Background: Interleukin-2 (IL-2), used alone or in combination with adoptive cellular therapy, is one of the most promising biologic therapeutic agents for cancer treatment.
Methods: The National Biotherapy Study Group conducted 15 trials of continuous-infusion IL-2 involving 788 patients with cancer, 638 of whom were evaluable for tumor response. The protocols included administration of IL-2 and lymphokine-activated killer (LAK) cells, IL-2 and cyclophosphamide, IL-2 and tumor-infiltrating lymphocytes, IL-2 and alpha-interferon (IFN), IL-2 and tumor necrosis factor, and IL-2 and LAK alternating with combination chemotherapy.
Results: Responses were detected in 33 of 188 patients (18%) with melanomas, 13 of 167 (8%) with renal cell carcinomas, and 1 of 76 (1%) with colorectal cancers. The median survival times in patients with melanoma and renal cell cancer were 9.6 and 9.3 months, respectively. The proportion of patients surviving 1 year were 35% and 43%, respectively. There were responses in 8 of 51 patients (16%) with lung cancer, but many of these patients received IL-2 and LAK alternating with platinum-based chemotherapy. Four of 23 patients (17%) responded who had breast cancer and received IL-2 and IFN. The protocols involving IL-2 plus adoptive cellular therapy produced a higher response rate than those not involving activated cells (48 of 312 [15%] versus 24 of 326 [7%], P = 0.003); however, there was no difference in survival. There was a 1.8% mortality rate attributed to the complications of IL-2 itself.
Conclusions: IL-2 produces durable tumor responses in some patients, especially in those with melanoma and renal cell carcinoma. Because the drug's toxicity is significant and the overall response rates are low, patient selection may be the most important factor in the clinical use of continuous-infusion IL-2 therapy.