High response rate after intratumoral treatment with interleukin-2: results from a phase 2 study in 51 patients with metastasized melanoma.

Background: Systemic high-dose interleukin-2 (IL-2) achieved long-term survival in a subset of patients with advanced melanoma. The authors reported previously that intratumorally applied IL-2 induced complete local responses of all metastases in >60% of patients. The objectives of the current study were to confirm those results in a larger cohort and to identify patient or regimen characteristics associated with response.

Methods: Patients with melanoma who had a median of 12 injectable metastases received intratumoral IL-2 treatments 3 times weekly until they achieved clinical remission. The initial dose of 3 million international units was escalated, depending on the individual patient's tolerance.

Results: Forty-eight of 51 patients were evaluable. Only grade 1/2 toxicity was recorded. A complete response that lasted >/=6 months was documented in 70% of all injected metastases. A complete local response of all treated metastases was achieved in 33 patients (69%), including 11 patients who had between 20 and 100 metastases. Response rates were higher for patients who had stage III disease compared with patients who had stage IV disease. No objective responses of distant untreated metastases were observed. The 2-year survival rate was 77% for patients with stage IIIB/IIIC disease and 53% for patients with stage IV disease. Efficacy and survival did not differ between patients who had >/=20 lesions and patients who had <20 lesions.

Conclusions: Intratumoral IL-2 treatment elicited complete local responses in a high percentage of patients. Further studies will be required to investigate the mode of action of this treatment and its impact on survival.