Adjuvant Radiotherapy in High Risk Locally Advanced DTC

This study is testing whether adjuvant radiation therapy (given after surgery) benefits patients with differentiated thyroid cancer — such as papillary or follicular thyroid cancer — that is considered high-risk and locally advanced, where surgery was unable to completely remove all the cancer. **You may be eligible if...** - You are aged 14–79 with a confirmed diagnosis of differentiated thyroid cancer - You had a total or near-total thyroidectomy (surgery to remove the thyroid) - Surgery did not remove all the cancer (incomplete or R1/R2 resection), with residual tumor less than 2cm³ in volume - Your major organ functions are normal **You may NOT be eligible if...** - You have already had head or neck radiation therapy - Your cancer has spread to distant parts of the body - You have received prior radioactive iodine (I-131), targeted therapy, immunotherapy, or chemotherapy - You are pregnant or breastfeeding - You have another active cancer within the past 5 years Talk to your doctor to see if this trial is right for you.