Evaluation of the prognostic significance of altered mammalian target of rapamycin pathway biomarkers in upper tract urothelial carcinoma

Abstract

Objective: To evaluate the prognostic value of altered mammalian target of rapamycin (mTOR) pathway biomarkers in upper tract urothelial carcinoma (UTUC).

Materials and methods: We performed a multi-institutional review of clinical and pathologic information on patients receiving extirpative surgery for UTUC from 1990 to 2008. Immunohistochemistry for phosphorylated-S6, mTOR, phosphorylated-mTOR, PI3K, phosphorylated-4EBP1, phosphorylated-AKT, PTEN, HIF-1a, raptor, and cyclin D was performed on tissue microarrays from radical nephroureterectomy (RNU) specimens. Prognostic markers were identified and the significance of altered markers was assessed with the Kaplan-Meier analysis and the Cox regression analysis.

Results: Six hundred twenty patients were included. Over a median follow-up of 27.3 months, 24.6% of patients recurred and 21.8% died of UTUC. On multivariate analysis, PI3K (odds ratio, 1.28; P = .001) and cyclin D (odds ratio, 3.45; P = .05) were significant predictors of clinical outcomes. Cumulative marker score was defined as low risk (no altered markers or 1 altered marker) or high risk (cyclin D and PI3K altered). Patients with high-risk marker score had a significantly higher proportion of high-grade disease (91% vs 71%; P <.001), non-organ-confined disease (61% vs 33%; P <.001), and lymphovascular invasion (35% vs 20%; P = .001). The Kaplan-Meier analysis demonstrated a significant difference in cancer-specific mortality (CSM) based on the risk groups. On Cox regression multivariate analysis for CSM incorporating non-organ-confined disease, grade, lymphovascular invasion, tumor architecture, and marker score, high-risk biomarker score was an independent predictor of CSM (hazard ratio, 1.5; 95% confidence interval, 1.04-2.3; P = .03).

Conclusion: Alterations in mTOR pathway correlate with established adverse pathologic features and independently predict inferior oncologic outcomes. Incorporation of mTOR-based marker profiles may allow for enhanced patient counseling, risk stratification, and individualized treatment regimens.