A retrospective study provides new evidence that thyroid cancer continues to be overdiagnosed and that aggressive screening and treatment of thyroid cancer has not led to higher survival rates. The research was published by Chen et al in The Lancet Diabetes & Endocrinology.
“Many studies have established that the incidence of thyroid cancer has dramatically increased for at least 4 decades, but the probability of dying of thyroid cancer has remained exactly the same,” said Zachary Zumsteg, MD, Associate Professor of Radiation Oncology and Biomedical Sciences at Cedars-Sinai Cancer and senior author of the study. “This means we are diagnosing and treating many cancers that would do no harm despite recent efforts to reduce overdiagnosis.”
Findings and Implications
Investigators analyzed data from more than 91,000 patients with thyroid cancer registered in public databases from 1975 to 2019 to determine trends in thyroid cancer incidence according to year of birth and year of diagnosis.
Dr. Zumsteg said efforts have been made to curb overdiagnosis of thyroid cancer over the past several decades, and previous research suggested that rates of thyroid cancer were finally beginning to decline in recent years.
“When we looked at a broader range of data, we found there has been no decline in thyroid cancer diagnoses,” he explained. “Rates have hit a plateau, with no further increases over the past decade or so. However, the plateau is at peak levels. We continue to diagnose many patients who will not benefit from surgery, and we have essentially made no progress in reducing unnecessary treatments.”
The research team also found that the main factor linked with increased thyroid cancer incidence appears to be the passage of time. They theorized that this is mainly due to increased detection of thyroid nodules in modern medical practice.
“People visiting the doctor in 1975 were less likely to receive imaging than those visiting the doctor in 2019,” Dr. Zumsteg said. “So today doctors are finding thyroid nodules that would not have been detected in previous decades, leading to more biopsies and diagnoses of small, slow-growing thyroid cancers that might not require treatment.”
The study also found that thyroid cancer incidence has increased disproportionately in middle-aged individuals, who are more likely to interact with the medical system.
“Our analysis found that in 1975, the probability of being diagnosed with thyroid cancer was basically the same in people of all ages,” Dr. Zumsteg said. “Over time, the increase has been concentrated in women ages 40 to 69 [years] and men ages 50 to 79 [years]. This especially affected women, who tend to interface with the medical system more often than men.”
Dr. Zumsteg said that thyroid cancer overdiagnosis could be addressed with a two-pronged approach. Raising the threshold for both imaging and biopsy of thyroid nodules would reduce overdiagnosis; less aggressive management would further reduce thyroid cancer overtreatment.
Additionally, using the active surveillance method may help—and there are several ongoing clinical trials of the method in this population, added study authors.
“The hope is that these trials will make clinicians and patients more comfortable with active surveillance and that updated clinical guidelines will bring the practice into widespread use,” said study co-author Allen Ho, MD, Co-Director of the Thyroid Cancer Program and Professor of Surgery at Cedars-Sinai. “If current trends continue, we will continue to overdiagnose thyroid cancer and to needlessly treat patients—doing more harm than good.”
Disclosure: For full disclosures of the study authors, visit thelancet.com.
