Here is some info I found on throat cancer...since she is having her thyroid removed, I am assuming its thyroid cancer.....
Thyroid cancer is unique among cancers. In fact, thyroid cells are unique among all cells of the human body. They are the only cells that have the ability to absorb iodine. Iodine is required for thyroid cells to produce thyroid hormone, so they absorb it out of the bloodstream and concentrate it inside the cell.
Most thyroid cancer cells retain this ability to absorb and concentrate iodine. This provides a perfect "chemotherapy" strategy. Radioactive Iodine is given to the patient with thyroid cancer after their cancer has been removed. If there are any normal thyroid cells or thyroid cancer cells remain in the patient's body (and any thyroid cancer cells retaining this ability to absorb iodine), then these cells will absorb and concentrate the radioactive "poisonous" iodine. Since all other cells of our bodies cannot absorb the toxic iodine, they are unharmed. The thyroid cancer cells, however, will concentrate the poison within themselves and the radioactivity destroys the cell from within. No sickness. No hair loss. No nausea. No diarrhea. No pain.
Most, but not all, patients with thyroid cancer need radioactive iodine treatments after their surgery. This is important to know. Almost all, however, should have the iodine treatment if a cure is to be expected.
Patients with medullary cancer of the thyroid usually do not need iodine therapy because medullary cancers almost never absorb the radioactive iodine. Some small papillary cancers treated with a total thyroidectomy may not need iodine therapy as well, but for a different reason.
These cancers (medullary and some small papillary cancers) are often cured with simple (complete) surgical therapy alone. This varies from patient to patient and from cancer to cancer. This decision will be made between the surgeon, the patient, and the referring endocrinologist or internist. Remember, radioactive iodine therapy is extremely safe. If you need it, take it.