Our experience with interferon alpha: renal cell carcinoma.

Our 3-year clinical experience using recombinant interferon (rIFN) alpha-C in patients with metastatic renal cell carcinoma (RCC) is summarized. This type of IFN is a new subspecies of the IFN-alpha protein family. Its specific activity is 1-2 x 10(9) U/mg protein, the highest among IFN-alpha species presently available. Pharmacokinetic study indicated good bioavailability of the preparation from the intramuscular injection. A phase II study was performed to assess the response rate related to rIFN-alpha C at a low dosage. A dose of 3 x 10(6) U daily was administered, followed by 3 x 10(6) U/m2 every other day to avoid severe toxicity. Among 33 treated patients, a partial remission rate of 9.7% and stable disease rate of 25.8% were achieved. Side effects were usually mild and the treatment was well tolerated by the patients. However, mental deterioration and behavioral changes were observed in five patients with RCC treated by rIFN-alpha C and were related to neurotoxicity of IFN. The role of vinblastine in addition to IFN in the treatment of RCC was assessed in nine patients who had failed on IFN alone. No response was observed. It appeared that vinblastine had little if any effect in being added to IFN as second-line therapy. We conclude that rIFN-alpha C has moderate activity in the treatment of RCC. Familiarity with the possible toxicity of this agent will lead to more careful management of patients.