Purpose: A randomized phase II/III trial was conducted to determine whether combination treatment with 13-cis-retinoic acid (13-CRA) plus interferon alfa-2a (IFN-alpha-2a) was superior to IFN-alpha-2a alone in patients with progressive metastatic renal cell carcinoma.
Patients and methods: Three hundred twenty patients were randomly assigned to treatment with IFN-alpha-2a plus 13-CRA or to IFN-alpha-2a alone. IFN-alpha-2a was given daily subcutaneously, starting at a dose of 3 million units (MU). The dose was escalated every 7 days from 3 to 9 MU by increments of 3 MU. Patients randomly assigned to combination therapy received oral 13-CRA 1 mg/kg/d plus IFN-alpha-2a.
Results: Median time to progression was 5.1 months for patients treated with the combination and 3.4 months for patients on IFN-alpha-2a alone (P = .008). Progression-free survival rates at 6 months were 43% for patients receiving combined therapy and 30% for patients on IFN-alpha-2a, and at 12 months, 27% and 17%, respectively. Median overall survival was 17.3 months for patients on IFN-alpha-2a and 13-CRA, and 13.2 months for patients treated with IFN-alpha-2a (P = .048). Twenty-two percent of the patients receiving the combination stopped treatment due to toxicity, as compared with 16% on IFN-alpha-2a.
Conclusion: Progression-free and overall survival for patients with progressive metastatic renal cell carcinoma treated with IFN-alpha-2a plus 13-CRA were significantly longer compared with patients on IFN-alpha-2a alone (P = .007 and P = .048, respectively). Improvement in efficacy in the combination arm was accompanied by increased, though not serious, toxicity.