ESTRO 2023 - Abstract Book

S512

Sunday 14 May 2023

ESTRO 2023

The impact of adaptation was patient dependent with respective ranges in the reduction of V35Gy of [1.3% to 28.2%], [- 0.5% to 44.7%] and [0.0% to 51.6%] for PCM_Superior, PCM_Middle and Larynx_SG.

Table 1 compares OAR dose metrics for Adapted vs Non-Adapted treatment plans.

Figure 1 shows DVH comparison of Adapted vs Non-adapted dose distributions and the mean and Standard Deviation (SD) of the difference in DVHs.

Conclusion PET-based adaptation, 2 weeks into a course of CRT, reduced doses to the SWOARS in close proximity to the oropharynx. Mean dose reduction to these organs was small, however substantial reductions were seen in high dose DVH metrics, approximating the range that is associated with development of long-term dysphagia. Ongoing recruitment and collection of late toxicity data in PEARL will determine the impact of these dosimetric advantages of adaptation on clinical outcomes, including late dysphagia. OC-0623 Ultra-High dose rate irradiation spares a large quantity of circulating lymphocytes in brain tumours F. de Kermenguy 1 , P. Maury 1 , B. Nathan 1 , E. Deutsch 1 , C. Robert 1 1 Gustave Roussy, Radiation Oncology, Villejuif, France