Background: Active surveillance (AS) aims to reduce overtreatment of low-risk prostate cancer (PC). Incorporating multiparametric magnetic resonance imaging (mp-MRI) and MR-guided biopsy (MRGB) in an AS protocol might contribute to more accurate identification of AS candidates.
Objective: To evaluate the value of 3. T mp-MRI and MRGB in PC patients on AS at inclusion and after 12-mo follow-up.
Design, setting, and participants: Patients with cT1c-cT2 PC, prostate-specific antigen (PSA) ≤10. ng/ml, PSA density <0.2. ng/ml/ml, and Gleason scores (GSs) of ≤6 and ≤2 positive biopsy cores were included and followed in an AS protocol including mp-MRI and MRGB. The mp-MRI and MRGB were performed at <3 and 12 mo after diagnosis. Reclassification was defined as GS >6, >2 positive cores at repeat transrectal ultrasound-guided biopsy (TRUSGB), presence of PC in >3 separate cancer foci upon both MRGB and TRUSGB, or cT3 tumor on mp-MRI. Outcome measurements and statistical analysis: Reclassification rates, treatment after discontinuation, and outcome on radical prostatectomy after discontinuing AS were reported. Uni- and multivariate analyses were performed to identify predictors of reclassification after 1 yr.
Results and limitations: From 2009 to 2013, a total of 111 of 158 patients were consecutively and prospectively included. Around initial diagnosis, 36 patients were excluded from the study protocol; mp-MRI + MRGB reclassified 25/111 (23%) patients, and 11 patients were excluded at own request. Reasons for reclassification were as follows: GS upgrade (15/25, 60%); cT3 disease (3/25, 12%); suspicion of bone metastases (1/25, 4%); and multifocal disease upon MRGB (6/25, 24%). Repeat examinations after 1 yr showed reclassification in 33/75 patients (44%). Reasons were the following: GS upgrade upon TRUSGB (9/33, 27%); volume progression upon TRUSGB (9/33, 27%); cT3 disease upon mp-MRI (1/33, 3%); GS upgrade upon MRGB (1/33, 3%); volume progression upon MRGB (1/33, 3%); multifocal disease upon MRGB (2/33, 6%); and upgrade or upstage upon both TRUSGB and MRGB (10/33, 30%). On logistic regression analysis, the presence of cancer at initial mp-MRI and MRGB examinations was the only predictor of reclassification after 1 yr (odds ratio 5.9, 95% confidence interval 2.0-17.6).
Conclusions: Although mp-MRI and MRGB are of additional value in the evaluation of PC patients on AS, the value of mp-MRI after 1 yr was limited. As a considerable percentage of GS ≥7 PC after 1 yr was detected only by TRUSGB, TRUSGB cannot be omitted yet.
Patient summary: More aggressive tumors are detected if low-risk prostate cancer patients are additionally monitored by magnetic resonance imaging. However, some high-grade tumors are detected only by transrectal ultrasound-guided biopsy. Multiparametric magnetic resonance imaging (MRI) and MR-guided biopsies are of additional value in the initial evaluation of prostate cancer patients on active surveillance. At repeat examinations after 1 yr, transrectal ultrasound-guided biopsies cannot be omitted yet, as MRI could not detect all aggressive tumors.

Active surveillance, Biopsy, Functional magnetic resonance imaging, Magnetic resonance imaging, Prostate cancer,
European Urology Focus
Erasmus MC: University Medical Center Rotterdam

Hamoen, E.H.J. (Esther Hendrika Johanna), Hoeks, C, Somford, D.M, van Oort, I.M, Vergunst, H, Oddens, J.R, … Barentsz, J. (2018). Value of Serial Multiparametric Magnetic Resonance Imaging and Magnetic Resonance Imaging-guided Biopsies in Men with Low-risk Prostate Cancer on Active Surveillance After 1 Yr Follow-up. European Urology Focus. doi:10.1016/j.euf.2017.12.008