ABSTRACT
PURPOSE: Patients with left-sided breast cancer (LSBC) are at increased risk of cardiac morbidity from adjuvant breast radiation therapy (ABRT). Breath-hold (BH) techniques substantially reduce the radiation received by heart during radiation therapy for LSBC. However, a subset of patients with LSBC are ineligible for BH techniques due to an inability to breath-hold or because of other comorbidities. To reduce radiation to the heart, we routinely use a custom-made breast shell for the treatment of patients with LSBC who are ineligible for BH techniques. This study evaluates the dosimetric impact of using a breast shell for patients with LSBC undergoing ABRT. METHODS AND MATERIALS: Sixteen consecutive patients with LSBC who failed BH and underwent ABRT using a breast shell during the period of 2014 to 2016 were identified. Treatment was planned using field-in-field tangents with a prescribed dose of 42.5 Gy in 16 fractions. Comparisons between plans with and without a shell were made for each patient using a paired t test to quantify the sparing of organs at risk (OARs) and target coverage. RESULTS: There was no statistically significant difference in the planning target volume of breast coverage. A statistically significant improvement was observed in sparing the heart, left ventricle (LV), and ipsilateral lung (P-value < .001). Plans with the shell spared OARs better than the no-shell plans with a mean dose of 2.15 Gy versus 5.15 Gy (58.2% reduction) to the heart, 3.27 Gy versus 9.00 Gy (63.7% reduction) to the LV, and 5.16 Gy versus 7.95 Gy (35% reduction) to the ipsilateral lung. The irradiated volumes of OARs for plans with and without shell are 13.3 cc versus 59.5 cc (77.6% reduction) for the heart, 6.2 cc versus 33.2 cc (81.2% reduction) for the LV, and 92.8 cc versus 162.5 cc (42.9% reduction) for the ipsilateral lung. CONCLUSIONS: A positioning breast shell offers significant benefit in terms of sparing the heart for patients with LSBC who are ineligible for BH techniques. It also can be used as a simple cardiac-sparing alternative in centers without BH capability.
ABSTRACT
INTRODUCTION: The purpose of this study was to compare volumetric modulated arc therapy (VMAT) with helical tomotherapy (HT) and three-dimensional conformal radiation therapy (3D-CRT) for craniospinal irradiation (CSI) in children with medulloblastoma. METHODS: Five children treated with 3D-CRT were retrospectively replanned with HT and VMAT. Tomotherapy plans used a single helical arc, thereby eliminating field junctions. VMAT plans used two arcs rotating alternatively clockwise and counterclockwise, respectively. Conformity and homogeneity indices, dose-volume histograms, integral doses, monitor units delivered, and beam-on times were compared. RESULTS: VMAT showed an improved mean conformity index of 1.05 in comparison with 3D-CRT (1.58, P = .04) and HT (1.34, P = .04). The mean homogeneity index of VMAT (1.13) was not significantly different from 3D-CRT (1.16) but higher than HT (1.08, P = .04). For normal tissues, VMAT resulted in a lower mean dose to the skin, eyes, lenses, optic nerves, cochlea, esophagus, heart, peritoneal cavity, bladder, and rectum compared with 3D-CRT (all P = .04). There were few significant differences in dose-volume statistics for normal tissues between VMAT and HT. The mean nontarget tissue integral dose for VMAT of 80.8 J was significantly lower than for 3D-CRT (91.5 J, P = .04) and HT (95.6 J, P = .04). Body and nontarget tissue integral doses were lowest with VMAT in every patient. CONCLUSIONS: For CSI, VMAT provides comparable normal tissue sparing with tomotherapy and may reduce the integral dose. Compared with 3D-CRT, VMAT improved normal tissue sparing at higher doses despite larger volumes receiving lower doses. These findings have potential implications in the risk of the development of late adverse effects and radiation-related second malignancies in children with curable primary disease.
