Purpose: The efficacy of interferon alfa has been established in treating advanced melanoma and renal cell carcinoma (RCC) patients. We conducted a phase I/II study to determine the maximum-tolerated dose (MTD), the safety and tolerability, and the preliminary efficacy of once-weekly pegylated interferon alfa-2b (IFNalpha-2b) in patients with advanced solid tumors (primarily RCC).
Patients and methods: To determine the MTD, 35 patients with a variety of advanced solid tumors received 0.75 to 7.5 micro g/kg/wk of pegylated IFNalpha-2b by subcutaneous injection for 12 weeks. An additional 35 previously untreated RCC patients received 6.0 and 7.5 micro g/kg/wk for up to 12 weeks. Patients with a response or stable disease after 12 weeks were eligible for the extension protocol and were treated for up to 1 year or until disease progression.
Results: The MTD for pegylated IFNalpha-2b at 12 weeks was 6.0 micro g/kg/wk. One year of 6.0 micro g/kg/wk was well tolerated with appropriate dose modification; no grade 3 or 4 fatigue occurred, and safety was comparable with that with nonpegylated IFNalpha-2b. The most common nonhematologic adverse events included mild to moderate nausea, anorexia, and fatigue. Six patients had grade 3 or 4 hematologic toxicity. Twenty-nine patients continued on the extension protocol. Four patients had a complete response, and five patients had a partial response. Among 44 previously untreated RCC patients, the objective response rate was 14%. Median survival for all RCC patients was 13.2 months.
Conclusion: Pegylated IFNalpha-2b was active and well tolerated in patients with metastatic solid tumors, including RCC, at doses up to 6.0 micro g/kg/wk.