According to data from the National Cancer Institute,(seer.cancer.gov) slightly more than 637,000 people in the United States were living with thyroid cancer in 2013. In 2016, it's estimated that 64,300 new cases of thyroid cancer will develop -- less than 4 percent of all new cancers -- and 1,980 people will die of the disease. Overall, the five-year survival rate for patients diagnosed with thyroid cancer is 98.1 percent.
Microscopic image of papillary thyroid carcinoma
Given these recent statistics, the U.S. Preventive Services Task Force (USPSTF) set out to update its 1996 recommendation on this topic.
On Nov. 22, the USPSTF posted a draft recommendation statement(www.uspreventiveservicestaskforce.org) and draft evidence review(www.uspreventiveservicestaskforce.org) on screening adults for thyroid cancer. Based on the evidence examined, the group recommended against screening for thyroid cancer in asymptomatic adults -- a "D" recommendation.(www.uspreventiveservicestaskforce.org)
The task force reviewed studies on the benefits and harms of screening and treatment for thyroid cancer and found that for patients asymptomatic for the disease, the harms of screening and treatment are likely to be greater than the benefits. These harms can include permanent surgical damage to thyroid function and to the nerves that control speaking and breathing.
- A recent draft statement from the U.S. Preventive Services Task Force recommends against screening asymptomatic adults for thyroid cancer.
- The task force reviewed studies on the benefits and harms of screening and treatment for thyroid cancer and found that for patients with no symptoms, the harms are likely to be greater than the benefits.
- In 1996, the task force also recommended against screening for thyroid cancer in asymptomatic adults using either neck palpation or ultrasound.
"While there is very little evidence of the benefits of screening for thyroid cancer, there is considerable evidence of the significant harms of treatment," said USPSTF member Karina Davison, Ph.D., M.A.Sc., in a news release.(www.uspreventiveservicestaskforce.org) "And in the places where universal screening has been tried, it hasn't helped people live longer, healthier lives."
Data the task force reviewed on the harms of screening specifically suggested overdiagnosis is likely a substantial issue.
"Population studies from several countries suggest that widespread screening for thyroid cancer is likely to result in overdiagnosis," said USPSTF Chair Kirsten Bibbins-Domingo, Ph.D., M.D., M.A.S., in the release. "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."
Update of Previous Recommendation
To update its 1996 recommendation, the USPSTF commissioned a systematic evidence review to examine the benefits and harms of screening for thyroid cancer in adults. This review also assessed the diagnostic accuracy of screening (including neck palpation and ultrasound) and the benefits and harms of treatment of screen-detected thyroid cancer, which weren't included in the previous evidence review.
In that earlier recommendation statement, the task force also recommended against screening for thyroid cancer in asymptomatic adults -- specifically, with either neck palpation or ultrasound -- a "D" recommendation.
Furthermore, at the time, the USPSTF issued a "C" recommendation for screening asymptomatic adults with a history of upper body irradiation (primarily head and neck) in infancy or childhood. It should be noted that in 1996, a C recommendation meant there was insufficient evidence to recommend for or against a service.
Family Physician's Take
Jennifer Frost, M.D., medical director for the AAFP Health of the Public and Science Division, told AAFP News there is no evidence that indicates treating thyroid cancer reduces mortality.
"If treatment doesn't improve outcomes, then early diagnosis through screening doesn't have value," she said. "Treatment, however, almost always has risks. In this case, the most common serious harms of treatment include hypoparathyroidism and laryngeal nerve palsy.
"Why do widespread screening in order to increase diagnosis when the treatment causes harm without improving mortality?"
Frost noted that with any cancer screening program, overdiagnosis needs to be carefully considered.
"This means diagnosing a cancer that would never have caused medical problems for the individual," she said. "This means they would not have died from the cancer or even had symptoms. So you diagnose a cancer that would never have caused a problem, then expose the patient to treatments that can cause significant harms."
Frost pointed to the overdiagnosis of thyroid cancer in South Korea, where an extensive screening program is in place. The rate of thyroid cancer diagnosis in 2011 was 15 times the rate before the screening program, yet the mortality rate has remained unchanged.
"It's important when recommending a screening program that the potential benefits outweigh the potential harms. In this case, it's clear the potential harms outweigh any benefit," she said.
The USPSTF is accepting public comments on this draft recommendation statement(www.uspreventiveservicestaskforce.org) and draft evidence review(www.uspreventiveservicestaskforce.org) until Dec. 26.
The AAFP will review the task force's draft materials and release its own recommendation after the USPSTF finalizes its recommendation statement.
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