Multi-scenario based robust intensity-modulated proton therapy (IMPT) plans can account for set-up errors more effectively in terms of normal tissue sparing than planning target volume (PTV) based intensity-modulated photon plans in the head and neck region

Radiation Oncology

Jonathan Farr¹  Sabine Levegrün³  Christoph Pöttgen³  Jehad Abu Jawad³  Andreas Kaiser²  Martin Stuschke² 

[1] Current address: Department of Radiologic Sciences, St. Jude Children's Research Hospital, Memphis TN, USA;West German Proton, Therapy Centre Essen, Essen 45147, Germany;Department of Radiotherapy, University Hospital Essen, Essen 45147, Germany

关键词: Re-irradiation;    Head and neck cancer;    Robust optimization;    IMPT;    Intensity modulated proton therapy;   

Others  :  1153754
DOI  :  10.1186/1748-717X-8-145

 received in 2013-06-03, accepted in 2013-06-13,  发布年份 2013

【 摘 要 】

Background

In a previous report, we compared the conformity of robust intensity-modulated proton therapy (IMPT) plans with that of helical tomotherapy plans for re-irradiations of head and neck carcinomas using a fixed set-up error of 2 mm. Here, we varied the maximum set-up errors between 0 and 5 mm and compared the robust IMPT-plans with planning target volume (PTV) based intensity-modulated photon therapy (IMRT).

Findings

Seven patients were treated with a PTV-based tomotherapy plan. Set-up margins of 0, 2, and 5 mm were subtracted from the PTV to generate target volumes (TV) TV_0mm, TV_2mm, and TV_5mm, for which robust IMPT-plans were created assuming range uncertainties of ±3.5% and using worst case optimization assuming set-up errors of 0, 2, and 5 mm, respectively. Robust optimization makes use of the feature that set-up errors in beam direction alone do not affect the distal and proximal margin for that beam. With increasing set-up errors, the body volumes that were exposed to a selected minimum dose level between 20% and 95% of the prescribed dose decreased. In IMPT-plans with 0 mm set-up error, the exposed body volumes were on average 6.2% ± 0.9% larger than for IMPT-plans with 2 mm set-up error, independent of the considered dose level (p < 0.0001, F-test). In IMPT-plans accounting for 5 mm set-up error, the exposed body volumes were by 11.9% ± 0.8% smaller than for IMPT-plans with 2 mm set-up error at a fixed minimum dose (p < 0.0001, F-test). This set-up error dependence of the normal tissue exposure around the TV in robust IMPT-plans corresponding to the same IMRT-plan led to a decrease in the mean dose to the temporal lobes and the cerebellum, and in the D2% of the brain stem or spinal cord with increasing set-up errors considered during robust IMPT-planning.

Conclusions

For recurrent head and neck cancer, robust IMPT-plan optimization led to a decrease in normal tissue exposure with increasing set-up error for target volumes corresponding to the same PTV.

【 授权许可】

   
2013 Stuschke et al.; licensee BioMed Central Ltd.

【 图 表 】

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