What Role Do Combinations of Interferon and Targeted Agents Play in the First-Line Therapy of Metastatic Renal Cell Carcinoma?

Interferons (IFNs) are a class of cytokines with pleotropic actions that regulate a variety of cellular activities. Clinical trials with recombinant IFNs (IFN-α2a and IFN-α2b) have demonstrated clinical activity in patients with advanced renal cell carcinoma (RCC). Their efficacy is characterized by a low overall tumor regression rate of < 15%, progression-free survival of 4-5 months, and overall median survival of 10-18 months. This cytokine became the standard of care for patients with metastatic RCC and was then used as the comparator arm in a series of phase II and III clinical trials that have defined a new treatment paradigm for patients with advanced RCC. This paradigm uses the tyrosine kinase inhibitors (TKIs) sorafenib and sunitinib, the mammalian target of rapamycin (mTOR) inhibitor temsirolimus, and the vascular endothelial growth factor monoclonal antibody bevacizumab. These 3 categories of agents were then investigated in combination with IFN-α in a series of preclinical and clinical studies. The collective data from these reports suggest the combination of IFN-α and bevacizumab is active and has a role in RCC therapy, whereas combinations with the TKIs or mTOR inhibitors have limited efficacy and/or excessive toxicity. The clinical and preclinical studies leading to these conclusions are reviewed herein.