Patients receive PEG-interferon alfa-2b subcutaneously (SC) once weekly. Treatment continues until basic fibroblast growth factor level is suppressed to normal or until a maximum weekly dose is reached. If there is disease progression, patients then discontinue treatment. If there is no disease progression, patients receive PEG-interferon alfa-2b SC weekly for up to 1 year in the absence of disease progression or unacceptable toxicity.