1980 Volume 20 Issue 11 Pages 1095-1101
The growth rate of malignant gliomas was estimated by serial CT scanning. The formula for calculation of a tumor volume t days apart can be expressed as follows.
Tc=log(1+GF)·t/logVB/VA
Tc: cell cycle time, GF: growth fraction, VA: initial volume of the tumor, VB: the volume t days later.
By applying the above formula, nine brain tumors were assessed; eight malignant gliomas and one metastatic tumor. The results show cell cycle times ranging from 5.7 days to 8.0 days, 7 days on the average.
The authors developed a new system by utilizing volume changes in tumor size on CT scans, and discuss the pros and cons in great detail. Abnormally enhanced areas within the tumor appear to increase at a constant rate. Our method is based on the fact that this relevant enhanced zone can be regarded as the real volume of the tumor itself. The volume ratio obtained from two serial CT scannings on different occasions appears to be approximately equal to the real volume ratio of the tumor proper. In practice, the cell loss factor is negligible, and the growth fraction is 0.3.
By using the cell cycle time calculated in this way, the growth rate of a tumor can be measured. Based upon this data, the efficacy of treatment and reappraisal of prognosis in malignant brain tumors can be judged more accurately. For example, even if tumor cells are reduced to 102 ?? 103 by combination of surgery and postoperative irradiation, it follows that in 300 to 500 days, the tumor will show up as a distinct mass lesion on CT scans, i.e. if there is no evidence of recurrence on CT scans 1.5 years after therapy, it is possible to say that a surgical cure has been achieved.
We will demonstrate how our thesis applies to and is confirmed in patients with recurrent medulloblastomas.