Trial Combining Pembrolizumab and Cesium 131 Brachytherapy With Salvage Surgery in HNSCC

Cs-131 brachytherapy seed is a low-energy-gamma isotope that is contained in a titanium capsule. Dosing will be determined by a radiation oncologist study team member based on CT scan and intraoperative findings. The number of seeds and spacing will be outlined preoperatively based on the proposed square area of exposure in the resection bed. The plan is to deliver a total of 60-70Gy of radiation to the site.

Pembrolizumab 200 mg will be administered as a 30-minute IV infusion every 3 weeks. The drug will be infused through a peripheral line or an indwelling catheter. The first dose will be given 2 weeks prior to surgery. Post-surgery, pembrolizumab will be started between 2 and 6 weeks and will continue every 3 weeks for a duration of 6 months. Study Drug may be administered up to 3 days before or after the scheduled Day 1 of each cycle due to administrative reasons. The Investigator's Brochure contains specific instructions for the preparation of the standard of care pembrolizumab infusion fluid.