New imaging technologies have led to the overdiagnosis of thyroid cancer, exposing thousands of people to unnecessary, costly, and potentially harmful treatments, according to a new analysis from three doctors at the Mayo Clinic in Rochester.
The problem is especially acute here in the United States.
Because of their concern, the Mayo doctors are recommending that a new term be used to describe low-risk thyroid lesions — a term that will better convey the minimal risk that such lesions pose to a patient’s health and that will steer both patients and doctors away from unnecessarily treating them.
“We need to rename them,” said Dr. Juan Brito, an endocrinologist and one of the authors of the analysis, in a phone interview Monday. “We need to put them in a different category.”
The analysis was published Tuesday in the journal BMJ.
A perplexing rise in diagnoses
During the past 30 years, the incidence of diagnosed cases of thyroid cancer has tripled in the United States, from 3.6 cases per 100,000 people in 1973 to 11.6 cases in 2009.
“It’s become one of the fastest-growing cancer diagnoses,” said Brito.
The rising incidence rate has been observed worldwide, but not uniformly, he added. Sweden, Japan and China, for example, have experienced a minimal increase in the incidence of this particular cancer.
Furthermore, almost all of the new cases of thyroid cancer being diagnosed — 90 percent — involve small papillary tumors, which studies have shown are very slow-growing and highly unlikely to go on to cause symptoms much less death.
That factor most likely explains why the death rate for thyroid cancer has remained the same while the diagnosis of new papillary thyroid cancers as skyrocketed.
Key factors behind the rise
As Brito and his colleagues, Dr. John Morris and Dr. Victor Montori, explain in their paper, more papillary lesions are being diagnosed because of advances in high-tech imaging technologies, such as ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI), which can now detect thyroid nodules as small as 2 millimeters.
Another factor are reimbursement policies that reward physicians for the use of those technologies, the Mayo doctors add. The routine use of neck ultrasonography has increased at least 80 percent since 1980.
Research has also shown that higher-income Americans — particularly those with good health insurance — are much more likely to be diagnosed with thyroid cancer than those in lower income brackets.
“The access to technology as well as the use and sometimes the abuse of that technology is driving the overdiagnosis,” said Brito.
Overdiagnosis often leads to overtreatment, including unnecessary surgery, Brito and his colleagues point out in their paper. Indeed, the number of thyroidectomies (surgeries that remove all or part of the thyroid gland) rose 60 percent in the United States between 1996 and 2006.
The thyroidectomy procedure is costly and associated with several serious and permanent complications, including nerve injury to the larynx. People who’ve had a total thyroidectomy — or even, in some cases, a partial one — must also take thyroid replacement therapy for the remainder of their lives, a treatment that poses its own health risks.
Radioactive iodine treatment is also being increasingly prescribed in the United States for low-risk papillary lesions. In 1973, one in 300 patients with thyroid cancer received these treatments. In 2006, that number had grown to two in five patients. Yet radioactive iodine treatments are not recommended for people with low-risk thyroid lesions. The treatments are associated with a reduced quality of life and a risk of developing other types of cancer, including leukemia and cancer of the salivary gland.
Need for new nomenclature
Brito and his colleagues acknowledge that there may be yet-unidentified reasons for the rapid rise in the incidence of thyroid cancer — radiation exposure from the widespread use of CT scans, for example. But the discrepancy between the incidence and death rates and the varying country-by-country incidence rates point most strongly to overdiagnosis as the reason behind the rise.
They call for doctors to engage their patients in more decision-making, and to explain to their patients that in many cases active surveillance rather than surgery is the most appropriate treatment for thyroid lesions.
“Patients can be reassured that if nodules later show more aggressive behavior the evidence suggests no additional harm from delayed surgical treatment,” the Mayo doctors write.
They also recommend that small papillary lesions be renamed macropapillary lesions of indolent course (micro PLICs) to more accurately reflect their minimal health risk to the patient.
Most thyroid lesions that are found “are not destined or meant to cause harm,” said Brito.
“But it’s very difficult not to do something when you have the label of cancer,” he added. “By removing that label, we can reframe the level of care for them.”