VALUE OF GRANULOCYTE-COLONY-STIMULATING FACTOR IN RADIOTHERAPY-INDUCED NEUTROPENIA - CLINICAL AND LABORATORY STUDIES

We report the effect of granulocyte colony stimulating factor (G-CSF) on neutropenia occurring during extended field radiotherapy in two gro ups of patients. The first group comprised 8 patients receiving cranio spinal irradiation for a variety of central nervous system (CNS) neopl asms. None of these patients received cytotoxic chemotherapy. G-CSF wa s administered when the absolute neutrophil count (ANC) approached 1.5 x 10(9)/l. Neutropenia was promptly corrected in all cases, thereby a voiding unscheduled interruptions in radiotherapy. Following each G-CS F administration, ANC reached a peak on the following day and then dec lined steadily. Mean ANC rose from 1.33 x 10(9)/l on the day of G-CSF treatment to 7.07 x 10(9)/l the next day. Patients received 2-6 G-CSF injections during radiotherapy. Experiments were carried out in vitro to assess the risk of G-CSF causing increased CNS tumour cell prolifer ation. 11 human CNS tumour cultures (2 medulloblastomas, 2 primitive n euroectodermal tumours and 7 astrocytic tumours) were cultured in the presence of G-CSF at a range of concentrations up to 100 ng/ml. Their proliferation was compared with that of a G-CSF dependent murine leuke mia cell line (NFS-60). None of the human tumour cultures demonstrated a significant increase in proliferation in response to G-CSF. 4 patie nts undergoing ''mantle'' type radiotherapy for Hodgkin's Disease or N on-Hodgkin's Lymphoma also received G-CSF treatment for neutropenia. A ll 4 had previously received cytotoxic chemotherapy. The number of G-C SF injections given per patient during radiotherapy ranged from 3-6. M ean ANC rose from 1.76 x 10(9)/l to 10.8 x 10(9)/l the next day. These results suggest that G-CSF is a reliable treatment for radiotherapy i nduced neutropenia and that an intermittent dosage schedule is effecti ve.