Regrowth Patterns of Supratentorial Gliomas: Estimation from Computed Tomographic Scans

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Abstract
To clarify the regrowth patterns of benign and malignant gliomas, we chose 27 intervals (between two operations or between an operation and autopsy) from 21 patients with pathologically verified recurrent supratentorial gliomas. Serial computed tomographic (CT) scans of these cases were analyzed to determine (a) the doubling time (Td) calculated from the change in volume of enhanced and low density areas, (b) the enhancement effect graded from 0 to 4 according to the Hounsfield number, and (c) the presence of dissemination and contralateral extension. We studied 5 benign gliomas (including 1 case of radiation necrosis), 8 malignant astrocytomas, and 8 glioblastomas. The Td's of enhanced areas on CT scans of benign gliomas, malignant astrocytomas, and glioblastomas were 937 ± 66.5 days, 65.1 ± 29.4 days, and 48.1 ± 20.9 days, respectively. The Td's of low density areas were 895 ± 130.6 days, 70.8 ± 22.2 days, and 50.5 ± 14.7 days. There was a significant correlation between the Td's of the enhanced and low density areas (0.97). The enhancement effect increased at recurrence in 55% of the cases, with an average increase of 1.1 grades. The increase in enhancement effect at recurrence showed a tendency to become smaller as the tumor's degree of anaplasia increased. Radiotherapy was effective in significantly retarding the growth rate of malignant gliomas, whose Td's were doubled. Although the Td's of both enhanced and low density areas of benign gliomas were significantly longer than those of malignant gliomas, there was no significant difference in the Td's of enhanced areas between malignant astrocytomas and glioblastomas. Dissemination and contralateral extension occurred at almost the same ratios in malignant astrocytomas and glioblastomas at recurrence. These data indicate that the regrowth pattern of malignant astrocytoma closely resembles that of glioblastoma in spite of morphological distinction. This method was easy and practical for evaluating the biological malignancy of supratentorial gliomas from CT scans, and it can offer us useful clinical information.

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