Does proximity of positive prostate biopsy core to capsular margin help predict side-specific extracapsular extension...

To determine whether quantifying the proximity of positive prostate biopsy cores to the capsular edge may aid in identifying patients at risk for extracapsular extension (ECE) at the time of radical prostatectomy (RP).

We reviewed a single-surgeon experience of 429 systematic transrectal prostate biopsies from 2010-2014. Marking ink was applied to the capsular edge ex vivo following specimen acquisition, and the proximity of cancer to the stained capsular edge was measured. Primary outcome was ECE at RP. Demographics, PSA, DRE findings, Gleason score, core location and involvement, and RP pathology were recorded. Predictors of ECE were identified using multivariable logistic regression. Receiver operating characteristic (ROC) analyses were performed to assess the predictive value of variables alone and in combination.

One hundred and one patients who underwent staining during biopsy received RP (202 hemiprostates). Thirty-three patients (40 hemiprostates) exhibited ECE. There were 343 positive stained biopsy cores. Mean proximity of carcinoma to capsule was 4.7 mm. On univariable analysis, proximity of positive core ≤ 1 mm to capsule was predictive of side-specific ECE (OR 2.86, p = 0.013), though significance was lost in multivariable models. Area under the curve (AUC) for proximity was 0.571 alone and 0.804 in combination with PSA, cT stage, and total biopsy Gleason score.

Proximity of positive biopsy core to capsular margin may supply additional information in predicting ECE but requires validation in a larger cohort. Implementation of a staining technique at the time of systematic biopsy may be helpful in counseling patients and determining utility of nerve-sparing approaches.