UroToday- There have been numerous studies examining the importance of margins in patients undergoing partial nephrectomy for a localized renal mass. The vast majority of these studies demonstrate that any margin, no matter how small, as long as it is negative, is sufficient to minimize the risk of tumor recurrence and that the traditional 2 cm margin preached in the old textbooks is not necessary. But the natural history of patients with a positive margin after surgery is poorly understood, thanks in part to the fact that positive margins after partial nephrectomy are rare. Here, Kwon and colleagues out of Memorial Sloan Kettering examine the outcome of patients with positive surgical margins following partial nephrectomy at their institution.

The authors report on 770 patients who underwent partial nephrectomy and have an evaluable surgical margin status, at their institution over a 16 year period. Of these 57 (7%) had a positive margin on final pathologic analysis, despite negative margins reported on frozen section. Interestingly 6 out of 63 patients (10%) with multifocal disease had a positive margin. Of these 57 patients with positive surgical margins, 24 were characterized as tumors of low malignant potential (benign tumors, papillary renal cell carcinoma (RCC) type I, chromophobe RCC) whereas 33 were classified as tumors of high malignant potential (clear cell RCC, papillary type II RCC, collecting duct RCC, sarcomatoid differentiation).

In their multivariate analysis, the only predictor of a positive surgical margin was an imperative (versus elective) indication for partial nephrectomy (p=0.003). With a median follow-up of 22 months (range 7-45 months), 2 out of 57 patients with positive surgical margins had a local recurrence (4%) versus 4 out of 713 with a negative surgical margin demonstrating a local recurrence (0.5%). Of note, no patient with a tumor of low malignant potential demonstrated a local recurrence despite having a positive surgical margin. The 5 year freedom from local recurrence was significantly better for patients with a negative margin (99%) than those with a positive margin (95%) (p=0.008). Interestingly, the presence of a positive surgical margin did not influence metastatic progression. The 5 year freedom from metastatic disease for patients with a positive surgical margin was 92%, which was not significantly different from the 5 year freedom from metastatic disease noted in patients with a negative surgical margin of 97% (p=0.603).

Positive surgical margins following partial nephrectomy for patients with a localized renal mass predicts a higher local recurrence rate but not metastatic progression, particularly for patients with tumors of high malignant potential. Further therapy or careful surveillance is required for these patients because of the increased risk of local recurrence.

Eric O. Kwon , Brett S. Carver , Mark E. Snyder , Paul Russo
BJU International (OnlineEarly Articles). doi:10.1111/j.1464-410X.2006.06623.x

Reviewed by UroToday Medical Editor Christopher G. Wood, MD, FACS

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