title: Volumetric-modulated arc therapy for left-sided breast cancer and all regional nodes improves target volumes coverage and reduces treatment time and doses to the heart and left coronary artery, compared with a field-in-field technique.
abstract: We compared two intensity-modulated radiotherapy techniques for left-sided breast treatment, involving lymph node irradiation including the internal mammary chain. Inverse planned arc-therapy (VMAT) was compared with a forward-planned multi-segment technique with a mono-isocenter (MONOISO). Ten files were planned per technique, delivering a 50-Gy dose to the breast and 46.95 Gy to nodes, within 25 fractions. Comparative endpoints were planning target volume (PTV) coverage, dose to surrounding structures, and treatment delivery time. PTV coverage, homogeneity and conformality were better for two arc VMAT plans; V95%(PTV-T) was 96% for VMAT vs 89.2% for MONOISO. Homogeneity index (HI)(PTV-T) was 0.1 and HI(PTV-N) was 0.1 for VMAT vs 0.6 and 0.5 for MONOISO. Treatment delivery time was reduced by a factor of two using VMAT relative to MONOISO (84 s vs 180 s). High doses to organs at risk were reduced (V30(left lung) = 14% using VMAT vs 24.4% with MONOISO; dose to 2% of the volume (D2%)(heart) = 26.1 Gy vs 32 Gy), especially to the left coronary artery (LCA) (D2%(LCA) = 34.4 Gy vs 40.3 Gy). However, VMAT delivered low doses to a larger volume, including contralateral organs (mean dose [Dmean](right lung) = 4 Gy and Dmean(right breast) = 3.2 Gy). These were better protected using MONOISO plans (Dmean(right lung) = 0.8 Gy and Dmean(right breast) = 0.4 Gy). VMAT improved PTV coverage and dose homogeneity, but clinical benefits remain unclear. Decreased dose exposure to the LCA may be clinically relevant. VMAT could be used for complex treatments that are difficult with conventional techniques. Patient age should be considered because of uncertainties concerning secondary malignancies.
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France tyranm@ipc.unicancer.fr.
authors.forename: Marguerite
authors.initials: M
authors.lastname: Tyran
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Hugues
authors.initials: H
authors.lastname: Mailleux
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Agnes
authors.initials: A
authors.lastname: Tallet
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Fau
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Gonzague
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Minsat
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Moureau-Zabotto
authors.affiliation: Service de Radiothérapie, Institut Paoli-Calmettes, 232, boulevard Sainte-Marguerite, 13009 Marseille, France.
authors.forename: Michel
authors.initials: M
authors.lastname: Resbeut
mesh_terms: D001943:Breast Neoplasms / Q000532:radiotherapy*; D003331:Coronary Vessels / Q000528:radiation effects; D005260:Female; D006321:Heart / Q000528:radiation effects; D006325:Heart Atria / Q000528:radiation effects; D006801:Humans; D011829:Radiation Dosage; D011874:Radiometry / Q000295:instrumentation / Q000379:methods; D000069584:Unilateral Breast Neoplasms / Q000532:radiotherapy
keywords: VMAT; breast cancer; field-in-field; left coronary artery