ESTRO 2024 - Abstract Book

S1314

Clinical - Head & neck

ESTRO 2024

1 University Hospital Hradec Kralove, Department of Oncology and Radiotherapy, Hradec Kralove, Czech Republic. 2 University of Defence, Department of Radiobiology, Hradec Kralove, Czech Republic. 3 Military University Hospital Prague, Institute of Radiation Therapy, Prague, Czech Republic

Purpose/Objective:

This study explored the potential of MRI-based adaptive radiotherapy to decrease radiation doses to dysphagia and aspiration related structures (DARS) in a heterogeneous cohort of patients (n=23) who received radiotherapy (RT) for different sites of head and neck cancer.

Material/Methods:

Pharyngeal constrictor muscles (PCM), cricopharyngeal muscle (CPM), proximal part of the esophagus (PE), supraglottic larynx (SGL), and transglottic larynx (TGL) were contoured in weekly MRI during the treatment as per international consensus guidelines and considered as DARS. To compare dysphagia-optimized radiotherapy (DORT) and MRI-based dysphagia-optimized adaptive radiotherapy (DOART), two virtual data sets were created for each patient using synthetic CTs created by deforming the initial planning CT. Dose-volume histograms (DVHs) of accumulated doses taken by deformable image registration (DIR) were generated and dosimetric parameters V50Gy – V70Gy and mean doses were measured for all DARS and for both DORT and DOART.

Results:

The most significant improvements in DARS-sparing were observed in regions of the highest doses (95% confidence interval, p < 0.05). For example, V70Gy in PCM decreased from 7.8 ± 5.5% to 2.6 ± 4.4% – this was a reduction by 67% (p < 0.001). Similarly, the relative decreases of V65 Gy in PCM, V60 Gy in SGL, V60 Gy in TGL, and V55 Gy in CPM were 37%, 32%, 46%, and 27%, respectively.

Conclusion:

It was shown that MRI-based DOART has the potential to significantly reduce the radiation burden of DARS in the area of high doses as a response to the decreasing volume of the primary tumour or lymphatic nodes. Preliminary findings of this study provide novel evidence to suggest that the concept of MRI-based DOART could contribute to spare DARS in clinical practice.

Keywords: Adaptive, Dysphagia, DARS

References:

[1] Caudell JJ, Schaner PE, Meredith RF, Locher JL, Nabell LM, Carroll WR, et al. Factors Associated With Long-Term Dysphagia After Definitive Radiotherapy for Locally Advanced Head-and-Neck Cancer. International Journal of Radiation Oncology*Biology*Physics 2009;73:410 – 5. https://doi.org/10.1016/j.ijrobp.2008.04.048.