A volumetric Modulated Arc Therapy (VMAT) combined with deep inspiration breath hold (DIBH) technique for adjuvant irradiation for left sided breast cancer
Background: The deep inspiration breath hold technique (DIBH) is widely used for left-sided breast radiotherapy (RT), in order to reduce the dose to the heart and the risk of cardiotoxicity. The volumetric arc therapy (VMAT) technique increases the dose conformity to the planning target volume (PTV). We hereby describe the procedure of combining VMAT and DIBH without a dedicated equipment, and report a dosimetric study related on our implemented technique. Methods: The DIBH technique is based on voluntary breath hold of the patient which is controlled by a laser on tattoo marks. Patients were selected depending their ability to breath hold for 25s, and VMAT plans were optimized with an arrangement of 4 arcs with a maximum delivery time of 20s each. A retrospective dosimetric study was undertaken on 30 patients treated with this technique: 10 received local (whole breast) RT (L-RT) with a simultaneous integrated boost (SIB), 10 a locoregional (LR)RT of the chestwall, 10 a LR RT of the whole breast with SIB. For these patients, their DIBH-VMAT treatment plans were compared to free breathing (FB) VMAT plans, and dose characteristics of PTV and organs at risk (OAR) were evaluated. Results: The PTV coverage was identical among plans under DIBH or FB. The mean heart dose was reduced from 2.8+/-0.9Gy in FB to 1.8+/-0.6Gy in DIBH for local RT, and reduced from 3.4+/-1.3Gy in FB to 2.2+/-0.5Gy in DIBH for LR-RT. The ipsilateral mean lung dose was reduced by a factor of 12% for LR-RT, but remained unchanged for L-RT with DIBH-VMAT compared to FB treatment. No significant differences were observed in the mean dose of contra-lateral organs with either DIBH or FB VMAT techniques. Conclusion: The VMAT-DIBH technique performed without a dedicated breath hold equipment, provided important dose reductions at the heart, while preserving the ipsilateral lung and contralateral normal tissues.