HAIRY-CELL LEUKEMIA AND ALPHA-INTERFERON TREATMENT - LONG-TERM RESPONDERS

Background and Objective. In the 1980s alpha-interferon (alpha-IFN) dr amatically improved the management of hairy cell leukemia (HCL), produ cing normalization of hematologic parameters including the disappearan ce of circulating hairy cells in the majority of treated patients, wit hin 6 months. The quality and durability of the response depended on t he duration of alpha-IFN treatment; progression of the disease consist ently followed discontinuation of alpha-IFN. In this report, we examin e the characteristics of long-term responders from our series of 44 HC L patients treated with alpha-IFN. Methods. We report follow-up data o n 44 HCL patients who underwent alpha-IFN as first-line treatment betw een 1985 and 1990. The alpha-IFN dose was 3x10(6) U daily for 12-15 mo nths, with 20 patients continuing to receive the same dose three times a week as maintenance treatment for an additional 6-12 months. Of the 44 patients, 8 achieved a CR, 28 a PR and 8 a MR, with an overall res ponse rate of 82%. Thirty-eight (86%) of these patients showed disease progression and were retreated with alpha-IFN (2 pts), 2-chlorodeoxy- adenosine (35 pts), or pentostatin (1 pt). So far, all 38 patients are alive and in good unmaintained second response, except for two patien ts who developed a second neoplasm. Results. Six of the 8 first comple te responders are alive and have not required further treatment after completing alpha-IFN. These long responders most often (5/6) presented a hairy cell index (HCl) < 0.50 at diagnosis; all 6 registered a sign ificant reduction in bone marrow infiltration (HCl <0.10) after induct ion therapy and underwent alpha-IFN maintenance treatment. These three parameters turned out to be statistically significant when the long-t erm responders were compared with the failure patients subset (p = 0.0 03 for HCl at diagnosis; p = 0.001 for HCl at the end of the induction phase; p = 0.003 for the maintenance phase). The median progression-f ree survival of these 6 longterm responders was 75 months (range, 62 t o 78). Interpretation and Conclusions. Overall, alpha-IFN represents a n excellent palliative treatment for most HCL patients. A small subset of these patients could become long-term responders following first-l ine alpha-IFN therapy alone. (C) 1997, Ferrata Storti Foundation.