title: Combined photon-electron beams in the treatment of the supraclavicular lymph nodes in breast cancer: A novel technique that achieves adequate coverage while reducing lung dose.
abstract: Radiation pneumonitis is a well-documented side effect of radiation therapy for breast cancer. The purpose of this study was to compare combined photon-electron, photon-only, and electron-only plans in the radiation treatment of the supraclavicular lymph nodes. In total, 13 patients requiring chest wall and supraclavicular nodal irradiation were planned retrospectively using combined photon-electron, photon-only, and electron-only supraclavicular beams. A dose of 50Gy over 25 fractions was prescribed. Chest wall irradiation parameters were fixed for all plans. The goal of this planning effort was to cover 95% of the supraclavicular clinical target volume (CTV) with 95% of the prescribed dose and to minimize the volume receiving ≥ 105% of the dose. Comparative end points were supraclavicular CTV coverage (volume covered by the 95% isodose line), hotspot volume, maximum radiation dose, contralateral breast dose, mean total lung dose, total lung volume percentage receiving at least 20 Gy (V(20 Gy)), heart volume percentage receiving at least 25 Gy (V(25 Gy)). Electron and photon energies ranged from 8 to 18 MeV and 4 to 6 MV, respectively. The ratio of photon-to-electron fractions in combined beams ranged from 5:20 to 15:10. Supraclavicular nodal coverage was highest in photon-only (mean = 96.2 ± 3.5%) followed closely by combined photon-electron (mean = 94.2 ± 2.5%) and lowest in electron-only plans (mean = 81.7 ± 14.8%, p < 0.001). The volume of tissue receiving ≥ 105% of the prescription dose was higher in the electron-only (mean = 69.7 ± 56.1 cm(3)) as opposed to combined photon-electron (mean = 50.8 ± 40.9 cm(3)) and photon-only beams (mean = 32.2 ± 28.1 cm(3), p = 0.114). Heart V(25 Gy) was not statistically different among the plans (p = 0.999). Total lung V(20 Gy) was lowest in electron-only (mean = 10.9 ± 2.3%) followed by combined photon-electron (mean = 13.8 ± 2.3%) and highest in photon-only plans (mean = 16.2 ± 3%, p < 0.001). As expected, photon-only plans demonstrated the highest target coverage and total lung V(20 Gy). The superiority of electron-only beams, in terms of decreasing lung dose, is set back by the dosimetric hotspots associated with such plans. Combined photon-electron treatment is a feasible technique for supraclavicular nodal irradiation and results in adequate target coverage, acceptable dosimetric hotspot volume, and slightly reduced lung dose.
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan. Electronic address: ahmed.salem@doctors.org.uk.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Salem
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Issa
authors.initials: I
authors.lastname: Mohamad
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Abdulmajeed
authors.initials: A
authors.lastname: Dayyat
authors.affiliation: Section of Medical Physics, Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Haitham
authors.initials: H
authors.lastname: Kanaa'n
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Nasim
authors.initials: N
authors.lastname: Sarhan
authors.affiliation: Section of Medical Physics, Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Ibrahim
authors.initials: I
authors.lastname: Roujob
authors.affiliation: Department of Obstetrics and Gynecology, Hashemite University, Zarqa, Jordan.
authors.forename: Abdel-Fattah
authors.initials: AF
authors.lastname: Salem
authors.affiliation: Section of Medical Physics, Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Shatha
authors.initials: S
authors.lastname: Afifi
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Imad
authors.initials: I
authors.lastname: Jaradat
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Rasmi
authors.initials: R
authors.lastname: Mubiden
authors.affiliation: Department of Radiation Oncology, King Hussein Cancer Center, Amman, Jordan.
authors.forename: Abdelateif
authors.initials: A
authors.lastname: Almousa
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D004583:Electrons / Q000627:therapeutic use; D006801:Humans; D008198:Lymph Nodes / Q000528:radiation effects*; D008207:Lymphatic Metastasis / Q000532:radiotherapy*; D059351:Organ Sparing Treatments / Q000379:methods*; D058958:Organs at Risk / Q000528:radiation effects; D017785:Photons / Q000627:therapeutic use; D011835:Radiation Protection / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D011882:Radiotherapy, High-Energy / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome
keywords: Breast cancer; Electron; Lung dose; Photon; Supraclavicular