Long Term Follow up of Hairy Cell Leukemia (HCL) Patients (PTS) Treated with Interferon-Alpha (IFN-α). The Importance of Maintenance.

HCL is a chronic B-cell lymphoproliferative disorder with a specific morphology and immunophenotype of the malignant lymphocytes. Although purine analoges are the recommended first-line treatment, they are associated with significant immune suppression and secondary neoplasia. IFN-α is an alternative treatment with fewer long term side effects and considerable efficacy.

AIM: The analysis of HCL patients treated with IFN-α as first-line therapy in a single Hematology Unit.

PATIENTS AND METHODS: 75 consecutive pts diagnosed and followed in our Department between 1980 and 2005, treated with IFN-α were analyzed.

RESULTS: 77.3% were males and their median age was 51 years (30–81). 57% had splenomegaly and 12% hepatomegaly at diagnosis. Their median hemoglobin was 11.3g/dL (4.5–14.3), their median leukocyte and absolute neutrophil counts were 3.1×10⁹/L (0.9–26) and 0.77×10⁹/L (0.03–3.9), respectively. Their median platelet count was 79×10⁹/L (20–295). 33% had hypergammaglobulinemia and their median percentage of bone marrow infiltration at diagnosis was 75%. 10% of the pts were splenectomized before IFN-α treatment. The median time from diagnosis to IFN-α initiation was 0.7 months. The majority of pts (68%) received IFN-α induction at a dose of 3MU/day, while 15% 3MU every other day. Median duration of IFN-α induction was 23.5 months. 8% of pts achieved a complete response with a negative bone marrow, while 73% had a partial remission with a >50% reduction of bone marrow infiltration and a complete restoration of all blood counts. The median time to complete hematologic restoration was 10.7 months. 79% of pts received IFN-α maintenance, the majority of whom (58%) at a dose of 3MU/week. 69% of pts never needed a 2d line treatment, while among those who did, 65% were retreated with IFN-α. The 10-year overall survival was 80%. There were 2 cases of secondary neoplasia. At last follow-up 9% of pts were dead due to unrelated causes, 3% due to 2ary neoplasia, while none died due to disease. Two factors were of prognostic significance for freedom from 2d treatment (FF2T). FF2T was significantly longer for pts older than 51 years old (p<0.0004) and for those receiving IFN-α maintenance compared to those who did not (p<0.03).

CONCLUSIONS: IFN-α has significant efficacy in HCL with a slow but sustained response. Continuous maintenance seems to be important in maintaining response. Younger patients might benefit less from IFN-α.