Thyroid carcinoma in man after exposure to ionizing radiation. A summary of the findings in Hiroshima and Nagasaki

Molecular profiling of papillary thyroid carcinomas in healthcare workers exposed to low dose radiation at the workplace

PURPOSE

Exposure to ionizing radiation, especially during childhood, is a well-established risk factor for thyroid cancer. The vast majority of radiation-induced cancers are papillary carcinomas (PTCs). These tumors typically have gene fusions in contrast to point mutations prevalent in sporadic PTCs. The aim of this study was to investigate the molecular profiles of PTC patients with workplace exposure to ionizing radiation.

METHODS

A retrospective review of 543 patients who underwent surgery with diagnosis of PTC was performed. A cohort of nine healthcare specialists previously exposed to radiation sources during their professional practice was selected and analyzed using the ThyroSeq mutation panel for point mutations and gene fusions associated with thyroid cancer.

RESULTS

The molecular analysis of surgical samples of PTCs was informative and revealed genetic alterations in five patients. BRAF V600E was found in four (67%) cases whereas RET/PTC1 fusion in one (17%) and one sample (17%) was wild type for point mutations and fusions. One sample completely failed molecular analysis while two others were negative for genes fusions but failed DNA analysis; these three samples were excluded.

CONCLUSIONS

In this limited cohort of healthcare workers exposed to low dose of ionizing radiation at the workplace and developed PTC, the molecular profiling determined BRAF V600E point mutation as the most common event, arguing against the role of workplace radiation exposure in the etiology of these tumors.

Risk of Benign and Malignant Thyroid Disorders in Subjects Treated for Paediatric/Adolescent Neoplasia: Role of Morphological and Functional Screening

Background: Patients treated for paediatric/adolescent (P/A) neoplasia have a high incidence of both benign and malignant thyroid diseases. Given the high incidence of sequelae, literature data show a clinical benefit of morpho-functional thyroid screening in paediatric/adolescent cancer survivors and a careful lifetime follow-up. Patients and methods: The incidence of thyroid alterations was evaluated in a consecutive series of 343 patients treated with chemotherapy (CHE) and radiotherapy (RTE) or only with CHE for P/A tumours between 1976 and 2018 (mean age at time of primary paediatric malignancy 7.8 ± 4.7 years). All patients underwent thyroidal morpho-functional evaluation between 2000 and 2019. Results: 178 patients (51.9%) were treated only with CHE and 165 (48.1%) with CHE+RTE. A functional and/or structural thyroid disease was diagnosed in 147 (42.5%; 24.2% in CHE and 62.4% in CHE+RTE group; p = 0.0001). Of note, 71 (20.7%) patients with no evidence of disease at first evaluation developed a thyroid alteration during the follow-up. Primitive hypothyroidism was diagnosed in 54 patients (15.7%; 11.2% in CHE vs. 20.6% in CHE+RTE group; p = 0.01) and hyperthyroidism in 4. Sixty-three patients developed thyroid nodules (18.4%; 4.0% in CHE and 14.1% in CHE+RTE group; p < 0.001); thyroid cancer was diagnosed in 30 patients (8.7%; 4.5% in CHE and 12.4% in CHE + RTE group; p = 0.007). Conclusions: In patients treated with CHE+RTE, the prevalence of hypothyroidism and nodular pathology, both malignant and benign, were significantly greater than in patients treated with CHE. However, also in the CHE group, the frequency of thyroid disease is not negligible and the pathogenetic mechanisms remain to be clarified. Our data suggest the clinical benefit of morpho-functional thyroid screening in P/A cancer survivors.

Individual response of humans to ionising radiation: governing factors and importance for radiological protection

Tissue reactions and stochastic effects after exposure to ionising radiation are variable between individuals but the factors and mechanisms governing individual responses are not well understood. Individual responses can be measured at different levels of biological organization and using different endpoints following varying doses of radiation, including: cancers, non-cancer diseases and mortality in the whole organism; normal tissue reactions after exposures; and, cellular endpoints such as chromosomal damage and molecular alterations. There is no doubt that many factors influence the responses of people to radiation to different degrees. In addition to the obvious general factors of radiation quality, dose, dose rate and the tissue (sub)volume irradiated, recognized and potential determining factors include age, sex, life style (e.g., smoking, diet, possibly body mass index), environmental factors, genetics and epigenetics, stochastic distribution of cellular events, and systemic comorbidities such as diabetes or viral infections. Genetic factors are commonly thought to be a substantial contributor to individual response to radiation. Apart from a small number of rare monogenic diseases such as ataxia telangiectasia, the inheritance of an abnormally responsive phenotype among a population of healthy individuals does not follow a classical Mendelian inheritance pattern. Rather it is considered to be a multi-factorial, complex trait.

Pathological characteristics of thyroid glands from Japanese Black Cattle living in the restricted area of the Fukushima Daiichi Nuclear Power Plant accident

To study the effect of ionizing radiation on thyroid glands, 66 Japanese Black cattle residing in the restricted area of the Fukushima Daiichi Nuclear Power Plant in 2013-2017 were pathologically examined. There were no clinical symptoms of thyroid disease in these cattle. Three cases of goiter and seven of atrophy were found in two among the four farms examined. Cases of goiter exhibited normal morphological structure without mass or nodule formation in thyroid glands. Cellular atypia or capsular invasion of the follicular epithelium was absent. The estimated integrated dose of external radiation in goiter cases ranged from maximum 797 mSv to minimum 24 mSv. All lobules in the seven atrophic thyroid glands were affected, but pathological findings, such as inflammatory cell infiltration or stromal fibrosis, were not observed. The estimated integrated dose of external radiation in atrophic thyroids ranged from maximum 589 mSv to minimum 8 mSv. Immunohistochemical analysis of anti-nitroguanosine and the TUNEL method in goiter and atrophic thyroid glands did not reveal any positive findings. The present study indicates that there was no significant relationship between a radiation effect and pathological findings in any thyroid glands.

Long-Term Endocrine and Metabolic Consequences of Cancer Treatment: A Systematic Review

The number of patients surviving ≥5 years after initial cancer diagnosis has significantly increased during the last decades due to considerable improvements in the treatment of many cancer entities. A negative consequence of this is that the emergence of long-term sequelae and endocrine disorders account for a high proportion of these. These late effects can occur decades after cancer treatment and affect up to 50% of childhood cancer survivors. Multiple predisposing factors for endocrine late effects have been identified, including radiation, sex, and age at the time of diagnosis. A systematic literature search has been conducted using the PubMed database to offer a detailed overview of the spectrum of late endocrine disorders following oncological treatment. Most data are based on late effects of treatment in former childhood cancer patients for whom specific guidelines and recommendations already exist, whereas current knowledge concerning late effects in adult-onset cancer survivors is much less clear. Endocrine sequelae of cancer therapy include functional alterations in hypothalamic-pituitary, thyroid, parathyroid, adrenal, and gonadal regulation as well as bone and metabolic complications. Surgery, radiotherapy, chemotherapy, and immunotherapy all contribute to these sequelae. Following irradiation, endocrine organs such as the thyroid are also at risk for subsequent malignancies. Although diagnosis and management of functional and neoplastic long-term consequences of cancer therapy are comparable to other causes of endocrine disorders, cancer survivors need individually structured follow-up care in specialized surveillance centers to improve care for this rapidly growing group of patients.

THYROID DISEASES AMONG ATOMIC BOMB SURVIVORS

Systematic epidemiological studies of Hiroshima and Nagasaki atomic bomb survivors have made substantial contributions to the understanding of radiation effects on human health. A recent study of atomic bomb survivors reported that an increased risk of thyroid cancer associated with childhood exposure might have persisted for more than 50 years after exposure. In analyses of non-cancer thyroid diseases, several cross-sectional studies, including the latest study focusing on survivors exposed in childhood, suggested that the risk of thyroid nodules increased, while risks of thyroid dysfunction and autoimmunity were not apparent several decades after radiation exposure. However, careful interpretations are needed because only limited data from cross-sectional studies are available. Further longitudinal studies are necessary to improve our understanding of the effect of radiation on the thyroid and its function.

Thyroid Cancer in Children and Adolescents

Aims and background

It was the aim of this paper to report clinical and pathologic characteristics and outcome of treatment in terms of relapse-free and overall survival in 36 patients under 20 years of age and treated for thyroid cancer at Padua University Hospital from January 1968 to December 1988 and followed until December 1992.

Methods

The median follow-up was 112 months (range 3 to 228 months). Age at diagnosis ranged from 4 to 20 years with a mean age of 15 years and a male/female ratio of 1:2.9. A thyroid nodule or a laterocervical mass was the most frequent sign of presentation. The routine diagnosis schedule included thyroid scintigram, neck echotomography and in the last decade fine needle aspiration biopsy.

Results

Sixteen (28%) patients had a family history of thyroid disease. Histology revealed that papillary carcinoma was present in 43 patients (76.8%), follicular carcinoma in 9 (16%), medullary carcinoma in 2 (3.6%) and lymphoma in 2 (3.6%). Fifty-four patients were treated with total thyroidectomy, of these 34 had bilateral neck dissection and 20 unilateral nodal dissection; 2 patients underwent simple lobectomy with unilateral dissection. Nodal involvement was present in 41 (73%) cases, and synchronous visceral metastases were detected with scan and/or chest X-ray in 10 (18%) cases. In the case of differentiated thyroid carcinoma, patients with residual disease or thyroid remnants were treated with 131I metabolic therapy. All patients were put on suppressive hormone therapy. At this writing, 52 (93%) patients were in complete remission and 4 (7%) had persistent disease. Recurrences developed in 2 (3.5%) patients: one presented lung metachronus metastases and one local recurrence; no deaths have occurred.

Conclusions

From this experience, total thyroidectomy appears to be the appropriate approach for differentiated tumors in children and adolescents because the disease is often diffuse, secondary deposits may be easily detected, and the value of thyroglobulin measurement can be improved. Following this strategy, overall recurrence risk was low and 131I therapy was curative in patients with nodal and lung metastases.

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.

Radiation exposure and thyroid cancer: a review

The association between radiation exposure and the occurrence of thyroid cancer has been well documented, and the two main risk factors for the development of a thyroid cancer are the radiation dose delivered to the thyroid gland and the age at exposure. The risk increases after exposure to a mean dose of more than 0.05-0.1 Gy (50-100mGy). The risk is more important during childhood and decreases with increased age at exposure, being low in adults. After exposure, the minimum latency period before the appearance of thyroid cancers is 5 to 10 years. Papillary carcinoma (PTC) is the most frequent form of thyroid carcinoma diagnosed after radiation exposure, with a higher prevalence of the solid subtype in young children with a short latency period and of the classical subtype in cases with a longer latency period after exposure. Molecular alterations, including intra-chromosomal rearrangements, are frequently found. Among them, RET/PTC rearrangements are the most frequent. Current research is directed on the mechanism of genetic alterations induced by radiation and on a molecular signature that can identify the origin of thyroid carcinoma after a known or suspected exposure to radiation.

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.

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.

A note from history: Landmarks in history of cancer, Part 6

In the 3 decades from 1940 to 1970, the United States became the nucleus for research, diagnosis, and treatment of cancer. The discovery of anticancer drugs, and the clinical demonstration that chemotherapy and radiation can cure cancer and have the ability to prevent recurrence of cancer, were incontrovertibly the most remarkable groundbreaking events. Consequently, the trend of less surgery and more multimodality therapy began. The introduction of radioautography, mammography, ultrasonography, computed tomography, Papanicolaou smear, and other novel laboratory tests furthered early detection of cancer and refined accurate diagnosis. The unequivocal linking of lung cancer to cigarette smoking made medical history. The delineation of the potential role of oncogenes adduced new thoughts about oncogenesis and cancer prevention, and pathologists finalized the classification and nosology of tumors. Finally, it is worth noting that although more advances were made in the detection, diagnosis, and treatment of cancers than any other period in history, the overall mortality rate of patients with cancer remained high and unchanged.

Follicular thyroid cancer in children and adolescents: clinicopathologic features, long-term survival, and risk factors for recurrence

Children and adolescents represent 1-1.5% of all patients with thyroid cancer (TC). The vast majority of TC in children and adolescents is papillary TC; follicular TC (FTC) is exceedingly rare. In this study, we evaluate the clinical and pathological features of FTC in children and adolescents. We also report the risk factors for post-operative tumor recurrence and the associated outcomes. Twenty children and adolescents (under 21 years old) with FTC have been treated and followed at Noguchi Thyroid Clinic and Hospital Foundation since 1946. All patients underwent surgery (lobectomy, 11; subtotal thyroidectomy, 8; and total thyroidectomy, 1), and 8 patients received postoperative external beam radiation therapy. The incidence of FTC in children and adolescents was 1.9% among all FTC patients treated in our hospital. Histopathology revealed vascular and capsular invasion in 9 and 20 patients, respectively. The tumor recurrence rate in FTC with vascular invasion is significantly higher than in those without it (p = 0.038). No other factors were significant. Patients with recurrences were treated with completion thyroidectomy and ¹³¹I radioactive iodine therapy. There were no significant differences in the rates of disease-free survival or cause-specific survival when pediatric/adolescent FTC patients were compared to adults with FTC. FTC is very rare among children and adolescents, but the outcomes are similar to those observed among adults. Vascular invasion is poor prognostic indicator in pediatric/adolescent FTC patients.

A pooled analysis of thyroid cancer incidence following radiotherapy for childhood cancer

Childhood cancer five-year survival now exceeds 70-80%. Childhood exposure to radiation is a known thyroid carcinogen; however, data are limited for the evaluation of radiation dose-response at high doses, modifiers of the dose-response relationship and joint effects of radiotherapy and chemotherapy. To address these issues, we pooled two cohort and two nested case-control studies of childhood cancer survivors including 16,757 patients, with 187 developing primary thyroid cancer. Relative risks (RR) with 95% confidence intervals (CI) for thyroid cancer by treatment with alkylating agents, anthracyclines or bleomycin were 3.25 (0.9-14.9), 4.5 (1.4-17.8) and 3.2 (0.8-10.4), respectively, in patients without radiotherapy, and declined with greater radiation dose (RR trends, P = 0.02, 0.12 and 0.01, respectively). Radiation dose-related RRs increased approximately linearly for <10 Gy, leveled off at 10-15-fold for 10-30 Gy and then declined, but remained elevated for doses >50 Gy. The fitted RR at 10 Gy was 13.7 (95% CI: 8.0-24.0). Dose-related excess RRs increased with decreasing age at exposure (P < 0.01), but did not vary with attained age or time-since-exposure, remaining elevated 25+ years after exposure. Gender and number of treatments did not modify radiation effects. Thyroid cancer risks remained elevated many decades following radiotherapy, highlighting the need for continued follow up of childhood cancer survivors.

Papillary microcarcinoma of the thyroid among atomic bomb survivors: tumor characteristics and radiation risk

BACKGROUND

: Radiation exposure is an established cause of clinical thyroid cancer, but little is known about radiation effects on papillary microcarcinoma (PMC) of the thyroid, a relatively common subclinical thyroid malignancy. Because the incidence of these small thyroid cancers has been increasing, it is important to better understand them and their relation to radiation.

METHODS

: PMCs were identified in a subset of 7659 members of the Life Span Study of atomic bomb survivors who had archived autopsy or surgical materials. We conducted a pathology review of these specimens and evaluated the histological features of the tumors and the association between PMCs and thyroid radiation dose.

RESULTS

: From 1958 to 1995, 458 PMCs were detected among 313 study subjects. The majority of cancers exhibited pathologic features of papillary thyroid cancers. Overall, 81% of the PMCs were of the sclerosing variant and 91% were nonencapsulated, psammoma bodies that occurred in 13% and calcification was observed in 23%. Over 95% had papillary or papillary-follicular architecture and most displayed nuclear overlap, clear nuclei, and nuclear grooves. Several of these features increased with increasing tumor size, but no association was found with radiation dose. A significant radiation-dose response was found for the prevalence of PMCs (estimated excess odds ratio/Gy = 0.57; 95% confidence interval, 0.01-1.55), with the excess risk observed primarily among women.

CONCLUSIONS

: Exposure to low-to-moderate doses of ionizing radiation appears to increase the risk of thyroid PMCs, even when exposure occurs during adulthood. Cancer 2010. (c) 2010 American Cancer Society.

Differentiated thyroid cancer

OBJECTIVE

The retrospective analysis of the case files of children with differentiated thyroid carcinoma (DTC) was performed to define the disease by its presentation, clinical course and outcome of radioiodine therapy.

METHODS

Between 1967 to October 2002, 1754 patients with thyroid cancer were treated in the Dept of Neuclear Medicine, AIIMS, out of which 122 (7%) were < or = 20 years of age (71 girls and 51 boys). The mean age was 15.8 +/- 3.6 years and the mean duration of follow-up was 90 +/- 59.3 months. Mean tumor size was 4.4 cm. Histologically, 85% of the patients had papillary and rest follicular carcinoma. Cervical lymph node involvement was seen in 64%, and distant metastases, mainly pulmonary, in 23% of the patients. The presentation of the disease was very aggressive in the first decade of life with male preponderance. All but one patient in this age group had nodal and/or distant metastases; in 83.3% the disease had spread to the lymph nodes and 67% had metastases to the lungs. The post-surgery 48-hour mean radioiodine neck uptake was 10.5 +/- 7.6%.

RESULTS

94% of the residual thyroid, 88% of nodal metastases and 71% of pulmonary metastases were ablated requiring mean cumulative doses of 2.8 +/- 2.7 GBq, 4.5 +/- 2.7 GBq and 10.4 +/- 7.9 GBq of 131I, respectively. Average number of doses required for remnant, nodal and pulmonary metastases ablation were 1.3, 2.2 and 3.3, respectively. 80% of the patients with only remnant thyroid tissue and 50% with cervical lymph node metastases got ablated with a single dose of 131I. Overall, 87% patients were currently free of disease. While, nine patients had nodal recurrence between surgery and radioiodine treatment, no recurrence was observed thereafter and 3 disease related deaths producing overall mortality of 2.5% (all in children < or =10 years of age) were seen in the mean follow-up of 7.5 years.

CONCLUSION

Differentiated thyroid cancer in children and adolescents is rare but aggressive. The biological behavior differs from that in adults and is related to the age. Younger the age (< or =10 years), more aggressive and widespread is the disease with male preponderance and high mortality. The post-surgical radioiodine ablation/therapy is an important and effective adjuvant in the management of DTC in children and adolescents and even though they present with advance disease, long-term survival and overall prognosis is good.

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.

High incidence of meningioma among Hiroshima atomic bomb survivors

Since the atomic bomb explosions in Hiroshima and Nagasaki, high incidences of leukemia, thyroid cancer and other tumors have been reported as atomic bomb-induced tumors. We investigated the incidence of meningioma among Hiroshima atomic bomb survivors. Sixty-eight patients surgically treated for meningioma who had been within 2.0 km of the hypocenter of the explosion were identified. Six hundred and seven non-exposed patients with meningioma were also studied. Treatment dates were from 1975 to 1992. The incidences of meningioma among 68 subjects within 2.0 km and 607 non-exposed patients were 8.7 and 3.0 cases per 10(5) persons per year, respectively. The incidences of meningioma among the survivors of Hiroshima in 5-year intervals since 1975 were 5.3, 7.4, 10.1, and 14.9, respectively. The incidences of meningioma classified by distances from the hypocenter of 1.5-2.0 km, 1.0-1.5 km and less than 1.0 km were 6.3, 7.6 and 20.0, respectively. The incidences of meningioma classified by doses to the brain of 0-0.099 Sv, 0.1-0.99 Sv and more than 1.0 Sv were 7.7, 9.2 and 18.2, respectively. The incidence of meningioma among Hiroshima atomic bomb survivors has increased since 1975. There was a significant correlation between the incidence and the dose of radiation to the brain. The present findings strongly suggest that meningioma is one of the tumors induced by atomic bombing in Hiroshima.

Irradiation and second cancers. The thyroid as a case in point

The thyroid gland is highly sensitive to radiation during childhood: the risk of thyroid tumours is increased for mean doses as low as 100 mGy and for higher doses, the risk increases linearly with the dose. Excess relative risk is important, being 7.7 for 1 Gy delivered to the thyroid gland during childhood. The risk of thyroid tumours is modified by several factors: a) age at exposure: in childhood, the risk decreases with increasing age at exposure and is not significant after 20 years; b) gender: females are two times more likely than males to develop thyroid tumours; c) genetic predisposition due to a defect in DNA repair mechanisms, and dietary and hormonal factors may modify the risk; d) the influence of fractionation and dose rate is not well established. Radioiodine 131 (1311) used for medical purposes has almost no tumourigenic effect on the adult thyroid gland. The consequences of the Chernobyl accident have clearly shown that the risk of thyroid cancer after exposure to 1311 in childhood is important, and that such exposure should be prevented by potassium iodine prophylaxis. RET/PTC rearrangements are found in 60-80% of papillary carcinomas and in 45% of adenomas occurring after radiation exposure. They are found in 5-15% of papillary carcinoma and in no follicular adenomas that occurred in the absence of radiation exposure.

Thyroid Carcinoma in Japan and the West: Similarities and Differences

Geographic or ethnic differences in the incidence of thyroid carcinoma, as well as in the histologic distribution of thyroid carcinoma between Japan and Western countries, have been described but are still unclear. The recent establishment of histologic criteria for the diagnosis of thyroid carcinoma by the WHO committee has facilitated the comparison of clinicopathological data of patients with thyroid carcinoma all over the world. The aim of the present review article is to clarify the epidemiological and clinicopathological differences of thyroid carcinoma between Japan and Western countries. We found recently no significant differences in the incidence, mortality, and histologic distribution of thyroid carcinoma between Japan and Western countries; this was contrary to our expectation. This is likely attributable to westernization of the Japanese diet, standardized medical levels, and international standardization of histologic criteria of thyroid carcinoma.

Thyroid abnormalities among children in the contaminated area related to the Chernobyl accident

Gradual increases of various radiation-related diseases including thyroid cancer following the Chernobyl accident have been recently reported. We have carried out systematic thyroid surveys in school children aged 10-15 years in the highly contaminated area and compared the results with a similar survey in a nonaffected neighboring area as a control. Systematic examinations of the thyroid gland were performed in 888 schoolchildren (408 males and 480 females) in the districts of Chechelsk city with 5 to over 40 Ci/km2 of radiation level for 137Cs. In the control area (Bobruisk city), 521 children with the same age range (229 males and 292 females) were examined. Thyroid surveys were carried out as follows: palpation, ultrasonography, blood examinations of thyroid function, and measurements of daily urinary excretion of iodine. Certain thyroid abnormalities were observed in the high radioactive fallout area more frequently than in the control region. In particular, the prevalence of multiple micronodular lesions in diffuse goiter in the contaminated area was significantly higher than in the control area. However, endemic goiter due to iodine deficiency was present in both districts. The environment factor of iodine deficiency might have resulted in the early occurrence of ultrasonographic thyroid abnormalities attributed to radioactive contamination.

Pediatric thyroid cancer after the Chernobyl disaster. Pathomorphologic study of 84 cases (1991-1992) from the Republic of Belarus

BACKGROUND

During the initial period after the Chernobyl accident, large amounts of radioactive iodine were released in fallout, resulting in serious exposure to the thyroid gland in the residents of areas around the nuclear power station. Beginning in 1990, a definite increase in the incidence of thyroid cancer was noted in children of the Republic of Belarus.

METHODS

Morphologic and clinical features of 84 cases of post-Chernobyl thyroid carcinoma in Belarussian children from 5 to 14 years of age are reported. The latent period for tumor development was 4-6 years, with a mean of 5.8 years.

RESULTS

Papillary carcinoma was found in 83 patients and medullary carcinoma in one. Besides typical papillary carcinoma (14%), solid (34%), follicular (33%), mixed (10%), and diffuse sclerosing (9%) variants were observed. The follow-up period ranged from 8 months to 2.5 years. One patient died, local recurrence developed in 2, and cervical lymph node metastases developed in 10. To date, the incidence of local recurrence or metastatic disease after surgery was significantly higher in patients 5-8 years of age and in residents of areas nearest to the Chernobyl station.

CONCLUSIONS

Post-Chernobyl pediatric thyroid carcinoma is characterized by a short latency, a higher proportion of tumors arising in young children, and an almost equal sex ratio. Microscopically, these tumors were usually aggressive, often demonstrating intraglandular tumor dissemination (92%), thyroid capsular and adjacent soft tissue invasion (89%), and cervical lymph node metastases (88%). Papillary carcinoma was diagnosed in 99% of cases, with an unusually high frequency of solid growth patterns. Morphologic changes in nonneoplastic thyroid tissue were present in 90% of the glands, and the most specific findings were vascular changes and perifollicular fibrosis.

Thyroid cancer epidemiology in England and Wales: time trends and geographical distribution

Thyroid cancer incidence has been increasing in many countries, whereas mortality has been falling due to better survival. Radiation is the best-established risk factor and there has been concern that recent rises in incidence might be related to fallout radiation from atmospheric nuclear weapon tests. We examined thyroid cancer time trends and geographical distribution in England and Wales and possible interpretations of these. During 1962-84, there were significant increases in incidence (P < 0.001) in each sex at ages under 45. Cohort analysis by single year of birth showed an overall increase in incidence risks in women aged 0-44 born since 1920, with a sudden rise in risk for the birth years 1952-55 followed by a lower risk for the more recent cohorts. In men, there was an overall increase in risk at ages 0-44 in successive birth cohorts, but the pattern was irregular. In each sex, the risk in persons aged 45 and over decreased slightly in successive generations. Geographically, highest incidence risks were in countries in North and Mid Wales, in which the risk was almost twice that in the rest of the country. This pattern was present only at ages 45 and over and was most clear in rural areas. The peak of thyroid cancer risk in women born in 1952-55 is consistent with a carcinogenic effect of fallout radiation, since these women were children in the late 1950s and early 1960s when fallout radiation was greatest in England and Wales. The focus of high thyroid cancer risks in Wales was in areas with high levels of fallout radiation. However, thyroid cancer risks in Wales were not high for more recent cohorts (the ones who were exposed to fallout early in life), and a focus on high risk of benign thyroid diseases was present in Wales well before nuclear weapons existed. The distributions of these benign thyroid diseases, or of factors causing them, seem more likely than fallout to explain the high risk areas for thyroid cancer in the country.

Multiple head and neck neoplasia following radiation for benign disease during childhood

A woman received radiation therapy to the adenoids for benign disease at the age of 10 years and subsequently developed an adenocarcinoma of the middle ear, a parathyroid adenoma, and a papillary carcinoma of the thyroid gland in adulthood. This appears to be the first such case on record. The literature of neoplasia after head and neck irradiation is briefly reviewed.

Studies of cancer among the Japanese A-bomb survivors

Studies of cancer among the Japanese survivors of the A-bombs dropped on Nagasaki and Hiroshima are the major source of information on radiation carcinogenesis in humans. They have already made important contributions to the estimation of the risk of radiation-induced cancer and to our understanding of key factors influencing risk, especially tissue sensitivity, age at exposure, and the temporal distribution of radiogenic cancers. The size of the exposed population still surviving virtually guarantees the continued productivity of the research conducted in Hiroshima and Nagasaki. It should not be supposed, however, that these studies will ever provide all the information needed for radiation protection standards or risk estimation. The experience of the A-bomb survivors simply does not include all important aspects of radiation exposure for which information is needed. Moreover, despite the size of the sample remaining under study, it is most unlikely that direct, empirical estimates can be made that will remove the necessity for dependence upon mathematical models to derive estimates of risk in the low-dose region.

Characteristics of thyroid cancer following irradiation

Studies in humans and animals have suggested that the distribution of histologic types of radio-induced thyroid cancers is different from that of naturally occurring tumors. In an attempt to verify that finding, histologic results of 31 patients with thyroid cancer, who had received irradiation to the head, neck or upper chest for other causes, were compared with those of 389 non irradiated patients. The two groups were homogeneous for age and sex. There was a significantly higher prevalence of the papillary type in the irradiated group, with an higher incidence of metastatic lymph nodes. Other histopathologic findings, coexisting with the papillary carcinoma (i.e., ground glass subtype, size less than 1.5 cm, multicentricity) did not differ significantly in the two groups. Some theoretical considerations concerning radio-induced thyroid carcinoma are proposed.

Differentiated thyroid cancer in children

Differentiated thyroid cancer in children remains a controversial disease entity. Its incidence has markedly declined over the last decade since the use of radiotherapy in the treatment of benign conditions of the head, neck, and thorax was abandoned. Other etiologic factors have become relatively more important. The clinical presentation of childhood thyroid cancer is similar to that found in adults, except for a higher frequency of local and distant metastases at the time of initial diagnosis. The specificity and sensitivity of diagnostic tests are limited; however, like in adults, fine-needle aspiration compares favorably with other available diagnostic methods. The therapeutic approach to a child with thyroid cancer represents the most controversial issue associated with the disease. This review provides a discussion of the rationale for the different therapeutic options and emphasizes the excellent prognosis and survival rates, especially when patients are subjected to aggressive treatment with total thyroidectomy followed by the administration of radioactive iodine.

Thyroid nodules in the irradiated patient--an indication for total thyroidectomy

Eight patients who received radiation therapy to the head, neck, or chest during infancy, childhood, or adolescence are reported. In these individuals, the presenting abnormality was a nodule of the thyroid gland, which was found to be benign at surgery. All patients were subsequently found to harbor a malignant lesion of the contralateral lobe. On the basis of this study and the discussion presented, we feel that a total thyroidectomy is the indicated therapeutic procedure in previously radiated patients presenting with a cold nodule.

Environmental factors altering thyroid function and their assessment

Chronic ingestion of modest doses of dietary iodine, radiation, and polyhalogenated biphenyls (PCB's and PBB's) are environmental factors with known or suspected adverse effects on the human thyroid. Iodine consumption in the United States is approaching 1 mg daily for a large segment of the population. Data are reviewed which support the need for concern regarding the long-term adverse effects of dietary iodine on thyroid function, particularly in certain susceptible individuals. Environmental sources of radiation pose a significant risk of thyroid cancer and hypothyroidism under certain circumstances which may be intentional, inadvertent, or accidental. Exposure to polyhalogenated biphenyls during manufacture or as industrial pollutants are hazardous to man and to wildlife in moderate or large quantities and perhaps also in small amounts. The need to investigate the potential harm posed by these factors in the quantities commonly encountered is emphasized.

Cyclical combination chemotherapy and thyroid function in patients with advanced Hodgkin's disease

Clinical and biochemical assessment of thyroid function was undertaken in patients with Hodgkin's disease at designated points following diagnosis. At diagnosis, two of 20 patients had either abnormally low routine thyroid indices, or elevated thyroid stimulating hormone (TSH) levels that were not due to iodine-based investigations. Following lymphography, 76.5% of patients had TSH levels that remained elevated for a median period of 3 months. No detectable thyroid dysfunction was induced during chemotherapy. Fifty-four patients were studied at a median time of 35 months after chemotherapy. One euthyroid patient had a nodular goitre, and one had abnormal thyroid indices. Tsh levels were elevated in 44% of patients, although the median TSH level for the group was normal. Half the patients had abnormal TRH stimulation tests. Sixty patients were studied after irradiation and chemotherapy. Four patients had clinical thyroid dysfunction, and 10% of routine thyroid indices were abnormal. TSH levels were abnormal in 80%, with a markedly elevated median level. All thyroid releasing hormone stimulation tests were abnormal.

Suppression of thyroid radioiodine uptake by various doses of stable iodide

We studied the effect of various doses of sodium iodide on thyroid radioiodine uptake in euthyroid volunteers by giving single doses of 10, 30, 50, and 100 mg and then daily doses of 10, 15, 30, 50, or 100 mg for 12 days thereafter. All single doses above 10 mg suppressed 24-hour thyroid uptake of 123I to 0.7 to 1.5 per cent. Continued daily administration of 15 mg of iodide or more resulted in values consistently below 2 per cent. A small but statistically significant fall in serum thyroxine (T4) and triiodothyronine (T3) and a rise in serum thyrotropin (TSH) concentrations were observed after eight and 12 days of iodide treatment. These data suggest that the thyroid uptake of radioactive iodine can be markedly suppressed by single-dose administration of 30 mg of stable iodide and that suppression can be maintained with daily doses of at least 15 mg. This study provides guidelines for stable iodide prophylaxis in the event of exposure to radioactive iodine.

Familial occurrence of papillary thyroid carcinoma

We report two kindreds from northern Norway with 7 and 4 cases of papillary thyroid carcinoma in otherwise healthy, nonirradiated subjects. While histologic features were comparable the patient's age at the time of diagnosis was lower and lymph node metastases were more frequent in familial than in nonfamilial cases of papillary thyroid carcinoma from the same region. We conclude that genetic factors can predispose the patient for development of papillary thyroid carcinoma. The high local incidence may be due to interaction between susceptibility gene(s) and environmental factors.

Postirradiation carcinoma in a thyroglossal duct remnant: follicular variant of papillary thyroid carcinoma

A case of carcinoma in a thyroglossal duct remnant is presented. The tumor was a rare follicular variant of the papillary type of thyroid carcinoma. The patient had received external beam radiation to the head and neck both as a child and as an adolescent. The recently reported increased incidence of thyroid carcinoma is believed to be related to the former practice of irradiating cervical thymic and lymphoid tissue in children. Since it is normal thyroid tissue that remains in the thyroglossal duct tract, this ectopic tissue presumably has the same malignant potential as that in the thyroid gland. Therefore, more cases of carcinoma in a thyroglossal duct remnant may be seen as those patients who underwent head and neck irradiation in childhood mature.

Anaplastic carcinoma of the thyroid following external irradiation

Two patients with anaplastic carcinoma of the thyroid following irradiation for Hodgkin's disease are presented, and the previously reported cases briefly reviewed. The risk of late development of thyroid carcinoma is life-long and high-dose irradiation in patients with prolonged life expectancy may result in anaplastic carcinoma as well as less malignant histological forms.

Anaplastic cardcinoma of the thyroid in a population irradiated for Hodgkin Disease, 1910--1960

Post-irradiation carcinoma of the thyroid is usually histologically well-differentiated. In general, those subjects who developed carcinoma had been exposed to low-to-moderate doses of irradiation for benign conditions. We reviewed the charts of 520 patients with Hodgkin's disease seen at Roswell Park Memorial Institute, and found 2 cases of anaplastic carcinoma amongst other thyroidal abnormalities. The existing reports of post-irradiation carcinoma are reviewed and suggestions are made for the management of heavily irradiated, potentially cured patients with Hodgkin's disease.

Thyroid abnormalities following neck irradiation for Hodgkin's disease

Thyroid function and scans were evaluated in fifty disease-free patients 2 to 16 years after receiving neck irradiation for the treatment of Hodgkin's disease. Twenty-five of 50 patients had abnormal thyroid studies: eight were hypothyroid, two were hypothyroid and had abnormal scans, and fifteen had abnormal scans. Of the 15 patients with abnormal scans, one had an isolated elevation of TSH (thyroid stimulating hormone) and one developed exophthalmos. These data, obtained within a relatively short follow-up period, indicate that morphologic and functional abnormalities of the thyroid gland are not uncommon in patients who have received irradiation to the thyroid gland in the course of treatment for Hodgkin's disease. There is need for continuous reevaluation of the thyroid status in such patients.