Case Studies in Thyroid Cancer - Episode 3
Andrew Gianoukakis, MD, reviews the treatment and management options for a 71-year-old woman with RAI- refractory differentiated thyroid cancer.
Andrew Gianoukakis, MD: The patient received 150 mCi of radioactive iodine. The post-therapy whole body scan showed uptake only in the neck, consistent with what we’d expect from a thyroid remnant. The patient was started on levothyroxine suppression therapy, which is commonly used to suppress further growth and progression.
Lori Wirth, MD: Andrew, I have a question for you. This patient who got the radioactive iodine, her body scan showed uptake in the neck only; that means that she’s disease-free, right?
Andrew Gianoukakis, MD: It does not mean that she’s disease-free.
Lori Wirth, MD: But her whole body scan is negative.
Andrew Gianoukakis, MD: That’s correct. Any thyroid cancer metastases are likely to have less radioiodine avidity than your normal thyroid tissue and that remnant that we’ve mentioned. So significant uptake in the remnant—which can be due to the size of the remnant, or the more tissue that’s left behind, the higher the likelihood of significant uptake in the neck—that can suck up the radioactive iodine and take it away from it being taken up by locally or distantly metastatic disease. This will then show up subsequently on your next scan, either diagnostic or post a second therapy. Uptake only in the neck, as in this case, does not rule out metastases, either locally or distantly, at the present time. However, when we can see uptake outside the central neck in the lateral neck or distantly, that clearly indicates either local or distant disease at the time of the initial therapy.
Follow-up at 6 months: the patient’s TSH [thyroid-stimulating hormone] was appropriately suppressed, and the thyroglobulin was noted to be 24 ng/mL with negative antithyroglobulin antibodies, thus allowing us to have confidence in that elevated level of thyroglobulin. At a thyroglobulin level of over 10 ng/mL, the more likely we are to find either local or distant disease if we begin to look both in the neck and outside the neck. Due to this level of thyroglobulin in addition to a neck ultrasound, a CT scan of the chest was performed, which showed small bilateral lung nodules, the largest being 1.1 cm. At follow-up 3 months later, another CT of the neck and chest noted interval minimal growth progression of 1.0 to 2.0 mm in several lung nodules, as well as 2 distinct 8.0-mm lung nodules. Next-generation sequencing was performed on the tissue and the PTC [papillary thyroid cancer] was noted to be BRAF positive and had a positive TERT mutation.
Lori Wirth, MD: Marcia, I’m going to ask you a question. For the next-generation sequencing, do you have to biopsy one of the lung nodules in order to do the testing, or can you do that testing off of the initial surgical specimen?
Marcia Brose, MD: In most cases, the initial surgical specimen will have the same genotype, especially any of the metastases that are found right in the context of the original surgery. It is true that it’s possible for people to accumulate more mutations as time goes on. If a person had a new metastasis, and it had been 20 years from their primary surgery, then it’s often helpful to get a new biopsy. Especially in that case, sometimes that older tissue is no longer available or is no longer good enough quality to test. In general, I think you’re fine up front going ahead and getting that initial somatic testing based on the original primary.
Lori Wirth, MD: Yes, I agree. BRAF V600E is a driver alteration; it’s going to be present in the primary tumor, and it’ll be present in the distant metastases as well.
Marcia Brose, MD: It’s only really the other mutations, AKT and others, that sometimes accumulate and might come up a little bit later that you might want to know about. However for BRAF, absolutely, you would pick that up properly from the very beginning.
This transcript has been edited for clarity.