Estimation of the growth rate of malignant gliomas by CT scanning

The actual tumor doubling time was calculated from a change in tumor volume on CT at two specific times. Ten brain tumors (nine malignant gliomas and one metastatic tumor) were assessed by this method. The actual doubling time ranged from 15.0 to 21.1 days, averaging 19 days. The area abnormally enhanced on CT increased at an exponential speed, and was thought to reflect the development of the tumor. This suggested that the volume ratio of a tumor estimated on two serial CT scannings at an appropriate interval might be approximately equal to the real volume ratio of the tumor. Experiments with phantoms and surgical specimens supported our hypothesis. By using the tumor doubling time calculated in this way, the growth rate of a tumor can be measured. The efficacy of treatment and reappraisal of prognosis in malignant brain tumors can be judged more accurately. Tumor growth rates thus calculated demonstrated that the tumor might reappear as a distinct mass lesion on CT in 300 to 500 days if tumor cells should be reduced to 102 - 103 by combination of surgery and postoperative irradiation. If there is no evidence of recurrence on CT in 1.5 years after therapy, it may be possible to guess that the tumor has been successfully cured. Our thesis was justified in patients with recurrent glioblastoma, malignant astrocytoma and medulloblastoma. (author)