The incidence of thyroid cancer has nearly tripled in the United States since the 1970s. However, this is mainly an epidemic of diagnosis, researchers reported.
Small papillary cancers are not likely to cause death or disease, and women are four times more likely to receive a diagnosis than men, even though autopsy findings show that these cancers occur more frequently in men.
For the research, published online Feb. 20 in JAMA Otolaryngology–Head & Neck Surgery, Dr. Louise Davies and Dr. H. Gilbert Welch reviewed diagnostic trends from the population-based Surveillance, Epidemiology, and End Results (SEER) 9 program, which covers four large U.S. metropolitan areas along with five states. They also reviewed mortality records from the National Vital Statistics System between 1975 and 2009 for the same areas, reported Dr. Davies of the Veterans Affairs Medical Center in White River Junction, Vt., and Dr. Welch of the Dartmouth Institute for Health Policy and Clinical Practice in Hanover, N.H.
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Women are four times more likely to receive a diagnosis than men, even though autopsy findings show that these cancers occur more frequently in men.
The researchers found that thyroid cancer incidence nearly tripled, from 4.9 to 14.3 per 100,000 individuals, in that time period (relative rate, 2.9) and that nearly all of the increase was attributable to diagnoses of small papillary cancers, the least aggressive form of thyroid cancer. The mortality rate from thyroid cancer remained stable – at 0.5 deaths per 100,000 – during the same time, Dr. Davies and Dr. Welch reported (JAMA Otolaryngol. Head Neck Surg. 2014 Feb. 20 [doi: 10.1001/jamaoto.2014.1]).
The investigators saw a much greater absolute increase in thyroid cancer in women, at 3.3-fold (from 6.5 to 21.4 cases per 100,000), than in men, at 2.2-fold (from 3.1 to 6.9), during the study period, which suggests that the burden of overdiagnosis fell heavily on women, they wrote.
Moreover, most thyroid cancers are treated "as though they are destined to cause real problems for the people who have them," Dr. Davies and Dr. Welch wrote, usually with total thyroidectomy, radiation, or both, putting patients at risk for complications and secondary cancers.
Patients – particularly women – might be better served with a less intensive diagnostic and treatment approach to these cancers, and even by relabeling them using a term other than cancer. Clinicians should take care to advise patients of the uncertainty surrounding the small papillary cancers and encourage them to consider the risks of treatment compared with active surveillance, the researchers said.
Dr. Davies and Dr. Welch received support from their institutions for their research; neither declared conflicts of interest.