Journal of International Oncology››2024,Vol. 51››Issue (7): 441-447.doi:10.3760/cma.j.cn371439-20231204-00072

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Dosimetric study of intensity-modulated radiotherapy and volumetric intensity modulated arc therapy based on the inner edge tangent field for radiotherapy after breast-conserving surgery of left-sided breast cancer

Zhao Biao1, Pu Qin1, Yuan Meifang1, Ma Lishuang1, Li Han1, Yang Yi1, Sun Chaoxi2()

  1. 1Department of Radiotherapy, Peking University Cancer Hospital Yunnan, Yunnan Cancer Hospital, Third Affiliated Hospital of Kunming Medical University, Kunming 650118, China
    2Department of Critical Care Medicine, Peking University Cancer Hospital Yunnan, Yunnan Cancer Hospital, Third Affiliated Hospital of Kunming Medical University, Kunming 650118, China
  • Received:2023-12-04Revised:2024-04-02Online:2024-07-08Published:2024-08-14
  • Contact:Sun Chaoxi, Email:sunchaoxi1201@126.com
  • Supported by:
    National Natural Science Foundation of China(81760423)

Abstract:

ObjectiveTo explore the dosimetry difference between intensity-modulated radiotherapy (IMRT) and volumetric intensity modulated arc therapy (VMAT) based on the inner edge tangent field (IETF) after left-sided breast conserving surgery.MethodsThe localization CT and target organ at risk (OAR) data of 35 patients with left-sided breast cancer treated with IMRT after breast conserving surgery at Department of Radiotherapy in Yunnan Cancer Hospital from June 2022 to June 2023 were selected. The IETF-IMRT and the IETF-VMAT plans were designed for the same patient based on IETF, the dosimetry differences of target areas and OAR, as well as the planned execution time were compared between the two groups.ResultsDosimetry of target areas: for IETF-IMRT and IETF-VMAT, the D98%of the planning target volume were (47.92±0.51) and (48.21±0.33) Gy, respectively, while the D50%were (52.04±0.22) and (51.91±0.26) Gy, respectively, and the D2%were (53.93±0.36) and (53.62±0.41) Gy, respectively, the conformity index were 0.84±0.03 and 0.87±0.02, respectively, while the homogeneity index were 0.12±0.01 and 0.10±0.01, respectively, with statistically significant differences (t=-3.87,P<0.001;t=3.53,P=0.001;t=5.30,P<0.001;t=-13.60,P<0.001;t=6.24,P<0.001). Dosimetry of OAR: for IETF-IMRT and IETF-VMAT, the left lung V5were (31.91±6.28)% and (33.99±6.31)%, respectively, and the V20were (11.71±2.06)% and (9.73±2.12)%, respectively, with statistically significant differences (t=-4.18,P<0.001;t=12.40,P<0.001). The right lung V5were (0.11±0.08)% and (7.13±3.12)%, respectively, and the Dmeanwere (1.05±0.12) and (2.71±0.27) Gy, respectively, with statistically significant differences (t=-33.62,P<0.001;t=-13.30,P<0.001). The spinal cord D2%were (1.08±0.11) and (4.83±1.40) Gy, respectively, with a statistically significant difference (t=-15.99,P<0.001). The left lung Dmeanwere (7.45±1.08) and (7.37±1.03) Gy, the heart Dmeanwere (4.21±0.96) and (4.41±0.48) Gy, and the right-sided breast Dmeanwere (3.74±1.52) and (3.48±1.11) Gy, respectively, with no statistically significant difference (t=1.16,P=0.253;t=-1.76,P=0.088;t=1.41,P=0.169). Planned execution time: the execution time of IETF-IMRT and IETF-VMAT was (10.73±1.21) and (2.18±0.17) min, respectively, with a statistically significant difference (t=44.71,P<0.001).ConclusionBoth IETF-IMRT and IETF-VMAT can meet clinical requirements, however the two techniques have their own characteristics. IETF-VMAT has better conformity and homogeneity of target region. The planned OAR dosimetry in both plans are significantly lower than the dose limit of postoperative radiotherapy for breast cancer, among which the left lung V5, the right lung V5, Dmeanand spinal cord D2%of IETF-IMRT are slightly lower, the left lung V20of IETF-VMAT is slightly lower. IETF-VMAT significantly reduces the planned execution time compared with IETF-IMRT, thus can greatly reduce the dose deviation caused by patient position change, and significantly improve patients experience and comfort of radiotherapy. Taken together, IETF-VMAT has advantages over IETF-IMRT in radiotherapy after breast conserving surgery of left-sided breast cancer.

Key words:Breast neoplasms,Inner edge tangent field,Breast conserving surgery for breast cancer,Intensity-modulated radiotherapy,Volumetric intensity modulated arc therapy,Dosimetry