The impetus for the study was to improve upon previous studies that used whole-mount specimens from men with a diagnosis of prostate cancer on TRUS biopsy as the reference standard, incorporating a work-up bias. This study reported on the performance characteristics of mp-MRI using template prostate mapping (TPM) as the reference standard.
Mp-MRI (T1/T2, dynamic contrast enhancement and diffusion weighting, 1.5Tesla, pelvic phased array) was performed before TPM in men with an elevated PSA (n=65), of whom 16 had no previous cancer diagnosis, and 49 had proven cancer on previous TRUS biopsy. Each mp-MRI was interpreted by three uro-radiology experts (R1-R3). Each prostate was divided into 4 regions of interest (ROI) and a score of 1 to 5 assigned to each ROI (1 - ‘no cancer’, 5 - ‘highly suspicious’). TPM was performed under general anesthesia with 5mm-spaced sampling using a brachytherapy template grid. Analysis was carried out for all cancer on TPM. Two definitions of clinical significance were applied: Definition 1) Gleason grade ≥4+3 and/or ≥6mm cancer core length (CCL) Definition 2) Gleason grade ≥3+4 and/or ≥4mm CCL.
Sixty-five consecutive men (260 ROIs) with a mean age 62 years and mean PSA 8.2ug/L (range 2.1–43) were evaluated. 130/260 (50%) of ROIs were positive for cancer on TPM. By definition 1 and 2, 38/260 (15%) and 69/260 (27%) had positive ROIs, respectively. Accuracy using area under receiver-operator characteristic curve (AUC) improved from 0.66 – 0.70 for all cancer to 0.71-0.85 and 0.72-0.83 for clinically significant cancer by definition 1 and 2. The negative predictive value of mp-MRI was 0.93-0.97 for definition 1 cancer and 0.85-0.90 for definition 2 cancers, respectively.
The investigators suggest that this finding could be used to address the over-diagnosis burden from PSA screening by using mp-MRI as a triage test to identify men who could avoid a prostate biopsy. However, cost-analysis of this approach was not included.
Presented by Nimalan Arumainayagam, et al. at the 26th Annual European Association of Urology (EAU) Congress - March 18 - 21, 2011 - Austria Centre Vienna, Vienna, Austria
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