Childhood thyroid cancer following the Chernobyl accident: a status report

Distribution of Thyroid Cancer in the Eastern Part of Turkey 27 Years After the Chernobyl Accident

Background

The Chernobyl accident caused widespread effects across Europe and huge areas where radiocontaminated. The effects of the Chernobyl accident on thyroid cancer have been investigated in most European countries. According to the data of the Turkish Atomic Energy Authority, the eastern part of the Black Sea region was the most radiocontaminated area in Turkey at the time of Chernobyl accident. We therefore aimed to examine the data of thyroid cancers at our center, Rize city which is located in the eastern Black Sea region.

Methods

This retrospective study included the patients with histologically proven thyroid cancer at our center between January 2008 and May 2012. Pathologic examinations of thyroidectomy materials were reviewed. We evaluated patients’ age, gender, size of the primary tumor (all sizes, < 1 cm, 1 - 2.9 cm, 3 - 3.9 cm and ≥ 4 cm), multicentricity, histologic subtypes of thyroid cancer, the presence of lymphatic, vascular, capsule and the extrathyroidal invasion.

Results

Five hundred and forty-seven of the 3,556 patients were diagnosed with thyroid cancer. The mean age of the patients was 49.31 ± 0.49 years. The histopathologic diagnosis of patients was papillary carcinoma in 533 (97.4%) and the tumor size was < 1 cm in 53.6% of the patients. The presence of multicentricity was detected in 47% of the patients.

Conclusion

The portion of thyroid carcinomas in all thyroidectomies was 15.4% in our institution 27 years after the Chernobyl accident.

Effect of the Fukushima nuclear power plant accident on radioiodine (¹³¹ I) content in human breast milk

BACKGROUND

Environmental pollution with radioiodine (iodine-131, (131) I) occurred after an accident at the Fukushima nuclear power plant (FNP) on March 11, 2011, in Japan. Whether environmental pollution with (131) I can contaminate human breast milk has not been documented.

METHODS

The (131) I content was determined in 126 breast milk samples from 119 volunteer lactating women residing within 250 km of the FNP, between April 24 and May 31, 2011. The degree of environmental pollution was determined based on the data released by the Japanese government.

RESULTS

An (131) I content of 210 Bq/kg in the tap water in Tokyo, which is located 230 km south of the FNP, on March 22 and of 3500 Bq/kg in spinach sampled in a city located 140 km southwest of the FNP on March 19 decreased over time to <21 Bq/kg on March 27 and 12 Bq/kg on April 26, respectively. Seven of the 23 women who were tested in April secreted a detectable level of (131) I in their breast milk. The concentrations of (131) I in the breast milk of the seven women were 2.3 Bq/kg (on April 24), and 2.2, 2.3, 2.3, 3.0, 3.5 and 8.0 (on April 25); the concentrations of (131) I in the tap water available for these seven women at the same time were estimated to be <1.3 Bq/kg. None of the remaining 96 women tested in May exhibited a detectable concentration of (131) I in their breast milk samples.

CONCLUSIONS

The contamination of breast milk with (131) I can occur even when only mild environmental (131) I pollution is present.

Papillary thyroid carcinoma: an update

The past two decades have seen numerous developments in the understanding of the origins and biology of papillary thyroid carcinoma. Advances in molecular biology, clinicopathologic studies of new entities, facility with fine-needle aspiration biopsy, and new radiologic imaging techniques have allowed for earlier diagnosis of these tumors. However, these advances have also caused controversies in cytologic and histopathologic diagnoses as well as therapy decisions. This paper will focus on several pathologic aspects of papillary carcinoma, which impact on its biology and prognosis.

Incidence trends for papillary thyroid carcinoma and their correlation with thyroid surgery and thyroid fine-needle aspirate cytology

CONTEXT

Papillary thyroid carcinoma (PTC) is the most prevalent endocrine malignancy. The reported incidence of PTC has more than doubled in many countries during the past half century. In Tasmania, an island state of the Commonwealth of Australia the incidence has increased by 24.7% per annum during the last two decades.

OBJECTIVE

Using the Tasmanian population as a model, this study sought to determine the relationship between changes in PTC incidence and trends for utilization of thyroid surgery and thyroid fine-needle aspiration biopsy (FNAB) cytology.

DESIGN

Hospital and pathology services in Tasmania provided data relating to all thyroid surgical, cytologic, and histopathology procedures undertaken between 1988 and 1998. The accuracy of PTC case ascertainment by the Tasmanian Cancer Registry was validated and the relationship between thyroid procedures and PTC incidence assessed.

RESULTS

A total of 3452 individuals underwent a thyroid procedure, comprising 1968 surgical and 1756 FNAB cytologic procedures. Of these, 184 patients were diagnosed with thyroid carcinoma, of whom 121 (65.8%) had PTC. Thyroidectomy and thyroid FNAB increased by 7.0% and 49.7% per annum, respectively. The likelihood of diagnosing PTC in thyroidectomy specimens increased by 99.7% per year in those patients preoperatively assessed by FNAB, compared to 10.1% per year in those for whom a preoperative FNAB was not performed. PTC incidence increased independently of PTC tumor size, although the greatest increase occurred for PTC 1 cm or less with a history of preoperative FNAB.

CONCLUSIONS

These results suggest increasing PTC incidence is largely attributable to greater diagnosis of small PTC, many of which are likely to have been asymptomatic, identified by neck ultrasonography and subsequent FNAB. However, the incidence of PTC larger than 1 cm in patients without history of preoperative FNAB has also risen, suggesting the occurrence of clinically relevant tumors may also have increased.

Absence of a specific radiation signature in post-Chernobyl thyroid cancers

Thyroid cancers have been the main medical consequence of the Chernobyl accident. On the basis of their pathological features and of the fact that a large proportion of them demonstrate RET-PTC translocations, these cancers are considered as similar to classical sporadic papillary carcinomas, although molecular alterations differ between both tumours. We analysed gene expression in post-Chernobyl cancers, sporadic papillary carcinomas and compared to autonomous adenomas used as controls. Unsupervised clustering of these data did not distinguish between the cancers, but separates both cancers from adenomas. No gene signature separating sporadic from post-Chernobyl PTC (chPTC) could be found using supervised and unsupervised classification methods although such a signature is demonstrated for cancers and adenomas. Furthermore, we demonstrate that pooled RNA from sporadic and chPTC are as strongly correlated as two independent sporadic PTC pools, one from Europe, one from the US involving patients not exposed to Chernobyl radiations. This result relies on cDNA and Affymetrix microarrays. Thus, platform-specific artifacts are controlled for. Our findings suggest the absence of a radiation fingerprint in the chPTC and support the concept that post-Chernobyl cancer data, for which the cancer-causing event and its date are known, are a unique source of information to study naturally occurring papillary carcinomas.

Terrorism in Japan

Although the 1995 Tokyo subway sarin attack probably was the most widely reported terrorist event in Japan to date (5,500 injured, 12 dead), the country has suffered numerous other large terrorism-related events in recent decades, including bombings of the headquarters of Mitsubishi Heavy Industries in Tokyo in 1974 (207 injured, 8 dead), the Hokkaido Prefectural Government office building in Sapporo in 1976 (80 injured, 2 dead), and the Yosakoi-Soran Festival in Sapporo in 2000 (10 injured, none dead). Japan also has experienced two other mass-casualty terrorist events involving chemical releases, including the 1994 Matsumoto sarin attack (600 injured, 7 dead) and the 1998 Wakayama arsenic incident (67 injured, 4 dead). Until 1995, emergency management in Japan focused on planning and preparedness at the local level for the frequent disasters caused by natural events. Since that time, substantial progress has been made in advancing emergency planning and preparedness for terrorism-related events, including the designation of disaster centers in each prefecture, the implementation of several education and training programs for nuclear, biological, and chemical terrorism, and the establishment of a national Anti terrorism Office within the Ministry of Health, Labor, and Welfare.

Enhancing Nuclear Emergency Preparedness

On January 31, 2002, Vermont's health commissioner requested potassium iodide (KI) for individuals in the 10-mile Emergency Planning Zone of the nuclear power facility. Vermont's KI distribution program emphasized public information about the role, risks, and benefits of KI. Predistribution ensured that individuals could receive KI in a 0- to 4-hour time period, to provide maximum protection. Five months after the program began, more than 1,000 individuals had received KI, and 3,000-4,000 KI doses have been distributed in schools. Efforts are ongoing to identify barriers to participation, provide public education, and evaluate KI distribution efforts.

Temporal trends and clinical correlates for the ret/PTC1 mutation in papillary thyroid carcinoma

BACKGROUND

The incidence of papillary thyroid carcinoma (PTC) has increased in Australia at a rate exceeding 10% per annum over the past two decades. In Tasmania the increase has averaged 24% per year between 1982 and 1997. Exposure to ionizing radiation is the best characterized risk factor for PTC. Oncogenic mutations of the RET proto-oncogene (ret/PTC rearrangements) have been associated with PTC arising following radiation exposure. In the present study it was sought to determine if PTC incidence trends were associated with an increased occurrence of the ret/PTC1 rearrangement.

METHODS

All cases of PTC diagnosed in Tasmania during the even numbered years 1978-1998 inclusive were sought for study (n = 98). Archival histopathology blocks for 62 cases were located. The RNA was successfully extracted from 41 tumours and ret/PTC1 status assessed by reverse transcription-polymerase chain reaction.

RESULTS

The ret/PTC1 mutation was found in 26 (63%) of PTC. The mean age at diagnosis for ret/PTC1-positive and ret/PTC1-negative tumours was 46.5 +/- 15.46 and 41.9 +/- 13.45 years, respectively. The ret/PTC1 positivity was significantly associated with larger tumour size. However, ret/PTC1 was not associated with an adverse prognosis. The prevalence of tumours positive for ret/PTC1 remained stable over the study period (1978-1998) and did not exhibit birth year or diagnosis year clustering.

CONCLUSION

This is the first study to map temporal trends for the prevalence of ret/PTC1 relative to incidence trends for PTC. Although the ret/PTC1 mutation was frequently identified in Tasmanian PTC, there was no clear relationship between ret/PTC1 and recent PTC incidence trends.

Temporal trends for thyroid carcinoma in Australia: an increasing incidence of papillary thyroid carcinoma (1982-1997)

The incidence of papillary thyroid carcinoma (PTC) has increased in many countries over the past 60 years. In Tasmania (an island state of the Australian Commonwealth with a well-documented history of iodine deficiency, subsequent supplementation and more recently a return to deficiency), there has been a fourfold rise in PTC incidence over the past two decades. The aim of this study was to evaluate thyroid carcinoma (TC) incidence trends in Australia, with particular reference to the roles of iodine nutrition, ionizing radiation, and ascertainment bias. Data from Australia's regional cancer registries were used to determine national TC incidence and mortality trends for the period 1982-1997. There were 9,053 new diagnoses of TC. Papillary, follicular, medullary, anaplastic, and "other diagnoses," accounted for 65.8%, 17.8%, 4.6%, 1.3%, and 10.5% of registered cases, respectively. TC incidence rates increased by 6.7% per year for females and 4.4% per year for males between 1982-1997 (p < 0.001). The increase was primarily because of a 10.7% per year and 8.3% per year rise in PTC incidence for females and males respectively (p < 0.001). The increase in PTC incidence was most significant for the population residing on Australia's eastern seaboard. The greatest relative and absolute increase in PTC (24.7% per year) occurred in Tasmania. These findings are consistent with a true increase in underlying PTC incidence rates. A link between current incidence trends and past iodine deficiency/radioiodine exposure during the 1950s and early 1960s is possible.

Thyrotoxicosis among Hanford, Washington, Downwinders: a community-based health survey

Sixty cases of thyrotoxicosis (including hyperthyroidism, Graves' disease, and toxic goiter), an unexpectedly large number compared with general population data, were reported in a voluntary health survey that included a period of approximately 50 yr, with 801 self-defined "Downwinders" who had lived near the Hanford, Washington, nuclear facility. In another self-selected group of medical patients (n = 423) who were examined over the same time period, only 2 cases of thyrotoxicosis were identified. Evidence is presented that suggests that the effects of bias from self-selection likely did not account for the magnitude of the apparent excess of thyrotoxicosis cases in the present study population. The findings are consistent with those of other studies, as well as with the hypothesis of an association of thyrotoxicosis with exposures to radioiodine.

Disaster medicine in the 21st century: future hazards, vulnerabilities, and risk

The prediction of future disasters drives the priorities, urgencies, and perceived adequacies of disaster management, public policy, and government funding. Disasters always arise from some fundamental dysequilibrium between hazards in the environment and the vulnerabilities of human communities. Understanding the major factors that will tend to produce hazards and vulnerabilities in the future plays a key role in disaster risk assessment. The factors tending to produce hazards in the 21st Century include population growth, environmental degradation, infectious agents (including biological warfare agents), hazardous materials (industrial chemicals, chemical warfare agents, nuclear materials, and hazardous waste), economic imbalance (usually within countries), and cultural tribalism. The factors tending to generate vulnerabilities to hazardous events include population growth, aging populations, poverty, maldistribution of populations to disaster-prone areas, urbanization, marginalization of populations to informal settlements within urban areas, and structural vulnerability. An increasing global interconnectedness also will bring hazards and vulnerabilities together in unique ways to produce familiar disasters in unfamiliar forms and unfamiliar disasters in forms not yet imagined. Despite concerns about novel disasters, many of the disasters common today also will be common tomorrow. The risk of any given disaster is modifiable through its manageability. Effective disaster management has the potential to counter many of the factors tending to produce future hazards and vulnerabilities. Hazard mitigation and vulnerability reduction based on a clear understanding of the complex causal chains that comprise disasters will be critical in the complex world of the 21st Century.

Tall cell papillary thyroid carcinoma metastatic to femur: evidence for thyroid hormone synthesis within the femur

A 67-year old man with a 3-month history of left hip pain had a history of Graves disease, treated with 131I 20 years before admission, and papillary thyroid carcinoma, treated with cervical lymphadenopathy 9 years before admission. Removal of a 3.5- x 5-cm mass from the left femur revealed it to be a tall cell variant of papillary thyroid carcinoma. Removal of this mass resulted in his thyrotropin level increasing from 2 (presurgery) to 23 mIU/mL, whereas his thyroxine level simultaneously decreased from 5.79 (presurgery) to 2.29 microg/dL 12 days after surgery despite continuation of levothyroxine of 0.137 mg/day. On histological examination, the tall cell variant in the femur was producing abundant thyroglobulin. This first case of a metastatic papillary thyroid carcinoma in bone producing thyroid hormone to the extent that the patient became hypothyroid after removal of this metastasis illustrates that metastatic thyroid lesion(s) may produce significant amounts of thyroid hormone.

Iodine nutrition and the risk from radioactive iodine: a workshop report in the chernobyl long-term follow-up study

The major fallout of radionuclides from the nuclear power station accident at Chernobyl on 26 April, 1986, occurred in regions of Ukraine and Belarus that are believed to be moderately deficient in dietary iodine. On 17 November, 2000, in conjunction with the Ukraine-Belarus-USA study of developing thyroid disease in a cohort of individuals exposed as children, a workshop was held to review what is known about iodine nutrition in the region, how this might influence the risk of thyroid tumor formation from radioiodine, and whether and how iodine nutrition should be monitored in this long-term project. This report is a summary of the workshop proceedings. Although no precise information about iodine intake in 1986 was found, the prevalence of mild goiter in the region's children suggested iodine deficiency and urinary iodine measurements begun in 1990 indicated that mild to moderate deficiency existed. Increased thyroid iodine uptake and increased thyroid size in 1986 resulting from iodine deficiency would have had counteracting influence on the thyroid radiation dose and knowledge of these parameters is required for dose reconstruction. More problematic is the possible role of iodine deficiency in the years following the accident. Theoretically, the resulting increase in thyroid cellular activity might increase the risk of tumorigenesis but experimental or clinical evidence supporting this hypothesis is meager or absent. Despite this limitation it was considered important to monitor iodine nutrition in the cohort subjects in relation to their place of residence and over time. Methods to accomplish this were discussed.

Effects of microsomal enzyme inducers on thyroid follicular cell proliferation and thyroid hormone metabolism

The effects of microsomal enzyme inducers on thyroid hormone homeostasis and the thyroid gland are of concern. We have investigated the effects of microsomal enzyme inducers on thyroid follicular cell proliferation and thyroid hormone metabolism in rats. We have shown that small increases in serum TSH can result in large increases in thyroid follicular cell proliferation. Furthermore, only those microsomal enzyme inducers that increase serum TSH--that is, phenobarbital (PB) and pregnenolone-16alpha-carbonitrile (PCN)-increase thyroid follicular cell proliferation, whereas those microsomal enzyme inducers that do not increase serum TSH--that is, 3-methylcholanthrene (3MC) and Aroclor 1254 (PCB)-do not increase thyroid follicular cell proliferation. Deiodination does not appear to be the reason why serum T3 concentrations are maintained in microsomal enzyme inducer-treated rats. We have also shown that those microsomal enzyme inducers that increase serum TSH increase T3 UDP-glucuronosyltransferase (UGT) activity, whereas those microsomal enzyme inducers that do not increase serum TSH do not increase T3 UGT activity. This finding suggests that induction of T3 glucuronidation, rather than T4 glucuronidation, mediates increases in serum TSH of microsomal enzyme inducer treated rats.

The epidemiology and etiology of differentiated thyroid carcinoma

Differentiated thyroid carcinoma (DTC) is a rare tumor with a relatively good prognosis, but in about 10% of cases it may be the cause of death. Papillary carcinoma is more frequent (about 70-80% of cases) and less aggressive than follicular cancer: the papillary/follicular ratio is increased in areas of high iodine intake. In recent years many genes have been found to be mutated in DTC, the most important of these being ras, ret, trk, and met. The relationship between radiation exposure and DTC is well recognized, especially in children. Since the Chernobyl nuclear accident, a high incidence of DTC has been found in children exposed to fallout.

Effects of time of administration and dietary iodine levels on potassium iodide (KI) blockade of thyroid irradiation by 131I from radioactive fallout

Radioiodines, particularly 131I, may be released into the environment in breach-of-containment nuclear reactor accidents and localize in and irradiate the thyroid with an attendant risk of neoplastic growth and other adverse health effects. Pharmacologic thyroid blockade by oral potassium iodide (KI) (50-100 mg in adults) can substantially reduce thyroid uptake of and irradiation by internalized radioiodine. In the current analysis, computer modeling of iodine metabolism has been used to systematically elucidate the effects of two practically important but highly variable factors on the radioprotective effect of KI: the time of administration relative to exposure to radioiodine and the dietary level of iodine. In euthyroid adults receiving iodine-sufficient diets (250 microg d(-1) in the current analysis), KI administered up to 48 h before 131I exposure can almost completely block thyroid uptake and therefore greatly reduce the thyroid absorbed dose. However, KI administration 96 h or more before 131I exposure has no significant protective effect. In contrast, KI administration after exposure to radioiodine induces a smaller and rapidly decreasing blockade effect. KI administration 16 h or later after 131I exposure will have little effect on thyroid uptake and absorbed dose and therefore little or no protective effect. The 131I thyroid absorbed dose is two-fold greater with insufficient levels of dietary iodine, 2,900 cGy/37 MBq, than with sufficient levels of dietary iodine, 1,500 cGy/37 MBq. When KI is administered 48 h or less before 131I intake, the thyroid absorbed doses (in cGy/37 MBq) are comparably low with both sufficient and insufficient dietary iodine levels. When KI is administered after 131I intake, however, the protective effect of KI is less and decreases more rapidly with insufficient than with sufficient dietary iodine. For example, KI administration 2 and 8 h after 131I intake yields protective effects of 80 and 40%, respectively, with iodine-sufficient diets, but only 65 and 15% with iodine-deficient diets. In conclusion, whether exposed populations receive sufficient or insufficient dietary iodine, oral KI is an effective means of reducing thyroid irradiation from environmentally dispersed radioiodine but is effective only when administered within 2 d before to approximately 8 h after radioiodine intake.

The Chernobyl accident and its consequences: update at the millennium

A marked increase in the incidence of papillary thyroid cancer in children has been documented in regions of the former Soviet Union most heavily contaminated by radioactive fallout from the Chernobyl nuclear power plant accident in April 1986. Accumulation of radioactive iodines by normal iodine trapping mechanisms resulted in significant radiation doses to the thyroid gland. Although it has long been known that thyroidal radiation resulted in nuclear and chromosomal abnormalities visible by light microscopy, modern molecular biology techniques are beginning to identify much smaller alterations in chromosomal coding sequences that are associated with malignant transformation. Although stable chromosomal abnormalities can be detected in Chernobyl-associated thyroid cancers, they are much less prevalent than in thyroid cancers developing after external beam irradiation. However, several unique chromosomal breakpoints have been described in radiation-associated thyroid cancers that are not commonly found in spontaneously occurring thyroid cancer. Furthermore, activation of specific subtypes of the ret/PTC tyrosine kinase oncogene appears to be more common in radiation-associated thyroid cancers than in spontaneous thyroid cancers. In summary, thyroid cancers developing in the aftermath of the Chernobyl accident provide a unique opportunity to search for chromosomal abnormalities that may be specific for radiation-induced thyroid cancer.

Thyroid cancer following exposure to radioactive iodine

The thyroid gland is one of the most sensitive organs for radiation-induced oncogenesis and the magnitude of the risk from external radiation is well understood. This is not the case for internal radiation derived from the radioiodines, a matter of practical importance because of medical use and potential accidental exposure. This article reviews current knowledge derived from the follow-up of patients receiving diagnostic or therapeutic 131I and populations exposed to radioactive fallout. The latter includes the nuclear power station accident at Chernobyl and the results of atomic bomb development and testing at Hanford, the Nevada Test Site and the Marshall Islands. The most cogent information comes from Chernobyl where an epidemic of childhood thyroid cancer has followed exposure to radioiodine that was mainly 131I. Although much has been learned from this experience about the nature of radioiodine induced thyroid cancer in young children, the reconstruction of thyroid radiation doses is too preliminary to provide accurate knowledge of the risk in comparison to that from external radiation. In the Marshall Islands, much of the exposure was from short-lived radioiodines as well as external radiation, obviating the possibility to determine the risk from 131I. Exposure to 131I in the continental United States from atomic bomb testing is expected to have caused some thyroid cancers, but only in the immediate vicinity of the Nevada Test Site has any evidence of radiation-induced thyroid neoplasms been adduced. This evidence is minimally significant statistically, and not significant for thyroid cancer per se. Medical use of radioiodine has not been observed to cause thyroid cancer but very few of the patients studied were young children, the group most sensitive to thyroid radiation. Despite these limitations, this information is sufficient to make some suggestions concerning protective measures in the case of nuclear accidents and the follow up of individuals who have been exposed.

Age-dependent thyroid absorbed doses for radiobiologically significant radioisotopes of iodine

In light of the post-Chernobyl increase in pediatric thyroid cancer incidence, among other recent events, there is renewed interest in radioiodine thyroid dosimetry and effects. Among the radioiodines produced in fission of 235U, only 131I [(T1/2)p = 8.04 d], 132I (2.3 h), 133I (20.3 h), and 135I (6.7 h) may undergo significant environmental dispersion. Age-dependent thyroid absorbed dose estimates for these radiobiologically significant radioiodines and for the "medical" radioisotopes 123I (13.2 h) and 125I (60 d) have been derived, incorporating the effect of absorption following inhalation or ingestion. This effect has generally been ignored in previously derived estimates of radioiodine absorbed doses to the thyroid. Based on the latest ICRP lung and gut models, inhaled radioiodine is absorbed at a rate of 0.175 h(-1) and exhaled at 0.101 to 0.118 h(-1) (depending on age) and ingested radioiodine is completely absorbed in the stomach at a rate of 1 h(-1). Whole-body compartmental models (SAAM II) were fit to previously published 24-h thyroid uptakes, thyroid half-times, and 48-h plasma concentration of protein-bound iodine. The resulting fitted models were used to calculate thyroid residence times of radioiodine. The mean thyroid absorbed doses [cGy/37 kBq (rad/microCi) injected intravenously] were then calculated using the age-dependent S(thyroid<--thyroid) factors (MIRDOSE III), with the highest doses (from 0.49 for 123I to 36 for 131I) in newborns and the lowest doses (from 0.014 for 123I to 1.4 for 131I) in adults in inverse relation to the thyroid mass. Although the thyroid absorbed dose for inhalation is substantially (30 to 70%) less than that for injection for all radioiodines and at all ages, it is markedly (25%) less for ingestion only for short-lived 132I.

Extensive surgery improves recurrence-free survival for children and young patients with class I papillary thyroid carcinoma

BACKGROUND

Children with papillary thyroid cancer (PTC) rarely die of their disease, but are at high risk for recurrence, particularly with multifocal tumors (which occur in 42% of children with PTC). It is not clear if more extensive surgery, with an increased risk of complications, lessens the risk for recurrence. The authors hypothesized that patients with disease presumed to be confined to the thyroid gland (class I PTC) could have multifocal disease, involving the contralateral lobe, of which the surgeon is unaware. Treatment with less than subtotal thyroidectomy might be associated with a higher risk of recurrence.

METHODS

The charts of 37 patients with Class I PTC diagnosed at < or =21 years of age between 1953 and 1996 were reviewed. The incidence of surgical complications and the risk of recurrence based on the extent of initial surgery ([1] lobectomy with or without isthmusectomy, [2] subtotal, or [3] total thyroidectomy) and adjunctive therapy with thyroid hormone or radioactive iodine (RAI) were examined.

RESULTS

Eight patients had recurrent PTC. Patients treated with lobectomy with or without isthmusectomy were more likely to have recurrence than patients treated with subtotal or total thyroidectomy (Odds ratio, 8.7; 95% CI 1.4 to 54). Although the incidence of complications was statistically similar among the 3 surgical groups, 3 patients, all treated with more extensive surgery, had permanent hypoparathyroidism. There were too few patients to determine whether treatment with thyroid hormone or RAI offered additional benefit.

CONCLUSIONS

In children with Class I PTC, more extensive surgery is associated with a lower risk of recurrence. This finding must be weighed against the risk of complications when determining the optimal treatment for individual patients.

Low prevalence of the ret/PTC3r1 rearrangement in a series of papillary thyroid carcinomas presenting in Belarus ten years post-Chernobyl

After the Chernobyl accident in 1986, there was a significant increase in the incidence of papillary thyroid cancer in fallout-exposed children from Belarus. Radiation-induced rearrangements of chromosome 10 involving the c-ret proto-oncogene have been implicated in the pathogenesis of these cancers. The ret/PTC3r1 rearrangement was the most prevalent molecular lesion identified in post-Chernobyl papillary thyroid cancers arising in 1991 and 1992. We identified the ret/PTC1 rearrangement in 29% of 31 papillary thyroid cancers presenting in Belarus in 1996. In the present report, we examined 14 cases from this series (plus 1 additional case) and found a ret/PTC3r1 rearrangement in only 1 (7%). The prevalence of ret/PTC3r1 in this series is significantly lower than previously reported (p = 0.0006, Fisher exact test). This result suggests a switch in the ratio of ret/PTC3 to ret/PTC1 rearrangements in late (1996) versus early (1991-1992) post-Chernobyl papillary thyroid cancers.

Clinical features associated with metastasis and recurrence of differentiated thyroid cancer in children, adolescents and young adults

OBJECTIVE

Differentiated thyroid cancer (DTC), including papillary (PTC) and follicular (FTC) variants, is unusual in children and accounts for only 10% of all cases. For that reason, knowledge of the clinical features which predict recurrence is limited. We reviewed 170 cases of childhood DTC to determine if specific clinical or pathological findings were associated with increased risk of recurrence.

DESIGN

This was a retrospective study of children and adolescents with DTC registered in the Department of Defense Automated Centralized Tumor Registry.

PATIENTS

We reviewed 137 cases of PTC and 33 cases of FTC diagnosed between 1953 and 1996 at < or = 21 years of age.

RESULTS

In the PTC group (median follow-up 6.6 years, range 2 month-39.5 years), only one patient died, but 21 developed local and 6 developed distant recurrence. By univariate analysis, recurrence was more common in patients with multifocal (odds ratio 7.5) or large tumours (odds ratio 4.1), and in those with palpable cervical lymphadenopathy (odds ratio 3.0) or metastasis at diagnosis (odds ratio 2.8). By multivariate analysis focality was the best predictor of recurrence (P = 0.0019). In the FTC group (median follow-up 5 years, range 6 month-38.1 years), no patient died of disease, but 5 developed recurrence. As with PTC, recurrence was more likely in patients with multifocal tumours (odds ratio 22.0).

CONCLUSIONS

Differentiated thyroid cancer in children and adolescents has low mortality, but a high risk of recurrence. Young patients with large, multifocal tumours that are already metastatic at diagnosis have the greatest risk of recurrence.

Prevalences of Gs alpha, ras, p53 mutations and ret/PTC rearrangement in differentiated thyroid tumours in a Korean population

OBJECTIVE

In thyroid tumours, ras, Gs alpha, p53 mutations and ret/PTC rearrangement have been reported with variable prevalences in different geographical regions. We studied the prevalence of these mutations and rearrangement in thyroid tumours in a Korean population. As MDM2 and Bcl-1 protein expressions have been suggested to be associated with p53 protein, we also studied possible relationships among them.

PATIENTS AND DESIGN

Eleven cases of adenomatous goitre, eight cases of follicular adenoma, five cases of follicular carcinoma and 37 cases of papillary carcinoma were included in this study. To find mutations and rearrangement, RT-PCR, SSCP and/or direct sequencing, after subcloning if necessary, were used, and immunohistochemical stainings were performed for p53, MDM2 and Bcl-2 proteins in cases of papillary carcinoma.

RESULTS

We could not find any rearrangement for ret/PTC-1, -2, -3 and mutation of Gs alpha. For the ras oncogene, K and H-ras mutations were not found, but N-ras mutations, point mutation of CAA to CGA in codon 61, were detected in one follicular adenoma (12.5%, 1/8) and one follicular carcinoma (33%, 1/3). p53 mutations were detected in only one case of papillary carcinoma (3%, 1/31: exon 8, codon 266 GGA-->GAA). In 30 cases of papillary carcinoma without p53 mutation, the prevalences of positive immunohistochemical staining were 13.3% for p53 protein, 53.3% for MDM2 protein and 56.7% for Bcl-2 protein. While over-expression of p53 protein was not significantly related to that of MDM2 and Bcl-2 proteins, over-expression of MDM2 and Bcl-2 in papillary carcinoma were associated.

CONCLUSION

ret/PTC rearrangement, Gs alpha, ras and p53 mutations are relatively rare in differentiated thyroid neoplasms from a Korean population, which may reflect genetic and environmental differences from patients in countries with high prevalences. P53 protein over-expression was noted in 13.3% of papillary carcinoma cases without p53 mutation and was not significantly related to MDM2 and Bcl-2 expression.

Isolation and analysis of UV and radio-resistant bacteria from Chernobyl

The accident at the Chernobyl nuclear power station in 1986 led to the dispersal of large amounts of a variety of radioactive materials, most importantly uranium, plutonium, 137Cs, 131I and 90Sr, over very large distances estimated to reach as far as Sweden, Norway, Turkey and possibly the USA. As a consequence, the soil on which the radioactive materials fell was contaminated and the degree of contamination varied with distance from the station, the direction and strength of the wind and the amount of atmospheric scavenging by rainfall at that time. Some of the radioactive materials have left a significant impact on mankind in the form of chromosomal aberrations including trisomy, various forms of cancers and death, whilst others are still in the ground where they will remain for a prolonged period to continue to exert their effects. Likewise, microbes living in the soil and exposed to radioactive materials may have been affected in a number of ways; some perished, and others survived due to the acquisition of advantageous mutation. Six years after the accident, soil samples contaminated with different levels of radioactivity were obtained from five regions within a 30 km radius of the nuclear power plant. From these soil samples spore-forming bacilli were isolated, quantified, identified and tested for resistance to X-rays, UVC and 4-nitroquinoline 1-oxide (4NQO). As a control, spore-forming bacilli were obtained from 'Zeleny mys' (an area 50 km south-east of the power station and emitting basal levels of radioactivity). A mutant of Escherichia coli hyper-resistant to a variety of DNA-damaging agents and its parent strain were also included in the study. Analysis of results reveals that a proportion of isolates of the same species from near the power station and the E. coli mutant SA236 were more resistant to X-rays, UVC and 4NQO compared with isolates from the control site and the E. coli parent strain, KL14, respectively.

Radioiodine-induced thyroid cancer: Studies in the aftermath of the accident at Chernobyl

While a great deal is known about the relationship between external radiation exposure and thyroid cancer, much less is known about the oncogenic effects of internal radiation exposure from isotopes of iodine. The accident at the Chernobyl nuclear power plant released massive quantities of radioiodine isotopes into the atmosphere. The large number of ensuing thyroid cancers in exposed children leaves little doubt that these malignancies have occurred as a result of the accident. However, carefully planned epidemiological studies are needed to confirm that these are due predominantly to I-131 exposure, to determine the dose-response relationship, to monitor for continuing effects and to evaluate other contributing factors. Preliminary evidence indicates that there is a distinct pattern of somatic genetic changes in the thyroid cancers from the Chernobyl area.

The ret/PTC1 rearrangement is a common feature of Chernobyl-associated papillary thyroid carcinomas from Belarus

An increase in the incidence of papillary thyroid cancer has been documented in individuals exposed to Chernobyl fallout in 1986. Experiments using cultured human cells have suggested that radiation can induce the ret/PTC1 rearrangement involving the ret proto-oncogene. To test the hypothesis that the ret/PTC1 rearrangement is involved in the pathogenesis of Chernobyl-associated papillary thyroid carcinomas, we studied a panel of 31 cases from Belarus. All individuals lived in fallout-contaminated oblasts (regions) of Belarus at the time of the accident: Gomel (n = 13), Brest (n = 12), Minsk (n = 4), and Grodno (n = 2). All were under age 20 at the time of the accident; 20 were born between 1982 and 1986. Individual thyroid radiation doses were estimated at 1.1 to 110 rem. Patients underwent surgery in Minsk in 1996. Fifteen patients had locally advanced disease (stage T4). The majority had regional lymph node involvement (stage N1, n = 27). There were no distant metastases. Surgical specimens were frozen at -80 degrees C, RNA was extracted and cDNA prepared. The polymerase chain reaction (PCR) was performed with specific primers for ret/PTC1, and c-ret and GAPDH as controls. Controls were positive in all 31 cases. Nine cases yielded a positive PCR product for the ret/PTC1 rearrangement (29%). Thus, the ret/PTC1 rearrangement is a feature of some Chernobyl-associated papillary thyroid cancers, and is one possible mechanism involved in the pathogenesis of these cancers.

Potassium iodide for thyroid blockade in a reactor accident: administrative policies that govern its use

A marked increase in thyroid cancer among young children who were in the vicinity of the Chernobyl nuclear power plant at the time of the 1986 accident strongly suggests a possible causal relationship to the large amounts of radioactive iodine isotopes in the resulting fallout. Although remaining indoors, restricting consumption of locally produced milk and foodstuffs, and evacuation are important strategies in a major breach-of-containment accident, stable potassium iodide (KI) prophylaxis given shortly before or immediately after exposure can reduce greatly the thyroidal accumulation of radioiodines and the resulting radiation dose. Concerns about possible side effects of large-scale, medically unsupervised KI consumption largely have been allayed in light of the favorable experience in Poland following the Chernobyl accident; 16 million persons received single administrations of KI with only rare occurrence of side effects and with a probable 40% reduction in projected thyroid radiation dose. Despite the universal acceptance of KI as an effective thyroid protective agent, supplies of KI in the US are not available for public distribution in the event of a reactor accident largely because government agencies have argued that stockpiling and distribution of KI to other than emergency workers cannot be recommended in light of difficult distribution logistics, problematic administrative issue, and a calculated low cost-effectiveness. However, KI in tablet form is expensive and has a long shelf life, and many countries have largely stockpiles and distribution programs. The World Health Organization recognizes the benefits of stable KI and urges its general availability. At present there are 110 operating nuclear power plants in the US and more than 300 in the rest of the world. These reactors product 17% of the world's electricity and in some countries up to 60-70% of the total electrical energy. Almost all US nuclear power plants have multistage containment structures with large steel and concrete shells and multiple redundancy of core cooling mechanisms. These successfully prevented the release of major amounts of radionuclides in the Three Mile Island partial loss-of-primary coolant accident in 1979. The Chernobyl accident, in a different type of reactor that is common in Eastern Europe, did not have effective outer shell containment and released almost 50 MCi of 131I compared to the 20 Ci of 131I released at Three Mile Island. Such accidents have precipitated extensive re-evaluation of the design and safety devices of all operating reactors. However, a major contributing factor to the accidents was human error and considerable efforts must be made to train plant operators so they have a better understanding of reactor operation and use of safety mechanisms.

Lessons from Chernobyl: the event, the aftermath fallout: radioactive, political, social

The accident at the Chernobyl nuclear power station on April 26, 1986, released about 300 MCi of radioactive substances, including about 40 MCi of 131I and 100 MCi of short-lived radioiodines. In the immediate surroundings there were 143 cases of acute radiation syndrome, 34 deaths, and hundreds of thousands of people displaced from their homes, many permanently. The social and psychologic stresses that followed have been enormous and long-lasting. This article focuses on the rising incidence of thyroid cancer in exposed children. Radiation-induced thyroid cancer following external radiation is well documented but there is little evidence in humans of thyroid cancer from internal radiation and the risk coefficient for radioiodine exposure is known. To achieve this, thyroid dose reconstruction and prospective follow-up of about 50,000 persons who were children in 1986 will be required. Thyroid cancer in children of southern Belarus began to increase in 1990 and there now are about 1,000 cases in Belarus and northern Ukraine. These aggressively growing tumors, almost all variants of papillary thyroid cancer, are typical for thyroid cancer in children not exposed to radiation, and a low mortality rate is to be expected. It also is expected, however, that malignant as well as benign thyroid neoplasms will continue to arise in these exposed children well into their adult life.