Room: AAPM ePoster Library
Purpose: partial breast irradiation (PBI) has been very well known as adjuvant radiation therapy technique to prevent breast cancer recurrence after breast conserving surgery (BCS). Among the various radiation treatment options available to target early stage breast cancer, we explored the benefits of gantry-static couch-motion optimization (GsCMO) technique for partial breast irradiation therapy.
Methods: GsCMO technique is an arc-type treatment delivery where gantry is kept static while couch moves with an increment of two degrees (both arcs look like butterfly wings). Two tangential arcs (coronal plane) with 6MV beams were utilized to re-plan 20 patients retrospectively for a total dose of 3850cGy in 10 fractions based on NSABP B-30/RTOG 0413 protocol and compared with standard gantry based VMAT planning utilizing partial arc (gVMAT) and partial arc with avoidance sector (gVMATa). Both medial and lateral arcs were simulated at two static (fixed) gantry angles and couch moved in an increment of two degrees. In terms of dosimetric analysis, the volume histogram (DVH) comparison was conducted.
Results: techniques (GsCMO, gVMAT, and gVMATa ) provided an adequate coverage to PTV (D95=100%). GsCMO significantly reduced the ipsilateral lung V30% for right side (mean, 75%) and left side (mean, 65%). Heart V5% reduced by 85% (mean) for right and 75% (mean) for left side. Ipsilateral breast V50% and mean dose were comparable for all techniques but for GsCMO, V100% reduced by 50% (mean) for right and left side. The automated delivery of all techniques was same (under 2 minutes).
Conclusion: GsCMO technique is a novel itself and can be easily implemented for partial breast irradiation treatment planning improving the plan quality and lowering the dose to organs-at-risk in a least toxic way. This isocentric based coronal arc technique is suitable for any size and location of breast lumpectomy cavities.