Combination Radiotherapy and Radiopharmaceutical Therapy Treatment Planning for Thyroid Cancer

This study is developing better treatment planning for patients with differentiated thyroid cancer (papillary or follicular type) that did not respond fully to initial surgery and radioactive iodine (RAI) therapy. Researchers want to combine targeted radiation (external beam radiotherapy) with radioactive iodine treatment more precisely and effectively. **You may be eligible if...** - You are between 18 and 85 years old - You have papillary or follicular thyroid cancer confirmed by biopsy that has not been cured by initial surgery and/or radioactive iodine - Your tumor still absorbs some iodine (iodine-avid) but not enough to be treated with RAI alone - You have adequate kidney and blood cell counts - Your performance status is reasonably good **You may NOT be eligible if...** - You are pregnant or breastfeeding, or sexually active and premenopausal without using contraception - You have contraindications to radioactive iodine or external beam radiation - You have advanced brain or spinal metastases that would be worsened by TSH stimulation (used to prepare for RAI) - You have had recent contrast dye exposure (within 6 weeks) that could interfere with radioactive iodine uptake Talk to your doctor to see if this trial is right for you.