Prostate stereotactic body radiotherapy: quantifying intra-fraction motion and calculating margins using the new BIR geometric uncertainties in daily online IGRT recommendations.
Br J Radiol
; 96(1146): 20220852, 2023 Jun 01.
Article
en En
| MEDLINE
| ID: mdl-37001054
ABSTRACT
OBJECTIVES:
To measure the magnitude of intra-fraction prostate motion (IFPM) during stereotactic radiotherapy (SBRT) delivered without intra-fraction tracking.To assess if current margins adequately cover IFPM.To derive margins using new guidelines.METHODS:
IFPM was determined in 20 patients receiving 36.25 Gy in 5 fractions using 97 pairs of pre- and post-treatment cone beam CT (CBCT) scans. Correlation of time between CBCT acquisitions and motion was determined. The magnitude of IFPM was compared to current margins (6 mm isotropic, 3 mm posterior). Margins were calculated using IFPM alone and updated guidelines.RESULTS:
The averaged 3D root mean square IFPM was 2.5 mm (4.2 mm). Independent prostate motion was predominantly posterior (70%) and inferior (63%). There was weak correlation between posterior (ρ = 0.38) and inferior (ρ = 0.36) IFPM and time. IFPM greater than current margins occurred in 8 of 97 fractions, six in the posterior direction. Margins were ≤3.5 mm using IFPM alone and ≤3.3 mm Left 3.5 mm Right, 7.0 mm inferior, 3.7 mm superior, 4.4 mm anterior and 3.3 mm posterior using new guidelines, compensating for motion in 92% of fractions.CONCLUSIONS:
Our current SBRT margins account for 92% of IFPM, predominantly posterior and inferior. Although updated guidelines suggest an increase in margins inferiorly, any increase must be balanced against the possibility of increased toxicity, particularly if biochemical control and side-effects are favourable with current practice. ADVANCES IN KNOWLEDGE The difference between current clinical margins and those determined using updated guidance is demonstrated. The implications must be considered against clinical outcomes.
Texto completo:
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Bases de datos:
MEDLINE
Asunto principal:
Neoplasias de la Próstata
/
Radiocirugia
/
Radioterapia Guiada por Imagen
Tipo de estudio:
Guideline
Límite:
Humans
/
Male
Idioma:
En
Revista:
Br J Radiol
Año:
2023
Tipo del documento:
Article
País de afiliación:
Reino Unido