MRI proves a viable contender for prostate screening, but hurdles loom

A pilot study using MRI as the primary screening test for prostate cancer has shown the imaging modality better at predicting the disease than popular—yet controversial—prostate-specific antigen (PSA) blood testing.

The authors of the study, which was conducted at the University of Toronto’s Sunnybrook research center and is running in the August edition of the Journal of Urology, used newspaper advertising to randomly recruit 47 men aged 50 to 75 and with no family history of prostate cancer.

All were examined with 3-Tesla multiparametric MRI and random or targeted biopsies, along with PSA testing.

Some 18 of the participants (38.3 percent) turned out to have cancer—and MRI was more than twice as good as PSA at finding it: The adjusted odds ratio of prostate cancer was 2.7 for MRI score (95 percent confidence interval) versus 1.1 for PSA level (95 percent confidence interval).

The MRI scans were equally impressive in predicting aggressive prostate cancer (Gleason score, 7 or higher), as the adjusted odds ratio of aggressive cancer was 3.5 for MRI score versus 1.0 for PSA.

Meanwhile, among the 30 patients with a normal PSA, the positive predictive value in those with an MRI score of 4 or more was 66.7 percent (6 of 9), and the negative predictive value in those with an MRI score of 3 or less was 85.7 percent (18 of 21).

In their discussion, lead author Robert Nam, MD, and colleagues call for further research evaluating the feasibility of adopting prostate MRI as a go-to screening option.

They note that cost would present one obvious hurdle, as would the potential for discordant MRI interpretations in high-volume, multi-reader settings.

“However, the potential savings resulting from detecting and treating aggressive prostate cancer at an earlier stage, and avoiding unnecessary prostate biopsy and treatment of indolent prostate cancer, could justify the cost of prostate MRI screening,” Nam and co-authors write. “Further, the costs of prostate MRI are similar to those of other screening tests such as colonoscopy, for which mass screening is recommended.”

In an accompanying opinion piece, urologist Pedro Recabal, MD, of Memorial Sloan Kettering Cancer Center acknowledges the pilot study as an important “small step” toward quantitative image biomarker validation.

But he also warns that, in order for MRI to become a standard screening tool, “rigorous criteria must be met to demonstrate analytical and clinical validity.”

“Current data are still insufficient to support a role for MRI in biopsy decision making,” Recabal writes. “As further technological improvements (such as automated processing and analysis of the images) contribute to overcome current limitations (cost, access and reproducibility), MRI may be integrated along with other risk assessment tools in a smarter early diagnosis algorithm.”