title: Evaluation of bolus electron conformal therapy compared with conventional techniques for the treatment of left chest wall postmastectomy in patients with breast cancer.
abstract: Postmastectomy radiation (PMRT) lowers local-regional recurrence risk and improves survival in selected patients with breast cancer. The chest wall and lower axilla are technically challenging areas to treat with homogenous doses and normal tissue sparing. This study compares several techniques for PMRT to provide data to guide selection of optimal treatment techniques. Twenty-five consecutive left-sided patients treated postmastectomy were contoured using Radiation Therapy Oncology Group (RTOG) atlas guidelines then planned using 4 different PMRT techniques: opposed tangents with wedges (3-dimensional [3D] wedges), opposed tangents with field-in-field (FiF) modulation, 8-field intensity modulation radiotherapy (IMRT), and custom bolus electron conformal therapy (BolusECT, .decimal, Inc., Sanford, FL). Required planning target volume (PTV) coverage was held constant, and then dose homogeneity and normal tissue dose parameters were compared among the 4 techniques. BolusECT achieved clincally acceptable PTV coverage for 22 out of 25 cases. Compared with either tangential technique, IMRT and BolusECT provided the lowest heart V25 doses (3.3% ± 0.9% and 6.6% ± 3.2%, respectively with p < 0.0001). FiF had the lowest mean total lung dose (7.3 ± 1.1Gy, with p = 0.0013), IMRT had the lowest total lung V20 (10.3% ± 1.6%, p < 0.0001), and BolusECT had the lowest mean heart dose (7.3 ± 2.0Gy, p = 0.0002). IMRT provided the optimal dose homogeneity and normal tissue sparing compared with all other techniques for the cases in which BolusECT could not achieve acceptable PTV coverage. IMRT generally exposes contralateral breast and lung to slightly higher doses. Optimal PMRT technique depends upon patient anatomy. Patients whose maximal target volume depth is about 5.7cm or less can be treated with BolusECT-assisted 12 or 15MeV electron beams. At these energies, BolusECT has comparable dose-volume statistics as IMRT and lower heart V25 than opposed tangential beams. Patients with larger depths are best treated with IMRT, which provides significant advantages in both dose homogeneity and normal tissue sparing compared with all other techniques.
authors.affiliation: Department of Radiation Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL. Electronic address: Daniel.Opp@moffitt.org.
authors.forename: Dan
authors.initials: D
authors.lastname: Opp
authors.forename: Kenneth
authors.initials: K
authors.lastname: Forster
authors.forename: Weiqi
authors.initials: W
authors.lastname: Li
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Zhang
authors.forename: Eleanor E
authors.initials: EE
authors.lastname: Harris
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D008408:Mastectomy; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D050397:Radiotherapy, Intensity-Modulated
keywords: Electron beam irradiation; Intensity-modulated radiation therapy; Postmastectomy radiation therapy