Using MRI for prostate cancer diagnosis and treatment

Review date: September 2021

Citation: Israel et al., In press. Clinical implementation of pre-biopsy MRI pathways for the diagnosis of prostate cancer. BJU International

Australia’s Clinical Practice Guidelines on Prostate Specific Antigen Testing and Management of Test-detected Prostate Cancer were published in early 2016, after approval of the recommendations by the Chief Executive Officer of the National Health and Medical Research Council in November 2015. Thus, current clinical practice is based on information that is now at least six years old.

Clinical management of prostate cancer has moved faster than Australia’s Clinical Practice Guidelines. When the existing Australian guidelines were written, it was noted that the document “focuses on the use of multiparametric MRI after a negative prostate biopsy, not on its use for the primary investigation of a positive PSA test, because this is not routine clinical practice”. However, several recently published studies show the benefit of MRI to guide decisions about prostate biopsy.

In July 2018, a Medicare rebate for prostate MRI (ordered by a urologist or oncologist for patients meeting specific criteria) was made available, which has seen this imaging modality become increasingly used “for the primary investigation of a positive PSA test”, albeit not in primary care.

Clinical trials have established that multiparametric MRI reduces overdiagnosis of non-threatening prostate cancers and unnecessary biopsies and reduces complications from biopsies that are performed. Whether these benefits translate to the less controlled environment of routine clinical practice is the subject of a recent study conducted in the Netherlands¹.

Men with high PSA levels (>3ng/ml) or suspicious digital rectal exam (DRE) findings, without previous prostate biopsy, were included in a retrospective cohort study across two sites: a university centre (566 men) and non-university centre (2031 men). All men underwent multiparametric MRI scans at the university centre, where appropriate radiological expertise was available.

Prostate biopsy was performed based on Prostate Imaging-Reporting and Data System (PI-RADS) scores. All men with PI-RADS scores of 4 to 5 received subsequent MRI-directed biopsy (either transrectal or transperineal), as did some men with PI-RADS scores of 3 (after multidisciplinary team review and shared decision-making with the patient).

Biopsy was avoided for 57% of men. Of those who underwent biopsy, 81% had prostate cancer —  Gleason Grade was ≥3 in 35%, ≥2 in 68% and 1 in 19%. The positive predictive value of PI-RADS scores of 3 to 5 for cancers with Gleason Grade ≥2 was 63%. Previous studies show negative predictive values of MRI for Gleason Grade >2 above 90%. The potential to miss some prostate cancers of clinical significance can likely be dealt with by providing a ‘safety net’ of six-monthly PSA tests and MRI if suspicion remains².

The benefit of using information from MRI to guide prostate biopsy that has been observed in previous studies^2,3 was replicated in the settings of the new study. The study also supports previous observations showing a benefit of targeted biopsy over systematic collection of biopsy samples for high Gleason Grade cancers⁴.

The 2016 Clinical Practice Guidelines on Prostate Specific Antigen Testing and Management of Test-detected Prostate Cancer mention a plan for review every three years. As we approach the date of the second period of review, a report of the outcome of a first review or an update of the guidelines has not appeared. When an update does appear, recommendations for the use of MRI will hopefully consider “its use for the primary investigation of a positive PSA test”.