Prostate tumors undetected by multiparametric magnetic resonance imaging (mpMRI) are smaller and of lower grade that those that are detected, according to a new study.
The findings are from a post hoc analysis of data from PROMIS (Prostate MR Imaging Study) cohort, which tested the performance of mpMRI and transrectal ultrasonography (TRUS)-guided biopsy in detecting significant cancers using 5 mm template mapping (TPM) biopsy as the reference standard. Investigators used 2 definitions of significant cancer: definition 1, Gleason 4+3 or higher of any length or maximum cancer core length (MCCL) of 6 mm or more of any grade; definition 2, Gleason 3+4 or higher of any length or MCCL 4 mm or more.
The analysis found that mpMRI missed significant disease in 7% of men with prostate cancer using definition 1 and 13% of men using definition 2, Joseph M. Norris, MSc, BM, BS, of University College London in the UK, and colleagues reported in European Urology.
Prostate cancer undetected by mpMRI had significantly lower overall and maximum Gleason scores and shorter MCCL than cancers that were detected (5 vs 8 mm). No tumors with overall Gleason score higher than 3+4 (Gleason Grade Groups 3 to 5) or maximum Gleason score greater than 4+3 (Gleason Grade Groups 4 to 5) on TPM biopsy were undetected by MRI, according to the investigators.
In addition, application of a PSA density threshold of 0.15 decreased the proportion of men with undetected cancer to 5% for definition 1 and 9% for definition 2. Application of a PSAD threshold of 0.10 reduced the proportion of men with undetected tumors to 3% and 3%, respectively.
“These findings reinforce the key role that mpMRI plays in risk stratification of men with suspected prostate cancer,” the authors concluded. “Further in-depth analysis of mpMRI-inconspicuous prostate cancer is currently being undertaken to enrich our understanding of the nature of undetected disease.”
Norris JM, Carmona Echeverria C, Bott SRJ, et al. What type of prostate cancer is systematically overlooked by multiparametric magnetic resonance imaging? An analysis from the PROMIS cohort [published online May 1, 2020]. Eur Urol. doi: 10.1016/j.eururo.2020.04.029