MRI could reduce unnecessary biopsy in one in four men with suspected prostate cancer

The use of multi-parametric MRI as a triage test may allow 27% of men with suspected prostate cancer to avoid a primary biopsy, according to results of a multicenter, paired-cohort, confirmatory study.

Further, multi-parametric MRI (MP-MRI) could reduce the diagnosis of clinically insignificant cancers by 5%.

Men with high serum PSA typically undergo transrectal ultrasound-guided (TRUS) prostate biopsy; however, this process can often lead to complications.

“Prostate cancer has aggressive and harmless forms. Our current biopsy test can be inaccurate because the tissue samples are taken at random. This means it cannot confirm whether a cancer is aggressive or not and can miss aggressive cancers that are actually there,” study researcher Hashim Ahmed, FRCS, PhD, BCh, clinician scientist and honorary consultant urological surgeon at University College London Hospitals, said in a press release. “Because of this, some men with no cancer or harmless cancers are sometimes given the wrong diagnosis and are then treated even though this offers no survival benefit and can often cause side effects. On top of these errors in diagnosis, the current biopsy test can cause side effects such as bleeding, pain and serious infections.”

Ahmed and colleagues sought to determine whether use of MP-MRI — which provides information on tissue anatomy and prostate volume, cellularity and vascularity — as a triage test might allow some men to avoid unnecessary TRUS-biopsy and improve diagnostic accuracy.

Researchers evaluated the diagnostic accuracy of MP-MRI and TRUS-biopsy against template prostate mapping (TPM)-biopsy, which was used as a reference test.

The analysis included 576 men with PSA concentrations up to 15 ng/mL who had no previous biopsy. The men underwent an MP-MRI scan followed by both TRUS-biopsy and TPM-biopsy.

Results from TPM-biopsy showed 408 (71%) of the men had cancer, including 230 (40%) men with clinically significant cancer.

When evaluating the 230 men with clinically significant cancer, the MP-MRI had correctly diagnosed 93% (95% CI, 88-96) of those cancers as aggressive, whereas TRUS-biopsy deemed only 48% (95% CI, 42-55) aggressive. This indicated that MP-MRI was more sensitive than TRUS-biopsy (P < .0001).

Of the 10 men with a negative MP-MRI scan, nine (89%) had no cancer or a harmless cancer.

However, TRUS-biopsy had greater specificity (96% vs. 41%) and positive predictive value (90% vs. 51%; P < .0001 for both) than MP-MRI.

Researchers then considered two scenarios in which MP-MRI was used as a triage test, and only men with a suspicious result would go on to biopsy. In the worse-case scenario, a standard TRUS-biopsy would be done. In the best-case scenario, biopsies would be guided by MP-MRI findings.

For both scenarios, 158 (27%) of all the men would have avoided biopsy. Absolute reduction in overdiagnosis of clinically significant cancers reached 28 (5%) per 576 men for the worst-case scenario and increased to 21% (31 [5%] more cases per 576 men) for the best-case scenario. The best-case scenario might lead to 102 (18%) more cases of clinically significant cancer detected by 576 men compared with the standard pathway of TRUS-biopsy for all men.

Serious adverse events occurred in 5.9% of patients, including eight cases of sepsis caused by a urinary tract infection and 58 cases of urinary retention, all which were due to the biopsies and not MP-MRI.

Researchers noted that giving TPM-biopsy before TRUS-biopsy may have caused swelling and changes to the prostate tissue, which could affect the accuracy of the TRUS-biopsy. Further, more research is needed to examine the cost-effectiveness of this approach and how it affects hospital capacity.

“Our results show that MP-MRI should be used before biopsy,” Ahmed said. “Our study found that using the two tests could reduce overdiagnosis of harmless cancers by 5%, prevent one in four men having an unnecessary biopsy, and improve the detection of aggressive cancers from 48% to 93%.

“While combining the two tests gives better results than biopsy alone, this is still not 100% accurate, so it would be important that men would still be monitored after their MP-MRI scan,” he added. “Biopsies will still be needed if an MP-MRI scan shows suspected cancer too, but the scan could help to guide the biopsy so that fewer and better biopsies are taken.” – by Alexandra Todak

Disclosure: Ahmed reports funding from Sonacare Medical, Sophiris and Trod Medical for other trials. Please see the full study for a list of all other researchers’ relevant financial disclosures.