Simple SummaryThis was a phase III randomized controlled trial investigating the outcomes of low-dose interleukin-2 (IL-2) plus interferon alfa (IFNα) versus sunitinib as the first line and axitinib as the second line in patients with low- and intermediate-risk metastatic renal cell carcinoma (mRCC). There was a trend toward better total progression-free survival up to the end of the second line for IL-2 + IFNα but no significant advantage in terms of overall survival. The study was underpowered to draw any definitive conclusions. The results showed no clear advantage of IL-2 + IFNα over sunitinib in the first line; however, it may be an option in some relatively low-risk mRCC cases due to the difference in the adverse events profile. This trial was registered with the University Hospital Medical Information Network (UMIN), center identifier UMIN 000012522.AbstractBackground: The sequence of first-line cytokine and second-line molecular targeted therapies may be suitable for some patients with metastatic renal cell carcinoma (mRCC) because of the expectation of complete remission and durable response achieved with cytokine therapy. Methods: This was a phase III randomized controlled trial investigating the outcomes of low-dose interleukin-2 (IL-2) plus interferon alfa (IFNα) versus sunitinib as the first line and axitinib as the second line in patients with low- and intermediate-risk mRCC. Results: Thirty-five patients were randomly assigned. The total progression-free survival (PFS) to the end of the second line was 29.0 months (95% CI, 11.7–46.3) in the IL-2 + IFNα group and 16.3 months (95% CI, 6.3–26.4) in the sunitinib group. The PFS hazard ratio for the IL-2 + IFNα group relative to the sunitinib group was 0.401 (95% CI, 0.121–1.328;p= 0.135). The hazard ratio for overall survival (OS) was 1.675 (95% CI, 0.418–6.705;p= 0.466), which was better in the sunitinib group than in the IL-2 + IFNα group but not statistically significant. The types of adverse events (AEs) differed significantly, although there was no significant difference in the incidence of AEs. Conclusions: There was a trend toward better total PFS for IL-2 + IFNα, but it was not significant. There was also no advantage of IL-2 + IFNα in terms of OS. The study was underpowered to draw any definitive conclusions. The results showed no clear advantage of IL-2 + IFNα over sunitinib in the first-line setting; however, it may be an option in some relatively low-risk mRCC cases due to the difference in the AE profile. This trial was registered with the University Hospital Medical Information Network (UMIN), center identifier UMIN 000012522.