Supratentorial recurrences of gliomas. Morphological studies in relation to time intervals with astrocytomas.

We report 137 recurrent supratentorial astrocytomas. The primary tumours diagnosed on the basis of a grading system with three stages were 72 astrocytomas I and 65 astrocytomas II. In the first group 14% of the recurrences were not changed, 55.5% became astrocytomas II, and 30.5% became glioblastomas. In the second group 55.4% were unchanged, and 44.6% became glioblastomas. The postoperative intervals untile reintervention or death were statistically examined. It seems that the recurrence time chielfy depends on the nature of the primary tumour. The transformation of an astrocytoma I to a glioblastoma takes longer than the transformation of an astrocytoma II into a glioblastoma. In about two thirds of all astrocytomas an increase of malignancy is to be expected. From the histological picture it is not possible in an individual case to predict the likelihood or speed of malignant change. With regard to the effect of irradiation the authors conclude that radiotherapy most probably does not produce malignancy.