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. 2012 Jun 27;23(12):3081–3091. doi: 10.1093/annonc/mds144

Figure 1.

Figure 1

Mean radiation dose to the esophagus, by region of the esophagus, for specific breast cancer radiotherapy fields. IMC, internal mammary chain. The upper, middle, and lower esophagus were defined as C6-T4, T4/5-T7/8, and T8-T10/11, respectively. aPercentage of cases and controls with radiotherapy who received a particular field, excluding women with unknown fields. Beam energies included cobalt-60 gamma rays (53%), orthovoltage x-rays (100–400 kVp; 36%), photons (4–18 MV; 18%), and electrons (6–20 MeV; 21%). bMost IMC fields were direct anterior fields. cWe categorized the location of each patient's supraclavicular fields relative to midline as at/over midline, off–midline, or unknown due to the variable contribution to the esophagus dose. The supraclavicular field at/over midline was positioned so that the esophagus was directly below the medial field edge on the patient skin surface. The supraclavicular field off-midline was positioned so that the esophagus was approximately 2 cm outside the medial field edge. Supraclavicular fields with unknown medial border were positioned at midline. Supraclavicular fields were simulated as direct beams.