EFFECTS OF RECOMBINANT HUMAN INTERLEUKIN-3 IN PATIENTS WITH RELAPSED SMALL-CELL LUNG-CANCER TREATED WITH CHEMOTHERAPY - A DOSE-FINDING STUDY

Purpose: The aim of the study was to determine the maximum tolerable dose of recombinant human interleukin-3 (rhIL-3) after combination chemotherapy and to evaluate the ability of rhIL-3 to influence hematopoietic recovery. Patients and Methods: Nineteen patients who had relapsed small-cell lung cancer (SCLC) received rhIL-3 after their second course of chemotherapy, which consisted of either cyclophosphamide, doxorubicin, and etoposide (CDE) every 3 weeks or vincristine, ifosfamide, mesna, and carboplatin (VIMP) every 4 weeks. Twenty-four hours after the last chemotherapy dose, rhIL-3 was administered subcutaneously (SC) once daily for 14 days on an outpatient basis. Escalating dosages (1, 2, 4, 8, and 16 μg/kg/d) of rhIL-3 were tested. Hematologic effects were evaluated by comparing blood cell recovery after chemotherapy cycle 1 and cycle 2 plus rhIL-3. Results: The adverse effects of rhIL-3 at dosages up to 8 μg/kg/d consisted mainly of low-grade fever and flulike symptoms. At 16 μg/kg, rhIL-3 headache became dose- limiting. Severe neutropenia (neutrophils < 0.5 x 109/L) after VIMP cycle 2 was shorter in duration than after cycle 1 (7 v 3 days; P < .05). At rhIL-3 dose levels 8 and 16 μg/kg, hematologic effects in seven patients who were treated with VIMP showed a significant hastened recovery of leukocyte and neutrophil counts during cycle 2 compared with cycle 1 and increased monocyte and eosinophil counts in cycle 2 compared with cycle 1. rhIL-3 also increased reticulocyte and platelet counts at a dose level of 8 μg/kg. No significant stimulation of basophils and lymphocytes was observed. Apart from the hematologic effects, rhIL-3 also augmented the release of cytokines such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), and lowered cholesterol levels. Conclusions: This study demonstrates that rhIL-3 can be safely administered after chemotherapy on an outpatient basis. rhIL-3 is tolerated well at doses up to 8 μg/kg/d and is biologically active in patients after myelosuppressive chemotherapy.