Sep 18, 2018
Successful treatment of advanced thyroid cancer often involves a combination of therapies. Dr. Sarika Rao discusses how we determine patient care plans.
Intro: MedStar Washington Hospital Center presents Medical Intel where our healthcare team shares health and wellness insights and gives you the inside story on advances in medicine.
Host: Thanks for joining us today. We’re talking to Dr. Sarika Rao, an oncologic endocrinologist at MedStar Washington Hospital Center. Today we’re talking about how to treat advanced thyroid cancer when standard treatments fail. Dr. Rao, can tell us about the main types of thyroid cancer?
Dr. Rao: Yeah, sure. So thyroid cancer is, the eleventh most common cancer out there. Just briefly, it’s more prevalent in women, but tends to be a little bit more aggressive in men. There are two main types of cells within the thyroid gland - there are follicular cells and there are C cells, c as in cat. So, follicularly-derived thyroid cancer would include papillary, follicular thyroid cancer - which there’s a subsection: Hurthle - which goes with that as well as anaplastic, that’s the most advanced and most aggressive thyroid cancer but it is follicularly derived. And then the C cells that also exist and these are neuroendocrine cells - and thyroid cancer from that specific cell is called medullary thyroid cancer. So, your follicularly derived cancers are the most common, where papillary is the most prevalent. About 80 to 85 percent of all thyroid cancers are papillary. And then your follicular and Hurthle are about 10 to 15 percent and anaplastic is less than 2 percent, so that’s very rare. And then your medullary is about 1 to 2 percent.
Host: How is thyroid cancer diagnosed and treated?
Dr. Rao: Generally, the treatment is, a patient finds a nodule, either on, other imaging studies, like a CAT scan or a PET scan for some other reason and a nodule is detected, or on physical exam, the physician or the patient finds, like a lump in the throat area. And then that is followed up with ultrasound and then potentially biopsy, depending on the features of the nodule. If it is thyroid cancer really the first step is surgery. Whether that’s taking out half the gland or taking out the entire gland, as well as lymph nodes, it depends on the type of thyroid cancer and the extent of the disease and the size of the nodule - it’s a very complex process but, you know, we always discuss this with, the endocrinologist and the surgeons to make a decision, in a multidisciplinary fashion. Many times, we take out the entire gland because, oftentimes, especially with the most common type of cancer which is papillary thyroid cancer, it can be multi-focal that you may not realize is on the other half of the gland. But usually a nodule is dominant when it’s greater than one centimeter that we can see on ultrasound. We can see smaller nodules than that, as well. Sometimes the ultrasound doesn’t pick up nodules on the other side. So, if a nodule is quite big on one side, then we are more likely to take out the entire gland because there’s a likely chance that a smaller cancerous site could be on the other side. But that’s a decision that’s made between the patient, surgeon and the endocrinologist.
Host: Could you describe the patient care process after surgery?
Dr. Rao: Right. So then, after surgery, we get the full pathology and determine the extent of the disease and how aggressive or not the cancer is. And then we follow that up with something called radioactive iodine ablative therapy. It’s a painless test. So, the way I like to explain it to my patients is, in general, thyroid loves iodine. But it involves a low iodine diet for a couple weeks prior to getting this treatment because you are trying to prime those remnant thyroid cells from, wanting that iodine even more, even though it’s a little bit different. So, making them hungry and taking up this radioactive iodine into the gland and then that will destroy any of the remnant tissue. So, they do this low iodine diet and then, most of the time, we do a diagnostic scan to see if there’s any evidence of uptake and by uptake I mean do any of those remnant cells take up that iodine and we can see it in a diagnostic scan, which is a low dose of this radioactive iodine that we give. Because, like we said before, your cells are very hungry for this iodine. We have a risk stratification for the patient. Like, depending on how advanced their disease is. And this form of treatment, by the way, is only for papillary follicular and maybe even Hurthle cell. There are two other forms of thyroid cancer which are a little bit more aggressive where we wouldn’t use this therapy, so I just want to be clear about that. So, depending on their risk stratification - how advanced their disease is and risk of recurrence, then we proceed forward with the ablative dose, which is usually a higher dose of this radioactive iodine. And then after that there are precautions where the patient needs to make sure that they’re keeping a little bit of distance from young children, or other animals, and that’s truly just so that no one else’s thyroid becomes affected. So, they’re radioactive, sort of, but it’s only for a few days and we give them a very instructive packet as to what to do. So, after that, and this, to me, is probably the most important aspect of thyroid treatment after your surgery, is TSH suppression.
Host: What is TSH suppression?
Dr. Rao: So, you don’t have a thyroid gland anymore, so you need that hormonal replacement with medications like Levothyroxine, which is a generic form, or Synthroid. And there are other different brands out there. In a patient who has a benign disease who had their thyroid out, we calculate a weight-based dosing for the replacement. Someone who had thyroid cancer, we actually give a little bit more of the Levothyroxine or the T4, which is the actual thyroid hormone that you no longer have, and this is so that, you give a little bit more of the dose in an effort to suppress a hormone that’s made in the pituitary which normally stimulates thyroid cells to function, called TSH. And TSH stands for thyroid stimulating hormone, so it does exactly that. So, by giving a higher dose of the actual thyroid hormone you’re effectively suppressing the TSH made in the pituitary so you’re preventing any form of stimulation of any remnant cells that may not have been ablated from the radioactive iodine or, in a patient who didn’t receive radioactive iodine, any remnant cells from getting bigger. So that is very important afterwards, and we have criteria for what we look at and what is safe for a patient. Remnant cells may or may not carry the thyroid cancer in it, but we just want to prevent recurrence of the disease. So, if you still have thyroid tissue the risk of recurrence could be higher in certain individuals and lower in others depending on, you know, the extent of the disease and that’s a risk stratification process. So, for remnant cells that are there, we try to ablate and kill them as much as we can because surgically there’s only so much you can take out. And cells, of course, you can’t see them they’re microscopic, so there’s likely to be some remnant cells after surgery and we just want to prevent recurrence of disease. That’s the goal.
Host: What are the typical outcomes after treatment?
Dr. Rao: So generally thyroid cancer is, in many situations, is well-behaved. Actually, in the SEER data, the percentage of death for thyroid cancer is only about 3 percent. It’s quite low. So usually, in my practice at least, I repeat an ultrasound at the six-month mark and then again at the one-year mark. And whether a patient received radioactive iodine therapy or not, at the one-year mark I will perform a test which is called a stimulated thyroglobulin test. The thyroglobulin is like our tumor marker for thyroid cancer, and its protein that’s made by the thyroid cells. So usually, you know, in someone who responded very well to therapy the thyroglobulin would be undetectable after surgery and/or radioactive iodine ablation. And that thyroglobulin is stimulated by TSH so that’s the whole purpose of keeping the TSH low because you don’t want it to be stimulated. Except when we do this test - we want to stimulate any remnant cells or any...whether it’s cancer or not, but especially if it’s in the thyroid bed. If it’s outside of the thyroid bed, then that is obviously more concerning for cancer.
Host: What do you mean by thyroid bed?
Dr. Rao: So, I call it thyroid bed because the thyroid is not there anymore, so at the base of the neck. Ok, so let’s say we are monitoring this patient and at the one-year mark have our ultrasound and maybe we see evidence of disease somewhere. We do this stimulated thyroglobulin level and we do another scan - again, this is with that low iodine diet that everyone quote unquote loves - and this is in an effort, to really identify disease in that manner. So, if you do the scan and you know that there is maybe evidence of disease in the ultrasound or maybe elsewhere that you’ve detected and that scan, when you perform the scan it does not take up that iodine anymore - or after several years of watching this you see growth of the disease after several treatments with radioactive iodine, then we call that radioactive refractory disease. And what that means is that your, those thyroid cells are no longer taking up the iodine, And also, in some of those cases, the tumor marker may or may not be as accurate anymore, again, due to the mutation that’s within that cell. So, at that point, you know, you decide on where the disease is - if it’s confined to the neck, maybe you want to consider reoperation. And that’s a discussion between you and the surgeon and the patient, whether they want that. Of course, all of this is dependent on age and other comorbidities and things like that, but, just in general, that’s one option, if it’s localized disease. Two, you could think about, there’s something called alcohol ablative therapy where maybe you just have one site of disease - that has been proven by biopsy, by the way, you know, let’s say we know this is thyroid cancer but, you know, it’s failed standard therapies - then you can use the alcohol to just focally ablate that particular nodule.
Host: So, you’re essentially killing the cancer cell?
Dr. Rao: You are, yeah, or that nodule where the thyroid cancer lives. And this is all localized treatment. Three, you could consider radiation therapy which we less commonly use, but it is an option. Oftentimes, if the thyroid cancer metastasizes to bone, like the spine or the ribs or something like that, which we often see with the follicular thyroid cancer, radiation therapy to those sites may be indicated because those are harder to surgically resect, unless it’s large enough. If you have multiple sites of disease, and if it’s slow-growing, you could also just consider watching the patient, especially if they’re asymptomatic. And finally, we thankfully have newer drugs - they’re called Tyrosine Kinase Inhibitors and it’s a systemic therapy. It’s a form of oral chemotherapy basically. And, these are for patients who have maybe rapidly progressive disease, those who are symptomatic or those who are asymptomatic, but their disease is in locations that, you know, may be more threatening moving forward, especially if maybe there’s invasion of the cancer into the trachea. So, this is a systemic form of therapy and we have two drugs currently approved for differentiated thyroid cancer called Sorafenib, which came out a few years ago, and Lenvatinib, which was approved in 2015, I believe, and on the market. And, generally, most of the, you know, oncologists or endocrinologists would prefer Lenvatinib at this time, if needed. But there is a very high threshold to when we use those medications. So that’s kind of a last effort. We do very close surveillance with these patients and sometimes that’s the safer option actually is to just watch it. That can be very taxing on a patient to just know that they have thyroid cancer that’s still in them or a cancer that’s still in them. But I’ve actually been very surprised with the response that I have gotten from my patients because I’m just very reassuring that, you know, we are closely watching this and, if something does happen, you know, we will address this quickly and in, you know, in a proper way. But it’s very methodical, in my mind, at least initially, as to how to approach recurrent disease.
Host: Thanks for joining us today, Dr. Rao.
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