Interferon maintenance therapy for patients with chronic lymphocytic leukemia in remission after fludarabine therapy

Many patients with chronic lymphocytic leukemia (CLL) achieve remission after treatment with fludarabine chemotherapy. Most of these patients, however, later experience relapse. In addition, immunologic deficits may persist even in patients in complete remission; lymphopenia, predominantly involving the CD4 population, is universal after fludarabine therapy. We used recombinant alpha interferon (IFN-alpha) maintenance therapy in patients with CLL who achieved remission in response to fludarabine therapy to determine its effect on residual disease, assessed by either bone marrow biopsy or flow cytometry, and on immune restoration. Thirty-one patients were treated with IFN-alpha (3 x 10(6) U by subcutaneous injection three times weekly). Twenty-two patients (71%) were in complete remission (CR) and nine (29%) were in partial remission (PR). Of the 22 patients in CR, 21 (95%) had evidence of residual disease at the start of IFN-alpha therapy. Low CD4 levels were noted in 93% of patients, low IgG levels in 45%, and anergy or hypoergy in 52%. Only one patient in PR achieved a CR on IFN-alpha therapy: the only patient who had had no prior fludarabine but had been treated with chlorambucil and prednisone. All patients in CR with minimal residual disease had persistent disease after IFN-alpha treatment. There were no increases in CD4 counts or IgG levels; three patients with borderline responses to skin testing had an increase in the number of positive tests while on IFN-alpha. The time to progression was no different in patients treated with IFN-alpha than in a historical control group of patients who had received no further therapy after fludarabine. In summary, the use of IFN-alpha maintenance did not eradicate residual disease, restore immune function, or prolong remissions in patients with CLL responsive to fludarabine.