AUA 2018: Frozen Sections for Margins During Partial Nephrectomy Do Not Influence Recurrence Rates

San Francisco, CA ( Frozen sections, or intra-operative pathologic evaluations, are often sent during various oncologic operations to help assist in the decision for further intraoperative management. In cystectomies, frozen sections are often sent from the distal ureters and urethra; in prostatectomy, frozen sections are sometimes sent from concerning lymph nodes; in penectomies/partial penectomies, proximal margins are sent to confirm adequate distance from disease; in partial nephrectomy for renal cell carcinoma (RCC), frozen sections are sometimes sent from the base of the resection bed to confirm complete excision.

Yet, from a practical standpoint, how useful are these frozen sections? Technically, a small sliver of tissue is sent from a small portion of a large resection bed. How accurately is the sampling site? Do frozen sections change management or outcomes?

The authors from Cleveland Clinic retrospectively analyzed their database of 1,090 patients who underwent open or robotic partial nephrectomy for clear cell RCC over 10-year period – of these, 172 had frozen section (FS) and 918 did not. Right off the bat, as FS was only done for specific indications (surgeon dependent, concern for margin), there is an inherent selection bias – unfortunately, it was not done routinely.

  • When asked, the frozen section was somewhat subjective (all taken due to concern for positive margin). In terms of location, it was taken from the tumor resection bed and tumor base – but not in all case. In the robotic cases, it was always taken from tumor base.
  • Frozen sections, if positive, results in additional resection until FS negative.
  • Total of 248 frozen sections were taken in 172 patients
Patients undergoing FS were similar to those who didn’t – they had less comorbidities, lower BMI, less robotic use, and longer operative time. Only 19 of 248 specimens were positive (7.7%) and some of those were repeats! Sensitivity, specificity, PPV and NPV of FS in terms of predicting final surgical margin was 0.78, 0.99, 0.95 and 0.98.

After a median follow-up of 24.8 months, 45/1090 (4.13%) patients had recurrence (follow-up protocol was standard across all the patients).

In terms of FS benefit, there was no difference in the cumulative incidence of recurrence between patients with and without FS (p=0.97). On multivariate competing risk analysis, FS was not associated with recurrence (HR 1.56; 95% CI: 0.65-3.76). However, as can be expected, tumor grade (g3-4 vs.1-2: hazard ratio, 2.45; 95% CI, 1.16-5.14) and stage (>pT2 vs. pT1a: hazard ratio, 2.86; 95% CI, 1.13-7.26) were associated with recurrence. The average direct charge per patient undergoing FS was $902.

Hence, an extra $1000 per patient was spent on a test that, even thought it was used in a selection population with theoretically higher risk of recurrence, did not identify patients at higher risk of recurrence. Perhaps it is time to stop FS altogether?

However, it should be noted that the authors did not address how often FS were positive intra-operatively – and if it changed management intra-operatively! They say they went back until FS negative – but how many of the 19 samples were actually on the same patient? How often did it change management? Perhaps the reason there was no difference in outcomes is because additional resection was completed at the time of surgery to ensure negative final margins?

As discussed with the presenter, similar results on the utility of distal ureteral FS at the time of cystectomy has been presented by USC in the past. Perhaps we are doing too many FS without much utility?

Presented by: Julien Dagenais, Cleveland Clinic, Cleveland, Ohio
Co-Authors: Juan Garisto, Jaya Chavali, Jihad Kaouk, Cleveland, OH

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, @tchandra_uromd at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA