To determine the efficacy and toxicity of a high-dose interleukin-2 (IL-2) regimen in patients with metastatic renal cell carcinoma.

Two hundred fifty-five assessable patients were entered onto seven phase II clinical trials. Proleukin (aldesleukin; Chiron Corp, Emeryville, CA) 600,000 or 720,000 IU/kg was administered by 15-minute intravenous (i.v.) infusion every 8 hours for up to 14 consecutive doses over 5 days as clinically tolerated with maximum support, including pressors. A second identical cycle of treatment was scheduled following 5 to 9 days of rest, and courses could be repeated every 6 to 12 weeks in stable or responding patients.

The overall objective response rate was 14% (90% confidence interval [CI], 10% to 19%), with 12 (5%) complete responses (CRs) and 24 (9%) partial responses (PRs). Responses occurred in all sites of disease, including bone, intact primary tumors, and visceral metastases, and in patients with large tumor burdens or bulky individual lesions. The median response duration for patients who achieved a CR has not been reached, but was 19.0 months for those who achieved a PR. Baseline Eastern Cooperative Oncology Group (ECOG) performance status (PS) was the only predictive prognostic factor for response to IL-2. While treatment was associated with severe acute toxicities, these generally reversed rapidly after therapy was completed. However, 4% of patients died of adverse events judged to be possibly or probably treatment-related.

High-dose IL-2 appears to benefit some patients with metastatic renal cell carcinoma by producing durable CRs or PRs. Despite severe acute treatment-associated toxicities, IL-2 should be considered for initial therapy of patients with appropriately selected metastatic renal cell carcinoma.