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Intrafractional prostate motion during external beam radiotherapy monitored by a real-time target localization
Xu Tong1, Xiaoming Chen, Jinsheng Li
1Third-Affiliated Hospital of Qiqihar Medical University. cn_tongxu@163.com.
Journal of Applied Clinical Medical Physics
|June 24, 2015
Summary
Real-time monitoring of prostate motion during radiotherapy revealed significant intrafractional shifts in some patients. Shorter treatment times, like VMAT, reduce motion-related uncertainties for improved prostate cancer radiotherapy.
Area of Science:
- Radiation Oncology
- Medical Physics
- Clinical Urology
Background:
- Intrafractional prostate motion during external beam radiotherapy can impact treatment accuracy.
- Real-time monitoring systems offer potential for quantifying and managing this motion.
Purpose of the Study:
- To investigate the clinical significance of real-time intrafractional prostate motion monitoring.
- To analyze the patterns and extent of prostate shifts during radiotherapy fractions.
Main Methods:
- Utilized a commercial 4D localization system to track intrafractional prostate motion.
- Analyzed 8,660 treatment fractions from 236 patients, focusing on motion exceeding 2-7 mm.
- Examined motion duration, proportion of tracking time, and specific patient subgroups with maximal motion.
Main Results:
- Over 56% of fractions showed prostate shifts >2 mm, with 27% exceeding 3 mm for intact prostates.
- Postprostatectomy patients exhibited higher motion rates (>35% >3 mm).
- Shorter treatment times (VMAT) showed lower intrafractional motion (>3 mm in 4%) compared to longer times (IMRT, 12%).
Conclusions:
- While generally small, intrafractional prostate motion necessitates caution in patients with frequent large shifts.
- Consideration of patient positioning adjustments or larger margins is advised for high-motion patients.
- Advanced, shorter-delivery techniques like VMAT are favorable for reducing treatment uncertainty due to intrafractional motion.
