Regorafenib in Patients With Progressive, Recurrent/Metastatic Adenoid Cystic Carcinoma

All eligible patients will receive a starting regorafenib dose of 120 mg daily taken orally for 3 weeks in a 4-week cycle. Patients for whom regorafenib dose reduction was not performed or required may have their treatment dose increased to the FDA-approved dose of 160 mg daily orally for 3 weeks in a 4-week cycle in cycle #2 or beyond (this is not mandatory). RECIST v1.1 tumor assessments will be made at baseline (CT or MRI) and then approximately every 2 cycles (or every 8 weeks (+/- 1 week)). After 10 months, imaging will be done every 3 cycles (or every 12 weeks (+/- 1 week)). Patients may remain on study until progression of disease or unacceptable toxicity