The utility of thyroglobulin
This is an example of the utility of thyroglobulin. This is a patient who had surgery and 131 iodine ablation over here. The thyroglobulin level was initially around 5 at the time they were off suppression. They were started on thyroxin suppression. Their TSH was brought low and their thyroglobulin declined. A year later their thyroxin was stopped, TSH went back up, there was a slight increase in the thyroglobulin levels but the 131 iodine scan was negative, so they were put back on suppression. Several months after that their thyroglobulin, even while on suppression, started to rise and then when they were taken off suppression there was a considerably greater increment in their thyroglobulin, and the scan at that time was positive showing recurrent disease with pulmonary mets, which was treated with a second treatment with radioiodine.
Finally, as far as the other treatment issue that is available is the question of what one should do as far as thyroxine suppression. This is just some data from a recent, retrospective study, in which patients were scaled regarding the degree of thyroxine suppression. There were some patients who had essentially undetectable TSH’s and other patients whose TSH was not quite fully suppressed. What this is showing is that in patients with – this is going back to a TNM staging – TNM stage I or II disease, that there was not very much of an impact on recurrence related to the degree of thyroxin suppression but that in these higher risk patients with stage III disease, particularly, that the patients who were more fully suppressed had a lower risk of recurrence. So again, certainly in some of the patients who might be at a higher a priori risk there’s justification in treating them with sufficient thyroxine to keep their TSH suppressed, I feel that to an undetectable level at least for the first several years after treatment.
What about the patients who, in a way, I suppose you might be more likely to see, or the ones we need to call for additional help on, are those with differentiated radioiodine resistant thyroid cancer. A couple of potential treatment options; there is a role for external beam irradiation in these patients. Chemotherapy has been, I’d say, disappointing at best, but there still may be a role for it. The most commonly used drug has been Adriamycin, either by itself or in combination with cisplatin, with other agents. There are a variety of kind of interesting approaches being tried right now. In addition I believe there is a Taxol trial going on, although I haven’t seen any results on it. There has also been this interest in redifferentiation, in trying to treat the tumor in such a way as to lessen its radioiodine resistance and enable it to be more effective in taking up radioiodine. Retinoic acid and its congeners has been used and there has also been this interesting finding that occasionally in patients treated with Adriamycin as chemotherapy, that if you repeat the scan after they have gone through a couple of treatment cycles, that there have been some patients who have then been shown to take up radioiodine.
Suggesting that in some way there was some type of redifferentiation that took place. But clearly, these patients who get to a stage of radioresistant disease are a very very troubling group to treat. My approach, in terms of these patients, is; the question is whether they have progressive disease and whether they are symptomatic. If they are not symptomatic – and many many patients, even with extensive thyroid cancer, may not be – or maybe minimally symptomatic, there is certainly reason to simply continue to follow those patients. If there are significant symptoms taking place, which may frequently relate to bony metastases, then I think the important issue is to localize the disease. If the disease if very focal, if it involves an isolated or bony matter or a large soft tissue lesion, then there is certainly a role for external beam irradiation and/or surgery, depending on the locations involved. If the patient is progressing, has diffuse disease, then I think that might be the situation in which there would be a role for systemic chemotherapy, using either Adriamycin or some combination of agents. Then as I mentioned, consider at least not giving up totally on radioiodine but consider another scan maybe after a few cycles to see if there might have been some redifferentiation issue.