Tolerance of the Spinal Cord to Hypofractionated Radiotherapy Based on a Generalized Biological Effective Dose (gBED) Model

摘要

A generalized biological effective dose (gBED) model was developed. The model accounts for non-uniform dose distribution and varying dose fractionation schemes commonly encountered in spine stereotactic body radiotherapy. The gBED calculation was applied to a multi-institutional clinical data to model myelopathy and spinal cord tolerance. Despite recent animal data suggesting partial volume tolerance, our study found that the dose at which myleopathy is observed correlated with the dose received in a small volume such as 0.1 cc. Our results justify the practice of constraining the dose to the small absolute volume for safe treatment to the spinal cord given modern intensity modulated radiotherapy. By accounting for dose inhomogeneity, the gBED was also found to be more sensitive than the traditional BED in predicting spinal cord tolerance.