A commentary on the biology and growth kinetics of low-grade and high-grade gliomas.

Cell kinetics studies of patients with various gliomas published in the past decade have shown that the average labeling index (LI) obtained from a pulse of 3H-thymidine is very high in medulloblastomas (12.0% +/- 1.3%, standard error of the mean) and glioblastoma multiforme (9.3% +/- 1.0%), low in well differentiated gliomas (less than 1%), and intermediate in anaplastic astrocytomas (4.0% +/- 0.8%). The higher the LI, the faster the tumor grows, probably reflecting a larger growth fraction. In tumor tissues obtained at autopsy, two glioblastomas diluted out the labeling compound in the 2- to 4-month interval after labeling, whereas three glioblastomas and two anaplastic astrocytomas retained labeled neoplastic cells for 3 weeks to 5 months. Most patients whose tumors contained foci of labeled cells at autopsy survived longer. Well differentiated gliomas harbored labeled cells for 2 1/2 to 7 years. These findings indicate that the kinetics of proliferation in well differentiated gliomas are different from those in glioblastomas or anaplastic astrocytomas.