ABSTRACT
BACKGROUND AND PURPOSE: TomoDirect (TD) can only operate in free-breathing. The purpose of this study is to compare TD with breath-hold 3D conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) techniques for left breast treatments, and to determine if the lack of respiratory gating is a handicap for cardiac sparing. MATERIALS AND METHODS: 15 patients treated for left breast had two computed tomography simulation, in free breathing (FB) and in deep-inspiration breath-hold (DIBH). Four treatments were planned: TD-FB, 3DCRT-FB, 3DCRT-DIBH and IMRT-DIBH. Dose to PTV, heart, lungs, right breast and patient were compared. RESULTS: A slightly lower cardiac mean dose is found for 3DCRT-DIBH than for TD-FB group (1.99Gy Vs 2.89Gy, p=0.0462), while no statistical difference is found for heart V20. TD-FB plans show the best PTV dose homogeneity (0.053, p<0.001) and the lowest left lung mean dose (5.16Gy, p<0.001). No major differences are found for the other organs. CONCLUSIONS: TomoDirect and breath-hold 3DCRT are complementary techniques for left breast treatments: for a minority of patients, respiratory gating is mandatory to lower cardiac dose; for the remaining majority of patients, TomoDirect achieves better PTV homogeneity and reduced left lung dose, with cardiac dose equivalent to 3DCRT-DIBH.
