ESTRO 2022 - Abstract Book

S933

Abstract book

ESTRO 2022

Figure 1. Mean mastication structure doses for patients with trismus (red) and without trismus (blue) given older (leftmost/structure) and newer (rightmost/structure) RT techniques. Tolerance doses for 10% risk of trismus: 30 Gy for masseter muscles; 15 Gy for TM joint, and 40 Gy for medial/lateral pterygoid muscles (Pauli N et al. Acta Oncol 2016: 55:788; Rao SD et al. Acta Oncol 2016:55:99; Kamal M et al. RO 2020:149:142; Hauge C et al. Acta Oncol 2018:57:1038). Conclusion Modern RT without mastication-structure-sparing intent resulted in 77% trismus reduction in HNC patients compared to patients treated with older techniques. Mastication structures mean doses by VMAT were generally below currently proposed tolerance doses, with dose reductions around 6-8 Gy for all structures compared to older techniques. The margin to “safe” dose levels were smaller for the medial pterygoid muscles compared to the other structures suggesting that focusing on this structure may lower trismus rates further.

PO-1099 Split course hypofractionated radiotherapy in elderly and frail patients with head and neck cancers.

K. Paciorek 1 , D. Kiprian 2 , A. Jarz ą bski 2

1 Maria Sklodowska-Curie National Research Institute of Oncology, I Department of Radiotherapy, Warsaw, Poland; 2 Maria Sklodowska-Curie National Research Institute of Oncology, Head & Neck Cancer Department, Warsaw, Poland Purpose or Objective To assess efficacy and toxicity of two split course fractionation schedules in elderly and frail patients with advanced head and neck cancers.

Materials and Methods