Carotid dosimetry after re-irradiation with 131Cs permanent implant brachytherapy in recurrent, resected head and neck cancer

Purpose: Permanent seed implant cesium-131 (Cs-131) brachytherapy provides highly localized radiation for patients with recurrent head and neck cancer (HNC), who may be ineligible for external beam radiation therapy due to a high-risk of toxicity. As carotid blowout is a concern in the setting of re-irradiation, a dose to the carotid artery was examined for Cs-131 brachytherapy implants. Material and methods: Eleven patients were implanted with Cs-131 adjacent to carotid at the time of resection for recurrent HNC. Vascularized tissue flaps were used in some patients. The carotid artery was contoured on the post-implant brachytherapy treatment plan, and the maximum carotid point dose and minimum carotid-seed distances are reported. The incidence of carotid blowout in the follow-up period was also measured. Results: The maximum carotid dose was 77 +/- 52 Gy (range, 3-158 Gy). The closest seed to the carotid artery was 0.8 +/- 0.8 cm (range, 0.2-2.6 cm). One patient without a flap experienced carotid blowout, which was attributed to a non-healing wound rather than to high radiation doses. Conclusions: Carotid artery doses from Cs-131 are reported. Vascularized tissue flaps should be considered when planning Cs-131 brachytherapy.