Original Research

Hypofractionated image-guided radiotherapy for the treatment of acoustic neuromas: A dosimetrically acceptable alternative to stereotactic radiosurgery in a resource-constrained environment

Hester Burger, Hannelie Mac Gregor, Ross Balchin, Jeannette D. Parkes
South African Journal of Oncology | Vol 1 | a19 | DOI: https://doi.org/10.4102/sajo.v1i0.19 | © 2017 Hester Burger, Hannelie Mac Gregor, Ross Balchin, Jeannette D. Parkes | This work is licensed under CC Attribution 4.0
Submitted: 28 March 2017 | Published: 01 June 2017

About the author(s)

Hester Burger, Division of Medical Physics, University of Cape Town, Groote Schuur Hospital, South Africa
Hannelie Mac Gregor, Division of Medical Physics, University of Cape Town, Groote Schuur Hospital, South Africa
Ross Balchin, Department of Psychology, University of Cape Town, Groote Schuur Hospital, South Africa
Jeannette D. Parkes, Division of Radiation Oncology, University of Cape Town, Groote Schuur Hospital, South Africa


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Abstract

Purpose: Treatment options for acoustic neuromas (ANs) are limited in low- and middle-income countries. The aim of this study was to investigate whether hypofractionated image-guided radiotherapy (IGRT) is a clinically acceptable treatment option for departments where no other radiosurgery options are available.
Methods and materials: Fifteen dynamic conformal arc plans that had been clinically utilised were evaluated against the Radiation Therapy Oncology Group (RTOG) radiosurgery criteria and published indices. Analysis involved evaluating critical structure doses and the volume of normal tissue receiving 12 and 10 Gy single fraction equivalent dose (V12Eq and V10Eq).
Results: Overall, there was only one RTOG protocol deviation in the whole patient group, where quality of coverage was compromised in order to achieve brainstem tolerance. Conformity indices were within clinically acceptable limits (CIPaddick ≥ 0.6) despite being inferior to the published Universitair Ziekenhuis Brussel (UZB) Gamma Knife and CyberKnife results (p < 0.0001). Homogeneity was superior to the Gamma Knife (p < 0.0001) and Novalis dynamic conformal arc (p = 0.0002) results. Gradient index results were inferior to all published techniques, but doses to the normal structures were well controlled with the exception of the cochlea. The V10Eq data showed increased sensitivity when compared with V12Eq.
Conclusion: Dynamic arc IGRT allows for good coverage of AN lesions, but the dose fall-off is not as steep as that obtained with mainstream radiosurgery systems. Contouring and planning should include detailed critical structures analysis. For normal brain parenchyma analysis, V10Eq is a superior risk indicator when compared to V12Eq for this technique. Dynamic arc IGRT offers a dosimetrically acceptable treatment alternative for patients without serviceable hearing, in departments where there are no mainstream radiosurgery treatment options available.

Keywords

acoustic; neuroma; hypofractionated; IGRT; radiosurgery; LMIC

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