Thyroid Cancer Diagnoses Declined Significantly During COVID-19 Pandemic

A new multi-institutional study has found there was a dramatic decline in thyroid cancer diagnoses during the COVID-19 pandemic, raising concerns about a potential wave of more advanced cancer cases in the future.

The study, published in the American Medical Association journal JAMA Otolaryngology–Head & Neck Surgery, examined trends in thyroid cancer incidence between 2016 and 2021. Using data from the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database, the research provides a comprehensive analysis of how the pandemic affected thyroid cancer diagnosis, particularly during the major COVID-19 variant waves from 2020 to 2021.

The study estimates that approximately 10,200 thyroid cancer cases went undiagnosed during the first two years of the pandemic. Among these, 5,400 were small papillary cancers, and 3,700 were larger papillary tumors.

The researchers warned that these missed diagnoses could lead to a rise in more advanced cases of thyroid cancer in the future. With smaller, more treatable cancers likely going unnoticed during the pandemic, many patients may now present with larger, more aggressive tumors.

“The sharp decline in diagnoses, particularly during the variant waves of the pandemic, could be a major public health concern in the future,” said Daniel Weinberger, PhD, an associate professor at the Yale School of Public Health and one of the study’s co-authors. “If patients are now presenting with more advanced disease, we could see a temporary spike in both morbidity and mortality rates for thyroid cancer.”

The study found that the most dramatic drop in thyroid cancer diagnoses coincided with COVID-19 waves that stressed health care systems globally. During the initial wave in early 2020, as well as the later Alpha and Delta variant surges, nonurgent health services were postponed, and many patients avoided health care settings. This created an environment where less aggressive cancers, which often go unnoticed, were left undiagnosed, the authors said.

Guidelines from institutions such as the Centers for Medicare & Medicaid Services and the American College of Surgeons encouraged postponing nonemergent surgeries and imaging procedures during these periods. This reduction in health care utilization is reflected in the lower number of thyroid cancer diagnoses during 2020 and 2021.

The research indicates that during the pandemic, thyroid cancer diagnoses dropped significantly across most cancer types. The decrease was most evident in papillary thyroid cancer, the most common form of the disease. From March 2020 to December 2021, the incidence of thyroid cancer overall fell markedly, with rates for smaller papillary cancers (less than 2 cm) down by 11% and larger papillary cancers by 14%.

The study also identified decreases in other forms of thyroid cancer, including follicular (down 8%) and medullary cancers (down 10%). Notably, anaplastic thyroid cancer, one of the most aggressive forms, also showed a 15% decrease, although the researchers suggest this could be partly due to unreported deaths among patients.

Despite the decline in diagnoses, the study found no significant change in the size of cancers at diagnosis. This suggests that the missed diagnoses were primarily smaller, incidentally discovered cancers that were typically found during routine care or unrelated imaging. Larger, more symptomatic cancers, such as anaplastic thyroid cancer, were still likely being diagnosed.

Thyroid cancer, which has varying levels of aggressiveness depending on the type, serves as a unique model for how public health emergencies can impact cancer care overall. While highly aggressive cancers such as anaplastic thyroid cancer require immediate intervention, small papillary cancers can remain undetected for long periods without severe immediate consequences.

“Thyroid cancer provides a window into how cancer care was affected more broadly by the pandemic,” said Weinberger, a co-director of the Yale School of Public Health’s Modeling Unit. “The delays in diagnosis seen here could very well be mirrored in other cancers, especially those that progress more slowly and do not pose an immediate threat.”

The findings underscore the need for ongoing monitoring of thyroid cancer trends as health care systems recover from the pandemic, the authors said. Future planning efforts should take into account the potential for a rise in more advanced thyroid cancers as undiagnosed cases come to light.

“Our study serves as a call to action for health care providers to ensure that we are not overlooking these potentially treatable cancers,” Weinberger said. “As we move forward, public health strategies must prioritize cancer screenings and timely care to prevent a surge in late-stage diagnoses.”

The study was led by the VA Disrupted Care National Project. Dr. Rebecca Bell, MD, of Dartmouth-Hitchcock Medical Center is the lead author. Dr. Louise Davies of the Dartmouth Institute for Health Policy & Clinical Practice is senior author. The study is part of a multi-year project sponsored by the U.S. Department of Veteran Affairs to understand the impacts of COVID-related disruptions on health care. The project participants are the VA of White River Junction Vermont, the VA of West Haven, Connecticut, and the VA of Palo Alto, California. It is being supported by academic partners at Yale, Dartmouth, and Stanford. Dr. Amy Justice, MD, PhD, C.N.H. Long Professor of Medicine and a professor of public health at Yale and a member of Yale Cancer Center, is the project lead in West Haven. Weinberger has been conducting statistical modeling work related to the burden of COVID-19 among different risk groups in the VA population during the course of the project.