Radioiodine ablation

The next thing, following surgery and assuming that a total thyroidectomy has been done, the next thing is going to be radioiodine ablation. Basically what is done here is the patient is allowed to become hypothyroid, their TSH rises and they then are given a tracer dose of 131 iodine which typically will show uptake in the neck, because even a total thyroidectomy, surgically complete, is rarely complete at the level of radioiodine uptake. Assuming that there is a remnant, then that is going to be ablated with 131 iodine. There are questions in terms of dosage which I propose not to get into right now. But following ablation with radioiodine the patient would then be placed on thyroxine therapy with the goal of suppressing the TSH and now we are down to what we will call surveillance. This is the kind of findings that one might see in a patient, in terms of the benefit of adjunctive radioiodine. This is a total body metastatic scan, an anterior and posterior image, in a patient who had undergone a surgically complete thyroidectomy. This is uptake in the salivary glands, that’s normal. This is, as you can see, a lot of uptake remaining in the thyroid bed and at least some of this would appear to be metastatic in origin, going all the way down to the level of the suprasternal notch. In addition, you can see areas of uptake in the lung. This is a xiphoid marker here, some residual iodine in the lung uptake is actually this over here. So that patient was given a therapeutic dose of 131 iodine, probably in that case 200 microcuries of iodine were given. And this is a scan that was done a year or two later. At this time the patient was again withdrawn from thyroxine, the TSH was again allowed to rise and they were again given a tracer dose of radioiodine. There is still this appropriate uptake into the salivary glands, but you can see now the neck and the chest are now clear. There is still some uptake in the large colon over here. In fact, this patient has been disease free since the time of this treatment.

And this again is just some data from Masoferre’s studies on recurrence and death rate again in patients with intermediate stage II and III disease in the absence or presence of radioiodine. And you can see that there were no deaths in the radioiodine treated group and a substantial decrease in the risk of recurrence as well.

Finally, the surveillance data. We’ve already sort of alluded to that. There are two major components to surveillance. One is the measurement of thyroglobulin, the thyroglobulin which is a normal thyroid product should be undetectably low in patients who have undergone total thyroidectomy and radioiodine ablation who are disease free. So a rising thyroglobulin is a marker of a return of thyroid tissue, obviously very suspicious for thyroid cancer. The other major surveillance tool that I alluded to is the use of the whole body metastatic survey. My recommendation is, assuming that we treat the patient which might typically occur eight weeks or so after their initial surgery, assuming that we treat the patient, that there is some remnant uptake. Certainly if there is metastatic uptake, I would repeat a scan a year later and a year after that I would want to see two negative scans at yearly intervals following radioiodine therapy before I’d stop doing yearly scans. If the scans continued to show metastatic uptake then of course one might want to consider further treatment with radioiodine to eradicate recurrent or residual disease. I’ll also then continue to follow the patients by measuring their thyroglobulins periodically and using that as an additional screen.

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