Geometric systematic prostate biopsy

Likelihood of sampling prostate cancer at systematic biopsy as a function of gland volume and number of cores

BACKGROUND

Pre-biopsy multiparametric magnetic resonance imaging (mpMRI) of the prostate is used to conduct targeted prostate biopsy (TB), guided by ultrasound and registered (fused) to the MRI. Systematic biopsy (SB) continues to be used together with TB or in mpMRI-negative patients. There is insufficient evidence on how to use SB to inform clinical decision-making in the mpMRI era. The purpose of this study was to estimate the effect of prostate volume and number of SB cores on sampling clinically significant prostate cancer (csPCa) using a simulation method based on clinical data.

METHODS

SBs were simulated using data from 42 patients enrolled in a transrectal ultrasound robot-assisted biopsy trial. Linear mixed models were used to examine the relationship between the number of SB cores and prostate volume on 1) clinically significant cancer detection probability (csCDP) and 2) percent of mpMRI depicted regions of interest (ROIs) sampled with the SB.

RESULTS

Median values and interquartile range (IQR) were 47.16 cm3 (35.61-65.57) for prostate volume, 0.57 cm3 (0.39-0.83) for ROI volume, and 4.0 (2-4) for PI-RADS v2.1 scores on MRI. csCDP increased with the increasing number of simulated SB cores and decreased substantially with larger prostate volume. Similarly, the percent of ROIs sampled increased with the increasing number of simulated SB cores and was lower for prostate volumes ≥60 cm3 compared to glands <60 cm3.

CONCLUSIONS

The effect of the number of SBs performed on detecting csPCa varies largely with gland volume. The common 12-core SB can achieve adequate cancer detection and sampling of ROIs in smaller glands, but not in larger glands. In addition to TB or in mpMRI-negative patients, the number of SB cores can be adjusted to prostate volume. Performing 12-core SB alone in ≥60 cm3 glands results in inadequate sampling and potential PCa underdiagnosis.

A Matched-pair Analysis Comparing Systematic Prostate Biopsy by Conventional Transrectal Ultrasound-guidance Versus Software-based Predefined 3D-Guidance

OBJECTIVE

To compare software-based three-dimensional-guided systematic prostate biopsy (3D-GSB) with conventional transrectal ultrasound-guided systematic biopsy (TGSB) regarding prostate cancer (PCa) detection rates (CDR).

METHODS

In total, 956 patients (200 TGSB patients and 756 3D-GSB patients) without prior positive biopsies and with a prostate-specific antigen value ≤20 ng/ml were eligible for analysis. TGSB and 3D-GSB cases were matched in a 1:1 ratio using propensity score matching with age, prostate-specific antigen, prostate volume, previous biopsy status, and suspicious palpatory finding as confounders. 3D-GSB was conducted with the semi-robotic prostate fusion-biopsy system Artemis. For each patient in both groups, SB was conducted in a similar pattern with 12 cores. All cores in 3D-GSB were automatically planned and mapped on a 3D-model as well as on the real-time transrectal ultrasound imaging. Primary end points were the clinically significant (cs) and overall CDR. Secondary end point was the cancer-positive core rate.

RESULTS

After matching, the csCDR was not significantly different between the 3D-GSB and the TGSB groups (33.3% vs 28.8%, P = .385). Overall CDR was significantly higher for 3D-GSB compared to TGSB (55.6% vs 39.9%, P = .002). 3D-GSB detected significantly more non-significant PCa than TGSB (22.2% vs 11.1%, P = .004). In patients with PCa, the number of cancer-positive SB cores was significantly higher by TGSB (42% vs 25%, P < .001).

CONCLUSION

3D-GSB was associated with a higher CDR than TGSB. However, no significant difference was shown in detection of csPCa between both techniques. Therefore, currently, 3D-GSB does not appear to add value to conventional TGSB.

Prostate Cancer Detection Rate of Freehand versus 3-Dimensional Template Mapping Biopsy Using a Magnetic Resonance Imaging-Ultrasound Fusion Device in Biopsy Naïve Men

PURPOSE

Targeted prostate biopsy devices include a 3-dimensional digital template grid to guide systematic biopsy locations. Following a template could better ensure uniform and well distributed sampling of the prostate compared to the traditional freehand biopsy approach, possibly decreasing the chance of false-negative biopsy. Thus, we determined cancer detection rates obtained by conventional freehand systematic sampling vs template mapping sampling using a magnetic resonance imaging-ultrasound fusion device.

MATERIALS AND METHODS

Men who underwent first line conventional or image guided prostate biopsy were identified retrospectively in an institutional review board approved protocol. Excluded from study were men with prior biopsy or treatment or fewer than 10 cores taken. Targeted cores obtained by image guided biopsy were censored from analysis to simulate systematic template biopsy. The resulting cancer detection rate was compared to that of conventional biopsy.

RESULTS

We identified 1,582 patients between 2006 and 2014 who met the criteria for analysis, including 1,052 who underwent conventional biopsy and 530 who underwent template biopsy with a magnetic resonance imaging-ultrasound fusion device. Patient age, prostate specific antigen and the number of systematic cores were the same in the 2 groups. Template biopsy detected any prostate cancer in 257 of 530 men (48.5%) and clinically significant cancer in 196 (37.0%) while conventional biopsy detected any cancer in 432 of 1,052 (41.0%) (p=0.005) and clinically significant cancer in 308 (29.2%) (p=0.002).

CONCLUSIONS

Template mapping systematic biopsy detected more prostate cancer than conventional sampling in biopsy naïve men. It is a promising cost-effective alternative to magnetic resonance imaging-ultrasound fusion biopsy as an upfront screening tool.