ESTRO 2024 - Abstract Book

S1262

Clinical - Head & neck

ESTRO 2024

High dose curative radiotherapy doses result in progressive decline in pulp sensitivity. Pulp tissue become less responsive and resistant; this along with the other degenerative effects such as enamel delamination, hyposalivation, rampant tooth decay, and a reduced pulp-dentin complex response of RT may predispose the pulpal tissue to necrosis. Hence, careful and an adequate dental prophylaxis should be performed in patients undergoing RT.

Keywords: pulp sensitivity

1179

Digital Poster

Palliative Expeditiously Adaptive Quad Shot Radiotherapy for Head and Neck Cancers (NCT04379505)

Weiren Liu 1 , Joshua P Schiff 1 , Comron Hassanzadeh 2 , Randall Brenneman 3 , Mackenzie Daly 4 , Karen Mller 1 , Casey Hatscher 1 , Robbie Beckert 1 , Anthony Apicelli 1 , Michael Moravan 1 , Wade Thorstad 1 , Eric Laugeman 1 1 Washington University in St. Louis School of Medicine, Radiation Oncology, St. Louis, USA. 2 MD Anderson Cancer Center, Radiation Oncology, Houston, USA. 3 Banner Health, Radiation Oncology, Loveland, USA. 4 University of Colorado School of Medicine, Radiation Oncology, Colorado Springs, USA

Purpose/Objective:

Quad shot radiotherapy is an integral aspect of palliative care for patients with head and neck cancers. However, the need for multiple CT simulation appointments for additional quad shot cycles can be burdensome, particularly for patients traveling from afar. We aimed to develop and evaluate the feasibility of an innovative workflow utilizing online adaptive radiotherapy to eliminate the need for additional CT simulation appointments for patients receiving quad shot palliative radiotherapy for head and neck cancers.

Material/Methods:

Ten patients with head and neck malignancies who were candidates for quad shot palliative radiotherapy were enrolled on this prospective study. Quad shot regimen entailed delivering up to three cycles, each comprising four fractions of 3.5 Gy delivered twice daily, with a total dose of 14 Gy per cycle. Cycles were spaced three to four weeks apart. Treatment was administered using an O-ring gantry unit equipped with CBCT-guided online adaptive capabilities. Prior to the first cycle, patients underwent standard CT simulation and creation of an Aquaplast mask for immobilization. The planning target volume (PTV) was a 5 mm volumetric expansion around the gross tumor volume (GTV), which was gross tumor on imaging. The study defined critical organs at risk (OARs) as the brain, spinal cord, and brainstem. Maximum dose constraints were 14 Gy for each OAR for patients with no prior radiotherapy and 2.0 Gy, 1.7 Gy, and 2.0 Gy for patients with a history of prior radiotherapy, corresponding to the brain, spinal cord, and brainstem, respectively. The simulation plan served as the treatment plan for the first cycle of treatment. However, for the initial fraction of the second and third quad shot cycles, the patient's GTV was recontoured and the treatment plan was re-optimized following institutional online adaptive radiotherapy protocol. The adapted plan was then used for treatment for the remaining three fractions in each cycle. For the first fraction