Intra-fraction motion during extreme hypofractionated radiotherapy of the prostate using pre- and post-treatment imaging - Abstract

AIMS: To determine intra-fraction displacement of the prostate during extreme hypofractionated radiotherapy using pre- and post-treatment orthogonal images with three implanted gold seed fiducial markers.

MATERIALS AND METHODS: In total, 265 image pairs were obtained from 53 patients who underwent extreme hypofractionated radiotherapy to a dose of 35 Gy in five fractions on standard linear accelerators. Position verification was obtained with orthogonal X-rays before and after treatment and were used to determine intra-fraction prostate displacement.

RESULTS: The mean intra-fraction prostate displacements were -0.03 ± 0.61 mm (one standard deviation), 0.21 ± 1.50 mm and -0.86 ± 1.73 mm in the left-right, superior-inferior and anterior-posterior directions, respectively. The mean intra-fraction displacement during the first two fractions was moderately correlated with the displacement in the remaining three fractions, with correlation coefficients of 0.63 (95% confidence interval 0.43-0.77) and 0.47 (95% confidence interval 0.22-0.65) in the superior-inferior and anterior-posterior directions, respectively. There was no significant correlation in the left-right direction with a coefficient of -0.04 (95% confidence interval -0.31-0.23).

CONCLUSIONS: The mean intra-fraction prostate displacement during a course of extreme hypofractionated radiotherapy is small. A strategy using the first two fractions to predict future displacements >5 mm warrants further validation.

Written by:
Quon H, Loblaw DA, Cheung PC, Holden L, Tang C, Pang G, Morton G, Mamedov A, Deabreu A.   Are you the author?
Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada; Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, ON, Canada.

Reference: Clin Oncol (R Coll Radiol). 2012 Jan 6. Epub ahead of print.
doi: 10.1016/j.clon.2011.12.001

PubMed Abstract
PMID: 22226683 Prostate Cancer Section