An analysis of plan robustness for esophageal tumors: comparing volumetric modulated arc therapy plans and spot scanning proton planning

Warren, Samantha, Partridge, Mike, Bolsi, Alessandra, Lomax, Anthony J., Hurt, Chris ORCID: https://orcid.org/0000-0003-1206-8355, Crosby, Thomas and Hawkins, Maria A. 2016. An analysis of plan robustness for esophageal tumors: comparing volumetric modulated arc therapy plans and spot scanning proton planning. International Journal of Radiation Oncology - Biology - Physics 95 (1) , pp. 199-207. 10.1016/j.ijrobp.2016.01.044

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Abstract

Summary Comparing spot-scanning proton therapy single-field optimization plans with volumetric modulated arc therapy plans indicated that single-field optimization can achieve significant sparing of normal tissue for midesophageal cancer compared with volumetric modulated arc therapy. However, the boost volume dose coverage in the simultaneous integrated boost proton plans appears less robust to setup errors. Robust optimization to ensure adequate target coverage of simultaneous integrated boost proton plans might be beneficial. Purpose Planning studies to compare x-ray and proton techniques and to select the most suitable technique for each patient have been hampered by the nonequivalence of several aspects of treatment planning and delivery. A fair comparison should compare similarly advanced delivery techniques from current clinical practice and also assess the robustness of each technique. The present study therefore compared volumetric modulated arc therapy (VMAT) and single-field optimization (SFO) spot scanning proton therapy plans created using a simultaneous integrated boost (SIB) for dose escalation in midesophageal cancer and analyzed the effect of setup and range uncertainties on these plans. Methods and Materials For 21 patients, SIB plans with a physical dose prescription of 2 Gy or 2.5 Gy/fraction in 25 fractions to planning target volume (PTV)50Gy or PTV62.5Gy (primary tumor with 0.5 cm margins) were created and evaluated for robustness to random setup errors and proton range errors. Dose–volume metrics were compared for the optimal and uncertainty plans, with P<.05 (Wilcoxon) considered significant. Results SFO reduced the mean lung dose by 51.4% (range 35.1%-76.1%) and the mean heart dose by 40.9% (range 15.0%-57.4%) compared with VMAT. Proton plan robustness to a 3.5% range error was acceptable. For all patients, the clinical target volume D98 was 95.0% to 100.4% of the prescribed dose and gross tumor volume (GTV) D98 was 98.8% to 101%. Setup error robustness was patient anatomy dependent, and the potential minimum dose per fraction was always lower with SFO than with VMAT. The clinical target volume D98 was lower by 0.6% to 7.8% of the prescribed dose, and the GTV D98 was lower by 0.3% to 2.2% of the prescribed GTV dose. Conclusions The SFO plans achieved significant sparing of normal tissue compared with the VMAT plans for midesophageal cancer. The target dose coverage in the SIB proton plans was less robust to random setup errors and might be unacceptable for certain patients. Robust optimization to ensure adequate target coverage of SIB proton plans might be beneficial.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Medicine
Additional Information:	Particle Therapy Special Edition
Publisher:	Elsevier
ISSN:	0360-3016
Funders:	Cancer Research UK
Date of First Compliant Deposit:	17 January 2017
Date of Acceptance:	22 January 2016
Last Modified:	05 May 2023 09:56
URI:	https://orca.cardiff.ac.uk/id/eprint/97491

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