Thyroid cancer overdiagnosis raises questions about overtreatment

Issue: November 2016

DENVER — The “epidemic” in thyroid cancer recently reported by a number clinical journals has raised questions about overdiagnosis of thyroid cancer and overtreatment of papillary microcarcinoma, according to a presenter at the 86^th Annual Meeting of the American Thyroid Association’s opening session.

Ian D. Hay, MD, PhD, FACE, FACP, FRCP, professor of medicine and endocrine research at the Mayo Clinic, reviewed data from a number of previously published studies evaluating the incidence of thyroid cancer, particularly papillary thyroid cancer (PTC) and papillary thyroid microcarcinoma (PTM).

Ian D. Hay

According to Hay, over the past 8 decades, PTM represented about one-third of PTC at the Mayo Clinic, and nearly 70% of those cases were classified by TNM staging as T1 tumors (≥ 2 cm).

In a New England Journal of Medicine perspective published last month, researchers stated that the incidence of thyroid cancer worldwide has consistently been increasing in recent decades and may be attributable to the use of new diagnostic techniques coupled with increased medical surveillance and access to health care services.

According to Hay, the perspective revealed that overall, in the 12 countries included in the analysis, an estimated 417,000 women and 90,000 men have been overdiagnosed with thyroid cancer.

“The major burden of overdiagnosis has fallen on women,” he said. “Patients, particularly women, need protection from the harms of unnecessary diagnosis.”

According to Hay, smaller thyroid cancers will most likely never result in symptoms or death.

“Medical imaging identifies small nodules, which are subject to biopsies, and about 5% have cancer cells,” he said. “The usual next step is surgical removal often followed by radioactive iodine and lifelong thyroid complications.”

Hay further reviewed a study performed at the Mayo Clinic, previously reported at this year’s Endocrine Society Meeting. Cases of PTC treated from 1935 to 2014 were reviewed.

“We hoped to find an appropriate aggressive approach for patients with PTM in the United States,” Hay said. “It is still a very controversial topic. We still live in times where some favor observation without surgical therapy, where others prefer near-total or total thyroidectomy and selected use of radioactive iodine for remnant ablation.”

There has been some success in treating a small group of patients without surgery or ethanol ablation, Hay said.

“As this audience appreciates, the recently published ATA guidelines now recommend unilateral lobectomy as the usual surgical procedure for adult patients with PTM,” he said.

Patients in the study were followed for as long as 63 years, and patient-years of observation exceeded 20,000. After an average follow-up longer than 15 years, only four patients died from thyroid cancer whereas nearly one-third died from other causes.

“We again demonstrated that patients with PTM had normal life expectancy and typically are cured with tumor resection,” Hay said. “We also found that the extent of surgery did not affect local regional recurrence rates. Moreover, 30-year recurrence rates were no different after lobectomy alone when compared with the rates seen with near-total or total thyroidectomy and followed by radioactive iodine remnant ablation.”

Hay added that the most important finding of the study was that surgery leads to more morbidity in terms of nerve and thyroid damage.

“Our patients who underwent near-total or total thyroidectomy had a small but significant risk for postoperative morbidity, whereas not one of our lobectomy patients had these risks postoperatively.” – by Amber Cox

Reference:

Hay ID. Changing Attitudes to the Most Common Endocrine Malignancy, T1 PTC. Presented at: 86th Annual Meeting of the American Thyroid Association; Sept. 21-25, Denver.

Vaccarella S, et al. N Engl J Med. 2016;doi:10.1056/NEJMp1604412.

Disclosure: Hay reports no relevant financial disclosures.