Establishment of a Therapeutic Ratio for Gamma Knife Radiosurgery of Trigeminal Neuralgia: The Critical Importance of Biologically Effective Dose Versus Physical Dose.

Details

Serval ID
serval:BIB_CCCAC9F546C7
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Establishment of a Therapeutic Ratio for Gamma Knife Radiosurgery of Trigeminal Neuralgia: The Critical Importance of Biologically Effective Dose Versus Physical Dose.
Journal
World neurosurgery
Author(s)
Tuleasca C., Paddick I., Hopewell J.W., Jones B., Millar W.T., Hamdi H., Porcheron D., Levivier M., Régis J.
ISSN
1878-8769 (Electronic)
ISSN-L
1878-8750
Publication state
Published
Issued date
02/2020
Peer-reviewed
Oui
Volume
134
Pages
e204-e213
Language
english
Notes
Publication types: Comparative Study ; Journal Article
Publication Status: ppublish
Abstract
How variations of treatment time affect the safety and efficacy of Gamma Knife (GK) radiosurgery is a matter of considerable debate. With the relative simplicity of treatment planning for trigeminal neuralgia (TN), this question has been addressed in a group of these patients. Using the concept of the biologically effective dose (BED), the effect of the two key variables, dose and treatment time, were considered.
A retrospective analysis was performed of 408 TN cases treated from 1997 to 2010. Treatment involved the use of a single 4 mm isocenter. If conditions allowed, the isocenter was placed at a median distance of 7.5 mm from the emergence of the trigeminal nerve from the brain stem. The effects were assessed in terms of the incidence of the complication, hypoesthesia, and in terms of efficacy using the incidence of pain free after 30 days and 1 and 2 years. These responses were evaluated with respect to both the physical dose and the BED, the latter using a bi-exponential repair model.
RE-evaluation showed that the prescription doses, at the 100% isodose, varied from 75 to 97.9 Gy, delivered in 25-135 minutes. The relationship between the physical dose and the incidence of hypoesthesia was not significant; the overall incidence was ∼20%. However, a clear relationship was found between the BED and the incidence of hypoesthesia, with the incidence increasing from <5% after a BED of ∼1800 Gy <sub>2.47</sub> to 42% after ∼2600 Gy <sub>2.47</sub> . Efficacy, in terms of freedom from pain, was ∼90%, irrespective of the BED (1550-2600 Gy <sub>2.47</sub> ) at 1 and 2 years. The data suggested that "pain free" status developed more slowly at lower BED values.
These results strongly suggest that safety and efficacy might be better achieved by prescribing a specific BED instead of a physical dose. A dose and time to BED conversion table has been prepared to enable iso-BED prescriptions. This finding could dramatically change dose-planning strategies in the future. However, this concept requires validation for other indications for which more complex dose planning is required.
Keywords
Cohort Studies, Follow-Up Studies, Humans, Radiation Dosage, Radiosurgery/methods, Radiosurgery/standards, Retrospective Studies, Treatment Outcome, Trigeminal Neuralgia/diagnosis, Trigeminal Neuralgia/radiotherapy, BED, Biologically effective dose, Radiation dose, Radiosurgery, Therapeutic ratio, Trigeminal neuralgia
Pubmed
Web of science
Funding(s)
University of Lausanne / Jeune Chercheur en Recherche Clinique, Constantin Tuleasca
Create date
15/10/2019 14:09
Last modification date
03/05/2020 7:02
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