Oligometastatic Squamous Cell Carcinoma of the Head and Neck

This is a randomized open-label multicentre phase III superiority study of the effect of adding SABR to the standard of care treatment pembrolizumab on progression free survival in patients with oligometastases of a squamous cell carcinoma of the head and neck (SCCHN), histological confirmation of the primary disease at first diagnosis, and PD-L1 CPS ≥1. After eligibility check and signing informed consent, all patients will be prospectively enrolled in a 1:1 ratio between current standard of care treatment (pembrolizumab, Arm 1) vs. SABR + standard of care treatment (Arm 2) to oligometastases. Any radical treatment to the synchronous primary/ recurrent primary tumor and/or involved cervical nodes (surgery or radiotherapy), as decided by the local tumor board/ treating physicians, should be completed prior to enrolment.Surgical removal of metastases is allowed for diagnostic purposes or for brain metastases, as long as these metastases count toward the total number of 5 and at least one metastasis is left for treatment with SABR. Such surgical procedures should be performed prior to enrolment.