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The US Preventive Services Task Force (USPSTF) recommends against screening for thyroid cancer in asymptomatic adults, giving the practice a grade of D.1 That is, the Task Force discourages use of screening with palpation or ultrasonography with a moderate degree of certainty that such screening has no net benefit or that the harm outweighs any benefits. The recommendation is based on a systematic evidence review2 that is an update of a prior USPSTF recommendation from 1996,3 which came to a similar conclusion.
Several factors contributed to the current recommendation.1 While the USPSTF acknowledges that there has been a substantial increase in the incidence of thyroid cancer detection over the last 3 decades, it cites multiple sources4-6 to support its assertions that there has not been a corresponding change in mortality and that prognosis from thyroid cancer, and differentiated thyroid cancer in particular, is excellent overall.1 Papillary thyroid cancer, the most common histologic subtype of differentiated thyroid cancer, now accounts for nearly 90% of incident cases, and it has by far the best prognosis of all histologic subtypes, with 10-year survival reported to be between 92% and 95%.4-6 On the one hand, the Task Force statement1 discusses the paucity of data supporting the accuracy of palpation, in particular, and benefits of early detection and treatment. On the other hand, it details the potential harms of screening (overdiagnosis) and complications associated with surgery, such as the risks of voice change, hypocalcemia, bleeding, and the toxic effects of radioactive iodine. Significant attention is directed to the organized cancer screening program in South Korea, whereby patients were offered thyroid screening using ultrasonography at a small additional cost starting in 1999; by 2011, the rate of thyroid cancer diagnosis in South Korea had skyrocketed and was 15 times the rate in 1993. However, while thyroid cancer incidence skyrocketed, mortality rates remained stable; this suggests overdiagnosis.7 Using data from Cancer Incidence in Five Continents,8 Vaccarella and colleagues from the International Agency for Research on Cancer and the Aviano National Cancer Institute9 reported in 2016 that 50% to 90% of thyroid cancers in women in high-income countries are the result of overdiagnosis.
But now there are new data suggesting that we pause and recalibrate. Recently, Lim et al10 provided new evidence that the overall incidence of thyroid cancer has increased by 3% annually over the last 3 decades, with increases observed in both the incidence and mortality rates for advanced-stage papillary thyroid cancer (3.5% per year since 1981). Overall incidence-based mortality for thyroid cancer from 1994 to 2013 substantially increased (1.1% per year), and it increased even faster for patients diagnosed with advanced-stage papillary thyroid cancer (2.9% per year). These findings are consistent with a true increase in the occurrence of thyroid cancer in the United States, expanding on the data reported by Chen et al11 in 2009 and challenging the prevailing hypothesis that overdiagnosis is the sole culprit for the changing epidemiology.
These results suggest that a new focus should be placed on understanding alternative explanations for this increase other than overdiagnosis, including potentially modifiable factors, such as obesity and environmental exposures outside of the known influence of radiation.12 The prevalence of RET proto-oncogene papillary thyroid carcinoma (RET/PTC) chromosomal aberrations, which are markers of ionizing radiation exposure, have declined in some populations, while point mutations such as BRAF V600E have increased, suggesting that chemical exposures may be more important than ionizing radiation in providing explanation for the increasing incidence of thyroid cancer.13 Furthermore, it would seem that additional energies and resources should be focused on supporting innovation and discovery around the management of locally advanced and metastatic thyroid cancer. While great progress has been made over the last decade advancing 4 different small-molecule therapies to market for the treatment of advanced differentiated (sorafenib and lenvatinib) and medullary (vandetanib and cabozantinib) thyroid cancers, it would seem that opportunity still exists for clinicians and scientists to work together to try to curb mortality related to thyroid cancer.
While the USPSTF acknowledges that its recommendation does not apply to high-risk patients, including those with a history of radiation exposure in childhood and adolescence, inherited genetic syndromes, or a personal history of thyroid cancer, it does so only in the text of the document.1 Most of these patients are asymptomatic at presentation, but they should be screened, and it would seem that this should be clearly stated in the USPSTF recommendation; currently, this recommendation is overly broad and unnecessarily terse. This important suggestion was made by the American Thyroid Association (ATA) task force that authored the 2015 practice guidelines for the management of adult patients with thyroid nodules and differentiated thyroid cancer in the United States.6 In addition, the recommendation against neck palpation as a screening tool for thyroid cancer could be overinterpreted by some clinicians as the USPSTF providing license to exclude examination of the neck as an essential component of routine clinical care and fastidious physical examination. Palpation of the thyroid gland itself, along with the central and lateral compartments of the anterior neck, can provide important information about thyroid nodules, goiter, lymphadenopathy, bruits, thrills, and other findings that could have critical bearing on a litany of benign and malignant conditions that extend far beyond the thyroid. Therefore, it would seem to be important to assert somewhere in the USPSTF statement that neck palpation should remain a necessary pillar of a good physical examination. In this vein, there is evidence that a good thyroid examination can be fairly easily taught and that it correlates rather well with ultrasonography for estimation of thyroid gland size.14
In the end, perhaps this is an opportune time to pause and recalibrate our collective approach to thyroid cancer screening, diagnosis, management, and surveillance. In the most recent ATA guidelines,6 there was a clear shift toward a “less is more” approach to differentiated thyroid cancer. Recommendations were made for (1) a higher threshold for thyroid nodule biopsy, (2) active surveillance as a potential alternative to surgery for a subset of papillary thyroid microcarcinomas, and (3) thyroid lobectomy as an alternative to total thyroidectomy for low-risk differentiated thyroid cancer. The indications for adjuvant radioactive iodine are fewer, and recommended doses of iodine 131 have decreased. If the explanation for the rise in thyroid cancer is, indeed, not just overdiagnosis, and if mortality from thyroid cancer is also increasing, then enthusiasm for this (non)screening recommendation should be more muted. For clinicians and scientists working in the field of thyroidology, this is an interesting and compelling time. Clearly, more research is needed to identify alternative causes for the increasing incidence of the disease, to inform efforts at prevention, and to develop novel approaches to the management of advanced thyroid cancer.
Corresponding Author: Julie Ann Sosa, MD, MA, Section of Endocrine Surgery, Department of Surgery, Duke University Medical Center, #2945, Durham, NC 27710 (email@example.com).
Published Online: May 9, 2017. doi:10.1001/jamasurg.2017.1338
Conflict of Interest Disclosures: Dr Sosa is a member of the data monitoring committee of the Medullary Thyroid Cancer Consortium Registry supported by NovoNordisk, GlaxoSmithKline, AstraZeneca, and Eli Lilly. No other disclosures are reported.
Sosa JA, Duh Q, Doherty G. Striving for Clarity About the Best Approach to Thyroid Cancer Screening and TreatmentIs the Pendulum Swinging Too Far?. JAMA Surg. 2017;152(8):721–722. doi:10.1001/jamasurg.2017.1338
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