Is there a preferred IMRT technique for left-breast irradiation?

Not all clinics have breath‐hold radiotherapy available for left‐breast irradiation. However intensity‐modulated radiotherapy (IMRT) has also been advocated as a means of lowering heart doses. There is currently no large‐scale, long‐term follow‐up data after breast IMRT and, since dose distributions may differ from classic tangent‐based radiotherapy, caution is needed to avoid unexpected worsening of the late toxicity profile. We compared four IMRT techniques for free‐breathing left‐breast irradiation. Consistent with the aforementioned concerns, our goal in planning was to prioritize organ at risk (OAR) sparing in a way that mimicked tangent‐based radiotherapy. Ten simultaneous integrated boost treatment plans (PTVelective=15×2.67 Gy;PTVboost=15×3.35 Gy) were created using 1) hybrid‐IMRT (H‐IMRT), 2) full IMRT (F‐IMRT), and 3) volumetric‐modulated arc therapy with two partial arcs (2ARC) and 4) six partial arcs (6ARC). Reduction in OAR mean and low dose was prioritized. End‐points included OAR sparing (e.g., heart, left anterior descending artery [LAD+3 mm], lungs, and contralateral breast) and PTV coverage/dose homogeneity. Under these conditions we found the following: 1) H‐IMRT provided the best mean and low dose OAR sparing, PTVelective coverage (mean V95%=98%),PTVboost coverage (V95%=98%), and PTV homogeneity. However, it delivered most intermediate–high dose to the heart, LAD+3 mm and ipsilateral lung; 2) 6ARC had the best intermediate–high dose sparing, followed by F‐IMRT, but this was at the expense of more dose in the contralateral lung and breast and worse PTV coverage (PTVelective mean V95%=96%/97% and PTVboost mean V95%=91%/96% for 6ARC/F‐IMRT). When trying to spare mean and low dose to OARs, the preferred IMRT technique for left‐breast irradiation without breath‐hold was H‐IMRT. This is currently the standard solution in our institution for left‐breast radiotherapy under free‐breathing and breath‐hold conditions. PACS numbers: 87.53kn, 87.53Jw, 87.55.D‐, 87.55.de, 87.55.dk