Cumulative Number of Altered Biomarkers in Mammalian Target of Rapamycin Pathway Is an Independent Predictor of Outcome in Patients With Clear Cell Renal Cell Carcinoma

Objective To evaluate the association of the altered expression of the mammalian target of rapamycin (mTOR) pathway components with oncologic outcomes in patients with nonmetastatic clear cell renal cell carcinoma (ccRCC). Materials and Methods Immunohistochemistry for phosphorylated-S6, phosphorylated-mTOR, mTOR, phosphorylated-AKT, hypoxia inducible factor-1α, Raptor, phosphatase and tensin homolog (PTEN), phosphoinositide 3-kinase (PI3K), and phosphorylated 4E-binding protein-1 was performed on tissue microarray constructs of patients treated for nonmetastatic kidney cancer from 1997 to 2010. The relationship between individual altered marker expression and a prognostic marker score (low, intermediate, and high, defined as ≤3, 4-5, >5 altered biomarkers, respectively) and oncologic outcome was assessed. Results The study included 419 patients with nonmetastatic ccRCC, with a median follow-up period of 26 months (range 6-150). The tumors were nonorgan confined (pT3-T4) in 86 (20.5%) and high Fuhrman nuclear grade (3-4) in 131 (31%). A low, intermediate, and high prognostic marker score was found in 214 (51%), 152 (36%), and 53 (13%) patients, respectively. Kaplan-Meier analysis demonstrated a statistically significant correlation between the risk groups and disease recurrence and cancer-specific survival. In a multivariate Cox regression analysis controlling for tumor stage and grade, a high marker score was an independent predictor of disease recurrence (hazard ratio 3.3, 95% confidence interval 1.33-8.39, P = .01), and a combination of a high and an intermediate score was an independent predictor of survival (hazard ratio 4.8, 95% confidence interval 1.27-4.78, P = .008). Conclusion The cumulative number of aberrantly expressed biomarkers correlated with aggressive tumor biology and inferior oncologic outcomes in patients with ccRCC. Our data support prospective pathway-based exploration of the mTOR signaling cascade to augment current clinicopathologic predictors of oncologic outcomes in patients with ccRCC.