All patients will receive IL-2 (14 planned doses with an additional cycle 14 days after the first). Responding patients with regressing disease are eligible for up to 6 IL-2 cycles. Patients assigned to SBRT arm will receive two doses of SBRT on the Wednesday and Friday before the Monday on which IL-2 starts.

All patients will receive IL-2 at 600,000 international units per kilogram (kg) by intraveneous bolus (IVB) every 8 hours for 14 planned doses with an additional cycle 14 days after the first. Responding patients with regressing disease are eligible for up to 6 IL-2 cycles. Patients assigned to SBRT arm will receive two doses of SBRT at 20 Gray (Gy) on the Wednesday and Friday before the Monday on which IL-2 starts.

Inclusion Criteria:

• Histological confirmation of predominant conventional (clear cell) renal cancer
• Patients must be ≥ 18 years of age
• Tumors amenable to SBRT in lungs (central locations preferred), mediastinum, chest wall, bones with a soft tissue component (other than long bones), or liver, liver hilum and associated lymph nodes (inclusive of immediately adjacent masses), 1 - 3 foci; no minimum size, but none greater than 7 cm. Patients may have other metastases but only a maximum of 3 will be treated
• Eastern Cooperative Oncology Group (ECOG) performance status of 0-1
• Women of childbearing potential must have a negative serum or urine pregnancy test within 72 hours prior to the start of protocol treatment. In addition, women of childbearing potential as well as male patients must agree to take appropriate precautions to avoid pregnancy
• Patients must agree to participate in the Prometheus IL-2 patient registry (PROCLAIM registry)
• Patients must sign a study-specific consent form

Exclusion Criteria:

• No metastatic site amenable to SBRT
• Patients with brain metastases not candidates for radiosurgery alone
• Previous radiation to sites proposed for SBRT
• Patients with active systemic, pulmonary, or pericardial infection
• Pregnant or lactating women, as treatment involves unforeseeable risks to the embryo or fetus
• Evidence of ischemia on exercise tolerance test, stress thallium study, or baseline EKG
• Clinically significant underlying pulmonary disease as measured by pulmonary function tests
• Blood tests within protocol-specified range
• Need for chronic steroids