Quad Shot Radiotherapy in Combination With Immune Checkpoint Inhibition

Pembrolizumab 200 mg will be given every 3 weeks to tumor progression or treatment tolerance.

"* Each cycle of quad-shot radiotherapy will be comprised of 14.8 Gy in 4 fractions (3.7 Gy per fraction) delivered twice daily (at least 6 hours apart) over two consecutive days.~* All patients will receive 1 cycle of quad-shot radiotherapy between ICI cycles 2-3.~* Subsequent cycles may occur between immunotherapy cycles 6-7 and 11-12, if more than 1 cycle can be safely delivered and the patient has experienced less than a partial response at protocol-specified tumor assessments (after C5 and C10). The eligibility for subsequent cycles will be at the discretion of the treating radiation oncologist.~Therefore, the total prescription dose will be:~* 14.8 Gy in 4 fractions for those that complete 1 cycle (all patients will receive 1 cycle)~* 19.6 Gy in 8 fractions for those that complete 2 cycles~* 44.4 Gy in 12 fractions for those that complete 3 cycles"