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Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
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Pelvic lymph node motion during cone-beam computed tomography guided stereotactic radiotherapy.
J Janssen1, F H E Staal1, J A Langendijk1
1Department of Radiation Oncology, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
Clinical and Translational Radiation Oncology
|May 27, 2024
Summary
Pelvic lymph node motion during stereotactic body radiotherapy (SBRT) is generally within 5 mm. This study suggests a potential to reduce planning target volume (PTV) margins for pelvic lymph node SBRT.
Area of Science:
- Radiation Oncology
- Medical Physics
- Oncology
Background:
- Stereotactic body radiotherapy (SBRT) is increasingly used for pelvic lymph node recurrence.
- Knowledge on pelvic lymph node motion during CBCT-guided SBRT is limited.
- Institutional margins for pelvic lymph node SBRT vary.
Purpose of the Study:
- To evaluate pelvic lymph node motion during CBCT-guided SBRT.
- To assess the adequacy of current 3-mm and 5-mm planning target volume (PTV) margins.
Main Methods:
- Analysis of 45 pelvic lymph node metastases.
- GTV centroid coordinates derived from planning CT and CBCT scans for motion analysis.
- Assessment of inter- and intrafraction motion, influence of treatment time and location, and PTV margin inclusiveness.
Main Results:
- Interfraction motion was within 5 mm in 96-97% of fractions; intrafraction motion was within 3 mm in 97-100% of fractions.
- Para-rectal lesions showed significantly greater motion.
- Mean lesion inclusiveness was 99% for 5-mm PTV margin and 96% for 3-mm PTV margin.
Conclusions:
- Pelvic lymph node motion during CBCT-guided SBRT is within the 5-mm PTV margin.
- There is an opportunity to reduce PTV margins for pelvic lymph node SBRT.
