Independent validation of the 2010 American Joint Committee on Cancer TNM classification for renal cell carcinoma: Results from a large, single institution cohort

Purpose: In 2010 the American Joint Committee on Cancer updated the renal cell carcinoma TNM classification. Without independent validation of the new classification its predictive ability for cancer specific survival and generalizability remains unknown. In this setting we determined the predictive ability of the 2010 TNM classification compared to that of the 2002 classification. Materials and Methods: Using the nephrectomy registry at our institution we retrospectively reviewed the records of 3,996 patients with unilateral or bilateral synchronous renal cell carcinoma treated with radical nephrectomy or nephron sparing surgery between 1970 and 2006. Cancer specific survival was estimated using the Kaplan-Meier method and predictive ability was evaluated using the concordance index. Results: There were 1,165 deaths (29.1%) from renal cell carcinoma a median of 1.9 years after surgery compared to a median followup of 7.4 years for survivors. The estimated 10-year cancer specific survival rate was 96%, 80%, 66%, 55%, 36%, 26%, 25% and 12% for patients with 2010 primary tumor classifications of pT1a, pT1b, pT2a, pT2b, pT3a, pT3b, pT3c and pT4, respectively (p <0.001). The multivariate concordance index for the 2002 and 2010 TNM classifications was 0.848 and 0.850, respectively. Conclusions: The new 2010 classification remains a robust predictor of cancer specific survival compared to the 2002 classification by dividing pT2 lesions into pT2a and pT2b, reclassifying ipsilateral adrenal involvement as pT4, reclassifying renal vein involvement as pT3a and simplifying nodal involvement as pN0 vs pN1. However, the 2010 TNM classification showed only modest improvement in predictive ability compared to the 2002 classification.