Immobilization-assisted abdominal deep inspiration breath-hold in post-mastectomy radiotherapy of left-sided breast cancer with internal mammary chain coverage

Meiqin Chen; Shoumei Zang; Hao Yu; Lihua Ning; Huijie Huang; Luyi Bu; Jia Ge; Mengyou Xu; Qiuying Tang; Feng Zhao; Guorong Yao; Senxiang Yan

doi:10.21037/qims-20-831

Immobilization-assisted abdominal deep inspiration breath-hold in post-mastectomy radiotherapy of left-sided breast cancer with internal mammary chain coverage

Quant Imaging Med Surg. 2021 Jul;11(7):3314-3326. doi: 10.21037/qims-20-831.

Authors

Meiqin Chen¹, Shoumei Zang², Hao Yu², Lihua Ning², Huijie Huang³, Luyi Bu², Jia Ge², Mengyou Xu², Qiuying Tang², Feng Zhao², Guorong Yao², Senxiang Yan²

Affiliations

¹ Department of Radiation Oncology, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou and Department of Radiation Oncology, Affiliated Jinhua Hospital, College of Medicine, Zhejiang University, Jinhua, China.
² Department of Radiation Oncology, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
³ Department of Radiation Oncology, YiLi Friendship Hospital, Yili, China.

Abstract

Background: Whether to prophylactically irradiate the ipsilateral internal mammary chain (IMC) in post-mastectomy radiotherapy (PMRT) remains controversial because of equivocal clinical benefits against the added toxicities. Our previous study revealed that the cardiac dose was decreased during left-sided breast radiotherapy with abdominal deep inspiration breath-hold (aDIBH) as compared with free-breathing (FB) and thoracic deep inspiration breath-hold (tDIBH). Here we present the dosimetric advantage of aDIBH for patients undergoing PMRT with IMC coverage.

Methods: We prospectively analyzed 19 patients with left-sided breast cancer who underwent PMRT. Patients underwent computed tomography (CT) simulation under both free-breathing (FB) and aDIBH. The heart, left anterior descending coronary artery (LAD), lungs, and the contralateral breast was defined as organs at risk (OARs). Three-dimensional conformal radiation therapy (3D-CRT), inverse planning intensity-modulated radiation therapy (IMRT), and volumetric modulated arc therapy (VMAT) were used to calculate the doses received by both the planning target volume (PTV) and OARs, which were compared using the Wilcoxon signed-rank test.

Results: Compared with FB, the D_mean of the heart and LAD were respectively reduced by 3.5 Gy (P<0.003) and 8.9 Gy (P<0.001) in 3D-CRT, 2.6 Gy (P<0.001), and 7.8 Gy (P=0.001) in IMRT, 1.5 Gy (P<0.001) and 4.5 Gy (P=0.001) in VMAT plans under aDIBH. Among all these plans, the D_mean of the heart was lowest in aDIBH _IMRT and 1.3 Gy lower than in aDIBH _VMAT (P=0.002). aDIBH _IMRT also resulted in a significantly reduced dose to the ipsilateral lung than plans under FB (P<0.05). D_mean and V5 to the contralateral lung and breast were higher in VMAT plans (P<0.05).

Conclusions: Using an immobilization-assisted aDIBH technique, radiation doses to the heart can be kept at reasonably low levels even if IMC is included in the clinical target volume (CTV). Among 3D-CRT, IMRT, and VMAT plans, IMRT plus aDIBH results in the best heart-sparing effect. We recommend that the aDIBH technique be routinely applied in suitable patients if the IMC is irradiated.

Keywords: Breast cancer; abdominal deep inspiration breath-hold (aDIBH); internal mammary chain (IMC); post-mastectomy radiotherapy (PMRT).