Analysis of thyroid malignant pathologic findings identified during 3 rounds of screening (1997‐2008) of a cohort of children and adolescents from Belarus exposed to radioiodines after the Chernobyl accident

Abstract

Background Recent studies of children and adolescents exposed to radioactive iodine-131 (I-131) after the 1986 Chernobyl nuclear accident in Ukraine showed significant dose-related increase in the risk of thyroid cancer, but the association of radiation doses with tumor histological and morphological features is not clear. Methods A cohort of 11,664 individuals in Belarus ≤18 years at the time of the accident underwent three cycles of thyroid screening in 1997-2008. I-131 thyroid doses were estimated from individual thyroid activity measurements taken within two months after the accident and dosimetric data from questionnaires. Demographic, clinical and pathological characteristics of thyroid cancer cases were analyzed using one-way analysis of variance, chi-square or Fisher's exact tests, and logistic regression. Results As a result of screening, 158 thyroid cancers were identified. The majority of cases had T1a and T1b tumors (93.7%), with many regional N1 (60.6%) but few distant M1 (<1%) metastases. Higher I-131 doses were associated with higher frequency of solid or diffuse sclerosing variants of thyroid cancer (P<0.01) and histological features of cancer aggressiveness, such as lymphatic vessel invasion, intrathyroidal infiltration, and multifocality (all P<0.03). Latency was not correlated with radiation dose. Fifty-two cases of self-reported thyroid cancers diagnosed prior to 1997 were younger at the time of the accident and had a higher percentage of solid variant cancers compared to screening-detected cases (all P<0.0001). Conclusions I-131 thyroid radiation doses were associated with significantly higher frequency of solid or diffuse sclerosing variants of thyroid cancer and various features of tumor aggressiveness.

Radiation-Induced Differentiated Thyroid Cancer Is Associated with Improved Overall Survival but Not Thyroid Cancer–Specific Mortality or Disease-Free Survival

“…Here, outcomes and histology were directly contrast in 92 RE+ DTC patients and 165 RE-DTC patients, all treated and followed at the same institution over the same time period for a median length of 27 years. In light of initial historic reports suggesting thyroid cancer after RE was more aggressive and, more recently, equivalent to thyroid cancer in the absence of RE, it was a surprise to observe in this cohort that OS for RE+ DTC patients is significantly better than that for RE-DTC patients (18). There was no difference between the groups for either DTC-specific mortality or risk of recurrence, similar to findings reported for the Chernobyl cohort (2,3).…”

The protocol and preliminary baseline survey results of the thyroid ultrasound examination in Fukushima [Rapid Communication]

“…Of these, eight underwent thyroid surgery and pathology revealed that one had a benign thyroid nodule while the remaining seven subjects had thyroid cancer. None of the thyroid cancers detected in our survey were the solid variant of papillary thyroid carcinomas that were predominantly observed in Chernobyl [13]. Our challenging commencement of TUE in Fukushima also raises another clinical problem on an appropriate treatment for early detection of childhood thyroid cancer, which should be separately discussed [14,15].…”

Malignancies after Chernobyl Accident: What Is True and What Is Untrue

“…Morphologically, TC in patients from contaminated territories were more aggressive than usual [11][12][13][14]. Correlations between radiation doses to the thyroid, tumor invasiveness and "aggressive solid-follicular" pattern were reported [9,10]. However, the time factor was not discussed in Bogdanova et al [9]: the cases with higher doses were probably diagnosed averagely earlier, when the pool of neglected cancers was still untapped.…”

“…Accordingly, there was a pool of undiagnosed TC prior to the accident. The percentage of more advanced cancers was negatively associated with the time between the accident and surgery [8][9][10] probably due to the gradual exhaustion by the screening of the pool of advanced cancers. Morphologically, TC in patients from contaminated territories were more aggressive than usual [11][12][13][14].…”