High-dose (HD) bolus IL-2 therapy is one of the most potent forms of immunotherapy for patients with metastatic melanoma and renal cell carcinoma.
Approximately 15% of patients respond to HD IL-2 therapy, with almost 5% going into complete remission; however, use of HD IL-2 therapy is limited due to the toxic effects associated with treatment. Because HD IL-2-associated toxicity is severe, it would be beneficial for clinicians to determine if a patient would respond favorably to this treatment prior to side effect onset. Previous studies indicate that regulatory T cell (Treg) populations increase in patients undergoing HD IL-2 therapy, and in this issue of the Journal of Clinical Investigation
, Lazlo Radvanyi and colleagues at M.D. Anderson Cancer Center performed an in depth analysis of Treg populations in melanoma patients undergoing HD IL-2 therapy. The authors identified a distinct population of Treg cells that expressed the inducible T cell costimulator (ICOS) that was highly proliferative following the first cycle of HD IL-2. Furthermore, melanoma patients with greater levels of ICOS+ Tregs in response to HD IL-2 had better clinical outcomes, suggesting that this Treg population may be useful to predict which patients would benefit from HD IL-2.