Fig. 2.

a MR image of the right parotid gland of a patient with recurrent adenoid cystic carcinoma (rT4aN0M0) before treatment (arrowhead). There was recurrence at the primary tumor site 36 months after the initial surgical treatment. Patients received PBT combined with intra-arterial chemotherapy at our institution (PBT total 74.8 GyE; CDDP total 250 mg/body). b Dose distribution map of proton beam therapy (the outside line shows <10 % of the prescription dose). c MR image of the same patient 38 months after treatment. The primary tumor lesion has disappeared, and this patient has achieved a complete response