The effect of interferon (human interferon-a; IFN) on the primary brain tumors has been reported. A decrease in the tumor volume of less than 50% of the initial volume was observed in two out of seven cases of systemic administration of IFN, and in two out of eight cases of daily local ad ministration. Changes of the DNA pattern in the tumor tissue, of performance status of the pa tients, and of the mean survival time after IFN therapy were investigated. DNA histograms were obtained by

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... ometry on 6 glioblastomas and 2 medulloblastomas before and after IFN therapy. In the two clinically effective cases, a decrement of the S phase and an increment of the Go, G, phases were observed after IFN therapy. These findings might reflect in hibition of cell transition from Go, G, phases into the S phase by IFN. Performance status and mean survival time of the IFN treated group (12 cases of glioblastoma) were compared with 53 previous cases of malignant astrocytoma and glioblastoma, treated by surgery and irradiation. The Karnofsky performance status for pre and post-IFN therapy was 50.8% and 27.5%, respectively. These statuses were similar to those for the pre and post-third operation (48.3%, 23.3%) for the recurrent malignant gliomas. Furthermore, the mean survival times after second operation were 10.9 months through IFN therapy, and 9.7 months through third operation, respectively. Therefore, it was concluded that IFN therapy might be as effective as the third operation for recurrent malignant gliomas.