Medical treatment of metastatic renal cancer include immunotherapy with interferon α and/or IL-2, or targeted therapies such as anti-angiogenic (anti-vascular endothelial growth factor (VEGF), anti-tyrosine kinase inhibitors and m-TOR). These treatments sometimes associated (or IL2 + INF or INF AntiVEGF) do allow for objective response in 15 to 30% of cases (net benefit of targeted therapies), but are carriers of potentially significant side effects and are very expensive. The treatment response is considered on imaging exams repetitive, costly and inconsistently reliable. A serum marker of tumor development would be particularly welcome.