To determine the efficacy and safety of intensity modulated radiation therapy combined with apatinib for inoperable or iodine refractory thyroid cancer.

Inclusion Criteria:

• Ability to understand character and individual consequences of the clinical trial. Willing to sign the written informed consent; Informed consent must be signed before the enrollment in the trial;
• Aged ≥ 18 years old;
• Pathologically confirmed inoperable or iodine refractory thyroid cancer, or postoperative residual disease detected by imaging studies, or progression disease within 12 months before enrollment. (all with measurable disease ≥10mm according to RECIST 1.1);
• ECOG0-2;
• Adequate laboratory values within 14 dyas of enrollment to study defined as follows: N ≥ 1500/mm^3; PLT ≥ 80,000/mm^3; HB≥90g/L;total bilirubin < 1.25ULN; AST/ALT < 2.5 ULN or < 5 ULN with metastasis; SCr ≤1ULN; CCR > 50ml/min;
• The survival period is expected to be greater than 3 months;
• Willing to accept adequate contraception for patients with childbearing potential.

Exclusion Criteria:

• Take chemotherapeutic chemotherapy (the use of low-dose chemotherapy for radiosensitization was allowed) or thalidomide and its derivative treatments;
• Take VEGFR-TKI within 1 month, such as vandetanib, cabozantinib, lenvatinib, sunitinib and sorafenib;
• Allergic to apainib;
• Uncontrolled high blood pressure and heart disease;
• Patients with gastrointestinal bleeding risk;
• Coagulation disorders(INR>1.5×ULNAPTT>1.5×ULN);
• Uroprotein positive (Uroprotein≥2+ or 24-hour urinary protein quantity >1.0g);
• Pregnant or lactating women.