Multi-parametric ultrasound is broadly similar to MRI for detecting prostate cancer but combing both would increase rates cancer detection
Multi-parametric ultrasound is a useful alternative to magnetic resonance imaging (MRI) for the detection of prostate cancer although detection rates would be improved by using both imaging modalities. This was the conclusion of a comparative study by a team from the Division of Surgical and Interventional Sciences, University College London, London, UK.
According to the World Cancer Research Fund, there were 1.3 million new cases in 2018 and which resulted in 358,989 deaths (3.8% of all deaths caused by cancer in men) in 2018. Among men who present with an elevated prostate specific antigen (PSA) level or a palpable abnormality after a digital-rectal examination, there is an increased potential for the diagnosis of prostate cancer.
According to a 2019 Cochrane systematic review, the use of a magnetic resonance imaging pathway has the most favourable diagnostic accuracy in clinically significant prostate cancer detection.
Nevertheless, multi-parametric MRI is not universally used and multi-parametric ultrasound appears to be a promising alternative approach with the available evidence confirming that combining different ultrasound scans significantly improves diagnostic performance in prostate cancer.
For the present study and given the widespread availability of multi-parametric ultrasound, the UK team sought to compare the overall level of agreement between ultrasound and MRI scanning for the diagnosis of clinically significant prostate cancer.
They undertook a prospective, multi-centre, paired-cohort study, in which patients with an elevated PSA or a digital-rectal examination abnormality, underwent both multi-parametric ultrasound (MPUS) and multi-parametric MRI (MPMRI). In cases where either modality identified positive findings, patients were referred for targeted biopsies.
The study had two primary endpoints: the proportion of positive results from both imaging tests and the level of agreement between them. The second outcome was the detection of clinically significant prostate cancer after biopsy defined as Gleason >4+3 of any length and/or maximum cancer core length of >6mm of any grade.
Multi-parametric ultrasound and cancer detection
A total of 370 men with a mean age of 64.5 years were included in the trial, of whom, 306 had both imaging scans and 257 underwent a subsequent prostate biospy.
MPUS was positive for 89 % of patients and MRMRI in 78% (difference 11.1%, 95% CI 5.1 – 17.1). In addition, the agreement in lesion detection between MPUS and MRMRI was 73.2%.
Any cancer was detected in 52% of the 257 patients with 32% being clinically significant. However, there were differences between the two modalities. Overall, MPUS detected 4.3% fewer clinically significant cancers than MRMRI although MPUS detected 7.2% (6/83) significant cancers missed by MRMRI but the latter detected 20.5% of significant cancers missed by MPUS.
Nevertheless, there was a 91.1% agreement between the two modalities on the detection of clinically significant cancer.
The authors determined that combining MPUS and MPMRI would have led to the detection of 99 clinically significant cancers. They added that while MPUS detected 4.3% few significant cancers and would have resulted in 11.3% more patients being referred for a biopsy, both imaging modalities had missed cancers detected by the other technique.
As a final point, they added that using both modalities would increase the detection of clinically significant cancers to either test alone.
Grey ADR et al. Multiparametric ultrasound versus multiparametric MRI to diagnose prostate cancer (CADMUS): a prospective, multicentre, paired-cohort, confirmatory study Lancet Oncol 2022