Minimizing normal tissue low dose bath for left breast Volumetric Modulated Arc Therapy (VMAT) using jaw offset

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Volumetric Modulated Arc Therapy (VMAT) offers improved dose distribution for whole breast radiation therapy.
• A significant concern with VMAT is the low-dose bath effect on critical organs like the heart and ipsilateral lung.

Purpose of the Study:

• To introduce and evaluate a novel VMAT technique, Jaw Offset VMAT (JO-VMAT).
• To assess JO-VMAT's efficacy in reducing leakage and scatter radiation to critical structures during whole breast radiation therapy.

Main Methods:

• Retrospective analysis of 10 left breast cancer patients using deep-inspiration breath hold (DIBH) CT scans.
• Comparison of three treatment plans: 3D field-in-field (3D-FiF), tangential VMAT (tVMAT), and JO-VMAT, created using the Eclipse treatment planning system.
• Dosimetric evaluation using dose-volume histogram (DVH) parameters for planning target volumes (PTVs) and organs at risk (OARs).

Main Results:

• JO-VMAT achieved comparable PTV coverage and homogeneity to other techniques, with improved conformity index.
• Significant reductions in maximum heart dose and low-dose bath parameters (V5Gy, V2Gy) for the heart and ipsilateral lung were observed with JO-VMAT compared to 3D-FiF and tVMAT.
• Minimal V2Gy dose to the contralateral lung and breast was achieved with JO-VMAT.

Conclusions:

• JO-VMAT is a feasible technique for whole breast radiation therapy, offering clinically comparable target coverage and homogeneity.
• JO-VMAT effectively eliminates the low-dose bath effect on critical OARs, including the heart and lungs.
• This technique demonstrates significant dosimetric advantages for left breast cancer patients.