Michaelii
I would try behavior modification before I underwent a major surgical procedure. You got through cancer treatments and that took some mental strength. After that I believe you can do anything that you set your mind to, including eating in a healthy and appropriate manner.
Thyroid cancers from radiation prominently occur in childhood radiation patients, not adults. Also if you are in the IMRT group, they do a pretty good job of missing it with the beam these days.
Radiation destroys the thyroid function, that means that you will go hypo thyroid not hyper thyroid.
Yo u