Papillary Thyroid Cancer Overdiagnosed; Therapy Unnecessary

Nancy A. Melville

July 25, 2013

The incidence of papillary thyroid cancer has more than tripled in the past 3 decades and directly correlates with several demographic and age-based markers of access to healthcare, suggesting widespread overdiagnosis of the disease, according to a new study published in the journal Thyroid.

"We need to recognize that subcentimeter papillary thyroid cancers are probably a normal finding, based on extensive data from autopsy series, showing that 5% to 30% of patients have a small occult papillary thyroid cancer in their thyroid glands when they die of other causes," said lead author Luc G.T. Morris, MD, from the Memorial Sloan-Kettering Cancer Center's Head and Neck Service in New York.

Dr. Morris and his colleagues, using data on 497 US counties from the National Cancer Institute's Surveillance, Epidemiolgy, and End Results program, evaluated 9 sociodemographic markers of healthcare access.

They cross-referenced the variables with incidence rates of papillary thyroid cancer and found that the most rapid increases in the cancer rates were among those with the best access to healthcare — Americans over age 65, who have access to broad health coverage through Medicare. Papillary thyroid cancer rates in that 65-years-and-over group increased by 8.8% annually over the past 3 decades.

The annual rate of increase in the under-65 group — a group that does not have universal access to health coverage — was 6.4%.

Before the 1990s, papillary thyroid cancer rates were similar between the under- and over-65 age groups, but diagnostic advances changed that, Dr. Morris told Medscape Medical News.

"All of a sudden, in the 1990s, it became much easier for a doctor to order a thyroid ultrasound for patients, and lots of nodules starting getting found on ultrasound and were easily biopsied, leading to the diagnosis of a lot more small thyroid cancers that were always there," he observed.

"Therefore, the rate of papillary thyroid cancer started increasing faster in people with nearly universal access to healthcare — people over 65."

But No Change in Mortality Over That Period

Papillary thyroid cancer incidence rates, meanwhile, vary widely across counties, from as low as 0 to up to 29.7 per 100,000 residents. A closer look at the counties' sociodemographic markers shows that the incidence rates line up with all 9 sociodemographic markers of healthcare access.

Higher incidence rates were associated with counties with higher rates of college education, white-collar employment, and family income. Conversely, the lower rates were seen in counties with higher percentages of residents who were uninsured, unemployed, of nonwhite ethnicity, and non–English-speaking; were living in poverty; and did not have a high school education.

Although the argument could be made that more papillary thyroid cancers are indeed developing and those with better access to healthcare are simply more likely to be diagnosed, increases of papillary thyroid cancer mortality rates would be expected under that scenario, and in fact mortality has not changed over the period, Dr. Morris stressed.

"Regardless of how much access to healthcare you have, your risk of dying of thyroid cancer is the same. If we were truly failing to diagnose a lot of papillary thyroid cancers in people without health insurance, we would expect these people to develop more late-stage, aggressive thyroid cancers and be more likely to die of thyroid cancer. This is not the case."

The authors note that the association of healthcare activity with the prevalence of papillary thyroid cancer satisfies 1 of 2 conditions typically considered to be criteria for true overdiagnoses, defined as diagnosis of a cancer that would not have caused any symptoms or harm if it had not been found.

The other condition is evidence that a large reservoir of subclinical disease exists, and they cite several studies that confirm that.

Many Downsides to Overdiagnosis of Thyroid Cancer

The diagnosis and treatment of such subclinical cancers, in addition to placing a heavy financial burden on the health system, cause a host of other significant problems, needlessly, Dr. Morris said.

Patients will typically undergo surgery and radioactive iodine therapy and require lifelong thyroid hormone replacement, as well as lifelong surveillance. In addition, while surgery is low risk, it is not entirely risk-free.

"For those 1% of patients who experience a complication from surgery, such as a nerve injury, this is a huge deal, especially if treatment was never truly necessary."

And then there is the substantial psychological impact of a cancer diagnosis, he added.

"Patients develop incredible anxiety about their cancer diagnosis, which is a life-changing moment in their lives," he explained.

"I see these patients in my office every week — people who are terrified they are going to die after being given a cancer diagnosis and literally will not go about their day-to-day lives ever the same."

Healthcare access has also been associated with overdiagnosis of many other cancers, including prostate cancer, which many men can harbor as low-risk, asymptomatic cancers that do not require treatment, Dr. Morris explained.

"Similarly, somewhere between 5% and 30% of Americans have a small papillary thyroid cancer in their thyroid glands, which will never cause any symptoms or problems for them," he said.

Physicians Should Follow Guidelines

Most medical society guidelines for when to biopsy a thyroid nodule recommend that very few thyroid nodules smaller than 1 cm should be biopsied, yet not all physicians follow the recommendations, Dr. Morris noted.

Greater adherence to the guidelines and awareness of the likely benign nature of the smaller nodules should help eventually address the problem of overdiagnosis, he said.

"In the future, it is likely that patients with small, low-risk papillary thyroid cancers will be offered active surveillance instead of surgery, akin to our current management of low-risk prostate cancer. We are already offering this option to patients at Memorial Sloan-Kettering Cancer Center."

Dr. Morris received funding from the National Institutes of Health. The other authors have disclosed no relevant financial relationships.

Thyroid. 2013;23:885-891. Abstract

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