Advances in cancer detection have saved many lives, but they have a serious drawback: Some cancers are being overdiagnosed. This leads to unnecessary treatment of tumors that never would have posed a threat if left alone.
For example, the reported rate of thyroid cancer in the United States has more than doubled since 1994, as scans have increasingly found tiny tumors that would have escaped notice in the past. Despite this surge in detection and treatment, the death rate for thyroid cancer has not budged — an indication that these tumors were not life threatening.
A new program at Memorial Sloan Kettering gives some people with very early-stage thyroid cancer the option of avoiding immediate surgery and instead having their tumor followed closely. MSK endocrinologist Michael Tuttle discusses thyroid cancer overdiagnosis and explains why the watch-and-wait approach is often the best choice.
What’s changed in the medical field that’s led to thyroid cancer now being overdiagnosed?
The main reason is that our technology got ahead of us. When I was a medical fellow in the early 1990s, the only thyroid cancers likely to be diagnosed were lumps I could feel with my hands. But around that time, ultrasound evaluations became available for use in routine clinical practice and identified many more small thyroid nodules than we could ever detect by touch. In addition, many CT and MRI images that happen to show the thyroid area were done for unrelated reasons — and often revealed tiny nodules.
When doctors see these nodules they often feel they must investigate further. With the help of ultrasound, it was increasingly easy to use a small needle to biopsy tiny nodules. Pathologists also started examining thyroid surgical samples much more closely, often finding very small specks of thyroid cancer even when the thyroid was taken out for an unrelated cause such as goiters.
I picture it like an iceberg. We used to see only what was floating above the water, but as we use more sensitive tests, we identify more cases below the water line. In fact, there have been multiple studies, some conducted by [MSK surgical oncologist] Luc Morris, showing how nonmedical factors contribute to this trend — for example, diagnosis rates are higher in counties with higher levels of income and more access to healthcare.
We now know that as much as 10 percent of the adult population has a small, subclinical thyroid cancer — meaning that it doesn’t cause symptoms — which comes to millions of cases in the United States. Currently, we’re diagnosing 60,000 cases a year, which is twice as many as two decades ago, but still only a fraction of the potential cases in the US population.
Why is this increase in diagnosis a potential problem for patients?
It has become clear that most of these very small thyroid cancers never pose a threat. The most common type, papillary thyroid cancer, grows very slowly. They are the same size in someone at age 80 that they were at age 40.
But when someone has cancer, they or their doctor often want it out, and all surgeries carry some risk. Here at MSK, the complication rate is small, because our surgeons are very experienced. Nationwide, however, about half of thyroid cancer removals are done by surgeons who perform fewer than ten a year. In a small percentage of patients, surgery can damage the nerve that controls the vocal cords or the glands that regulate calcium in the bloodstream. In addition, patients whose thyroid is removed have to take hormones the rest of their lives. While most do fine, about 10 to 20 percent tell me they don’t feel good on the thyroid pills. They feel fatigued and have to press harder to function at their normal level.
So when you’re looking at a slow-growing cancer that’s not likely to be fatal, it is very important to question whether immediate surgery is required, especially if it could harm quality of life.
How does MSK follow this approach of watchful waiting?
We have begun a tactic of active surveillance — a method pioneered very successfully at MSK with low-risk prostate cancer, another slow-growing type that historically has been overtreated. When someone comes in with a small papillary thyroid cancer that appears to be confined to the thyroid gland, we now try to determine whether he or she is a good candidate for observation.
If our thyroid cancer team feels that immediate surgery is not required, we offer the chance to have an ultrasound every six months for two years, when we will look closely at the site of the cancer and the nearby lymph nodes to see if there is any change. After two years, we start spacing out the ultrasounds, to every nine or 12 months.
We know that in the vast majority of cases, if thyroid cancer progresses, it’s going to happen very slowly — in which case our surgical treatments will almost certainly be as effective in the future as they would be now. There is a small chance we will identify spread of cancer cells to lymph nodes around the thyroid at some point. But the chance of this is actually the same whether we do active surveillance or take out the thyroid up front.
I tell my patients that it’s OK if I’m wrong in the short term — we can do surgery later and be just as effective.
Some small tumors are not appropriate for this method, depending on location and other factors, but those are a tiny group. We’ve been following more than 225 patients for a median period of about two years. Out of those patients, only about four or five have tumors that have grown.
How have patients reacted to this option? Is there any reluctance to leave cancer untreated?
Some patients do want surgery right away. But a surprising number are interested in avoiding the operation. Many don’t want to be on pills, or they’ve had family members or friends who have had thyroid surgery and don’t feel well. I find that a lot of people choose observation as a bridge to postpone treatment — they’ve just gotten a new job, or something else is going on, and they don’t want surgery now if it’s not essential. I remind them that they can always change their minds at any time, and that I may change my mind if I see something I don’t like.
Of course, when you’re seeing an individual patient, it is impossible to know if his or her thyroid cancer will be stable for years under observation or if it will grow over the next year or two.
Is there a way to get a better idea of which tumors will actually grow?
This is a very important question we are actively researching. The laboratories of [MSK physician-scientist] James Fagin and [MSK genomics researcher] Michael Berger are actively doing research to try to determine whether there is a genetic signature that would allow us to predict what’s going to happen. If we can identify which mutations are important, we could just use a small needle to biopsy the cancer, analyze the genes, and be able to more accurately predict the likelihood that an individual cancer will progress.
I think patients would find that kind of information very helpful in deciding whether to be watched or proceed to immediate surgery. So even though active surveillance is working well in the vast majority of our patients with very small papillary thyroid cancers, we’re trying to use our molecular research laboratories to give us an even clearer idea of which tumors will cause problems so we can give our patients the best option.