Currently, tumor stage and grade remain the only widely accepted prognostic indicators of clear-cell renal cell carcinoma (CC-RCC). As such, there is a need to identify other prognostic markers because behavior of CC-RCC cannot always be determined by stage alone. Recent studies of human CC-RCC cell lines suggest that insulin-like growth factor-I receptor (IGF-IR) may have some prognostic value for patients with CC-RCC. Using a population-based cohort of 48 female patients with CC-RCC and long-term follow-up, we tested the hypothesis that the immunohistochemical detection of IGF-IR expression in CC-RCC is associated with poorer cancer-specific survival after adjustment for stage and age at diagnosis. Kaplan-Meier analysis suggested that patients with CC-RCC that exhibited greater than 50% IGF-IR expression experienced a significantly poorer cancer-specific survival compared with patients with CC-RCC that exhibited less than 50% IGF-IR expression. The difference in survival was apparent at 2 years and remained throughout follow-up. Based on a Cox proportional hazard model that adjusted for stage and age at diagnosis, patients with tumors that exhibited greater than 50% IGF-IR staining were 4 times more likely to die of CC-RCC compared with patients whose tumors exhibited less than 50% staining (HR = 4.2; 95% confidence interval [CI]; 1.1-17.1). A smoothing spline with 4 degrees of freedom supported the results from the categorical analysis. Evidence from this population-based pilot investigation is consistent with laboratory data suggesting that expression of IGF-IR may have some prognostic implication for patients presenting with CC-RCC; however, confirmation in a larger study is needed.
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