Positive surgical margins (PSMs) after partial nephrectomy for renal cell carcinoma (RCC) are more common than previously reported, but they have no significant effect on five-year survival, according to researchers.

In a study of 664 patients who underwent PN for RCC in Ontario, Canada, 71 (10.7%) had PSMs after surgery. Pathologic stage and fat invasive predicted PSMs.

At a median follow-up of 7.9 years, the unadjusted five-year disease-specific survival (DSS) and overall survival (OS) rates were 90.9% and 84.4%, respectively, for patients with PSMs and 91.9% and 88.6% for those without PSMs, a nonsignificant difference between the groups, Ifeanyi Ani, MD, of the University Hospitals of Cleveland Case Medical Center in Cleveland, and colleagues reported in an online report in BJU International.

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“Although margin positivity did not affect DSS or OS, the oncological goal of any PN for RCC is to achieve a negative margin,” the authors wrote. “If, however, a PSM is found, surveillance may be a reasonable approach, avoiding the potential morbidity and cost of re-resection and completion nephrectomy.”
The study subjects, which the researchers identified using the Ontario Cancer Registry, had a mean age of 57.7 years and 61.6% were men. The tumor size was less than 2.0 cm in 25% of patients, 2.0-3.9 cm in 59%, 4.0-6.9 cm in 13%, and 7 cm or larger in 3%.

The investigators noted that PN has become the standard surgery for small renal masses, with cancer-specific survival equivalent to that of radical nephrectomy, but the significance of PSMs in PN specimens continues to be debated.

Additionally, Dr. Ani and colleagues pointed out that the 10.7% prevalence of PSMs found in their study is higher than previously reported (0%-8%). “We believe this [10.7%] figure may reflect the true prevalence of PSMs given that the present study evaluated population-level data from all hospitals in the province of Ontario, Canada,” the investigators wrote. “The main strength of the present study lies in the elimination of the sampling and selection biases influencing previous estimates of PSMs.”

The main limitation of the new study was its retrospective design, “making is susceptible to a number of potential biases,” the researchers stated.

In a previous study of 29 patients with PSMs after PN who underwent subsequent complete parenchymal re-resection or completion nephrectomy, investigators at Washington University School of Medicine in St. Louis, Mo., concluded that a PSM “does not necessarily mean that cancer remains in the renal remnant in most cases,” according to a report in Urology (2011;77:1400-1403).

Of the 29 patients, eight underwent nephrectomy, with no residual cancer found in the renal remnant. Twenty-one patients underwent total re-resection of the margin and only two were found to have cancer. The patients who underwent radical nephrectomy experienced a 25 mL/min/1.73 m2 decrease in estimated glomerular filtration rate; those who underwent re-resection of the margin with preservation of the renal unit had a 4 mL/min/1.73 m2 decrease.

The researchers, led by Sam B. Bhayani, MD, concluded that clinical correlation is recommended before re-excision or completion nephrectomy after finding a PSM, “with careful consideration of the impact on subsequent renal function weighed against the possibility of residual disease.”