Shorter treatment times reduce the impact of intra-fractional motion : A real-time 4DUS study comparing VMAT vs. step-and-shoot IMRT for prostate cancer.
Strahlenther Onkol
; 194(7): 664-674, 2018 07.
Article
em En
| MEDLINE
| ID: mdl-29523907
ABSTRACT
PURPOSE:
To evaluate the impact of shorter treatment times on intra-fractional motion of the prostate during external beam radiotherapy.METHODS:
53â¯h of intra-fractional motion of the prostate were recorded in real-time by 4D ultrasound (4DUS) during 720 fractions in 28 patients, 14 of which whom treated with step-and-shoot intensity-modulated radiotherapy (IMRT) and 14 of whom were treated with volumetric arc therapy (VMAT).RESULTS:
The average VMAT fraction was recorded for 2â¯min 43â¯s and was substantially shorter than the average step-and-shoot IMRT fraction at 6â¯min 13â¯s. Average radial displacement of the prostate per fraction was substantially and significantly reduced from 1.31⯱ 1.28â¯mm (nâ¯= 357 step-and-shoot IMRT fractions) to 0.96⯱ 1.04â¯mm (nâ¯= 363 VMAT fractions), pâ¯= 0.00004. Radial, vertical, and longitudinal root-mean-square (r.â¯m.â¯s.) error per fraction was reduced from 1.55 to 1.12â¯mm (-28%, pâ¯< 0.0001), from 1.16 to 0.77â¯mm (-34%, pâ¯< 0.0001), and from 0.79 to 0.56â¯mm (-29%, pâ¯= 0.0002), respectively. Lateral intra-fractional motion was generally small and did not differ significantly. The prostate remained during 95% of fraction time within 4.55â¯mm of the isocenter in case of step-and-shoot IMRT and within 2.45â¯mm in case of VMAT. The variance of displacements increased linearly with time, and the rate was the same for both step-and-shoot IMRT and VMAT patients.CONCLUSIONS:
The position of the prostate changed less during shorter fractions, limiting fraction-average and end-of-fraction variance. This substantially and significantly reduced the impact of intra-fractional motion during shorter VMAT fractions as compared to longer step-and-shoot IMRT fractions.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Neoplasias da Próstata
/
Adenocarcinoma
/
Radioterapia de Intensidade Modulada
/
Posicionamento do Paciente
/
Movimentos dos Órgãos
Limite:
Aged
/
Humans
/
Male
Idioma:
En
Revista:
Strahlenther Onkol
Assunto da revista:
NEOPLASIAS
/
RADIOTERAPIA
Ano de publicação:
2018
Tipo de documento:
Article
País de afiliação:
Alemanha