Daily image-guided radiation therapy significantly reduces setup errors, but it does not minimize intrafractional target mobility; respiratory-induced target motion is one of the reasons for this. Therefore, the main aim of this study was to evaluate the impact of respiratory-induced prostate motion on the clinical target volume (CTV) margins.
The analysis comprised 50 videos stored in digital format and recorded in a group of 50 patients during image-guided radiation therapy for prostate cancer. Fluoroscopy time was 10 seconds. Respiratory motion of the prostate in the anterior-posterior and lateral direction was assessed on the basis of a fiducial marker (GoldAnchor) implanted into the prostate before the treatment planning procedure.
The average values and standard deviations of respiratory-induced prostate motion in the superior-inferior and left-right (lateral) directions were 2.6 ± 2.1 mm and 0.7 ± 0.7 mm, respectively. The CTV margins calculated according to the van Herk formula based on respiratory prostate motion were 8 mm in the superior-inferior direction and 2 mm in the lateral direction.
Respiratory-induced prostate mobility during radiotherapy is significant especially in the superior-inferior direction, and can thus induce a geographical error. This confirms the need for determining CTV margins for this type of respiratory-induced mobility.
Tumori 2016; 102(3): 330 - 334
Article Type: ORIGINAL RESEARCH ARTICLE
AuthorsDawid Bodusz, Leszek Miszczyk
- • Accepted on 21/09/2015
- • Available online on 31/10/2015
- • Published in print on 02/06/2016