Proton Therapy for Local-regionally Advanced Breast Cancer Maximizes Cardiac Sparing

Abstract Purpose: To evaluate the potential of proton therapy in sparing cardiac/coronary structures when compared with 3-dimensional conformal radiation therapy (3DCRT), helical tomotherapy (HT), and intensity-modulated radiation therapy using volumetric modulated arc therapy (VMAT). Materials and Methods: Comparative treatment planning was performed using computed tomography scans of 10 patients with left-sided stage III breast cancer after mastectomy, targeting the chest wall, axilla levels I to III, and the supraclavicular and internal mammary nodes (IMN) to 50.4 Gy (radiobiologic equivalent [RBE]) in 28 fractions. Organs at risk were heart, lungs, contralateral breast, unspecified healthy tissues, and coronary arteries. Plans were also compared that included IMNs for protons, but not for photons. Results: Mean heart dose of 1.2 Gy (RBE) was lowest with protons when compared with 6.8, 10.2, and 8.2 Gy for 3DCRT, HT, and VMAT, respectively (P < .05). The mean left anterior descending artery (LAD) dose ...