Case Studies in Thyroid Cancer - Episode 2
Experts in thyroid cancer discuss treatment considerations surrounding the use of radioiodine therapy in patients with thyroid cancer.
Lori Wirth, MD: Let’s talk about this case: this is an elderly woman who underwent thyroidectomy for papillary thyroid cancer. Andrew, you’re the endocrinologist of the group, so you know the most about radioiodine treatment; do all patients need radioactive iodine [RAI] after thyroidectomy when they’re diagnosed with thyroid cancer?
Andrew Gianoukakis, MD: Times have changed. It was only a few years ago that the recommendation was that just about everyone with thyroid cancer would receive radioactive iodine after surgery. Over the past decade, radioactive iodine use has become more limited. It’s not recommended to be used in the lower-risk cases, and due to data suggesting efficacy, it’s recommended to be used in higher-risk cases such as this one. With a larger tumor, lymph nodes that are positive, with the largest lymph node over 2.0 cm, this case would be considered an ATA [American Thyroid Association risk stratification system] intermediate risk, where radioactive iodine would be recommended; we would lean toward treating this patient with radioactive iodine. But as noted, in other cases it may not be necessary.
Lori Wirth, MD: Can you describe what the list of higher-risk features are that put a cancer into the intermediate or higher-risk group of patients for whom we’d give radioactive iodine?
Andrew Gianoukakis, MD: There’s quite a list of characteristicsthat are offered in the most recent ATA guidelines, which are under review. We are close to having new guidelines, but based on the current guidelines there are adverse risk factors associated with increased risk of recurrence: aggressive histology of the papillary thyroid cancer tumor, vascular invasion, wide invasiveness of follicular tumors, lymph nodes of 2.0 cm or greater, the size of primary tumor. These suggest an increased risk of recurrence that then warrants radioactive iodine therapy.
Lori Wirth, MD: Andrew, for the uninitiated among us, since we’re mostly not endocrinologists, what are the goals of radioactive iodine treatment for patients with thyroid cancer? Are we trying to cure them by adding radioactive iodine, or are there other goals?
Andrew Gianoukakis, MD: The goal of the initial radioactive iodine therapy is to ablate the thyroid remnant. In most cases, even the best surgeons will leave some normal thyroid tissue remnant in the neck, so the goal of the initial surgery is to ablate that remnant as well as potentially treat any micrometastases that exist and are radioiodine avid. In addition to treating micrometastases, getting rid of the thyroid remnant allows the thyroglobulin level to be a more sensitive and specific marker of disease, rather than thyroid tissue, since we’ve surgically removed and then ablated the overwhelming majority of normal thyroid tissue.
Lori Wirth, MD: The corollary of the patients who have 1 or more of those high-risk features, I guess we know in general, the patients who don’t necessarily need to have radioactive iodine: patients who have small tumors, no lymph nodes, or small volume disease metastatic to the lymph nodes, negative margins.
Andrew Gianoukakis, MD: Right, as well as good histology.
Marcia Brose, MD: I’ll just chime in as well. There’s one other group of patients who might have at the time of diagnosis a significant burden of disease, maybe in the chest, who need a rapid response. Even if radioactive iodine causes shrinkage, it tends to be slow, so occasionally patients who are symptomatic at the time of their original surgery also might not be considered good candidates for radioactive iodine up front because they need a more rapid response, and they can’t wait for that process to happen. Thankfully, it’s rare.
Lori Wirth, MD: I was just going to say the same thing. Good point, and thankfully we don’t see those patients very often. Andrew, you talked about the American Thyroid Association’s low-risk, intermediate, and high-risk categories at the time of diagnosis; I think we covered that. Is there further risk assessment for patients who present with thyroid cancer garden variety, they have the thyroidectomy, then they get radioactive iodine? Is there further assessment that’s done that involves ongoing risk assessment?
Andrew Gianoukakis, MD: After the initial therapy, which will include surgery plus or minus radioactive iodine, we will first look at the post-therapy scan. If the post-therapy scan shows disease outside of the central bed, that portends a higher risk for recurrence, particularly of course, if an unsuspected metastatic lesion or lesions are picked up most notably or commonly in the lungs.
Lori Wirth, MD: Andrew, I didn’t want to interrupt you, but you’re talking about a whole body nuclear medicine scan after the radioactive iodine to see where the uptake is, correct?
Andrew Gianoukakis, MD: Correct. After that initial assessment, which has occurred within the first couple of months of diagnosis, surgery, RAI therapy, and the post-therapy scan, we begin to follow patients with neck ultrasounds and thyroglobulin levels, as well as antithyroglobulin antibodies, to be able to have confidence in our thyroglobulin levels. The risk assessment that was performed initially as noted is then followed up by a continuous ongoing risk assessment, where our concern and our level of surveillance is either decreased and modified to a less aggressive surveillance, or a more aggressive surveillance, depending on the follow-up ultrasound and thyroglobulin levels, and how the patient responds to that initial therapy of surgery +/- radioactive iodine.
This transcript has been edited for clarity.