MedicalResearch.com Interview with:
Dr. Luc G. T. Morris, MD, MSc
Head and Neck Service, Department of Surgery
Memorial Sloan Kettering Cancer Center
New York, New York
Medical Research: What is the background for this study? What are the main findings?
Dr. Morris: Over the past 30 years, the incidence of thyroid cancer in the US has tripled. It used to be a mystery why this was happening. But recently, many researchers have shown that this is mainly happening because of improvements in medical technology that allow us to better identify and biopsy small nodules in the thyroid gland. Many of these small nodules turn out to be thyroid cancers. In fact, up to 30% of healthy persons have small cancers in their thyroid glands, and nearly all of these would not go on to cause any problems for the person if the cancer were never discovered. In other words, a large reservoir of small thyroid cancers has always been present, like a huge submerged iceberg, but we are just getting better at finding them. Therefore, the dramatically rising incidence of thyroid cancer is best characterized as an “epidemic of diagnosis,” not an epidemic of disease. This is highly relevant to patients found to have these small thyroid cancers, because it means that many of these cancers would not have caused problems for the patient, and that there would be no benefit (only potential harm) to diagnosing and surgically removing them.
Medical Research: What should clinicians and patients take away from your report?
Dr. Morris: In the past few years, thyroid cancer specialists have begun to understand this, and have begun to recommend that physicians be more selective about investigating and biopsying small thyroid nodules. These recommendations have slowly begun to be reflected in national clinical practice guidelines such as those by the American Thyroid Association.
In this paper, we show that the once rapidly rising incidence of thyroid cancer in the US has actually leveled off. This has occurred at the same time as clinical practice guidelines have begun to urge less aggressive investigation of small thyroid nodules. We infer, but cannot prove, that the leveling off may be due to changes in physician practices.
These findings mirror recent events in South Korea, where the incidence of thyroid cancer increased even more dramatically (15-fold in 10 years), due to widespread ultrasonography screening. Concerned physicians appealed to the public about overdiagnosis of small thyroid cancers, leading to a dramatic reversal, and an actual drop in thyroid cancer diagnoses. We anticipate that a similar course correction may be beginning to occur in the US.
Morris LT, Tuttle R, Davies L. Changing Trends in the Incidence of Thyroid Cancer in the United States. JAMA Otolaryngol Head Neck Surg. Published online April 14, 2016. doi:10.1001/jamaoto.2016.0230.