High-dose hypofractionated pencil beam scanning carbon ion radiotherapy for lung tumors: Dosimetric impact of different spot sizes and robustness to interfractional uncertainties.
Phys Med
; 85: 79-86, 2021 May.
Article
em En
| MEDLINE
| ID: mdl-33984821
ABSTRACT
PURPOSE:
The robustness against setup and motion uncertainties of gated four-dimensional restricted robust optimization (4DRRO) was investigated for hypofractionated carbon ion radiotherapy (CIRT) of lung tumors.METHODS:
CIRT plans of 9 patients were optimized using 4DRRO strategy with 3â¯mm setup errors, 3% density errors and 3 breathing phases related to the gate window. The prescription was 60â¯Gy(RBE) in 4 fractions. Standard spots (SS) were compared to big spots (BS). Plans were recalculated on multiple 4DCTs acquired within 3â¯weeks from treatment simulation and rigidly registered with planning images using bone matching. Warped dose distributions were generated using deformable image registration and accumulated on the planning 4DCTs. Target coverage (D98%, D95% and V95%) and dose to lung were evaluated in the recalculated and accumulated dose distributions.RESULTS:
Comparable target coverage was obtained with both spot sizes (pâ¯=â¯0.53 for D95%). The mean lung dose increased of 0.6â¯Gy(RBE) with BS (pâ¯=â¯0.0078), still respecting the dose constraint of a 4-fraction stereotactic treatment for the risk of radiation pneumonitis. Statistically significant differences were found in the recalculated and accumulated D95% (pâ¯=â¯0.048 and pâ¯=â¯0.024), with BS showing to be more robust. Using BS, the average degradations of the D98%, D95% and V95% in the accumulated doses were -2.7%, -1.6% and -1.5%.CONCLUSIONS:
Gated 4DRRO was highly robust against setup and motion uncertainties. BS increased the dose to healthy tissues but were more robust than SS. The selected optimization settings guaranteed adequate target coverage during the simulated treatment course with acceptable risk of toxicity.Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Radioterapia de Intensidade Modulada
/
Radioterapia com Íons Pesados
/
Terapia com Prótons
/
Neoplasias Pulmonares
Tipo de estudo:
Etiology_studies
Limite:
Humans
Idioma:
En
Ano de publicação:
2021
Tipo de documento:
Article