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Intensity-modulated radiotherapy using implanted fiducial markers with daily portal imaging: assessment of prostate organ motion.

Chen J, Lee RJ, Handrahan D, Sause WT

Department of Radiation Oncology, LDS Hospital, Salt Lake City, UT 84143, USA. jergin.chen@hci.utah.edu

PURPOSE: To assess our single institutional experience with daily localization, using fiducials for prostate radiotherapy. METHODS AND MATERIALS: From January 2004 to September 2005, 33 patients were treated with 1,097 intensity-modulated radiation treatments, using three implanted fiducials. Daily portal images were obtained before treatments. Shifts were made for deviations > or =3 mm in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP) dimensions. RESULTS: Of 1,097 treatments, 987 (90%) required shifts. Shifts were made in the LR, SI, and AP dimensions in 51%, 67%, and 58% of treatments, respectively. In the LR dimension, the median distance shifted was 5 mm. Of 739 shifts in the SI dimension, 73% were in the superior direction for a median distance of 6 mm, and 27% were shifted inferiorly for a median distance of 5 mm. The majority of shifts in the AP dimension were in the anterior direction (87%). Median distances shifted in the anterior and posterior directions were 5 mm and 4 mm, respectively. The median percentage of treatments requiring shifts per patient was 93% (range, 57-100%). Median deviations in the LR, SI, and AP dimensions were 3 mm, 4 mm, and 3 mm, respectively. Deviations in the SI and AP dimensions were more often in the superior rather than inferior (60% vs. 29%) and in the anterior rather than posterior (70% vs. 16%) directions. CONCLUSIONS: Interfraction prostate motion is significant. Daily portal imaging with implanted fiducials improves localization of the prostate, and is necessary for the reduction of treatment margins.

Published 4 June 2007 in Int J Radiat Oncol Biol Phys, 68(3): 912-9.
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