Thumbs Down to Routine Thyroid Cancer Screening, Says USPSTF

Roxanne Nelson, BSN, RN

November 22, 2016

Routine screening for thyroid cancer is not recommended, according to new draft recommendations from the US Preventive Services Task Force (USPSTF).

The new draft recommendations are largely consistent with the last final recommendation on this topic that was released in 1996 and argues against routine screening for thyroid cancer in asymptomatic adults (D recommendation).

"While there is very little evidence of the benefits of screening for thyroid cancer, there is considerable evidence of the significant harms of treatment," Task Force member Karina W. Davidson, PhD, MASc, commented in a statement. "And in the places where universal screening has been tried, it hasn't helped people live longer, healthier lives."

The Task Force emphasizes that this recommendation applies only to screening in asymptomatic adults and not to persons who may be at an increased risk for thyroid cancer because of a history of high radiation exposure, inherited genetic syndromes associated with thyroid cancer, or a history of the disease.

Last year, the USPSTF made a similar recommendation regarding routine screening for thyroid disease. At that time, they concluded there was insufficient evidence to recommend screening for thyroid dysfunction in adults who were not pregnant and didn't have any symptoms.

That 2015 recommendation for thyroid dysfunction screening closely followed on the heels of a similar statement made just a year earlier, wherein the USPSTF also concluded there was insufficient evidence to make any recommendation for or against thyroid screening in asymptomatic adults. This same recommendation was also made 10 years earlier in 2004.

Would Result in Overdiagnosis of Thyroid Cancer

Several studies have reported that thyroid cancer may be overdiagnosed and subsequently overtreated, and the data that the USPSTF reviewed on the harms of screening also suggest that overdiagnosis is likely an important issue.

"Population studies from several countries suggest that widespread screening for thyroid cancer is likely to result in overdiagnosis," commented Task Force Chair Kirsten Bibbins-Domingo, PhD, MD, MAS, in a statement. "People who are treated for small or slow-growing tumors are exposed to risks from surgery or radiation, but do not receive any benefit because the tumors are unlikely to affect the person's health during their lifetime."

The incidence of thyroid cancer in the United States has tripled in the past 30 years, from 3.6 per 100,000 in 1973 to 11.6 per 100,000 in 2009, and the incidence of thyroid cancer detection has increased by 4.5% each year during the past decade, faster than for any other cancer.

However, the USPSTF notes, there has not been a corresponding change in the mortality rate, which has held steady at 0.5 deaths per 100,000 persons since 1979. The estimated 5-year survival rate is 98.1%, ranging from 99.9% for localized disease to 55.3% for metastatic disease.

"There are two factors driving the overdiagnosis of thyroid cancer," explained Juan P. Brito, MD, MSc, assistant professor of medicine, Division of Endocrinology, Mayo Clinic, Rochester, Minnesota. He was not involved in the Task Force and was approached for comment.

"One is new and increased use of imaging techniques that expose the thyroid gland and find thyroid cancer as an incidental finding, and the other is neck palpation in asymptomatic patients," he said.

But even though the recommendation opposes screening of asymptomatic individuals, it is unclear what effect it may actually have on clinical practice.

"In Korea, they have an epidemic of thyroid cancer caused by ultrasonographic thyroid screening," Dr Brito told Medscape Medical News. "In the US this is not a problem because patients are not screened with ultrasounds but rather they are found incidentally or screened by palpation."

"The recommendation by the task force should have an impact on the latter — screening by palpation — but on the other hand, palpation of necks has been part of what doctor believe is a 'good' physical exam," Dr Brito noted. "Telling doctors that physical exam is not always a good idea, and that it may be harmful, is not a very popular recommendation."

Therefore, the new USPSTF recommendation will affect the rate of thyroid cancer diagnosis and overdiagnosis only if clinicians stop screening with palpation, as other small papillary thyroid cancers will be picked up incidentally by imaging techniques, he argues.

"For patients with no symptoms but high risk of cancer, screening for thyroid cancer should be discussed with patients in a way they understand the potential benefits and harms," he added.

Another expert agreed that it would be problematic to ask physicians not to palpate the neck and throat of a patient during a physical exam.

"The USPSTF recommendations make sense except that palpation of the neck is part of a routine exam," said Neil Hockstein, MD, director of Head and Neck Multidisciplinary Center at the Helen F. Graham Cancer Center & Research Institute at Christiana Care, New Castle, Delaware. He was also not involved with the Task Force and was approached for comment.

"Neck palpation is generally not performed to specifically screen for thyroid cancer," he told Medscape Medical News.

The throat and neck are checked to assess for a wide range of disorders. "You want to check the lymph nodes, or assess for thyromegaly," he noted. "So if there is a recommendation not to examine patients, that can be controversial. That really would not fit with clinical practice."

He reiterated that patients are not routinely screened by ultrasonography for thyroid cancer, and doctors would agree that it's not good practice in the absence of any symptoms.

Dr. Hockstein added that the guidelines are therefore "filling a void that doesn't exist by adding in palpation."

Other Recommendations

The USPSTF updated recommendations are in line with current clinical guidelines. They note that routine thyroid screening is not specifically recommended by any professional society or organization.

The American Cancer Society does not recommend screening for thyroid cancer by using palpation, and the American Academy of Family Physicians recommended against screening for thyroid cancer by using ultrasonography in asymptomatic individuals.

The Canadian Task Force on the Periodic Health Examination does not include examining the thyroid in its updated Preventive Care Checklist Form. The American Association of Clinical Endocrinologists, American College of Endocrinology, and Associazione Medici Endocrinologi issued guidelines this year diagnosing and managing thyroid nodules, but there are no recommendations for routine screening in the general population.

The 2015 guidelines from the American Thyroid Association for managing thyroid nodules and differentiated thyroid cancer in adults also do not address routine population-based screening. However, they do state that there is insufficient evidence to support screening individuals who have a family history of follicular cell-derived differentiated thyroid cancer.

Therefore, to date, South Korea appears to be the only country in the world that regularly screens asymptomatic individuals y using ultrasonography.

The draft recommendation is open for public comment until December 26, and the draft recommendation statement and draft evidence review have been posted on the USPSTF website.

Comments can be submitted at www.uspreventiveservicestaskforce.org/tfcomment.htm.

Dr Brito and Dr Hockstein have disclosed no relevant financial relationships. None of the investigators involved in the recommendations has any affiliations or financial involvement that conflicts with the material presented in this report.

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