ESTRO 2024 - Abstract Book

S1185

Clinical - Head & neck

ESTRO 2024

In 570 HNC patients treated with definitive radiotherapy (RT), parotid glands flow (FLOW PAR ), submandibular/sublingual glands flow (FLOW SMSL ) and patient-reported daytime (XER DAY ) and nighttime xerostomia (XER NIGHT ) were prospectively measured before, and at 6 (M6) and 12 months (M12) after RT. Using linear mixed effect models, relations of mean dose to the parotid glands (D mean,par ), D mean,SCR , non-SCR parotid gland tissue (D mean,nonSCR ), submandibular glands (D mean,sub ) and oral cavity (D mean,oral ) with salivary flow and xerostomia were analysed while correcting for known confounders.

Results:

As expected, D mean,par was associated with FLOW PAR (p<0.001), while D mean,sub affected FLOW SMSL (p<0.001). After dividing the parotid gland into the SCR and non-SCR region, D mean,SCR proved to be responsible for the negative effect of D mean,par on FLOW PAR (p≤0.03), while D mean,nonSCR was not associated with FLOW PAR (p≥0.11). Typical trajectories illustrated the enhanced effect of D mean,SCR on FLOW PAR (Figure A-B). For example, increasing D mean,SCR by 10 Gy at fixed D mean,nonSCR , reduced FLOW PAR by 0.022 (27%) and 0.024 ml/min (22%) at M6 and M12, respectively. In contrast, increase of D mean,nonSCR while keeping D mean,SCR constant did not significantly decrease FLOW PAR (0.002 [3%] and 0.004 ml/min [4%] at M6 and M12, respectively).