Real-Time Study of Prostate Intrafraction Motion During External Beam Radiotherapy With Daily Endorectal Balloon
- Department of Radiation Oncology, Hospital of University of Pennsylvania, Philadelphia, PA (United States)
Purpose: To prospectively investigate intrafraction prostate motion during radiofrequency-guided prostate radiotherapy with implanted electromagnetic transponders when daily endorectal balloon (ERB) is used. Methods and Materials: Intrafraction prostate motion from 24 patients in 787 treatment sessions was evaluated based on three-dimensional (3D), lateral, cranial-caudal (CC), and anterior-posterior (AP) displacements. The mean percentage of time with 3D, lateral, CC, and AP prostate displacements >2, 3, 4, 5, 6, 7, 8, 9, and 10 mm in 1 minute intervals was calculated for up to 6 minutes of treatment time. Correlation between the mean percentage time with 3D prostate displacement >3 mm vs. treatment week was investigated. Results: The percentage of time with 3D prostate movement >2, 3, and 4 mm increased with elapsed treatment time (p < 0.05). Prostate movement >5 mm was independent of elapsed treatment time (p = 0.11). The overall mean time with prostate excursions >3 mm was 5%. Directional analysis showed negligible lateral prostate motion; AP and CC motion were comparable. The fraction of time with 3D prostate movement >3 mm did not depend on treatment week of (p > 0.05) over a 4-minute mean treatment time. Conclusions: Daily endorectal balloon consistently stabilizes the prostate, preventing clinically significant displacement (>5 mm). A 3-mm internal margin may sufficiently account for 95% of intrafraction prostate movement for up to 6 minutes of treatment time. Directional analysis suggests that the lateral internal margin could be further reduced to 2 mm.
- OSTI ID:
- 22054474
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 81, Issue 5; Other Information: Copyright (c) 2011 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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