Page 133 - New epidemiological and PSMA-expression based paradigms in salivary gland tumors

Tubarial salivary glands: A potential new organ at risk for radiotherapy
The characteristics of the 723 evaluable respondents (initial cohort 750), included in the clinical study, are listed in Table 1 in the Supplementary material. The derived gland OAR delineations are illustrated in an anatomical atlas (Fig.4 in the Supplementary material). The RT dose distribution and delineation of the new gland are shown in Fig.5 for an example patient.
For crude physician-rated toxicity, the mean RT dose to the new glands was associated at all time points with ≥ grade 2 xerostomia (oral intake alterations, e.g. copious water, other lubricants, diet limited to purees and/or soft, moist foods), and with ≥ grade 2 dysphagia (symptomatic and altered eating/swallowing) (Table 1 and Table 2 in the Supplementary material). After correction for confounding factors, this association was reduced but still significant at 12- and 24-months. In other words, the effect of RT on dysphagia and xerostomia was explained by RT dose in multiple organs at risk, among which the new glands. However, independently from the dose to the parotid glands as the most relevant OAR, an increase in RT dose to the new glands lead to an increase in toxicity risk (normal tissue complication probability, NTCP) (Fig.5 in the Supplementary material). For patient-rated xerostomia, the crude association between mean RT dose to the new glands and moderate to severe toxicity was present at all time points, but was reduced and no longer significant after correction for confounding.
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Figure 5: Radiotherapy evaluation of region of the torus tubarius with overlying gland Evaluation of radiotherapy dose to the newly described glands overlying the torus tubarius: Axial CT-slice with projected radiation dose distribution as color-wash (left) and MR-slice (right, 3-Tesla, T2-dixon with gadolinium) of a 53-year old patient who received radiotherapy for cT3N1M0 oropharyngeal cancer.
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