Localized prostate cancer

In the current diagnostic pathway for prostate cancer, men with an elevated prostate-specific antigen (PSA) or other risk factors typically undergo transrectal ultrasound (TRUS)-guided biopsy. However, there are several potential drawbacks — clinically indolent cancers may be identified by chance, clinically significant lesions may be missed, and important cancers may be incorrectly classified as unimportant. In many cases, men may unnecessarily undergo radical treatment to the prostate, resulting in side effects such as erectile dysfunction and incontinence. Multiparametric magnetic resonance imaging (MP-MRI) holds promise as a triage test for men with elevated PSA levels to determine the need for TRUS biopsy. The 11-centre UK Prostate MRI Imaging Study (PROMIS) compared MP-MRI and TRUS biopsy with an accurate reference test (template prostate mapping biopsy with sampling of the prostate every 5 mm) in 576 men with an elevated PSA (up to 15 ng/mL) and no prior biopsy.1 Results presented at ASCO 2016 revealed MP-MRI to be significantly more sensitive than TRUS biopsy (93% vs. 48%; p<0.0001), with a higher negative predictive value (89% vs. 74%; p<0.0001), but lower positive predictive value (51% vs. 90%; p<0.0001) and specificity (96% vs. 41%; p<0.0001). Clinically significant disease — defined as a Gleason score of 4 or higher or a high burden of low-grade disease — was missed in 119 cases by TRUS biopsy, including 13 Gleason 4 + 3 or higher cancers. MP-MRI missed only 17 cases of clinically significant disease and no Gleason 4 + 3 or higher cancers. While TRUS-biopsy performs poorly in both detecting and ruling out clinically significant prostate cancer, MP-MRI shows promise as a triage test, with the ability to identify up to one-quarter of men who might safely avoid unnecessary biopsy, without impairing the detection of clinically significant cancer. This research adds to the growing body of evidence highlighting the role of prostate MRI in clarifying prostate cancer diagnosis