Dawid Bodusz1, Leszek Miszczyk1. 1. Radiotherapy Department, Maria Skłodowska-Curie Memorial Cancer Center and Institute of Oncology, Gliwice Branch, Gliwice - Poland.
Abstract
PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
PURPOSE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
Authors: Christoph Oehler; Nina Roehner; Marcin Sumila; Jürgen Curschmann; Fabrizio Storelli; Daniel Rudolf Zwahlen; Uwe Schneider Journal: Curr Oncol Date: 2022-08-31 Impact factor: 3.109