Novel stratification of the recurrence risk following surgical extirpation of clear cell renal cell carcinoma using tissue biomarkers in the mammalian target of rapamycin pathway.

Abstract

4581 Background: Aberrant activation of the mammalian target of rapamycin (mTOR) pathway promotes invasiveness and metastatic potential in a variety of malignancies. The aim of the present study was to evaluate the association of altered expression of mTOR pathway components with recurrence outcome in non-metastatic clear cell renal cell carcinoma (ccRCC) patients. Methods: Immunohistochemistry for phos-S6, phos-mTOR, mTOR, phos-AKT, HIF-1α, RAPTOR, PTEN, PI3K, and phos-4EBP1 was performed on tissue microarrays of patients treated for non-metastatic kidney cancer between 1997-2010. Patients were defined as having a low (<) or high risk (≥) of nomogram predicted recurrence (2001 MSKCC RCC post-op) using an 8% cutoff. The relationship between individual marker expression, as well as combined marker score (low, intermediate and high defined as ≤ 3, 4-5, >5 altered biomarkers; respectively) with the actual and predicted relapse rates was assessed. Results: The study included 419 non- metastatic ccRCC patients (pT1-T2 79.5%, pT3-T4 20.5%, Fuhrman nuclear grade 1-2 in 69%, 3-4 in 31%). 219 and 200 patients had low (<8%) and high (≥8%) nomogram-predicted 5-year risk of recurrence respectively. With a median follow-up of 2.2 years, recurrences were detected in 5 (2.3%) of the predicted low risk and 30 (15%) of the predicted high risk patients. mTOR pathway biomarker profiles were not predictive for patients at low predicted risk of recurrences. For patients at high predicted risk of recurrence, low, intermediate and high combined marker scores were found in 84 (42%), 79 (39.5%), and 37 (18.5%), respectively. The actual rates of recurrence were noted for 8.3% of low, 13.9% of intermediate and 32.4% of high combined marker score in a statistically significant distribution (p=0.027). Conclusions: The cumulative number of aberrantly expressed mTOR biomarkers correlates with a higher rate of recurrence. The combined marker score may help further stratify patients with high nomogram predicted risk of recurrence. Our data supports prospective evaluation of these biomarkers to augment current clinico-pathologic predictors of outcomes in ccRCC.