頭頸部がんの再照射

Reirradiation for head and neck cancer

頭頸部がんでは根治的放射線治療または術後照射後に，局所・領域再発あるいは二次がんを経験することがある。救済手術は長期制御を期待し得る標準的な局所治療であるが，腫瘍の進展範囲，既照射後の線維化，血管・神経・粘膜との近接，全身状態や機能温存の観点から実施困難な症例も少なくない^1）。このような場面で再照射は重要な選択肢となる。一方で，脊髄，脳幹，下顎骨，咽喉頭，頸動脈などの正常組織はすでに高線量を受けており，治療可能性と重篤な晩期有害事象の危険が常に併存する。

Reirradiation is an important local treatment option for selected patients with recurrent or second primary head and neck cancer after prior radiotherapy. Patient selection should integrate treatment intent, performance status, baseline function, tumor volume, resectability, prior dose, and cumulative dose to organs at risk. Intensity-modulated radiation therapy（IMRT） is useful for complex or postoperative targets, whereas stereotactic body radiation therapy（SBRT） may be appropriate for selected small-volume disease. Proton and carbon ion therapy can reduce normal tissue dose or provide biological advantages in selected cases, but superiority over photon therapy has not been universally established. Severe toxicity, especially carotid blowout, necrosis, dysphagia, and treatment-related death, requires careful counseling and follow-up.