Glioma pp 179-188 | Cite as

Clinical Implications of Radiobiological Studies on CNS Tolerance

  • A. J. van der Kogel


The radiation tolerance of the central nervous system (CNS) has been the subject of many clinical and experimental studies. Because of the radioresistance of high grade gliomas there has been a continuous search for ways to increase the dose on substantial volumes of brain tissue without a concomitant increase in necrosis, although a small risk of complications is considered acceptable. This situation is in contrast to that of the spinal cord, which is rarely the primary target but which is often inevitably an object of radiation directed at paravertebral tumors. Necrosis of the spinal cord is such a devastating complication that its “tolerance” is usually set at a dose level associated with an extremely small risk of late complications. This difference in clinical terms of reference is one of the main reasons for the erroneous assumption of at least a 10 Gy difference in tolerance dose (at 2 Gy per fraction) for brain and spinal cord. This dogma has been strengthened by the formal publication of 5% complication doses (TD5) as being 50 Gy for spinal cord and 60 Gy for brain (Rubin and Casarett 1972). Because the latency of CNS complications is mostly in the range of 1–2 years or even longer, it is difficult to obtain reliable estimates of the incidence of radiation encephalopathies or myelopathies. Nevertheless, it is of interest to note that from a few studies reporting the incidence of myelopathies, a 0–5% incidence dose of approximately 60 Gy can be derived by probit analysis (Fig. 1), which is similar to figures reported for brain (Sheline et al. 1980). In Fig. 1 the incidence of myelopathy in monkey spinal cord is also presented (Schultheiss et al. 1990), which clearly supports the human data while also stressing the relevance of this animal model.


Spinal Cord Tolerance Dose Radiation Tolerance Repair Kinetic Radiation Myelopathy 
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© Springer-Verlag Berlin Heidelberg 1991

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  • A. J. van der Kogel

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