頸動脈破裂症候群：QUAD shotと密封小線源治療を用いた当院の再照射戦略

Carotid blowout syndrome：our institutional reirradiation strategy using QUAD shot and interstitial brachytherapy

頭頸部癌の根治照射後に局所再発や二次がんが生じた場合，手術的サルベージが困難な症例は少なくなく，再照射が唯一の局所制御手段となることが多い。しかし再照射は，すでに高線量を受けた正常組織への追加照射であるため，初回治療よりも重篤な晩期有害事象を引き起こすリスクが高い。なかでも頸動脈破裂症候群（carotid blowout syndrome：CBS）は，致死的な大量出血をきたしうる最も警戒すべき合併症であり，再照射計画における線量制約の中心的課題となっている。

Carotid blowout syndrome（CBS）is a critical, potentially fatal complication of head and neck reirradiation. This article summarizes evidence on carotid dose constraints, converging on a cumulative EQD2 threshold of approximately 120-125 Gy, and describes our institutional strategy combining QUAD shot and interstitial brachytherapy. Among 18 patients reirradiated with carotid EQD2≧70 Gy, no clinically significant rupture occurred in the 17 evaluable patients；median survival was 176 days, with 44％ surviving ≧6 months. Brachytherapy may reduce functional late toxicity because of its highly conformal dose distribution but remains underutilized in Japan, an issue we are addressing through hands-on training courses.