Infusional interleukin-2 and 5-fluorouracil with subcutaneous interferon-alpha for the treatment of patients with advanced renal cell carcinoma: a southwest oncology group Phase II study

Background: A Phase II trial was conducted to determine the response rate of patients with advanced renal cell carcinoma to a three-drug combination of 5-fluorouracil (5-FU), interleukin-2 (IL-2), and interferon-alpha-2b (IFN-alpha).

Methods: A 2-stage accrual plan was used that was designed to determine whether response to this regimen was consistent with a true response rate of >/= 30%. The regimen was comprised of 5 treatment days weekly for 4 weeks every 6 weeks. Each weekly treatment was comprised of 5-FU, 1750 mg/m(2), continuous intravenous (i.v.) infusion over 24 hours followed by IL-2, 6 MIU/m(2)/day, continuous i.v. infusion for 4 days. IFN-alpha, 6 MU/m(2), was given subcutaneously on Days 1, 2, and 5.

Results: Thirty-eight patients were entered on study, 3 of whom were ineligible. Among the 35 eligible patients there were 3 confirmed partial responses (PR) and 1 complete response (CR), for an overall response rate of 11% (95% confidence interval, 3-27%). One patient considered as having a PR had minimal evidence of residual disease and was free from disease progression at > 2.5 years of follow-up, as was the patient with CR. Three additional patients not qualified as having a PR were showing signs of response at the time they were removed from protocol, and another patient who was removed from protocol early for management of an infection subsequently responded to the same regimen off protocol. Thirteen patients were considered nonassessable (NASS) for response, many of whom had multiple poor risk features and were unable to complete 1 cycle of treatment.

Conclusions: This multicenter study failed to confirm an advantageous overall response rate for this three-drug regimen. However, there were two durable responses and indications of responsiveness not scored as PRs among patients with more favorable risk factor patterns, and many poor risk NASS patients. For these reasons, the response rate reported in the current study may be a conservative reflection of the effectiveness of this regimen.