Pharyngeal Constrictor-Sparing Salvage Stereotactic Body Radiation Therapy With Tongue-Out for In-Field Recurrence After Definitive Radiation Therapy for Head and Neck Cancer: Guide to Tongue-Out Radiation Therapy.

Abstract

This report details a pharyngeal constrictor muscle (PCM)-sparing stereotactic body radiation therapy (SBRT) using our institutional technique of "tongue-out" radiation therapy (TORT) for treating a local recurrent cancer in the uvula (GTV_uvula) in a patient with history of a definitive chemotherapy with radiation therapy (70 Gy with weekly cisplatin) for a locally advanced laryngeal cancer 4 years ago. TORT includes optimizing the patients' reproducible tongue-out position using readily available medicine cup (30 cc) followed by sculping the thermoplastic mask with tongue-out, and real-time visual monitoring of the tongue position during the computed tomography simulation scan, cone beam computed tomography acquisition, and treatment. Between arcs during volumetric modulated arc therapy, time for tongue relaxation and saliva swallowing can be given to the patient. Without TORT, the patient's GTV_uvula abutted the medial aspect of superior PCM (medial-sPCM) and a substantial volume of the previously irradiated superior PCM (sPCM) would have received high radiation dose from this salvage SBRT (32.5 Gy in 5 fractions). Comparing without TORT, the shortest distance between medial-sPCM-to-GTV_uvula was increased by 13 mm with TORT, which reduced radiation dose to sPCM in the salvage SBRT plan. The mean dose to sPCM was decreased from 20.5 Gy without TORT to 12.7 Gy with TORT. With TORT, minimal sPCM volumes fell within higher isodose line: volume receiving ≥ 60% prescription dose (V_60%Rx), V_80%Rx, and V_100%Rx to sPCM was, 4.8 versus 0.7 cc (without vs with TORT, respectively), 2.9 versus 0.19 cc, and 1.6 versus 0.04 cc, respectively. Maximum dose (D_max) to medial-sPCM was 34.6 Gy without TORT versus 22.7 Gy with TORT. These high doses to the sPCM and intrafractional swallowing-related geographic misses of GTV_uvula were avoided through the application of TORT in this salvage reirradiation setting. The patient successfully finished salvage SBRT with TORT resulting in no dysphagia or mucositis and maintained complete response at 12 months after treatment.