Author: Shreeya Nanda
The decision is based on a systematic review of 67 studies, also reported in JAMA, evaluating various aspects of screening, such as the benefits and harms of screening asymptomatic individuals and of treating screen-detected cancers, as well as the diagnostic accuracy of screening modalities.
Although there were no trials directly comparing the benefits of early versus late or delayed treatment, two separate observational studies compared the outcome of treatment versus no surgery or surveillance. However, as neither study accounted for confounding variables, robust conclusions could not be drawn, say Jennifer Lin, from Kaiser Permanente Center for Health Research in Portland, Oregon, USA, and colleagues.
By contrast, they identified 52 studies, including 335,091 patients, that provided information on the harms of treating screen-detected thyroid cancers. A meta-analysis of the data showed that the incidence of permanent hypoparathyroidism varied between 2% and 6%, while the rate of permanent vocal cord paralysis ranged from around 1% to 2%.
Among patients who received radioactive iodine therapy, the excess absolute risk for secondary cancers ranged from 11.9 to 13.3 per 10,000 person–years. And the incidence of dry mouth ranged widely, from approximately 2% to 35%.
The USPSTF commissioned the systematic review due to the rising incidence of thyroid cancers against a background of stable mortality, which is suggestive of overdiagnosis. And in view of the results, the task force concluded with “moderate certainty” that the harms outweigh the benefits of screening, upholding the “D” recommendation.
The USPSTF emphasizes, however, that this recommendation pertains only to the general asymptomatic adult population, and not to individuals who present with throat symptoms, lumps or swelling, or those at high risk for thyroid cancer.
Editorialists Louise Davies (Department of Veterans Affairs Medical Center, White River Junction, Vermont, USA) and Luc Morris (Memorial Sloan Kettering Cancer Center, New York, USA) welcome the decision, noting that “[e]pidemiologic data from around the world demonstrate that finding more cases of cancer, as has occurred over the past approximately 15 years, has not made death from the disease less likely.”
They write in JAMA Otolaryngology–Head & Neck Surgery: “While suggestions to ‘check your neck’ are well intentioned, the USPSTF recommendation indicates that these practices should not be encouraged or endorsed.”
Other commentators are more circumspect. Julie Ann Sosa (Duke University Medical Center, Durham, North Carolina, USA) and co-authors point out in JAMA Surgery that both the incidence and mortality rates of advanced-stage papillary thyroid cancer have risen over the years, as has the overall thyroid cancer incidence-based mortality.
These findings “[challenge] the prevailing hypothesis that overdiagnosis is the sole culprit for the changing epidemiology,” they write.
Sosa and colleagues continue: “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.”
Writing in an accompanying piece in JAMA, Anne Cappola (University of Pennsylvania, Philadelphia, USA) notes that “[t]he rationale for the recommendation against screening is compelling,” but she does not want the conversation about screening to stop.
Like Sosa et al, Cappola does not think that over diagnosis explains all and she believes that “additional research into possible environmental etiologies is needed, particularly to inform prevention efforts.”