Long-term complete response to very-low-dose interleukin-2 therapy in patients with metastatic renal cell carcinoma: report of two cases

Before the advent of molecular-targeted agents, immunotherapy using cytokines, such as interferon-α (IFN-α) and interleukin-2 (IL-2), had been the mainstay of treatment for patients with metastatic renal cell carcinoma (mRCC), and this therapy may still be occasionally recommended for such patients. In this report, we present two cases of mRCC who were treated with very-low-dose IL-2 therapy and subsequently achieved complete response (CR). Both cases received adjuvant IFN-α therapy following radical nephrectomy; however, multiple lung metastases developed 4 and 12 months after surgery, and low-dose IL-2 (0.7 million U/day) was then administered twice per week for 14 and 35 months, respectively. In both cases, metastatic lesions completely regressed 3 and 20 months after the start of IL-2 therapy, and these responses have persisted for 81 and 67 months, respectively, to date. These findings suggest that immunotherapy with IL-2, even at a very-low-dose setting, may achieve the induction of CR in mRCC; accordingly, IL-2-based immunotherapy should be considered as the initial treatment for appropriately selected patients with mRCC.