Patient description: The patient is a 60 year old man complaining of frequent headaches, generalized bone pain and difficulty chewing that started 6 years ago and is worsening. Examination shows bilateral swellings around the molars. The swellings have increased since his last examination. Several extraoral lesions are detected in the head and face. The swellings are non-tender and attached to the underlying bone. Further evaluation shows increased uptake of radioactive substance as well as an increase in urinary pyridinoline. His serum alkaline phosphatase is 300 IU/L (the normal range is 44- 147 IU/L). His family history is only significant for hypertension in his mother and DM type 2 in his father. The diagnosis of Paget's Disease of Bone was confirmed and Bisphosphonate will be started as first-line therapy.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Head and Neck Cancer Participant must be informed of the investigational nature of the study and must be able to sign a written informed consent Participants with histologically or cytologically confirmed solid malignancy that has recurred in the head and neck (above the clavicles) region, e.g., participants with recurrent cutaneous squamous cell carcinoma, salivary gland tumors or esthesioneuroblastoma are eligible for this clinical trial Participants must have undergone previous curative intent therapy, with radiation as a primary or adjuvant therapy Participants may have distant metastatic disease, as long as the locoregional site of recurrence is deemed eligible for radiation therapy, and treatment of the loco-regional disease is deemed as taking precedence over treatment of the remaining systemic disease Participants must have at least one evaluable (measurable or non-measurable) recurrent lesion that is amenable to radiation therapy Participants must demonstrate uptake of CLR 131 via SPECT/CT imaging, as determined by the study radiologist, in the specified site of recurrent/metastatic disease that is to be treated with radiation therapy. There is a subset of up to 6 patients who may continue with CLR 131 treatment without uptake on the SPECT/CT scan after the test dose Participants must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 Participants must have a life expectancy of at least 6 months The participant has adequate hematologic function, as evidenced by an absolute neutrophil count (ANC) ≥ 1500 / µL  Recurrent tumor recommended for surgical resection based on multidisciplinary Head and Neck Oncology Tumor Board Review Thyroid cancer Known hypersensitivity to iodine Other concurrent severe and/or uncontrolled concomitant medical or psychiatric conditions (e.g. active or uncontrolled infection, uncontrolled diabetes) that could cause unacceptable safety risks or compromise compliance with the protocol, per investigator discretion Chemotherapy or major surgery within 4 weeks, or radiotherapy within 2 weeks prior to test dose of CLR 131 Participants with clinically significant adverse events due to agents administered more than 4 weeks prior to test dose of CLR 131 (alopecia and fatigue excluded). Clinical significance to be determined by investigator The participant is pregnant, breastfeeding, or expecting to conceive or father children within the projected duration of the trial, starting with the screening visit through 6 months after the last dose of trial treatment Any ongoing or active infection, including active tuberculosis, hepatitis B or C, or known infection with the human immunodeficiency virus (HIV) Concurrent treatment with any other anti-cancer or investigational agents. Participants cannot be receiving concomitant chemotherapy, radiotherapy, experimental therapy or any other therapy not otherwise outlined by the trial for the purposes of anti-cancer treatment Participants with a history of or concurrent second primary malignancy (stage III or IV) within 5 years to study enrollment are excluded