Purpose:

The purpose of the correlative studies is to evaluate levels of serum factors of circulating VEGF and soluble VEGFR, circulating tumor cells and circulating endothelial cells assayed at baseline and over the course of initial treatment in order to explore relationships with baseline patient factors, measurable disease response and clinical progression.

Hypothesis soluble markers of angiogenic growth factors and receptors, and circulating endothelial and tumor cells can serve as markers for biologic activity of temsirolimus and/or sorafenib.

It is recognized that the measurable disease RECIST criteria response rate with mTOR inhibition is likely to be low and that the benefit of such therapy will also include effects on disease stabilization. Disease stabilization is difficult to interpret in the phase II setting. Thus, it is desirable to develop biomarkers which will provide additional information on novel treatment effects and how they might relate to disease progression

Inclusion Criteria:

• All patients enrolled from Canadian centres for the Wyeth Pharmaceuticals sponsored multicenter, open-label phase III study evaluating second line therapy with either temsirolimus or sorafenib in patients progressing after sunitinib therapy, are eligible for this correlative studies protocol.
• Patients must provide written informed consent.

Subjects from Canadian centres who have agreed to participate in the trial entitled "A randomized trial of Temsirolimus and Sorafenib as second line therapy in patients with advanced renal cell carcinoma who have failed first line Sunitinib therapy" will be approached to participate in this Exploratory Biomarker study