Thyroid cancer screening

Abstract

Whether screening for a disease is beneficial or not is widely debated. Last week, the US Preventive Services Task Force (USPSTF) recommended against screening for thyroid cancer in adults who show no signs or symptoms of the disease, concurring with its 1996 recommendation. The USPSTF reviewed evidence for the benefits and harms of screening for and treatment of thyroid cancer, concluding that the harms outweigh the benefits. Benefits are small for various reasons. First, thyroid cancer is fairly rare, at 3·4% of newly diagnosed cancer cases projected in the USA in 2017 and 0·3% of cancer deaths. Second, observational studies of patients receiving surgery do not show survival benefits compared with those receiving surveillance. Finally, screening leads to increased incidence of thyroid cancer, but not decreased mortality. A cancer screening programme launched in South Korea in 1999, which included thyroid cancer screening, caused diagnosis to increase by 15 times between 1993 and 2011, but mortality remained stable. This discrepancy occurs because tumours are often identified that are so small or slow growing that they would have remained asymptomatic, making treatment unnecessary. Harms from treatment, however, are moderate, including low blood calcium concentrations and vocal cord paralysis caused by surgical thyroid gland removal, as well as occurrence of a second cancer and salivary gland harms caused by radiotherapy. The USPSTF stressed that this recommendation does not apply to patients with symptoms of potential thyroid cancer or to high-risk patients. Further investigation is needed since no direct studies have compared screening with no screening or immediate surgery with surveillance, and the benefit of screening in high-risk patients has not been studied. As new research is done, recommendations can be amended. This April, the USPSTF revised its 2012 recommendation against screening for prostate cancer in all age groups to recommend considering it in men aged 55–69 years in light of new evidence. As the research base for thyroid cancer screening is strengthened, these recommendations can be tailored appropriately. For the USPSTF recommendation see https://www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementFinal/thyroid-cancer-screening1 For the USPSTF recommendation see https://www.uspreventiveservicestaskforce.org/Page/Document/RecommendationStatementFinal/thyroid-cancer-screening1