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Evaluation of Prescription Dose Using Follow-Up Images of Head and Neck IMRT

M YAMASHITA1,2*, M Kokubo1, H Tanabe1, M Sueoka1, H Mizuno2, M Koizumi2, (1) Kobe City Medical Center General Hospital, Kobe, ,JP, (2) Osaka University Graduate School of Medicine , Suita, JP

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: In head and neck radiotherapy, intensity-modulated radiotherapy (IMRT) is useful, providing a high dose to the target and reducing the dose to the organ at risk (OAR) as much as possible. In this study, we evaluate the dose of persistent and recurrent in head and neck IMRT performed in our hospital, and provide indices for planning in future treatment.

Methods: Clinac iX (Varian) was used for Linac, Eclipse (Varian) was used for the treatment planning system, and AcurosXB (Ver13.6.23) was used for the dose calculation algorithm.
The subjects were 154 head and neck IMRT patients from January 2013 to December 2019. The irradiation method used VMAT and SIB-IMRT. The follow-up images after radiotherapy were used to evaluate the dose of persistent, recurrence, and metastasis near the irradiation fields.

Results: 10 cases had persistent or recurrent or metastatic disease in the oropharynx, 16 in the hypopharynx, and 8 in others among 154 cases. Evaluation was performed in 30 cases, the prescribed dose of 14 persistent cases had Mean dose of 100.9% (Max 106.8%, Min 85.9%). The those of 11 recurrence cases had Mean dose of 99.0% (Max 105.0%, Min 84.7%). The those of 5 metastasis cases near the irradiation fields had Mean dose of 67.3% (Max 87.9%, Min 29.2%).

Conclusion: Persistent are considered that the dose to the primary tumor was insufficient, so the dose needs to be increased when the dose to the OAR is within an acceptable. Recurrence may be associated with a recurrence of the primary lesion, which may reduce the dose to the prevention area. Regarding persistent and recurrent, the required dose was administered as planned, but the tumor was not controlled, suggesting that the prescribed dose needs to be reconsidered.

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Keywords

Radiation Therapy, Intensity Modulation, Dose Response

Taxonomy

IM- Radiation Dose and Risk: General (Most Aspects)

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