Nivolumab Plus Lenvatinib Against Anaplastic Thyroid Cancer (NAVIGATION)

Inclusion Criteria: 1. Histologically confirmed as anaplastic thyroid cancer 2. Unresectable anaplastic thyroid cancer 3. Have measurable lesions defined by the RECIST version 1.1 4. Have adequate organ function 5. Cardiac function test within 28 days before enrollment 12-lead electrocardiogram no clinically significant abnormality as shown below: heart disease, severe arrhythmia, etc. 6. Patients who are 20 years or older 7. Eastern Cooperative Oncology Group (ECOG) performance status 0-1 8. Ability to swallow oral medications 9. Women of childbearing potential 10. Life expectancy of more than 90 days 11. Have signed written informed consent to participate in this study Exclusion Criteria: 1. Active brain metastases or leptomeningeal metastases 2. Diverticulitis or Symptomatic ulcerative disease 3. Treatment required complication of systemic infectious disease 4. Medical history of active, known, or suspected autoimmune disease 5. Complication of pulmonary fibrosis or interstitial pneumonitis 6. Medical history of clinically significant cardiovascular disease within 180 days of initial dose as New York Heart Association (NYHA) class above 2 leveled congestive heart failure, unstable angina, cardiac infarction or cardiac arrhythmia with paroxysmal or required treatment 7. Regardless of usage of antihypertensive drug, systolic blood pressure \<=140 mm Hg and diastolic blood pressure \<=90 mm Hg 8. Have active double cancer 9. Currently receiving other interventional clinical study treatment