Axillary involvement at presentation. (A) Axial, coronal, and sagittal views of a proton plan (left) and an IMRT plan (right) for a patient presenting with axillary involvement. Use of proton therapy in this case spares the left breast. (B) Regardless of which treatment modality is chosen, IMRT (left panel) and proton (right panel), limiting the volume exposed to radiation should include attention to avoiding a low-dose bath. (C) Limiting lung dose. If avoiding the lung is the primary objective in a given patient, especially if the patient has received pulmonary toxic chemotherapy (eg, any combination of bleomycin, busulfan, gemcitabine, brentuximab, etc.), proton therapy may better spare the lungs by reducing the low-dose bath seen with photons.