Treatments have come a long way since 1992, when the FDA approved interleukin-2 (IL-2). IL-2 was the first systemic therapy of its kind. It uses cytokine, a cellular hormone produced by white blood cells, to destroy tumor cells. IL-2 is still offered, and can cure a small percentage of patients with metastatic kidney cancer, but the side effects can be severe, including serious infection, fever, heart attack, and bleeding. You may need to stay in the hospital during treatment.