(Sunday, 7/29/2018) 3:00 PM - 6:00 PM
Room: Exhibit Hall
Purpose: To investigate whether intensity modulated radiation therapy (IMRT), multiple arc volumetric modulated arc therapy (MA-VMAT), Non-coplanar VMAT (NC-VMAT) and Helical Tomotherapy (HT) can provide comparable dose coverage than standard VMAT (the standard of care in our clinic) while reducing doses to organs at risk (OARs) for post-mastectomy radiotherapy (PMRT).
Methods: 9 patients who received left side mastectomy and treated with standard VMAT were retrospectively studied. Two partial arcs at co-planar plane with 45°collimator angle were used for standard VMAT. IMRT, MA-VMAT, NC-VMAT and HT plans were created for each patient. All plans used a prescribed dose of 50Gy in 25 fractions. Four to five beams were used for IMRT; six coplanar partial arcs that each covered approximately 60°were used for MA-VMAT, and the jaw opening was minimized for each arc; two partial arcs that each covered approximately 220°with 15° and 345°couch angle were used for NC-VMAT. Collimator was rotated for each arc to align with the long axis of planning target volume (PTV) for IMRT, MA-VMAT and NC-VMAT. A field width of 5.02cm, pitch of 0.287 and modulation factor of 3 were used for HT planning.
Results: All techniques produced clinically acceptable PMRT plans and comparable tumor control probability. IMRT has been shown to reduce the dose to contralateral breast, but it could increase the dose to lung and heart. MA-VMAT, NC-VMAT have been shown to provide better PTV coverage and OARs sparing than standard VMAT. HT has been shown to provide better PTV coverage and significantly lower dose to contralateral breast, but it introduced higher dose to lung and heart compare to standard VMAT.
Conclusion: Patients with increased risk of radiogenic cardiovascular disease or secondary cancer in contralateral breast may benefit from NC-VMAT and MA-VMAT.
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