[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.