Radiation treatment dose optimisation using Poisson tumour control probability parameters

G. A. Cho, M. A. Ebert, L. Holloway, Z. Kuncic, C. Baldock, D. I. Thwaites

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Abstract

This study examines the Poisson tumour control probability (TCP) γ₃₇ and D₃₇ parameters of a uniformly irradiated numerical tumour model using changes in tumour burden as a surrogate for treatment response information. An optimum dose Di for a tumour sub-volume element Vi is described that maximizes TCP as a function of fixed tumour integral dose ξ. TCP was calculated for spatially-varying clonogen density for a total 10⁸ cells and radiosensitivity α with mean radiosensitivity in the range 0.4-1.0 Gy⁻¹. A bivariate normal distribution is used to describe the radiosensitivity α and the linear term of the linear-quadratic (LQ) cell kill governed the changes in the regional tumour burden within sub-volumes Vi. The optimum dose distribution, Di, for Vi is obtained as a function of fixed tumour integral dose ξ. For a uniform dose delivery and for TCP = 37%, γ₃₇ and D₃₇ are described by the effective radiosensitivity αeff and the effective clonogen number N0eff, respectively. αeff is equivalent to differential dose changes in the number of clonogenic cells (tumour burden). The γ₃₇ values were found to be inversely correlated with variance of the probability density function of the α distribution. For the biologically optimum dose distribution, γ₃₇ was found to converge to the theoretical maximum limit and D₃₇ was found to reduce relative to that obtained for the uniform dose case. The TCP parameters γ₃₇ and D₃₇ could thus be useful in optimising individual radiation treatment doses even when tumour heterogeneity is taken into account.
Original languageEnglish
Pages (from-to)012047-1-012047-6
Number of pages6
JournalJournal of Physics: Conference Series
Volume489
DOIs
Publication statusPublished - 2014
EventInternational Conference on the Use of Computers in Radiation Therapy (17th : 2013) - Melbourne
Duration: 6 May 20139 May 2013

Bibliographical note

Copyright the Author(s). First published in Journal of physics : conference series 489 article 012047. The original publication is available at doi:10.1088/1742-6596/489/1/012047, published by IOP Publishing. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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