Dosimetric Comparison of Postmastectomy Radiotherapy Plans for Synchronous Bilateral Breast Cancer, Including Regional Lymph Node Irradiation

Xiuxiu Wu; Jianghua Huang; Xiao Lin; Xingxing Zhang; Huangping Lu; Wei Sun; Song Duan; Juntian Shi; Xiaobo Huang

doi:10.1177/15330338231214449

Dosimetric Comparison of Postmastectomy Radiotherapy Plans for Synchronous Bilateral Breast Cancer, Including Regional Lymph Node Irradiation

Technol Cancer Res Treat. 2023 Jan-Dec:22:15330338231214449. doi: 10.1177/15330338231214449.

Authors

Xiuxiu Wu^{1

2}, Jianghua Huang^{1

2}, Xiao Lin^{1

3}, Xingxing Zhang^{1

2}, Huangping Lu^{1

2}, Wei Sun^{1

2}, Song Duan^{1

2}, Juntian Shi^{1

2}, Xiaobo Huang^{1

3}

Affiliations

¹ Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Medical Research Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
² Department of Radiation Oncology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.
³ Department of Breast Tumor Center, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, China.

Abstract

Background: To investigate the optimal radiotherapy plans for synchronous bilateral breast cancer (SBBC) patients receiving postmastectomy radiotherapy (PMRT), including regional lymph node irradiation (RNI).

Methods: For 10 SBBC patients who underwent bilateral mastectomy and received bilateral PMRT with RNI, 3 integrally optimized plans with a single isocenter were designed for each patient in this retrospective study: intensity-modulated radiation therapy (IMRT) with 9 fixed beams (9F-IMRT), volumetric-modulated arc therapy (VMAT) with 2 pairs of half arcs (2F-VMAT), VMAT with 2 pairs of outer tangential arcs and 1 pair of 200-degree arcs (3F-VMAT). The paired t-test (in the case of normal variables) and Friedman's test (in the case of nonnormal variables) were applied to compare the planning target volumes (PTVs) and organs at risk (OARs) values of the 3 techniques.

Results: The 3 techniques provided adequate target dose coverage and comparable results for PTVs. For OARs, 3F-VMAT yielded the lowest mean or median values of the left lung (15.02 ± 1.57 Gy) and right lung (14.91 ± 1.14 Gy), heart (6.19 (1.96) Gy), coronary artery (15.96 ± 5.76 Gy) and liver (8.10 ± 2.70 Gy) which were significantly different from those of 9F-IMRT and 2F-VMAT. The percentages of volume at various doses (V₅, V₁₀, V₂₀, and V₃₀) of 3F-VMAT plans were also lower than or comparable with those of 9F-IMRT and 2F-VMAT. The monitor units (MUs) of 3F-VMAT were 31% higher than those of 9F-IMRT and comparable with those of 2F-VMAT; however, there were time savings and halved beam-on times (BOTs) compared to 9F-IMRT.

Conclusions: The 3F-VMAT plan yielded comparable target coverage compared with 9F-IMRT and 2F-VMAT, was superior in dose sparing of normal tissues and enabled shorter BOTs, improving treatment efficiency. In our research, 3F-VMAT was the optimal radiotherapy technique for SBBC patients receiving PMRT including RNI.

Keywords: dosimetric comparison; intensity-modulated radiation therapy; postmastectomy radiotherapy; regional lymph node; synchronous bilateral breast cancer; volumetric-modulated arc therapy.

MeSH terms

Breast Neoplasms* / etiology
Breast Neoplasms* / radiotherapy
Breast Neoplasms* / surgery
Female
Humans
Lymph Nodes
Mastectomy
Organs at Risk / radiation effects
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods
Radiotherapy, Intensity-Modulated* / methods
Retrospective Studies