Methods Four hundred twenty-five patients with metastatic renal-cell carcinoma were randomly assigned to receive either a continuous intravenous infusion of interleukin-2, subcutaneous injections of interferon alfa-2a, or both. The main outcome measure was the response rate; secondary outcomes were the rates of event-free and overall survival. Predictive factors for response and rapid progression were identified by multivariate analysis.

Results Response rates were 6.5 percent, 7.5 percent, and 18.6 percent (P<0.01) for the groups receiving interleukin-2, interferon alfa-2a, and interleukin-2 plus interferon alfa-2a, respectively. At one year, the event-free survival rates were 15 percent, 12 percent, and 20 percent, respectively (P=0.01). There was no significant difference in overall survival among the three groups. Toxic effects of therapy were more common in patients receiving interleukin-2 than in those receiving interferon alfa-2a. Response to treatment was associated with having metastasis to a single organ and with receiving the combined treatment. The probability of rapid progression of disease was at least 70 percent for patients with at least two metastatic sites, liver metastases, and a period of less than one year between the diagnosis of the primary tumor and the appearance of metastases.

Conclusions Cytokines are active in a few patients with metastatic renal-cell carcinoma. The higher response rate and longer event-free survival obtained with a combination of cytokines must be balanced against the toxicity of such treatment. (C)1998, Massachusetts Medical Society.