Abstract
BackgroundDespite dosimetric benefits of volumetric modulated arc therapy (VMAT) in breast cancer patients with implant reconstruction receiving regional nodal irradiation (RNI), low dose to the thoracic structures remains a concern. Our goal was to report dosimetric effects of adding deep inspiration breath hold (DIBH) to VMAT in left-sided breast cancer patients with tissue expander (TE)/permanent implant (PI) reconstruction receiving RNI.MethodsTen consecutive breast cancer patients with unilateral or bilateral TE/PI reconstruction who were treated with a combination of VMAT and DIBH to the left reconstructed chest wall and regional nodes were prospectively identified. Free breathing (FB) and DIBH CT scans were acquired for each patient. VMAT plans for the same arc geometry were compared for FB versus DIBH. Prescription dose was 50 Gy in 25 fractions. Dosimetric differences were tested for statistical significance.ResultsFor comparable coverage and target dose homogeneity, the mean dose to the heart reduced on average by 2.9 Gy (8.2 to 5.3 Gy), with the addition of DIBH (p < 0.05). The maximum dose to the left anterior descending (LAD) artery was reduced by 9.9 Gy (p < 0.05), which related closely to the reduction in the maximum heart dose (9.4 Gy). V05 Gy to the heart, ipsilateral lung, contralateral lung and total lung (p < 0.05) decreased on average by 29.6%, 5.8%, 15.4% and 10.8% respectively. No significant differences were seen in the ipsilateral lung V20 Gy or mean dose as well as in the mean contralateral breast/implant dose. However, V04 Gy and V03 Gy of the contralateral breast/implant were respectively reduced by 13.2% and 18.3% using DIBH (p < 0.05).ConclusionCombination of VMAT and DIBH showed significant dosimetric gains for low dose to the heart, lungs and contralateral breast/implant. Not surprisingly, the mean and maximum dose to the heart and to the LAD were also reduced. DIBH should be considered with the use of VMAT in breast cancer patients with implant reconstructions receiving RNI.
Highlights
Despite dosimetric benefits of volumetric modulated arc therapy (VMAT) in breast cancer patients with implant reconstruction receiving regional nodal irradiation (RNI), low dose to the thoracic structures remains a concern
The unique advantage of VMAT over multibeam Intensity modulated radiation therapy (IMRT) is that it requires fewer monitor units (MU) and shorter delivery time, enabling its combination with deep-inspiratory breath hold (DIBH) techniques that may further minimize dose to the heart
Patient selection As part of an IRB-approved protocol at Memorial SloanKettering Cancer Center assessing the efficacy of VMAT for the treatment of breast cancer patients with reconstruction(s), we prospectively identified 10 consecutive breast cancer patients who were treated with a combination of VMAT and deep inspiration breath hold (DIBH) to the left reconstructed breast/ chest wall and regional nodes (RN)
Summary
Despite dosimetric benefits of volumetric modulated arc therapy (VMAT) in breast cancer patients with implant reconstruction receiving regional nodal irradiation (RNI), low dose to the thoracic structures remains a concern. Owing to the anatomic challenges of targeting the internal mammary nodes in women with prosthetic reconstructions, conventional techniques in the setting of immediate reconstruction can significantly increase the dose to the heart and lungs, or fail to obtain adequate coverage of target volumes, compared to non-reconstructed patients receiving RT [5, 6]. Treatment planning techniques such as VMAT and multibeam IMRT have been exploited over the past decade to improve cardiopulmonary sparing for patients with immediate breast reconstruction.
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