MRI-Guided Prostate Biopsy Strategy Reduces Testing, Avoids Clinically Insignificant Cancer Diagnoses

Author: By Lynda Williams, Senior medwireNews Reporter 

medwireNews: STHLM3–MRI study findings show that use of magnetic resonance imaging (MRI)-guided biopsy in combination with standard biopsy is noninferior to standard biopsy alone for detection of clinically significant prostate cancer in men with elevated prostate-specific antigen (PSA). 

“When normalized to a population of 10,000 men 50 to 74 years of age in which those with elevated PSA levels (≥3 ng per milliliter) are referred for biopsy, the combined biopsy approach in men with positive MRI scans would result in 409 fewer men undergoing biopsy, 366 fewer biopsies with benign findings, and 88 fewer clinically insignificant cancers detected than with the standard biopsy approach”, say Martin Eklund, from the Karolinska Institutet in Stockholm, Sweden, and co-authors. 

“These numbers represent 48%, 73%, and 62% lower incidences, respectively, with the use of MRI and the combined biopsy approach”, they write, adding that “[t]he reduced biopsy rate and potential downstream savings that result from less overtreatment offer potential cost savings that may offset the additional costs of MRI.” 

The study published in The New England Journal of Medicine and reported at the 36th Annual European Urology Association Congress enrolled 12,750 men from the general population in Stockholm County to undergo prostate cancer screening, 1532 of whom had a PSA level of at least 3 ng/mL.  

In total, 929 men were randomly assigned to undergo MRI with targeted biopsy of up to three prostate areas with clinically suspicious disease, defined as a Prostate Imaging Reporting and Data System (PI-RADS) score of 3–5. This was followed by a standard 10–12 core ultrasound-guided biopsy for those with a positive MRI. The remaining 603 men received only a standard ultrasound-guided biopsy. 

Men without any suspicious areas on MRI were able to avoid biopsy unless they had a Stockholm3 test score of at least 25%, indicating a high risk of clinically significant disease based on clinical variables, polygenic score, and PSA and other biomarkers, the investigators explain. 

Overall, 36% of the MRI group underwent biopsy, based on a PI-RADS score of 3–5 or a Stockholm3 test score of 25% or greater despite a negative MRI; 73% of the standard biopsy group underwent the procedure. 

In the intention-to-treat analysis, clinically significant prostate cancer – defined as a Gleason score of 3+4 or greater – was detected in 21% of the MRI group versus 18% of controls, a 3 percentage point difference that met the threshold for noninferiority of the MRI protocol versus standard biopsy.  

Patients who underwent MRI-directed biopsy were also significantly less likely than controls to be diagnosed with clinically insignificant prostate cancer (4 vs 12%) or benign disease (11 vs 43%).  

Patient age, PSA or prior negative biopsy did not affect the likelihood of detecting clinically significant or insignificant prostate cancer with MRI biopsy, the researchers note. 

However, the researchers observe that if the experimental arm had undergone the MRI-guided biopsy only, 30 clinically significant prostate cancers would have been missed, taking the proportion of positive tests to 17%, a rate that did not meet noninferiority versus standard biopsy. Eighteen clinically insignificant prostate cancers would also have gone undetected, so that detection of 1.7 clinically significant tumours would be delayed for each clinically insignificant cancer undetected. 

“Our results therefore support the use of standard biopsy in addition to targeted biopsy for men who have positive MRI results, an observation that is in line with previous findings”, they conclude. 

Reference  

Eklund M, Jäderling F, Discacciati A, et al. MRI-targeted or standard biopsy in prostate cancer screening. N Engl J Med; Advance online publication 9 July 2021. DOI: 10.1056/NEJMoa2100852