Volumetric arc therapy: A viable option for right-sided breast with comprehensive regional nodal irradiation in conjunction with deep inspiration breath hold.

Abstract

Deep inspiration breath hold (DIBH) is an innovative technique routinely used for left-sided breast radiotherapy to significantly reduce harmful dose to the heart and ipsilateral lung. Currently, there is scant literature exploring DIBH for right-sided whole breast and regional nodal irradiation (WB & RNI). The purpose of this study is to examine if DIBH produces a clinically significant reduction in organ at risk (OAR) dose for right-sided WB + RNI, whilst comparatively analysing the use of volumetric arc therapy (VMAT) versus tangential inverse modulated radiotherapy (t-IMRT). Ten patients, previously treated for left sided breast cancer (with a FB and DIBH CT scan), were selected from our database to be retrospectively replanned to the right breast and nodal regions. Planning target volumes (PTV) were marked to include the whole right breast and regional nodes, encompassing the supraclavicular fossa (SCF) and internal mammary nodes (IMN). PTVs and OARs were contoured on the Pinnacle workstation according to the Radiation Therapy Oncology Group (RTOG) guidelines. VMAT and t-IMRT plans were generated to a prescribed dose of 50 Gy in 25 fractions on both the DIBH and FB data sets for dosimetric analysis. Coverage of the right breast (mean, D95%) and SCF (D95%) were significantly improved with VMAT in comparison to t-IMRT, with no statistically significant variation on the IMN PTV (D95%). The use of DIBH did not impact PTV coverage compared with FB. VMAT reduced dose to the ipsilateral lung (mean, V20Gy), combined lungs (mean, V20Gy) and liver (D2cc); conversely dose to the heart (mean), left lung (mean, V5Gy) and contralateral breast (mean) were increased. For both techniques DIBH significantly improved dose to OARs including the ipsilateral lung (mean, V20Gy, V5Gy), total lung (mean, V20Gy), heart (mean, V25Gy) and liver (D2cc) when compared to FB. DIBH could be considered for patients treated with right-sided WB and RNI due to a significant decrease in heart, ipsilateral lung, total lung and liver doses. VMAT significantly improves PTV coverage over t-IMRT whilst reducing dose to the ipsilateral lung and liver, albeit to the detriment of the left lung, contralateral breast and heart. The increase in heart dose can be mitigated by the use of DIBH. We recommend if VMAT is utilised for superior target volume coverage, DIBH should also be implemented to reduce OAR toxicity.