Using MRI to Avoid Unnecessary Biopsies
Typically, men with elevated PSAs have transrectal ultrasound-guided (TRUS) prostate biopsies to look for prostate cancer. However, TRUS biopsies can have errors in diagnosis because tissue samples are taken at random, and they cannot confirm whether a cancer is aggressive or not. Biopsies can also cause side effects such as bleeding, pain and infections.
In the PROMIS trial, 576 men with suspected prostate cancer had multiparametric MRI (MP-MRI) scans, which researchers used to help differentiate between aggressive and harmless cancers before performing biopsies. The MP-MRI scans provided information about the cancer’s size, density, and how well connected it was to a man’s bloodstream.
The men in the study underwent two types of biopsies: a TRUS biopsy and a template prostate mapping biopsy (TPM biopsy). The TPM biopsy was used as a control for comparing the MP-MRI scan and TRUS biopsy.
The TPM biopsies indicated 71% of the men in the study had prostate cancer, and 40% of the men had clinically significant cancer. The MPMRI scan was almost twice as sensitive in detecting the clinically significant cancers as the TRUS biopsy. The MPMRI scan correctly diagnosed nearly all (93%) of the aggressive cancers, whereas the TRUS found less than half (48%). Also, 89% of men who had a negative MP-MRI scan either had no cancer or harmless cancers upon biopsy.
The study authors estimated that adding a MP-MRI scan before biopsy could help 27% of men avoid unnecessary biopsies and reduce by 5% the number of men who are overdiagnosed with prostate cancer that would not cause harm.
Dr. Hashim Ahmed, the study’s lead author, said, “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.”
In the U.S., most insurance companies will not cover a MP-MRI scan unless the patient has already had a negative biopsy and still has a rising PSA.
Lancet. 2017 Jan 19. pii: S0140-6736(16)32401-1. doi: 10.1016/S0140-6736(16)32401-1. [Epub ahead of print]