Purpose: In metastatic renal cell carcinoma (mRCC), survival benefit associated with objective response rates of 16-20 % with high-dose interleukin-2 (HDIL-2) is well established and discussed. Based on recently emerged data on efficacy of cancer immunotherapy, we hypothesized that the survival benefit with HDIL-2 extends beyond those achieving objective responses, i.e., to those who achieve stable disease as the best response to treatment.
Materials and methods: All sequential treatment naïve mRCC patients treated with HDIL-2 at the University of Utah (1988-2013) and University of Michigan (1997-2013) were included. Best responses on treatment were associated with survival outcomes using log-rank and COX regression with a landmark analysis at 2 months.
Results: 391 patients (75 % male; median age 55 years) were included and belonged to the following prognostic risk categories: 20 % good, 64 % intermediate, and 15 % poor. Best responses on treatment were complete response (9 %), partial response (10 %), stable disease (32 %), progressive disease (42 %), and not evaluable for response (7 %). No significant differences in progression-free survival (HR 0.74, 95 % CI 0.48-1.1, p = 0.14) or overall survival (HR 0.66, 95 % CI 0.39-1.09, p = 0.11) were observed between patients achieving partial response versus stable disease. Significant differences in progression-free survival (HR 0.13, 95 % CI 0.09-0.22, p < 0.0001) and overall survival (HR 0.33, 95 % CI 0.23-0.48, p < 0.0001) were observed between patients achieving stable disease compared to those with progressive disease and who were not evaluable.
Conclusions: Survival benefit with HDIL-2 is achieved in ~50 % patients and extends beyond those achieving objective responses.
Keywords: Clinical benefit; High-dose interleukin-2; Immunotherapy; Metastatic kidney cancer; Survival outcomes.