Improving the accuracy of biologically effective dose estimates, from a previously published study, after radiosurgery for acoustic neuromas

Hopewell, John W., Moore, Joshua, Villafuerte, Conrad J., Paddick, Ian, Jones, Bleddyn, Hill, Mark A. and Tsang, Derek S. 2023. Improving the accuracy of biologically effective dose estimates, from a previously published study, after radiosurgery for acoustic neuromas. World Neurosurgery 172 , e130-e143. 10.1016/j.wneu.2022.12.119

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Abstract

Objective: To recalculate biological effective dose values (BED) for radio-surgical (SRS) treatments of acoustic neuroma from a previous study. BEDs values were previously overestimated by only using beam-on times in calculations, so excluding the important beam-off-times (when DNA repair continues) which contribute to the overall treatment time. Simple BED estimations using a mono-exponential approximation may not always be appropriate but if used should include overall treatment time. Methods: Time intervals between iso-centres were estimated. These were especially important for the Gamma Knife Model 4C cases since manual changes significantly increase overall treatment times. Individual treatment parameters, such as iso-centre number, beam-on-time and beam-off-time were then used to calculate BED values using a more appropriate bi-exponential model that includes fast and slow components of DNA damage repair over a wider time range. Results: The revised BED estimates differed significantly from previously published values. The overestimates of BED, obtained using beam-on-time only, varied from 0 - 40.3%. BED subclasses, each with a BED range of 5 Gy2.47, indicated that revised values were consistently reduced when compared with originally quoted values, especially for 4C compared with Perfexion cases. Furthermore, subdivision of 4C cases by collimator number further emphasised the impact of scheduled gap times on BED. Further analysis demonstrated important limitations of the mono-exponential model. Target volume was a major confounding factor in the interpretation of the results of this study. Conclusions: BED values should be estimated by including beam-on and beam-off times. Suggestions are provided for more accurate BED estimations in future studies.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Mathematics
Subjects:	R Medicine > RC Internal medicine > RC0254 Neoplasms. Tumors. Oncology (including Cancer)
Publisher:	Elsevier
ISSN:	1878-8750
Date of First Compliant Deposit:	27 January 2023
Date of Acceptance:	28 December 2022
Last Modified:	04 May 2023 07:27
URI:	https://orca.cardiff.ac.uk/id/eprint/156336

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