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Modeling the target dose fall-off in IMRT and VMAT planning techniques for cervical SBRT
A Brito Delgado1, D Cohen1, T Y Eng1
1Department of Radiation Oncology, School of Medicine, Cancer Therapy & Research Center, The University of Texas Health Science Center San Antonio, San Antonio, TX 78229, USA.
Summary
Stereotactic body radiotherapy (SBRT) for cervical cancer shows improved dose fall-off with triple, non-coplanar volumetric modulated arc therapy (VMAT) arcs, especially using 10 MV photons. This VMAT approach enhances organ-at-risk sparing, particularly for smaller tumors.
Area of Science:
- Radiation Oncology
- Medical Physics
Background:
- Stereotactic body radiotherapy (SBRT) is increasingly used for cervical cancer.
- Optimizing dose distribution and fall-off is crucial for treatment efficacy and toxicity reduction.
Purpose of the Study:
- To compare dose distributions and target dose fall-off between intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) for cervical cancer SBRT.
- To evaluate the impact of 6 and 10 MV photon beam energies on these parameters.
Main Methods:
- Fifteen cervical cancer patients underwent treatment planning with IMRT (10 non-coplanar beams) and VMAT (dual or triple non-coplanar arcs) using 6 and 10 MV photons.
- Dose metrics for planning target volume (PTV) and organs at risk (OARs) were evaluated.
- Dose fall-off was modeled using concentric rings around the PTV.
Main Results:
- Triple, non-coplanar VMAT (VMAT_3-arc) with 10 MV photons demonstrated statistically significant steeper dose fall-off compared to IMRT.
- VMAT_3-arc improved sparing of the bladder and bowel.
- Dose fall-off was faster for smaller targets, indicating target size dependency for OAR sparing.
Conclusions:
- Triple, non-coplanar VMAT with 10 MV photons provides superior dose fall-off for cervical SBRT.
- This technique enhances OAR sparing, with benefits more pronounced in smaller tumors.
- VMAT_3-arc represents an effective strategy for optimizing cervical cancer SBRT.
