Carcinoma, Squamous

This is a multi-center clinical study enrolling up to 28 participants. The primary objectives are to determine the objective response rate (ORR) established by the confirmed best overall response (BOR) following intratumoral administration of DaRT - Diffusing Alpha-Emitters Radiation Therapy. Secondary objectives are to: 1. Determine Progression Free Survival (PFS) up to 12 months after Alpha DaRT sources insertion. 2. Assess Overall Survival (OS) of patients treated with DaRT up to 12 months. 3. Assess Local control up to 12 months after DaRT insertion.

Patients undergoing primary radiochhemotherapy for locally advanced head and neck squamous cell carcinomas are included in this study. In addition to standard of care treatment patients will undergo addiational blood draws and MR imaging studies. Circulating cell free tumor DNA will be analysed in the blood samples. BIological data, imaging data and clinical data (such as patient and tumor characteristics, oncologic outcome, side effects) will be analysed in a biomathematical modelling approach.