MON-508 Clinicopathological Features of Papillary Thyroid Cancer After Fukushima and Chernobyl Accidents

The phenomenon of a sharp increase in the incidence of thyroid cancer worldwide is now under debate. Screening activity, diagnostic improvements or real rise in incidence as a result of unknown carcinogens are discussed. Studies in Belarus after Chernobyl showed that the synergistic influence of radiation and nitrates might lead to an increased thyroid cancer (TC) risk in children. For better understanding of the etiology, we compared the published clinical data of pediatric TC patients after the nuclear emergency of Fukushima with the observations we made after the Chernobyl accident.

In a large-scale survey after the Fukushima accident, 300,476 subjects were screened and by September 2018, 191 subjects were diagnosed with thyroid malignancy or suspected malignancy by fine needle aspiration. Mean age of TC patients was 17.8 years at presentation. Mean tumor size was 14.9 mm. Postoperative lymph node metastasis, extra-thyroidal invasion, and pulmonary metastasis were detected in 79%, 45%, and 2.1% of all cases, respectively. Only 4.8% TC cases were staged as low risk pT1aN0M0 (Suzuki et al. 2018). For comparison, in Belarus patients mean age was 13.0 years at presentation (1078 cases), mean tumor size 14.4 mm. Lymph node metastases were observed in 74%, pulmonary metastasis in 11% and extra-thyroidal extension in 48.5 - 64.1% (with respect to latency period). The low risk (pT1aN0M0) TC patients were diagnosed in 19.2% cases.

The most of TC cases from Japan and Belarus were clinically significant, not “overdiagnosed” and screened on time. Given that the accidental thyroid doses were very low in Japanese cases, it would be very important to evaluate and compare the exposure to endocrine disruptors as e.g. nitrates and low radiation doses from diagnostic procedures (dental X-ray examination and computed tomography).

Referece:

Suzuki S, Matsumoto Y, Ookouchi C, Nakano K, Iwadate M, Suzuki S, Nakamura I, Fukushima T, Mizunuma H, Yamashita S, Takenoshita S. The clinicopathological features of childhood and adolescent thyroid cancer in Fukushima after the Fukushima Daiichi nuclear power plant accident. Thyroid. 2018; Supplement 1, (Poster 136).

MON-LB096 Methodical Aspects of Using New Low-cost Device for Bipolar Radiofrequency Ablation: Thyrablator

The rising incidence and optimization of management of nodular goiter and thyroid cancer are actual problems for many countries. In last decade radiofrequency ablation (RFA) is becoming more useful treatment option helping to avoid an overtreatment and surgical complications. This technique was developed in 2002 in South Korea and many European countries (Italy, Denmark, Spain, Germany, Austria) are offering RFA in special thyroid clinics. The first study of the effectiveness and feasibility of thyroid nodule RFA in the USA was conducted at Mayo Clinic in 2013, however number of patients and experience until now are very limited. Currently both monopolar and bipolar RFA techniques are used. To ablate small thyroid nodules (less than 2 cm in diameter), in 2017, in framework of american-belarusian clinical trial we started to use a new, originally developed, and patented, low-cost device for bipolar RFA - «Thyrablator». In comparison to a conventional monopolar electrode for RFA, Thyrablator, was designed as a sterile, disposable needle for the fine needle biopsy (20-gauge). It can be used with any type electrosurgical unit, operating in bipolar mode, attached to the generator with a removable connector and no need for a grounding pad. Thyrablator can also be used for drainage of cysts and for injection of liquids to enhance the ablative effect or for anesthetic instillation. Methodically ultrasound-guided percutaneous bipolar RFA was performed with local anesthesia, "moving-shot" technique, with the power of 3 to 5 Watt for duration of 30 to 60 seconds. It requires less time and power for successful ablation of nodes than stated in reports for monopolar electrode. An average reduction of nodule volume was approximately up to 60% after 3 months of follow-up. Conclusion. The first clinical trial showed a promising methodical approach of the new low-cost bipolar RFA device - Thyrablator. More studies are needed for active implementation bipolar RFA in clinical practice in the USA and training programs should begin preparing experienced interventional thyroidologists to treat patients, achieving good results and low complications rate. Unless otherwise noted, all abstracts presented at ENDO are embargoed until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. Abstracts presented at a news conference are embargoed until the date and time of the news conference. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.

Thyroid Cancer Induction: Nitrates as Independent Risk Factors or Risk Modulators after Radiation Exposure, with a Focus on the Chernobyl Accident

In recent decades, differentiated thyroid cancer (DTC) incidence has been increasing worldwide. The important contributions to this phenomenon of "overdiagnosis" driven by wider use of improved ultrasound systems are amply documented, notwithstanding the "real" carcinogenic effects of ionizing radiation, e.g., from the Chernobyl accident or health care interventions. Less well understood is the role of nitrates - as environmental pollutants, in diet, and in medication - in thyroid carcinogenesis. Increasing exposure to nitrates is associated with rising incidence of esophageal, stomach, bladder, and colon cancers. Recent data suggest that in agricultural areas with higher mean nitrate levels in groundwater, DTC risk is also elevated. Our work in Belarus after Chernobyl has shown that children in districts with high nitrate concentrations in drinking water had significantly higher thyroid cancer incidence after irradiation than did their counterparts in areas with lower nitrate concentrations. Notwithstanding thyroid shielding, increasing use of computed tomography and dental X-rays heightens radiation exposure of the salivary glands in the general population, especially in children and adolescents. When nitrate intake is increased, salivary gland irradiation may potentially result in carcinogenic elevations in plasma nitric oxide concentrations. In conclusion, excess nitrate intake seems to be an independent risk factor for DTC. Additionally, we hypothesize from our data that high nitrate levels modulate the carcinogenic effect of radiation on the thyroid. Cohort studies, case-control studies, or both, are needed to quantify the effects of nitrates on DTC risk in the presence or absence of radiation exposure, e.g., that associated with diagnostic or therapeutic health care interventions.

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Recently, radiofrequency ablation has been increasingly used for the treatment of thyroid nodules. The widespread introduction of this method, however, hampered by the lack of data on efficacy and safety of different devices that are currently on the market, the selection of the optimal mode of procedure also remains to be elucidated. Experimental data obtained during the application of the original patented device is presented. The results make it possible to move from ex vivo experiments to clinical practice.

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In the last 60 years dramatically increased the content of nitrates in groundwater due to intensive use of nitrogen fertilizers in agriculture. Research in post-Chernobyl period has shown that a sharp increase in the incidence of thyroid cancer depends not only on the level of thyroid dose, but also on the level of nitrates in groundwater.

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The main results of thirty-year period of repeated screening programs and observational studies in contaminated and non-contaminated regions of Belarus are analyzed. The possible reasons of discrepant and contradictory data about the consequences of Chernobyl catastrophe delivered by different study groups during early period after the accident are discussed. High incidence of thyroid nodular disease and cancer in children and adolescence after the catastrophe are described. The research shows high effectiveness of screening in early diagnosis thyroid disorders and radiation-induced thyroid cancer in different regions of Belarus and in various time points.

Major Factors Affecting Incidence of Childhood Thyroid Cancer in Belarus after the Chernobyl Accident: Do Nitrates in Drinking Water Play a Role?

One of the major health consequences of the Chernobyl Nuclear Power Plant accident in 1986 was a dramatic increase in incidence of thyroid cancer among those who were aged less than 18 years at the time of the accident. This increase has been directly linked in several analytic epidemiological studies to iodine-131 (¹³¹I) thyroid doses received from the accident. However, there remains limited understanding of factors that modify the ¹³¹I-related risk. Focusing on post-Chernobyl pediatric thyroid cancer in Belarus, we reviewed evidence of the effects of radiation, thyroid screening, and iodine deficiency on regional differences in incidence rates of thyroid cancer. We also reviewed current evidence on content of nitrate in groundwater and thyroid cancer risk drawing attention to high levels of nitrates in open well water in several contaminated regions of Belarus, i.e. Gomel and Brest, related to the usage of nitrogen fertilizers. In this hypothesis generating study, based on ecological data and biological plausibility, we suggest that nitrate pollution may modify the radiation-related risk of thyroid cancer contributing to regional differences in rates of pediatric thyroid cancer in Belarus. Analytic epidemiological studies designed to evaluate joint effect of nitrate content in groundwater and radiation present a promising avenue of research and may provide useful insights into etiology of thyroid cancer.