Tangential Volumetric Modulated Arc Therapy for Locally Advanced Breast Cancer

Abstract

Cardiovascular toxicity from breast radiation therapy (RT) is a concern to patients and providers. Herein, we present a cardiac-sparing strategy using tangential volumetric modulated arc therapy (tVMAT) in comparison with standard 3-dimensional conformal RT. Ten patients with left-sided breast cancer previously treated with adjuvant RT covering the breast, as well as the axillary and supraclavicular nodal regions, were selected for the study. For each patient, 2 plans were created: a dual-isocenter 3-field 3-dimensional conformal RT plan and a monoisocentric tVMAT plan. The prescription for both techniques was 50 Gy in 25 fractions to the breast and nodal target volumes. Compared with 3-dimensional conformal RT, tVMAT provided more uniform coverage to the breast and regional lymph nodes (mean conformity index: 1.42 for tVMAT vs 2.42 for 3-dimensional conformal RT; P < .01), and the maximum point dose for tVMAT was lower on average (112.8% for tVMAT vs 121.5% for 3-dimensional conformal RT; P < .001). Coverage to the lymph nodes was superior for tVMAT (average minimum coverage to 95% of entire nodal target volumes: 99.5% of prescribed dose for tVMAT vs 94.9% for 3-dimensional conformal RT; P < .001). Organ-at-risk sparing was improved with tVMAT, with a lower average V20Gy for the left lung (15.0% for tVMAT vs 24.6% for 3-dimensional conformal RT; P < .01) and lower mean heart dose (156 cGy for tVMAT vs 200 cGy for 3-dimensional conformal RT; P < .01). Tangential volumetric modulated arc therapy is a promising technique for the treatment of intact breast and regional lymphatics, and it may improve target coverage and organ-at-risk avoidance compared with 3-dimensional conformal techniques.