Dose-Effect Relation of Salivary Gland Irradiation

Determining the Dose-Effect Relation of Salivary Gland Irradiation and Cell Loss With PSMA PET

Optimization of radiotherapy to reduce xerostomia is difficult, because many gland locations cannot be seen with current imaging modalities and biological dose-effect are currently insufficiently understood. PSMA PET is a new diagnostic instrument which can visualize the presence of vital acinar cells in salivary gland locations throughout the head and neck, with a sensitive and quantitative signal. A reduction of PSMA accumulation in salivary glands is thought to correlate with loss of vital acinar cells. The PET images can be correlated with radiotherapy dose distributions in gland-based or voxel-based evaluations. This makes PSMA PET a suitable instrument to derive the radiobiological dose-effect relations that are required to develop better and gland-specific dose constraints for radiotherapy. The results of this study can contribute to lower toxicity and better quality of life in patients treated with high-dose radiotherapy in the head and neck.

Primary objective of this prospective observational study is to determine the gland-based dose-effect relation between conventionally fractionated radiotherapy (RT) and long-term loss of acinar cells, per salivary gland type. The study population consists of a maximum of 20 patients with HNSCC referred for high-dose (CC)RT. There is no therapeutic intervention. Diagnostic intervention is PSMA PET/CT.

Inclusion Criteria:

• HNSCC of the head-neck area, cTx-4 N0-3 M0
• Accepted for EBRT in a conventionally fractionated schedule of 6-7 weeks.

Exclusion Criteria:

• Age <18y
• Pregnancy or lactation
• Participation in conflicting studies, e.g. with non-standard treatment and/or imaging
• Inability to provide informed consent