Radiation Risk of Screening-Detected Diffuse Goiter in a Belarusian Cohort Exposed as Children or Adolescents to Iodine-131 after Chernobyl.

BACKGROUND

We previously reported a significantly increased risk of thyroid cancer due to radioactive iodine-131 after the 1986 Chernobyl nuclear accident in a cohort of children and adolescents from Belarus. Radiation-related cancer risks were five times higher among those with diffuse goiter; however, the relationship between radiation dose and diffuse goiter is not well understood.

METHODS

We used logistic regression to analyze data from 10,278 study participants [mean thyroid dose = 0.63 gray (Gy)] who were screened 10 to 15 years after exposure according to a standardized protocol, which specified thyroid size assessment by both ultrasound and palpation.

RESULTS

Diffuse goiter was identified in 1,811 subjects and was significantly associated with 131I dose (P < 0.001). The linear model provided the best fit to the data at doses <0.5 Gy [odds ratio (OR) at 1 Gy = 2.45; 95% confidence interval, 1.70-3.41] and linear-exponential model at doses <1.5 Gy (OR at 1 Gy = 1.84). Age at exposure and indicators of iodine deficiency both before the accident (place of residence) and during screening (urinary iodine levels) significantly modified the dose-response (all P values < 0.01).

CONCLUSIONS

The first systematic evaluation of radiation risks of diffuse goiter after environmental exposure found a strong, statistically significant association with thyroid dose.

IMPACT: Our study shows that radiation exposure is associated with a significantly increased risk of developing diffuse goiter. Future epidemiologic studies of iodine-deficient irradiated populations should assess thyroid size.