We sought to determine whether saturation of the index lesion during magnetic resonance
imaging-transrectal ultrasound fusion guided biopsy would decrease the rate of pathological
upgrading from biopsy to radical prostatectomy. We analyzed a prospectively maintained,
single institution database for patients who underwent fusion and systematic biopsy
followed by radical prostatectomy in 2010 to 2016. Index lesion was defined as the
lesion with largest diameter on T2-weighted magnetic resonance imaging. In patients
with a saturated index lesion transrectal fusion biopsy targets were obtained at 6
mm intervals along the long axis of the index lesion. In patients with a nonsaturated
index lesion only 1 target was obtained from the lesion. Gleason 6, 7 and 8–10 were
defined as low, intermediate and high risk, respectively. Included in the study were
208 consecutive patients, including 86 with a saturated and 122 with a nonsaturated
lesion. Median patient age was 62.0 years (IQR 10.0) and median prostate specific
antigen was 7.1 ng/ml (IQR 8.0). The median number of biopsy cores per index lesion
was higher in the saturated lesion group (4 vs 2, p <0.001). The risk category upgrade
rate from systematic only, fusion only, and combined fusion and systematic biopsy
results to prostatectomy was 40.9%, 23.6% and 13.8%, respectively. The risk category
upgrade from combined fusion and systematic biopsy results was lower in the saturated
than in the nonsaturated lesion group (7% vs 18%, p = 0.021). There was no difference
in the upgrade rate based on systematic biopsy between the 2 groups. However, fusion
biopsy results were significantly less upgraded in the saturated lesion group (Gleason
upgrade 20.9% vs 36.9%, p = 0.014 and risk category upgrade 14% vs 30.3%, p = 0.006).
Our results demonstrate that saturation of the index lesion significantly decreases
the risk of upgrading on radical prostatectomy by minimizing the impact of tumor heterogeneity.