MAINTENANCE THERAPY: Patients receive high-dose recombinant interferon alfa-2B subcutaneously (SC) on days 1, 3, and 5. Treatment repeats every 6 weeks for up to 48 weeks in the absence of disease progression or unacceptable toxicity. Or patients receive ipilimumab IV over 90 minutes on day 1. Treatment repeats every 12 weeks for 3 years in the absence of disease progression or unacceptable toxicity.