Should High-Dose Interleukin-2 Still be the Preferred Treatment for Patients with Metastatic Renal Cell Cancer?

Interleukin-2 (IL-2) was the preferred treatment for medically fit patients with advanced kidney cancer, but recently, several targeted therapies have been approved for metastatic renal cell carcinoma. We wished to determine the long-term survival rate for patients with kidney cancer treated with IL-2 and whether the use of intense inpatient IL-2 has declined since the introduction of targeted therapies. Patients who received IL-2 were identified from clinical trial enrollment, pharmacy logs, and financial billing records. Survival was determined from the earliest date of IL-2 therapy. There were 79 patients hospitalized for high-dose infusional IL-2 between March 1989 and March 2009. Median age was 58 years, and 27% were older than 65 years at the time of treatment. At the time of this analysis, 72 patients had deceased. Median survival was 9.9 months, but 5-year survival was 19.4%. The average number of patients with IL-2 increased from 2.2 per year during 1989-1992 to 5.6 during 1993-2001 after FDA approval, but dropped to 2.0 during 2002-2009. High-dose IL-2 is associated with a 5-year survival rate that is higher than objective response rates, suggesting a delayed immunotherapy benefit for some patients. The use of intensive IL-2 has declined dramatically in recent years, but unless a long-term survival benefit can be shown for these new targeted products, we feel that inpatient IL-2 remains the preferred initial treatment.