Feature article

MRI increases detection of prostate cancers and reduces overdiagnosis, finds study

Susan Mayor


Using magnetic resonance imaging (MRI) to guide targeted biopsies increased the detection of clinically significant cancer by 12% when compared with standard transrectal ultrasonography guided biopsy, in the first large randomised trial to compare these two approaches in men with suspected prostate cancer.1

MRI revealed no sign of prostate cancer in more than one in four men, avoiding the need for unnecessary biopsy or treatment.

“This is the first international multi-centre randomised trial to show the benefits of using MRI at the start of the prostate cancer diagnosis process,” said the lead author, Veeru Kasivisvanathan, from University College London, UK.

He added, “In men who need to have investigation for prostate cancer for the first time, using an MRI to identify suspected cancer in the prostate and performing a prostate biopsy targeted to the MRI information leads to more cancers being diagnosed than the standard way that we have been performing prostate biopsy for the last 25 years.”

Prostate cancer is currently diagnosed by taking 10-12 biopsy samples from the prostate, using an ultrasound guided procedure with a probe inserted into the anus under local anaesthetic. It involves estimating the position of a possible tumour and sometimes misses clinically significant tumours.

The PRECISION trial randomly allocated 500 men with clinical symptoms or signs of prostate cancer to MRI and targeted biopsy if their scan showed an abnormality suggestive of prostate cancer or to standard transrectal ultrasonography guided biopsy. The men showed raised prostate specific antigen (PSA) levels but had not previously had biopsies to investigate possible prostate cancer.

The primary outcome was the proportion of men with clinically significant cancer, defined as the presence of a single biopsy core indicating disease of Gleason score 3+4 or greater (higher scores indicate more aggressive prostate cancer).

Participants in either group with negative test results were subsequently followed up by standard surveillance, typically of their PSA levels.

The results, reported in the New England Journal of Medicine,1 showed that 71 (28%) of the 252 men allocated to MRI had scans that were not suggestive of prostate cancer, so they did not undergo biopsy.

Clinically significant cancer was detected in 95 patients (38%) in the MRI targeted biopsy group, compared with 64 (26%) in the standard biopsy group (adjusted difference 12% (95% confidence interval 4% to 20%); P=0.005).

Significantly fewer men in the MRI targeted biopsy group had clinically insignificant cancer diagnosed (–13% (–19% to –7%); P<0.001).

A higher percentage of biopsy cores were positive for cancer in the MRI targeted biopsy group (422 of 967 cores; 44%) than in the standard biopsy group (515 of 2788; 18%).

“A diagnostic pathway with initial MRI assessment followed by biopsy when required can not only reduce the overall number of biopsies performed but can give more accurate results than TRUS [transrectal ultrasonography] biopsy alone,” said Kasivisvanathan.

He suggested that this new pathway is cost effective by reducing the number of men undergoing prostate biopsies, as it achieves earlier diagnosis of cancers requiring treatment and avoids treatment of harmless cancers.

But he warned, “The ability to perform good quality MRI and the ability to interpret the MRI information are specialist skills. We will, therefore, need appropriate training for clinicians to use the technology and changes in health services to increase availability and capacity to perform prostate MRI.”

The trial was funded by the National Institute for Health Research and the European Association of Urology Research Foundation.

References

  1. V KasivisvanathanAS RannikkoM Borghi. MRI-targeted or standard biopsy for prostate-cancer diagnosis. N Engl J Med2018. 10.1056/NEJMoa1801993.

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