Researchers analyzing the first round of thyroid survey data after the 2011 Fukushima Daiichi nuclear accident observed both age- and sex-dependent differences in the detection rates of thyroid cysts, nodules and cancer in children, with nearly twice as many girls diagnosed with cytologically suspected cancers vs. boys, according to published findings.
The findings, researchers noted, will be useful baseline data as researchers continue to monitor disease prevalence in the region, where concern remains regarding the risk for childhood thyroid cancer.
“This article shows the age- and gender-specific prevalence of thyroid cysts, nodules and cancers found in Thyroid Ultrasound Examination program for residents aged 18 years or younger after the [nuclear] accident,” Hiroki Shimura, MD, PhD, of the Radiation Medical Science Center for the Fukushima Health Management Survey at Fukushima Medical University, Japan, told Endocrine Today. “There was an age-dependent increase in the detection rate of thyroid nodules and cancer, but that of cysts reached a peak at age 11 to 12 years. Sex affected the prevalence of thyroid nodules and cancers after the onset of puberty, but only a small difference was exhibited in that of cysts.”
Shimura and colleagues analyzed data from 294,905 children living in Fukushima prefecture who underwent voluntary thyroid ultrasound examinations as part of the first round of the Fukushima Health Management Survey, conducted October 2011 to March 2014. Participants with thyroid nodules of at least 5.1 mm or cysts of at least 20.1 mm were recommended for a secondary confirmatory exam (n = 2,032). Researchers used logistic regression analysis to assess any associations between prevalence of thyroid cysts, nodules and cancers, and age and sex.
Within the cohort, researchers detected thyroid cysts in 45.7% of boys and 50% of girls. The proportion of children with cysts of 3 mm or smaller increased with age, peaking at age 11 to 12 years (55.3% for boys; 60.9% for girls) before decreasing with age in both sexes. The proportion of children with larger cysts (3.1 mm to 20 mm) increased with age.
Researchers observed thyroid nodules (both benign and malignant) in 1% of boys and 1.7% of girls and detected thyroid cysts in 48.8% of boys and 52.5% of girls with thyroid nodules. There was an age-dependent increase in the detection rate of thyroid nodules beginning at age 10 years for girls and age 14 years for boys, when the rate reached 1% for both.
Among children recommended for fine-needle aspiration cytology, 174 boys and 367 girls underwent the procedure; 38 boys and 74 girls were diagnosed with malignancy or suspected malignancy. Researchers observed a sex-dependent difference in cancer detection rate after age 14 years; the overall adjusted detection rate of thyroid cancer was 0.028% in boys and 0.056% in girls.
“Since the expected latency for radiation-induced thyroid cancer is considered 4 to 5 years, the fact that the examination period in this study was within 3 years after the nuclear accident reasonably suggested that this study was performed before any radiation-induced influence,” Shimura said. “Therefore, the results demonstrated in this study will confer as reference data to future epidemiological studies of nodular thyroid diseases in children, adolescents and young adults.”
The full-scale survey will be repeated every 2 years for each participant until age 20 years and then every 5 years thereafter, Shimura said.
Read more at First thyroid data: Age-, sex-dependent differences for cysts, nodules in Fukushima children