Prostate biopsy: targeting cancer for detection and therapy

Abstract

Despite improvements in cancer detection, prostate biopsy still lacks the ability to accurately map locations of cancer within the prostate. Improvements in prostate imaging may allow more accurate mapping of overall disease volume. Magnetic resonance (MR) spectroscopy allows improved specificity in detecting even small foci of disease within the peripheral zone. Improvements in MR-guided biopsy techniques may allow this technology to be adapted to therapeutics as well. Computer modeling of individual prostates serves as a means of designing optimized plans for prostate biopsy. The use of novel targeted biopsy schemes may allow an integration of available technologies in detection and localization of prostate cancer. Computer-directed needle biopsies based on anatomic landmarks within the prostate and computerized three-dimensional reconstruction of the gland may allow a highly reproducible means of identifying small foci of cancer, targeting them for therapy, and monitoring for recurrence. The TargetScan(R) system (Envisioneering Medical Technologies, St. Louis, MO) is the first technology to integrate available targeting methodologies in a systematic fashion.

Figure 1

Several extended biopsy templates have been proposed over the past years. All attempt to incorporate increased core number and sampling of the far-lateral region of the peripheral zone. (A) The 13-core, “5-region” biopsy, incorporates 4 far-lateral cores. (B) The 11-core, multisite-directed biopsy includes several midsagittal cores. (C) The current 12-core biopsy used at New York University incorporates a far-lateral sextant sampling.

Figure 2

The current New York University approach to men with negative prostate biopsy. PSA, prostate-specific antigen; DRE, digital rectal examination.

Figure 3

A T2-weighted endorectal magnetic resonance image demonstrates decreased signal intensity in the left peripheral zone (arrow), consistent with cancer. Follow-up biopsy failed to demonstrate cancer, suggesting the finding was a false positive.

Figure 4

Endorectal magnetic resonance spectroscopic imaging demonstrating the presence of extensive prostate cancer. (A) An illustration of the spectral display of metabolites within a single voxel (shown in the inset) of the prostate. In this case, the presence of high choline (large peak) and no citrate confirms the presence of prostate cancer. (B) Mapping of voxels over the whole prostate demonstrates diffuse cancer as evidenced by choline to citrate/creatine ratios > 0.8.

Figure 5

Digitized whole-mount prostate sections are stacked to create a 3-dimensional prostate image incorporating locations of cancer. Simulated biopsy puncture lines predict the likelihood of cancer detection. Reprinted from Bauer JJ et al, with permission from Elsevier.

Figure 6

The TargetScan® transrectal ultrasound-guided prostate biopsy system. Image courtesy of Envisioneering Medical Technologies.

Figure 7

The fixed transducer probe is positioned in the rectum. The transducer crystal moves within the probe to positions designated by the program software. Image courtesy of Envisioneering Medical Technologies.

Figure 8

The TargetScan® probe carriage allows (A) side-to-side rotation of the probe to align the needle with the radial position of the intended biopsy. The biopsy is performed with a bendable needle passed through a needle guide (B), which can be sequentially advanced along the probe to the appropriate distance from the apex. Image courtesy of Envisioneering Medical Technologies.

Figure 9

The TargetScan® image allows simultaneous biplanar visualization of needle tracts relative to the gland apex and rectal wall. Radial lines plotted from the needle guide position allow determination of the degree of probe rotation. Image courtesy of Envisioneering Medical Technologies.