Treatment delineation impact on Gamma Knife radiosurgical response of vestibular schwannoma

Prognostic factors of tumor control after Gamma Knife radiosurgery for vestibular schwannomas (VS) are largely unknown. This paper attempts to establish an explanation for tumor response by exploring the possible relation between the accuracy of tumor delineation by physicians and the tumor response derived from an imaging database. This relationship has not yet been reported. To this end, we measure the differences between the treatment delineation and a delineation by the specialist using the following metrics: tumor volumes, number of slices, slice area and slice similarity. By observing data from 40 patients, comprising of 20 successfully and 20 unsuccessfully treated patients, we find that there is no evidence that a less accurate delineation leads to a higher failure rate. The results even show the opposite: the delineation of the successful group is less accurate than the delineation of the unsuccessful group, when the treatment delineation is
compared to a retrospectively created delineation by a VS specialist. This suggests that, within the limitation of this research and experiment so far, the more difficult it is to delineate the tumor during treatment planning, the more likely it is to achieve treatment success.