PDR001 Combination Therapy for Radioiodine-Refractory Thyroid Cancer

Inclusion Criteria: * Cohort A Only: Confirmation in a CLIA certified laboratory that one of the patient's thyroid tumors (primary tumor, recurrent tumor, or metastases) does not possess a BRAFV600- mutation (non-V600- BRAF mutations, including BRAF translocations, may be included in this cohort). * Cohort A Only: Evidence of progressive disease (e.g. presence of new or growing lesion(s) on radiologic imaging and/or new or worsening tumor-related symptoms) within 14 months of study enrollment * Cohort B Only: Confirmation in a CLIA certified laboratory that one of the patient's thyroid tumors (primary tumor, recurrent tumor, or metastases) possesses a BRAFV600- mutation (e.g. V600E, V600K, V600D). * Cohort B Only: Patients must have documented progression (evidence of tumor growth or appearance of new tumor) on prior BRAF directed therapy (e.g. (but not limited to) vemurafenib, dabrafenib) and must have tolerated this therapy without \> Grade 3 toxicity on their most recent evaluation (excluding Grade 4 asymptomatic laboratory abnormalities). * Patients must have pathologically or cytologically confirmed differentiated thyroid cancer of follicular origin (including papillary thyroid carcinoma, follicular thyroid carcinoma, hurthle cell carcinomas, poorly differentiated thyroid carcinoma and their respective variants). * Patients must have RECIST v1.1 measurable disease. * Patients must have recurrent or metastatic disease not amenable to curative surgery or radiation. * Age …