TNM Staging System for Renal Cell Carcinoma Is Imprecise
TORONTO—The TNM stratification system does not accurately characterize cancer-free survival in lymph node-positive renal cell carcinoma (RCC), but the number and density of positive nodes do, new findings suggest.
A team led by Alessandro Volpe, MD, Assistant Professor of Urology at the Maggiore della Carita Hospital and the University of Eastern Piedmont, Novara, Italy, studied 50 patients with pN1 RCC and 103 with pN2 RCC who underwent radical nephrectomy and lymph node dissection between 1987 and 2006 in three urology centers.
The extent of the lymphadenectomy was at the discretion of the primary surgeon. Patients had a mean age of 60 years. The average follow-up was 12 months for all patients and 53 months for those who remained alive. Of the 153 patients, 107 had stage T3 or T4 disease. Fifty had N1 status and 103 had N2, while 80 had metastases.
The median number of lymph nodes that were removed was 10, and there was an average of three positive lymph nodes per patient. Furthermore, the average lymph node density was 30%.
Although the investigators found no significant difference in five-year cancer-free survival between pN1 and pN2 patients, they observed a significant difference in cancer-free survival between those with a lymph node density of less than 60% and 60% or greater and between patients with fewer than four and those with four or more positive lymph nodes.
The five-year cancer-free survival rates were 24.5% for those with lymph node density of less than 60% versus 16.7% for those with a density of 60% or greater. The rates were 27% for patients with fewer than four positive lymph nodes versus 14% for those with four or more positive nodes.
Based on study findings, “the current TNM classification of nodal involvement for RCC should be revised,” said Dr. Volpe, who presented findings at the Canadian Urological Association's 64th Annual Meeting. “In addition, lymph node density seems to have a significant prognostic value.”
Commenting on the study, meeting attendee Michael Jewett, MD, Professor of Urology at the University of Toronto, noted that the results are difficult to interpret because the study was retrospective and because the patients' lymph-node density may simply have been a function of the extent of the lymph-node dissection.
“So the results suggest it is beneficial to have more extensive dissection, but they need to be confirmed,” Dr. Jewett said.