A Comparison of Systemic Versus Inhaled Recombinant IL-2 Administration for the Treatment of Metastatic Renal Cell Carcinoma

The aim of the current study was to compare the objective response and survival rates of patients with mRCC treated with IL-2 administered either systemically (SYST, subcutaneously) or via inhalation (INH), using relatively large sample sizes to afford a more meaningful comparison. We used univariate and multivariate analyses to retrospectively evaluate the data from two different databases generated from 277 patients treated with IL-2 during the 1993-1997 period, one developed at the University Hospital Hamburg-Eppendorf, and the other at Chiron-Amsterdam. Patients treated with INH IL-2 tended to have a poorer ECOG performance status than patients receiving SYST IL-2. Of 75 patients receiving INH IL-2, eight (10.7%) achieved an objective response; of 202 patients administered SYST IL-2, 45 (22.2%) achieved an objective response. The median survival time was 13.8 months for patients receiving INH IL-2 and 13.1 months for patients treated with SYST IL-2. One- and two-year survival rates were also comparable for the two treatment modalities (one-year: INH, 55%; SYST, 56%; two-year: INH, 28%; SYST, 26%). There was no significant difference in the likelihood of survival for patients receiving INH IL-2 versus SYST IL-2 (risk ratio = 0.82, P = 0.27). Patients administered INH IL-2 experienced considerably less toxicity and complications than patients administered SYST IL-2. We conclude that INH IL-2 treatment is at least as effective as SYST IL-2 treatment in promoting the survival of patients with mRCC. Given that INH IL-2 treatment of patients with a poorer ECOG performance status elicited a survival rate comparable to that seen with SYST IL-2 treatment of patients with a superior performance status, the potential exists for INH IL-2 treatment to be even more effective for patients having a better performance status. Additionally, INH IL-2 treatment is considerably less toxic and associated with fewer complications than SYST IL-2 treatment, thus providing a therapeutic option for otherwise untreatable patients, offering patients a relatively good quality of life, and requiring fewer co-medications. Nonetheless, selection of an IL-2 treatment modality should be based on several patient-related considerations. Moreover, these two IL-2 treatment modalities need not be mutually exclusive.