- At least 2 weeks must have elapsed since the end of prior systemic treatment and/or 4 weeks since completion of radiotherapy with resolution of all treatment-related toxicity to NCI CTCAE Version 4.0 grade ≤1 (or tolerable grade 2) or back to baseline (except for alopecia, lymphopenia, or hypothyroidism) prior to starting study drug treatment. Any number of prior therapies for recurrent/metastatic salivary gland cancer are allowed.