Single-Agent Interleukin-2 in the Treatment of Metastatic Melanoma

Questions: What is the role of single-agent interleukin-2 (il-2) in the treatment of adults with metastatic melanoma? If there is a role for single-agent il-2, what patient population can appropriately be considered for treatment? If there is a role for single-agent il-2, what dose and schedule are appropriate? What are the toxicities associated with il-2? Perspectives: Many agents have been investigated for antitumour activity in melanoma, but few have shown promising response rates. Early detection, appropriate surgery, and adjuvant therapy have all improved outcomes, but approximately one third of patients with early-stage disease will nevertheless develop metastases. Single-agent il-2 has attracted much attention over the past several years. A number of randomized trials and many phase ii trials investigating single-agent il-2 suggest that this systemic treatment produces durable responses in melanoma patients. Given the dismal survival of patients with metastatic melanoma and the limited availability of effective treatments, the Melanoma Disease Site Group (dsg) of Cancer Care Ontario’s Program in Evidence-Based Care (pebc) felt that the durable responses seen with il-2 treatment warranted closer examination. Outcomes: Primary outcomes of interest included objective response rate, complete response rate, duration of response, toxicity, and quality of life. Secondary outcomes of interest included progression-free survival and overall survival. Methodology: A systematic review was developed, and clinical recommendations relevant to patients in Ontario were drafted. The practice guideline report was reviewed and approved by the Melanoma dsg, which comprises medical oncologists, surgeons, and dermatologists. External review by Ontario practitioners was obtained through a mailed survey, the results of which were incorporated into the practice guideline. Final review and approval of the practice guideline was obtained from the pebc’s Report Approval Panel. Results: The present practice guideline reflects the integration of the draft recommendations based on a systematic review of the available evidence with the feedback obtained from external review by practitioners and the Report Approval Panel. Practice Guideline: No studies have compared il-2 to the current standard of care—dacarbazine (dtic)—or to placebo in the treatment of metastatic melanoma. After reviewing and weighing the evidence that does exist, the opinion of the Melanoma dsg is that high-dose il-2 is a reasonable treatment option for a select group of patients with metastatic melanoma: (1) Patients should have a good performance status (Eastern Cooperative Oncology Group 0–1) and a normal lactate dehydrogenase level. (2) Patients should have fewer than three organs involved or have cutaneous and/or subcutaneous metastases only, and no evidence of central nervous system metastases should be present. In this select group of patients, il-2 treatment can produce durable complete remissions. High-dose il-2 is recommended to be given at 600,000 IU/kg per dose, delivered intravenously over 15 minutes, every 8 hours, for a maximum of 14 doses. High-dose il-2 delivery is recommended to be done in a tertiary-care facility by staff trained in the provision of this treatment and with appropriate monitoring. To facilitate treatment and to develop expertise in this therapeutic modality, the dsg recommends that high-dose il-2 programs be established in one or two centres in Ontario. Qualifying Statements: High-dose il-2 has response rates that are similar to those seen with standard chemotherapy. However, unlike chemotherapy, il-2 demonstrates low but durable complete response rates that may lead to years of benefit for patients with metastatic melanoma. Based on the available data assessing prognostic factors and patient selection, patients with non-visceral metastases and fewer metastatic sites have a much higher response rate. In these select patients, high dose il-2 may be considered for first-line therapy. The lack of large randomized trials comparing il-2 to dtic or other chemotherapy means that recommendations for this guideline are based largely on phase ii data and limited phase iii data. Further randomized data will not soon become available, because no randomized trials are currently ongoing or planned. Interleukin-2 is currently widely used in the United States, and it is an approved therapy in both Canada and the United States.