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Review
. 2021 Apr;163(4):971-979.
doi: 10.1007/s00701-020-04664-4. Epub 2020 Dec 15.

Extracranial dose and the risk of radiation-induced malignancy after intracranial stereotactic radiosurgery: is it time to establish a therapeutic reference level?

Ian Paddick  1 , A Cameron  2 , A Dimitriadis  3
Affiliations
Review

Extracranial dose and the risk of radiation-induced malignancy after intracranial stereotactic radiosurgery: is it time to establish a therapeutic reference level?

Ian Paddick et al. Acta Neurochir (Wien). 2021 Apr.

Abstract

Background: To measure extracranial doses from Gamma Knife Perfexion (GKP) intracranial stereotactic radiosurgery (SRS) and model the risk of malignancy after SRS for different treatment platforms.

Methods: Doses were measured for 20 patients undergoing SRS on a GKP at distances of 18, 43 and 75 cm from the target, corresponding to the approximate positions of the thyroid, breast and gonads respectively. A literature review was conducted to collect comparative data from other radiosurgery platforms. All data was used to calculate the dose to body organs. The National Cancer Institute (NCI) RadRAT calculator was used to estimate excess lifetime cancer risk from this exposure. Five different age groups covering childhood and younger adults were modelled for both sexes.

Results: Extracranial doses delivered during SRS with the GKP were a median 0.04%, 0.008% and 0.002% of prescription dose at 18 cm, 43 cm and 70 cm from the isocentre respectively. Comparison with the literature revealed that the extracranial dose was lowest from GKP, then linacs equipped with micro-multileaf collimators (mMLC), then linacs equipped with circular collimators (cones), and highest from Cyberknife (CK). Estimated lifetime risks of radiation-induced malignancy in the body for patients treated with SRS aged 5-45 years were 0.03-0.88%, 0.36-11%, 0.61-18% and 2.2-39% for GKP, mMLC, cones and CK respectively.

Conclusions: We have compared typical extracranial doses from different platforms and quantified the lifetime risk of radiation-induced malignancy. The risk varies with platform. This should be taken into account when treating children and young adults with SRS. The concept of a therapeutic reference level (TRL), similar to the diagnostic reference level (DRL) established in radiology, is proposed.

Keywords: Cyberknife; Extracranial dose; Gamma Knife; Linac; Radiation-induced malignancy; Radiosurgery; SRS.

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Conflict of interest statement

All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript with the exception of Mr. Ian Paddick who reports ad hoc consultancy fees from Elekta Instruments AB, outside the submitted work; Dr. Cameron reports personal fees and non-financial support from Elekta, outside the submitted work.

Figures

Fig. 1
Fig. 1
Graph showing extracranial doses from intracranial treatment versus distance from the target for different radiosurgery platforms from the literature
Fig. 2
Fig. 2
Excess extracranial lifetime risk of cancer treated with intracranial SRS at age 5–45 years old utilising 4 different SRS platforms and 2 different doses in both sexes: a Gamma Knife Perfexion. b Linac mMLC. c Linac cones. d Cyberknife
See this image and copyright information in PMC

Comment in

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