Just FYI. I had cobalt radiation to my neck at age 4 for recurrent tonsillitis. At age 9, I developed Thyroid Cancer. I had a radical neck surgery at age 9 and had no further problem with the cancer, but at age 60, I began having the Cobalt decay and radiation fibrosis symptoms that Cobalt is known for.
If you have access to an academic Late Effects Clinic, would suggest getting an appointment. I have been so thankful for the Late Effects Clinic and the docs that help you understand and give you an idea of what to expect.