Predictive utility of serum cytokine levels in patients with metastatic renal cell carcinoma (MRCC) treated with interferon alfa (IFNa)

14503 Background: IFNa may prolong survival in MRCC patients (pts) due to stimulation of cell-mediated immunity. We hypothesized that IFNa exerts an anti-tumor effect by upregulation of Th1 cytokines and that patients (pts) with elevated serum levels of Th1 cytokines either at baseline (BL) or after treatment with IFNa would have a superior clinical outcome. Methods: Cytokine profiling was performed on 104 pts with MRCC treated in a randomized phase III trial with IFNa 0.5 million units (MU) subcutaneously (SC) twice daily or 5 MU SC daily. Serum samples were collected at BL (n = 104) and after 8 weeks of IFNa therapy (C1) (n = 89). Cytokine concentrations were determined using a 16-plex immunoassay. The linear mixed-effect model was fit to assess the change of cytokine levels from BL to C1. Cox proportional hazards model was fit to evaluate the effect of BL cytokine levels or change of cytokine levels from BL to C1 on the risk of death. Results: Of 16 cytokines evaluated (IL-1b, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12 p40, IL-13, IL-15, IL-17, IFNa, IFNg, GM-CSF, TNFa, VEGF), lower BL TNFa, IL-8 (Th1), and IL-13 (Th2) levels were associated with clinical benefit (major response or progression-free status at 6 months) (p = 0.01 and 0.03, respectively). By multivariate analysis, only extremely low or high levels of IFNa (p = 0.02) and IL-12 (p = 0.002) at BL were associated with an increased risk of death. IFNa therapy after C1 produced higher levels of several Th1 cytokines (IL-8, IL-12 p40, IL-15) (p < .001) and lower levels of Th2 cytokines (IL-4, IL-13). Unexpectedly, there were significantly lower levels of TNFa and GM-CSF (Th1) and higher levels of IL-10 (Th2) with IFNa. Only an increase of IL-2 levels from BL to C1 (RR 1.45; p = 0.05) correlated with an increased risk of death. Conclusions: Lower BL serum levels of TNFa, IL-8, and IL-13 were associated with clinical benefit to IFNa. Although IFNa therapy favored a shift towards a Th1 response, this effect alone did not correlate with clinical outcome. No significant financial relationships to disclose.