Background: Relevant biomarkers in RCC are needed to identify appropriate candidates for selected targeted therapies. Mutations in the von Hippel-Lindau (VHL) gene result in the accumulation of HIF and increased expression of proangiogenic factors, including VEGF. Methods: Metastatic clear RCC patients with available baseline tumor samples who received first-line oral VEGFR-TKI were included in this analysis. VHL mutation/hypermethylation status and HIF1α and HIF2α immunohistochemical staining were analyzed from paraffin-embedded tumors. Additionally, a panel of candidate VEGF and VEGFR2 genetic SNPs was determined from peripheral blood samples. HIF was scored as negative or positive based on staining intensity (0-10% and > 10%, respectively). Results were evaluated for associations with clinical outcome. Results: 80 patients were included: 71 evaluable for HIF expression, 63 for VHL status and 52 for SNPs. 73% received treatment with sunitinib and median follow-up was 21.5 months. Unlike VHL status, HIF1 and HIF2 positive expression showed a significant correlation with PFS and OS. HIF1α was also predictive for response rate (RR). On multivariate analysis adjusting for other prognostic factors, HIF1α and HIF2α remained the most significant independent predictive factors for survival (adjusted HR 0.09, 95% CI 0.03-0.28, p < 0.0001 and HR 0.13, 95% CI 0.04-0.37, p < 0.0001; respectively). We did not find any statistically significant differences based on the VEGF and VEGFR2 SNPs analyzed. Conclusions: HIF1α and HIF2α levels represent the most important independent predictive factors of outcome for VEGFR-TKI therapy in metastatic RCC. These findings may contribute to optimize treatment with targeted agents.

	HIF1α		HIF2α
	HIF1α +	HIF1α -	HIF2α +	HIF2α -
N (%)	38 (53.5)	33 (46.5)	46 (64.8)	25 (35.2)
RR (%)	67	27	55	37
OR (p value)	0.18 (p=0.001)		0.50 (p=0.20)
Median PFS (months)	22.8	13.6	21.4	9.6
HR (p value)	0.36 (p<0.0001)		0.61 (p=0.04)
Median survival (months)	43.7	16.6	42.5	20.3
HR (p value)	0.31 (p<0.0001)		0.52 (p=0.04)