Selective Coverage Versus Comprehensive Coverage Radiotherapy in Poorly Differentiated and Anaplastic Thyroid Cancer

Inclusion Criteria: * Age ≥ 18 years old * Pathologically confirmed as ATC, thyroid cancer containing ATC components, PDTC (in accordance with Turin criteria), or other thyroid cancers with poorly differentiated components, and the MDT considers the biological behavior similar to PDTC. * Evaluated by the MDT and proposed to receive external beam radiotherapy, including postoperative R0/R1, R2 gross residual, inoperable local lesion, and local recurrence. * ECOG performance status 0-2 * expected survival ≥ 3 months * major organ functions can meet the requirements for radiotherapy and the proposed systemic treatment. * The subject voluntarily participates in the study and signs a written informed consent form, willing to follow up according to the protocol and fill in the quality of life scale. Exclusion Criteria: * Has received radiotherapy to the head and neck or upper mediastinum region in the past, and the target area of this study overlaps significantly with it, and the normal tissue limit cannot be met. * Has severe uncontrolled infections, active bleeding, unaddressed airway crises, severe dysfunction of the heart, lungs, liver, kidneys or other diseases that cannot be safely treated with radiotherapy. * Pregnant or lactating women; women of childbearing age who do not agree to take effective contraceptive measures. * Has other active malignant tumors within 5 years or simultaneously (excluding cured localized tumors such as skin basal cell carcinoma, skin squamous cell carcinoma, superficial bladder cancer, prostate carcinoma in situ, cervical carcinoma in situ, breast carcinoma in situ, etc.) * Cannot complete radiotherapy fixation, simulation positioning or follow-up imaging assessment. * Other situations that the researcher deems unsuitable for participation in this study.