Differentiated Thyroid Cancer: Increasing Incidence

Lori J. Wirth, MD: Hello, I’m Lori Worth. I am the Elizabeth and Michael Ruane chair of oncology at Massachusetts General Hospital, and an associate professor of medicine at Harvard Medical School in Boston. With me here today is Dr Jennifer Sipos, a professor of medicine and a member of the Division of Endocrinology at Ohio State University in Columbus, where she is also the associate vice chair for diversity and inclusion. Hi, Jen.

Jennifer Sipos, MD: Hello.

Lori J. Wirth, MD: We’re going to talk today about thyroid cancer. We’re going to talk broadly about thyroid cancer, and then focus on how we treat our patients with iodine-refractory differentiated thyroid cancer. One of the interests that we have today is in how we work together across disciplines. How do we share patients with medical oncology and endocrinology? I’ll really enjoy having this conversation with you, Jen, as you are an endocrinologist, and I am a medical oncologist.

Jennifer Sipos, MD: Thank you, Lori. I’m excited to be here.

Lori J. Wirth, MD: One of the things that is interesting is this skyrocketing incidence of thyroid cancer in our population, and in many developed populations around the world these days. How do you see that increasing incidence? Is it something that we need to be thinking about in terms of bad thyroid cancers, or is it just a phenomenon of overdiagnosis?

Jennifer Sipos, MD: Thank you, Lori. There’s definitely been a lot of interest in this area over the past 10 years or so, since we’ve started to see that increasing incidence trend. We know that the incidence of small thyroid cancers is on the rise. We know that there’s a reservoir of undiagnosed small cancers when we look at surgical series with patients who go to the OR [operating room] for nonmalignant causes needing a thyroidectomy. We see that the incidence rate is around 10% to 15%. Then when we look at autopsy series, the incidence rate of thyroid cancer for people who died for some other reason is consistently in the 10% to 15% range, on average, in the United States. There’s definitely a large reservoir of undiagnosed disease. The incidence of those undiagnosed, indolent cancers is about 1000-fold higher than what we clinically diagnose. We’re able to tap into that reservoir. When we start doing imaging for some other reason and incidentally notice thyroid nodules, which we know are very common, then that work-up leads to the diagnosis of a small cancer.

But we also know from these studies in which we’ve looked at this trend in thyroid cancer that it’s not just the small cancers that are on the rise. We’re also seeing an increased incidence of larger tumors, and more aggressive tumors. There’s probably some other factor, besides increased diagnostic scrutiny, that is leading to this increased incidence of thyroid cancers in general. It’s important to understand what’s causing this trend. But it’s also important to understand, as clinicians, that we need to be able to distinguish those indolent cancers and small tumors that the patient would have died with, not from, from those tumors that we’ve identified and which would have gone on to become more aggressive cancer. We need to be able to understand where this patient’s tumor falls on that spectrum so we can better address how to treat that tumor. If it’s an indolent tumor, we don’t need to be very aggressive with it. But if it’s one that would go on to become more aggressive, we want to be proactive in its management.

Transcript Edited for Clarity