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New targeted agents have become the mainstream of treatment in metastatic renal cell carcinoma (mRCC) and substituted the previous cytokine-based therapies. Vascular endothelial growth factor (VEGF) pathway is the principle target for drugs like sunitinib, sorafenib and bevacizumab. As VEGF is regulating dendritic cell (DC) function, inhibition of VEGF results in activation of DCs and a shift towards cellular (type 1) immunity, which is believed to favor cancer rejection. Recent studies have established the immune-stimulating effects of sunitinib that may as well be a marker for effectiveness. On the other hand, sorafenib not only inhibits VEGF receptor (VEGFR) but is also a B-Raf inhibitor (a component of the ras - MAPK pathway) and this leads to downregulation of immune responses. Sorafenib has not yet shown benefit in first-line treatment of mRCC when compared to interferon (IFN)-alpha and sorafenib-mediated immunosuppression may partially account for that. Mammalian target of rapamycin (mTOR), the target of temsirolimus, is an element of the DC activation pathway. There are no data for in vivo effects of temsirolimus in the immune system. The addition of IFN-alpha to temsirolimus resulted in inferior outcomes than temsirolimus alone. IFN-alpha has however still a place in mRCC treatment, as bevacizumab has been approved in combination with IFN-alpha. New clinical trials address the effects of the combination of cytokines with targeted agents. The immune-modulating effects of targeted treatments may be important in pharmacodynamic outcomes, effectiveness or the development of adverse events.

Background: Sunitinib is a protein tyrosine kinase-inhibitor targeting VEGFR, c-kit and PDGFR. It has been approved for the treatment of metastatic renal-cell carcinoma and gastrointestinal stromal tumors. Although it has been shown to prolong disease-free and overall survival in renal-cell carcinoma patients, only 70% of the treated population receive a clinical benefit (CB) from the treatment. Markers that could predict clinical benefit to sunitinib would be an important aid in monitoring and following their treatment. We assessed the outcome and plasma proangiogenic factors in patients with metastatic renal cell carcinoma (mRCC) treated with sunitinib in our institution., Methods: We have treated 42 patients with metastatic clear-cell renal carcinoma with sunitinib. Plasma concentrations of VEGF-A, sVEGFR2 and PDGF were determined by ELISA., Results: At the time of analysis 39 patients were evaluable for response and 30 patients had obtained a clinical benefit (CB). Median progression-free survival was 268 days (8.93 months) and median overall survival was 487 days (16.23 months). Interestingly, disease stabilization or objective response resulted in comparable overall survival. Most treatment-related adverse events were of mild-to-moderate intensity with one treatment-related death. Plasma sVEGFR2 and PDGF levels had no predictive value. Fold-increase in plasma VEGF was significantly lower in patients that obtained a CB as compared to patients that progressed after two cycles of treatment. Plasma VEGF did not increase in patients with initial CB at the time of progression., Conclusion: Sunitinib showed substantial activity in mRCC. Disease stabilization or objective response resulted in comparable overall survival and both outcomes should be considered positive. Fold-increase in plasma VEGF predicts for CB and could be a candidate marker. Progression after initial CB is not associated with elevated plasma VEGF, implying a different mechanism of resistance.