'Mohs surgery of the prostate': the utility of in situ frozen section analysis during robotic prostatectomy.

OBJECTIVE • To evaluate a novel technique to lower positive surgical margin rates while preserving as much of the neurovascular bundles as possible during nerve-sparing robotic prostatectomy. MATERIALS AND METHODS • In situ intraoperative frozen section (IFS) was performed during robotic-assisted laparoscopic prostatectomy (RALP) when there was macroscopic concern for a positive margin or residual prostate tissue. • When IFS was positive, additional sections were taken from the same area until the IFS was negative, similar to the procedure of Mohs micrographic surgery. • Positive surgical margin and biochemical recurrence rates were compared between the patients who underwent IFS and those who did not. RESULTS • Of 970 patients consecutively undergoing RALP at a single institution, IFS was performed on 177 (18%). • Eleven patients (6%) had IFS positive for carcinoma, whereas another 25 (14%) had benign prostatic tissue in the IFS specimen. • IFS and non-IFS patients had similar pathological and nerve-sparing characteristics. • The IFS group had significantly lower rates of positive surgical margins, 7% vs 18% (P = 0.001) but similar rates of biochemical recurrence (5%) at a median follow-up of 11 months. CONCLUSIONS • In situ IFS is an effective way of reducing positive margins during RALP. • Twenty percent of patients who underwent IFS, representing 4% of the overall RALP population, had either malignant or benign prostate tissue removed from their prostatic fossa. • Although a reduction of biochemical recurrence was not demonstrated, the follow-up is short and a difference may become apparent as the data mature.