Multiparametric Magnetic Resonance Imaging (mpMRI) of Prostate
Cancer lesions - How much do we have to learn?
Abstract
Introduction and Objective: The introduction of functional mp-MRI imaging has enabled imaging
to evolve from a having a limited role in local staging of prostate cancer to being able to detect
tumours with a relatively high sensitivity and specificity. This study is aimed at determining the
accuracy of multiparametric Magnetic Resonance Imaging (mpMRI) during the learning curve of
radiologists in a tertiary-referral cancer centre using MRI targeted, transrectal ultrasound guided
transperineal fusion biopsy (MTTP) for validation.
Material and Methods: Prospective data on 340 consecutive patients was collated. Patients
underwent mpMRI read by two radiologists in line with ESUR standards followed by MTTP biopsy
of the lesion (targeted biopsy). ). Our first 70 patients in 2012 (Group A) and the last 70 patients of
2013 (Group E) were compared. A 5-point likert scale of probability was used to determine lesions
suspicious for cancer, with scores ≥3 taken as a positive MR-target. We compared sequential groups
to determine the learning curve. Statistical analysis was performed with chi-square correlation test.
Results: We detected a positive mpMRI in 64 patients from group A (91%) and 52 patients from
the group E (74%). Prostate cancer (CaP) detection rate on mpMRI increased from 42% (27/64) in
group A and 81% (42/52) in group E (p value 0.003). CaP detection rate by targeted biopsy
increased from 27% (17/64) in group A and 63% (33/52) in group E (p value 0.001). The negative
predictive value of MRI for significant cancer (> Gleason 3+3) was 88.9% in group E vs 66.6% in
group A (see Table).
Conclusions: We demonstrate an improvement in detection of CaP for MRI reporting over time,
suggesting a learning curve for the technique. Despite an improved negative predictive value for
significant cancer, this did not reach a level whereby biopsy can be avoided in MR negative cases.