To determine whether sub-classification of positive surgical margins increases predictive ability for biochemical recurrence and aids clinical decision making in patients undergoing radical prostatectomy.
We studied 2,147 pT2 and pT3a prostate cancer patients with detailed surgical margin parameters and biochemical recurrence status. We compared a base model, a linear predictor calculated from the Memorial Sloan Kettering Cancer Center post-operative nomogram (prostate specific antigen, pathologic tumor grade and stage), with the addition of surgical margin status to 5 additional models (base model plus surgical margin sub-classifications) to evaluate enhancement in predictive accuracy. Decision curve analysis was performed to determine the clinical utility of parameters that enhanced predictive accuracy.
Among 2,147 men, 205 had positive surgical margins, and 231 developed biochemical recurrence. Discrimination for the base model with addition of surgical margin status was high (c-index=0.801) and not meaningfully improved by adding surgical margin sub-classification in the full cohort. In analyses considering only men with positive surgical margins (N=55 with biochemical recurrence), adding surgical margin sub-classification to the base model increased discrimination for total length of all positive margins – alone or with maximum Gleason grade at the margin (c-index improvement = 0.717 to 0.752 and 0.753, respectively). Decision curve analysis demonstrated a modest benefit to clinical utility with the addition of these parameters.
Specific sub-classification parameters add predictive accuracy for biochemical recurrence and may aid clinical utility in decision making for patients with positive surgical margins. These findings may be useful for patient counseling and future adjuvant therapy trial design.

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