[MRI navigated stereotactic prostate biopsy: fusion of MRI and real-time transrectal ultrasound images for perineal prostate biopsies].

BACKGROUND: A key challenge for prostate cancer (PC) therapy is to exactly diagnose tumor lesions. In this context we describe a new stereotactic prostate biopsy system, which integrates pre-interventional MRI with peri-interventional ultrasound for targeted perineal prostate biopsies. Furthermore, the novel system allows exact documentation of biopsies in three dimensions.

PATIENTS AND METHODS: Stereotactic biopsy was performed in 50 consecutive men with suspicion of PC [median age 67 years (42-77), mean PSA 8.9±6.8 ng/ml, and mean prostate volume 51±23.7 ml]. Twenty-five of these patients (50%) had already had a negative transrectal ultrasound (TRUS)-guided biopsy. All men underwent multiparametric, contrast-enhanced 3T MRI without endorectal coil. Suspicious lesions were marked before the obtained data were transferred to a novel stereotactic biopsy system. Using a custom-made biplane TRUS probe mounted on a stepper, 3-D ultrasound data were generated and fused with the MRI. As a result, suspicious MRI lesions were superimposed onto the TRUS data. Next, 3-D biopsy planning was performed including systematic biopsies from the peripheral zone of the prostate. According to local standards patients were treated with perioperative quinolone antibiotics and applied a rectal enema the evening before the procedure. Perineal biopsies were taken under live US imaging, and the location of each biopsy was documented in an individual 3-D model. Feasibility, safety, target registration error, and cancer detection were evaluated.

RESULTS: The median number of biopsies taken per patient was 24 (12-36). In 27 men of the initial cohort of 50 consecutive patients presented here, biopsy samples showed PC (54%). In patients undergoing their first biopsy, cancerous lesions were diagnosed in 13 of 19 patients (68%). The result was positive in 36% of men undergoing a re-biopsy without previous cancer diagnosis (9/25). A positive correlation between MRI findings and histopathology was found in 72%. In MRI lesions marked as highly suspicious, the tumor detection rate was 100% (13/13). Looking at single cores from highly suspicious lesions, 40 of 75 (53%) biopsies were positive. The target registration error of the first 1,159 biopsy cores was 1.7 mm. Regarding adverse effects, one patient experienced urinary retention and one patient a perineal hematoma. Urinary tract infections did not occur.

CONCLUSION: Perineal stereotactic prostate biopsies guided by the combination of MRI and ultrasound allow effective examination of suspicious MRI lesions. Each biopsy core taken is documented accurately for its location in 3-D enabling MRI validation and tailored treatment planning. The morbidity of the procedure was minimal.