片側頸部を標的とした強度変調回転照射における線量制約の検討

This study aimed to estimate the prevalence and rate of contralateral neck metastasis following unilateral neck volumetric-modulated arc therapy （VMAT）, and to determine the relevant dose constraints for at-risk organs in head and neck cancer patients undergoing unilateral neck VMAT. We enrolled 33 patients with head and neck cancer who underwent unilateral neck VMAT between 2015 and 2021. The prescribed dose to the high-risk planning target volume （PTV） was 60 to 70Gy, and the dose to the low-risk PTV was 50Gy2 （biological equivalent dose of 2Gy） with simultaneous integrated boost. Four patients had contralateral neck metastasis; however, these patients were salvaged. We evaluated the dose to the at-risk organs at virtual contralateral neck VMAT treatment planning, which allowed the effective dosage of PTV in all 33 patients. The average maximum doses to the spinal cord and brain stem were 12.8Gy and 11.1Gy, respectively. The average mean dose to the ipsilateral parotid gland of previously treated unilateral neck VMAT plan was 5.0Gy. The relevant dose constraints to the spinal cord, brain stem, and ipsilateral parotid gland of the unilateral neck VMAT plan were 32.2Gy, 42.9Gy, and 21.0Gy, respectively, in our department.