Prostate cancer screening isn’t a guideline-directed screening test yet, but this could change with the use of MRI and other tools. A series of papers published in several JAMA journals late last week indicates the progress that’s being made.
As we’ve discussed in previous issues, prostate screening with PSA tests hasn’t met the threshold for clinical benefit achieved by other population-based screening exams.
- PSA-based screening has been characterized by lower mortality benefits and relatively high rates of overdiagnosis and complications from follow-up procedures.
But some researchers believe that PSA screening could be made more effective by using additional diagnostic tools like imaging and blood tests to focus on potentially high-risk disease for biopsy while active surveillance is used for less threatening prostate lesions.
In the ProScreen trial in Finland, researchers tested the combination of PSA, a kallikrein four-panel blood test, and MRI in selecting patients for biopsy.
- Patients were sent to MRI if they had PSA scores of 3.0 ng/mL or higher and kallikrein scores of 7.5% or higher; those with abnormal MRI scans got targeted biopsy.
The researchers tested the ProScreen protocol in a study of 61.2k men, with 15.3k invited to screening and 7.7k getting screened. Over a preliminary three-year follow-up period, researchers found …
- 9.7% of men met the PSA threshold for a suspicious lesion; this fell to 6.8% after the kallikrein test and 2.7% after MRI, illustrating the protocol’s ability to reduce biopsies
- Biopsy yield for high-grade cancer was 1.7%, which an editorial called a “remarkably high yield”
- Overdetection of low-grade disease was 0.4%, compared to 3.2% in a comparable previous study
In a second study, this one in JAMA Oncology, researchers performed a meta-analysis of 80.1k men from 12 studies in which MRI was used to direct patients to prostate biopsy after PSA testing, finding that MRI-directed protocols had …
- Higher odds of detecting clinically significant prostate cancer (OR=4.15) compared to PSA screening alone
- Lower odds ratio for biopsy (OR=0.28)
- Lower odds ratio for detecting clinically insignificant cancer (OR=0.34)
Finally, a secondary analysis in JAMA of a large UK trial illustrates the challenges of prostate screening without MRI guidance. Researchers reviewed 15-year outcomes of the Cluster Randomized Trial of PSA Testing for Prostate Cancer (CAP), a study of 415k men,196k of whom were screened from 2002 to 2009 without the use of MRI, finding …
- PSA screening increased detection of low-grade cancer (2.2% vs. 1.6%) but not intermediate or high-grade disease
- Screening reduced prostate cancer mortality by a small amount (0.69% vs. 0.78%)
The Takeaway
Taken together, new studies offer a roadmap toward making MRI an integral part of prostate screening, such that perhaps in years to come it can join other cancer tests as a population-based screening tool.
