ESTRO 2024 - Abstract Book

S1276

Clinical - Head & neck

ESTRO 2024

same relationship as in the original model. This demonstrates that the dose-effect relations as described in the models are consistent in both study cohorts, implying that these models are robust within these different cohorts. These results are encouraging towards a broader and global integration of the CITOR NTCP models.

Keywords: NTCP modeling, comprehensive toxicity risk profile

1278

Digital Poster

Stereotactic Body RadioTherapy (SBRT) for palliation of head and neck (H&N) cancer: a planning study

Anoop HARIDASS 1 , Russell Dawson 2 , Rachel Brooker 1 , James Iddenden 2 , Sharon Mcginn 1 , Louise Turtle 1 , Caroline Brammer 1 , Ehab Ibrahim 1 1 Clatterbridge Cancer Center, Radiation Oncology, Liverpool, United Kingdom. 2 Clatterbridge Cancer Center, Physics, Liverpool, United Kingdom

Purpose/Objective:

To assess feasibility of SBRT planning and delivery in head and neck squamous cancer (HNSCC)patients in the setting of palliative radiotherapy.

Material/Methods:

Anonymised treatment planning (TP) CT datasets of HNSCC patients with low and high volume disease, previously treated with palliative radiotherapy, were imported into the contouring & planning system after obtaining appropriate permissions. Contouring of the target volumes (TV) and organs at risk (OARs) was carried out as per SBRT protocol document and previous literature (1,2). GTV_SBRT was contoured on the TP CT scan using data from the diagnostic imaging and clinical information. PTV_SBRT was created from the GTV with a 3mm margin expansion. CTV_pall was GTV_SBRT with a 5mm margin, this was edited away from natural boundaries and extended to include all of the involved nodal level/s and organ subsite as per local standard of care. The resultant CTV_Pall was expanded by 5mm to form the PTV_Pall. SBRT and conventional conformal palliative plans were created on the contoured volumes. The prescribed dose was 40Gy in 5# for SBRT delivered every other weekday and 20Gy in 5# daily for the palliative RT. The two plans were compared for coverage and assessed using DVH parameters including mean and Dmax dose to the composite mucosal structure to determine differences.

Dosimetric parameters: GTV_SBRT V40Gy >99%; PTV _SBRT D95%>40Gy Dmax<42.8Gy

Relevant organs at risk for the involved areas including ( but not restricted to) spinal cord, brain stem, mandible, carotid arteries, larynx,pharyngeal constrictors, esophagus, parotid glands, sub mandibular glands (SMG) brachial