a P value of < .001.
Additionally, a smaller proportion of men in the experimental biopsy group had clinically insignificant cancers (4% vs. 12%; difference, 8 percentage points; 95% CI,
11 to 5).
Nordström said the future of prostate cancer screening will likely include both blood tests and MRI.
“There is now a substantial amount of evidence that might facilitate implementation discussions. I think we are ready to take the implementation of next-generation prostate cancer screening further,” he said. “However, on that journey we also have to incorporate new knowledge on how to assure top quality in the diagnostic chain, health-economic issues and optimal retesting schemes.”
References:
Eklund M, et al. N Engl J Med. 2021;doi:10.1056/NEJMoa2100852.
Nördstrom T, et al. Abstract P1014. Presented at: Annual European Association of Urology Congress (virtual meeting); July 8-12, 2021.
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Nördstrom T, et al. Abstract P1014. Presented at: Annual European Association of Urology Congress (virtual meeting); July 8-12, 2021.
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