Author: Alyssa Gadsby, William J. Godwin, Jennifer L. Harper, Daniel G. McDonald, Jean L. Peng, Alek K. Rapchak, Sean A Roles, Austin M. Skinner, Stephanie Tan 👨🔬
Affiliation: Medical University of South Carolina 🌍
Purpose: Multi-Criteria Optimization (MCO) theoretically allows for increased dose control during optimization. This study is the first to compare standard optimization (SO) and MCO for accelerated partial breast irradiation (APBI) for (a)right-side, (b)left-side and (c)left-side using deep inspiration breath hold (DIBH).
Methods: Fifteen APBI cases were randomly selected. Cases were previously contoured following the APBI-IMRT-Florence Trial and treated with clinically acceptable five field IMRT plans, developed with SO, to 30Gy in 5 fractions. Cases were then optimized using MCO. Groups (a)and(b) utilized flattened 6MV. Group(c) utilized 6MV FFF. Field arrangements followed clinical trial suggestions and were identical for each SO and MCO comparison. SO, and MCO plans utilized identical constraints for targets and organs at risk (OARs), and included PTV coverage (V100Rx>95%,Dmax<105%Rx, and Dmin>28Gy), ipsilateral uninvolved breast (V15Gy<50%), ipsilateral lung (V10Gy<20%), contralateral lung (V5Gy<10%), contralateral breast (Dmax<1 Gy), and heart (V3Gy<10%). Dosimetric characteristics of SO and MCO plans, as well as plan characteristics such as time of optimization and total monitor units (MU) were compared. Statistical significance (p<0.05) was assessed using the student’s t-test.
Results: MCO demonstrated steeper dose fall-off in adjacent OARs compared to SO. Time to run MCO was less than 2 mins per case with GPU enhanced calculation. MCO provided statistically significant reduction of V15Gy for the ipsilateral uninvolved breast of approximately 4% and a reduction of V10Gy for the ipsilateral lung of approximately 2%. For DIBH plans utilizing FFF , MCO showed statistically significant reduction of heart V3Gy and Dmean. PTV Dmax for MCO plans increased by approximately 1%. MUs for MCO plans increased for flattened beams and FFF by 20% and 30% on average, respectively.
Conclusion: Performing MCO for APBI plans following SO requires minimal time, and provides additional sparing of OARs, including the ipsilateral uninvolved breast, ipsilateral lung, and heart without compromising target coverage.