Forward Planned Fluence-Painted Reduced Fields with Tangential Parent Beams for Total Breast Irradiation
M Hawkins*, S Wentworth, B Sintay, D Wiant, Cone Health Cancer Center, Greensboro, NCSU-E-T-606 Sunday 3:00PM - 6:00PM Room: Exhibit Hall
Purpose: Whole breast radiotherapy is routinely planned with tangential fields and forward planned reduced fields. We compare this technique to a novel method of tangential fields and forward planned sliding window IMRT reduced fields. Planning time and dose homogeneity were compared.
Methods and Materials:
We reviewed the dosimetry for 10 patients planned in Eclipse 10 (Varian Medical Systems, Palo Alto, CA) and in XiO (Elekta AB, Stockholm, Sweden). Plans were initially created in XiO using 6MV tangents. Reduced fields were iteratively created with higher energy (10/18MV) and weighted appropriately until a clinically acceptable plan was reached. One field per tangent was usually required (although more were allowed if necessary). In our novel technique, initial beams were recreated in Eclipse and weighted to produce a symmetric plan. One higher energy (10/15MV) reduced field from each side was created, and weighted 10% of the total dose. An electronic compensator was created (using a penetration depth of 50%) for each reduced field. Their fluences were manually edited to reduce hotspots to produce a clinically acceptable plan.
For dosimetric comparison, the maximum point dose and the volumes of tissue receiving 108%, 105%, and 100% of prescription were compared. A homogeneity estimation was made by comparing ratios of tissue volumes receiving 105%/100%. Finally, planning time for each method was recorded.
The planning time for each technique was similar. Dose homogeneity and global maximum point dose were uniformly improved with the fluence painted technique. Maximum dose was reduced on average by 1.93% using the flunece painted method. The volumes receiving 105% and 108% of the prescribed dose were reduced by an average of 82.1 cc and 6.2 cc, respectively, for the fluence painted method.
Our technique shows improvements to dosimetric measures that may result in better outcomes including less toxicity for our breast patients.