Small thyroid cancers diagnosed more often for women than men despite same rate on autopsy
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Women are about four times more likely than men to be diagnosed with papillary thyroid cancer during their lifetime, even though the prevalence of thyroid cancer at autopsy is roughly the same in men and women, according to study findings.
A population-based cohort study published in JAMA Internal Medicine showed women in the U.S. were diagnosed with small papillary thyroid cancers at a ratio of 4.39:1 compared with men. However, in a systematic review and meta-analysis of studies analyzing papillary thyroid cancer prevalence at autopsy, there was no significant difference in the prevalence between men and women.
“Women are at much greater risk of having small, asymptomatic papillary thyroid cancers identified than men,” Louise Davies, MD, MS, senior faculty in the VA Outcomes Group at the Veterans Affairs Medical Center in White River Junction, Vermont, told Healio. “Women should be aware that many of these small thyroid cancers that come to attention in the absence of symptoms or evidence of cancer spread could be managed with active monitoring. Active monitoring is a treatment program of regularly scheduled ultrasounds of the thyroid and neck with intervention undertaken only if the tumor changes or grows.”
Davies and colleagues conducted an analysis of thyroid cancer incidence and mortality recorded in the National Cancer Institute’s Surveillance, Epidemiology and End Results Program-9 Registry from 1975 to 2017. Tumor size was analyzed from 1983 to 2017. Data on thyroid cancer mortality were extracted from the CDC’s National Vital Statistics System and from SEER. Thyroid cancer incidence and mortality rates were reported per 100,000 individuals and were age-adjusted to the U.S. standard population in 2000.
Women diagnosed four times more than men
Thyroid cancer diagnoses climbed over time, peaking at 22.4 cases per 100,000 women and 7.8 cases per 100,000 men in 2013. Papillary thyroid cancer was the histologic type of 90% of thyroid cancer from 2010 to 2017. Women had a papillary thyroid cancer incidence of 13.3 cases per 100,000 women by 2017 compared with 4.3 cases per 100,000 men. In 2017, women were diagnosed with papillary thyroid cancer at a ratio of 4.39:1 compared with men. As cancer lethality increased, the ratio moved closer to 1:1, with medullary and anaplastic cancers diagnosed more equally between men and women.
“We were surprised how, as the lethality of the cancer type increased, the rate of diagnosis among men and women became nearly equal,” Davies said. “We suspected that low-risk thyroid cancers were found more often in women than men, but this finding, which shows a stepwise change toward equality as lethality increases, was quite striking.”
Thyroid cancer mortality from 1975 to 2017 ranged from 0.4 to 0.6 per 100,000 women and 0.3 to 0.6 per 100,000 men. Women died of thyroid cancer from 1992 to 2017 at a ratio of 1.02:1 compared with men. Mortality for papillary thyroid cancers ranged from 0.11 to 0.29 per 100,000 for women and 0.12 to 0.28 per 100,000 for men. Women died of papillary thyroid cancer at a ratio of 0.96:1 compared with men.
No sex disparity at autopsy
Researchers also conducted a systematic review and meta-analysis of studies reporting the prevalence of papillary thyroid cancer in autopsy results for both men and women. Embase, PubMed and Web of Science were searched from inception to May 31, 2021. Studies examining the whole thyroid gland and reporting the number of thyroid glands examined and subclinical thyroid cancer autopsy prevalence for men and women were included.
The meta-analysis included eight studies with 12 pooled study populations. Subclinical papillary thyroid was prevalent in 14% of women and 10.8% of men. The difference in prevalence between men and women was not statistically significant. Within the eight individual studies, none had a significant difference in subclinical papillary thyroid cancer risk between men and women.
Davies said a randomized trial is needed comparing patient-reported outcomes and long-term cancer outcomes among people treated with active monitoring, surgery and thermal ablation.
“This will provide much needed evidence to help support both women and men in making the treatment choice that is right for them when these small, asymptomatic cancers are found,” Davies said. “We also need to continue research into understanding why low-risk papillary thyroid cancer is identified so much more often in women than men and develop solutions to mitigate the disparity. Finally, there is some concern that new risk factors may be emerging for the development of thyroid cancer, and this should remain part of our work, so that we can prevent thyroid cancer in the future.”
For more information:
Louise Davies, MD, MS, can be reached at louise.davies@dartmouth.edu.
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