Targeted Prostate Biopsy: Lessons Learned Midst the Evolution of a Disruptive Technology

Abstract

Lessons learned during a 6-year experience with more than 1200 patients undergoing targeted prostate biopsy via MRI/ultrasound fusion are reported: (1) the procedure is safe and efficient, requiring some 15-20 minutes in an office setting; (2) MRI is best performed by a radiologist with specialized training, using a transabdominal multiparametric approach and preferably a 3T magnet; (3) grade of MRI suspicion is the most powerful predictor of biopsy results, eg, Grade 5 usually represents cancer; (4) some potentially important cancers (15%-30%) are MRI-invisible; (5) Targeted biopsies provide >80% concordance with whole-organ pathology. Early enthusiasm notwithstanding, cost-effectiveness is yet to be resolved, and the technologies remain in evolution.

Figure 1. Value of Targeted Biopsy to Evaluate Men for Active Surveillance (Example Case)

A man aged 68 years was referred for active surveillance when a conventional biopsy revealed a small focus of low-grade prostate cancer. A confirmatory biopsy was later performed using magnetic resonance imaging/ultrasound (MRI/US) fusion to target a suspicious region. Top row: Multiparametric MRIs from a T2-weighted image (A), a diffusion-weighted image (B), and a dynamic contrast-enhanced image (C). The delineated region of interest (arrows) was assigned a grade 4 or 5 level of suspicion. Bottom row: During fusion biopsy, the region of interest from an MRI is superimposed on a US image (D). Systematic and targeted biopsy cores (tan lines) were obtained and recorded on a digital reconstruction of the prostate using an MRI/US fusion device (Artemis; Eigen, Grass Valley, Calif) (E). A targeted biopsy revealed potentially lethal, high-grade cancer, and radical prostatectomy was performed. A whole-mount prostate sample reveals high-grade cancer (large arrow) that was not detected on an earlier conventional biopsy (F). The small arrow indicates a focus of low-grade cancer that was identified on an earlier “blind” biopsy. Targeted biopsy provides more accurate characterization of whole-gland pathology than conventional (blind) biopsy and is increasingly used to evaluate men for active surveillance. In the example case, a targeted biopsy revealed that the patient was a poor candidate for active surveillance. Reprinted with permission, American Cancer Society.

Figure 2. Example of Falsely Negative MRI in Patient P.M

Patient is a 68 year old Caucasian male (PSA 3.8 ng/ml), who on a previous conventional biopsy was found to have a microfocus of Gleason 3+3=6 prostate cancer. He was considered for active surveillance, and mpMRI of prostate was obtained (A): prostate volume was found to be 35cc; no region of interest (ROI) was identified, even retrospectively. Mapping biopsy was performed by following the 12-point template of the Artemis device (B). A tissue core from the left lateral apex revealed 6 mm of Gleason 3+5=8 prostate cancer (C, 4×; D, 20×). Radical prostatectomy was performed, revealing a tumor on the left side of the prostate with diameters of 15mm × 12mm × 9 mm. In our experience, the incidence of falsely negative MRI (i.e., Gleason Score ≥7 with no MRI evidence of tumor) is 15% when using biopsy evidence and approaches 30% when using whole mount prostatectomy evidence. When biopsy is clinically indicated, a negative MRI should not preclude mapping biopsy.