Thyroid Radiation Dose and Other Risk Factors of Thyroid Carcinoma Following Childhood Cancer

Radiation Therapy Technology Advances and Mitigation of Subsequent Neoplasms in Childhood Cancer Survivors

PURPOSE

In this Pediatric Normal Tissue Effects in the Clinic (PENTEC) vision paper, challenges and opportunities in the assessment of subsequent neoplasms (SNs) from radiation therapy (RT) are presented and discussed in the context of technology advancement.

METHODS AND MATERIALS

The paper discusses the current knowledge of SN risks associated with historic, contemporary, and future RT technologies. Opportunities for research and SN mitigation strategies in pediatric patients with cancer are reviewed.

RESULTS

Present experience with radiation carcinogenesis is from populations exposed during widely different scenarios. Knowledge gaps exist within clinical cohorts and follow-up; dose-response and volume effects; dose-rate and fractionation effects; radiation quality and proton/particle therapy; age considerations; susceptibility of specific tissues; and risks related to genetic predisposition. The biological mechanisms associated with local and patient-level risks are largely unknown.

CONCLUSIONS

Future cancer care is expected to involve several available RT technologies, necessitating evidence and strategies to assess the performance of competing treatments. It is essential to maximize the utilization of existing follow-up while planning for prospective data collection, including standardized registration of individual treatment information with linkage across patient databases.

Thyroid abnormalities in patients with Hodgkin lymphoma: The importance of close surveillance

INTRODUCTION

Survival in paediatric patients with Hodgkin lymphoma (HL) has increased over the last decades. However, these patients are at increased risk of developing late thyroid sequelae due to the treatment with irradiation and alkylating agents.

METHODS

We conducted an observational and retrospective study in patients with a diagnosis of HL between 2007 and 2022, in a hospital that is a paediatric oncology reference centre, through the review of electronic health records. We collected data on demographic (age, sex), clinical, radiological and histopathological variables, the dosage of alkylating agents and radiotherapy (RT) and on thyroid disorders using Microsoft Excel. The data analysis was conducted with SPSS version 17, using the Fisher exact test for qualitative data, a nonparametric test for quantitative data and Kaplan-Meier curves.

RESULTS

Sixty patients received a diagnosis of HL from 2007 to 2022. The median duration of follow-up was 78.5 months. There were 4 detected cases of hypothyroidism, 5 of thyroid nodules and 1 of subclinical hyperthyroidism. Treatment with RT was significantly associated with the development of hypothyroidism (P= .026), thyroid nodules (P= .01) and thyroid disease overall (P= .003). We estimated that the risk of thyroid disease increased 8-fold with each additional Grey received (hazard ratio, 1.081; 95% CI, 1.014-1.152; P= .017).

CONCLUSION

Hodgkin lymphoma patients treated with RT are at increased risk of late thyroid disorders, mainly hypothyroidism and malignancy. This risk is greater the higher the RT dosage and the longer the follow-up. We did not find evidence of an association between the use of alkylating agents and an increase in the risk of thyroid disease.

Radiation-Related Thyroid Cancer

Radiation is an environmental factor that elevates the risk of developing thyroid cancer. Actual and possible scenarios of exposures to external and internal radiation are multiple and diverse. This article reviews radiation doses to the thyroid and corresponding cancer risks due to planned, existing, and emergency exposure situations, and medical, public, and occupational categories of exposures. Any exposure scenario may deliver a range of doses to the thyroid, and the risk for cancer is addressed along with modifying factors. The consequences of the Chornobyl and Fukushima nuclear power plant accidents are described, summarizing the information on thyroid cancer epidemiology, treatment, and prognosis, clinicopathological characteristics, and genetic alterations. The Chornobyl thyroid cancers have evolved in time: becoming less aggressive and driver shifting from fusions to point mutations. A comparison of thyroid cancers from the 2 areas reveals numerous differences that cumulatively suggest the low probability of the radiogenic nature of thyroid cancers in Fukushima. In view of continuing usage of different sources of radiation in various settings, the possible ways of reducing thyroid cancer risk from exposures are considered. For external exposures, reasonable measures are generally in line with the As Low As Reasonably Achievable principle, while for internal irradiation from radioactive iodine, thyroid blocking with stable iodine may be recommended in addition to other measures in case of anticipated exposures from a nuclear reactor accident. Finally, the perspectives of studies of radiation effects on the thyroid are discussed from the epidemiological, basic science, and clinical points of view.

The risk of cancer following high, and very high, doses of ionising radiation

It is established that moderate-to-high doses of ionising radiation increase the risk of subsequent cancer in the exposed individual, but the question arises as to the risk of cancer from higher doses, such as those delivered during radiotherapy, accidents, or deliberate acts of malice. In general, the cumulative dose received during a course of radiation treatment is sufficiently high that it would kill a person if delivered as a single dose to the whole body, but therapeutic doses are carefully fractionated and high/very high doses are generally limited to a small tissue volume under controlled conditions. The very high cumulative doses delivered as fractions during radiation treatment are designed to inactivate diseased cells, but inevitably some healthy cells will also receive high/very high doses. How the doses (ranging from <1 Gy to tens of Gy) received by healthy tissues during radiotherapy affect the risk of second primary cancer is an increasingly important issue to address as more cancer patients survive the disease. Studies show that, except for a turndown for thyroid cancer, a linear dose-response for second primary solid cancers seems to exist over a cumulative gamma radiation dose range of tens of gray, but with a gradient of excess relative risk per Gy that varies with the type of second cancer, and which is notably shallower than that found in the Japanese atomic bomb survivors receiving a single moderate-to-high acute dose. The risk of second primary cancer consequent to high/very high doses of radiation is likely to be due to repopulation of heavily irradiated tissues by surviving stem cells, some of which will have been malignantly transformed by radiation exposure, although the exact mechanism is not known, and various models have been proposed. It is important to understand the mechanisms that lead to the raised risk of second primary cancers consequent to the receipt of high/very high doses, in particular so that the risks associated with novel radiation treatment regimens-for example, intensity modulated radiotherapy and volumetric modulated arc therapy that deliver high doses to the target volume while exposing relatively large volumes of healthy tissue to low/moderate doses, and treatments using protons or heavy ions rather than photons-may be properly assessed.

Surgical outcomes in survivors of childhood cancer undergoing thyroidectomy: A single-institution experience

BACKGROUND

Childhood cancer survivors (CCS) are at increased risk for thyroid disease, and many require definitive management with thyroid surgery. Despite this, there is limited evidence on surgical outcomes among CCS. We sought to evaluate postoperative outcomes at our institution among CCS undergoing thyroid surgery compared to patients without a history of primary childhood malignancy.

PROCEDURE

Medical records were reviewed for 638 patients treated at the Children's Hospital of Philadelphia Pediatric Thyroid Center between 2009 and 2020. Rates of surgical complications, including recurrent laryngeal nerve (RLN) paralysis and hypoparathyroidism, among CCS were compared to patients with sporadic/familial thyroid cancer, Graves' disease, and other benign thyroid conditions. Operative time and intraoperative parathyroid hormone levels were also evaluated.

RESULTS

There were no significant differences in long-term surgical complication rates, such as permanent RLN paralysis and hypoparathyroidism, between CCS and patients without a history of primary childhood malignancy (all p > .05). For all surgical outcomes, there were no significant differences in complication rates when CCS were compared to those undergoing surgery for sporadic/familial thyroid cancer or Graves' disease (all p > .05). CCS with benign final pathology had significantly higher rates of transient hypoparathyroidism compared to patients with benign thyroid conditions (p < .001).

CONCLUSIONS

Our study suggests that CCS are not at higher risk of long-term complications from thyroid surgery when treated by high-volume surgeons within a multidisciplinary team.

Thyroid function after diagnostic 123I-metaiodobenzylguanidine in children with neuroblastic tumors

BACKGROUND

Metaiodobenzylguanidine (MIBG) labeled with radioisotopes can be used for diagnostics ¹²³I^-) and treatment (¹³¹I^-) in patients with neuroblastic tumors. Thyroid dysfunction has been reported in 52% of neuroblastoma (NBL) survivors after ¹³¹I-MIBG, despite thyroid protection. Diagnostic ¹²³I-MIBG is not considered to be hazardous for thyroid function; however, this has never been investigated. Therefore, the aim of this study was to evaluate the prevalence of thyroid dysfunction in survivors of a neuroblastic tumor who received diagnostic ¹²³I-MIBG only.

METHODS

Thyroid function and uptake of ¹²³I^- in the thyroid gland after ¹²³I-MIBG administrations were evaluated in 48 neuroblastic tumor survivors who had not been treated with ¹³¹I-MIBG. All patients had received thyroid prophylaxis consisting of potassium iodide or a combination of potassium iodide, thiamazole and thyroxine during exposure to ¹²³I-MIBG.

RESULTS

After a median follow-up of 6.6 years, thyroid function was normal in 46 of 48 survivors (95.8%). Two survivors [prevalence 4.2% (95% CI 1.2-14.0)] had mild thyroid dysfunction. In 29.2% of the patients and 11.1% of images ¹²³I^- uptake was visible in the thyroid. In 1 patient with thyroid dysfunction, weak uptake of ¹²³I^- was seen on 1 of 10 images.

CONCLUSIONS

The prevalence of thyroid dysfunction does not seem to be increased in patients with neuroblastic tumors who received ¹²³I-MIBG combined with thyroid protection. Randomized controlled trials are required to investigate whether administration of ¹²³I-MIBG without thyroid protection is harmful to the thyroid gland.

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.

Childhood Cancer: Occurrence, Treatment and Risk of Second Primary Malignancies

Cancer represents the leading cause of disease-related death and treatment-associated morbidity in children with an increasing trend in recent decades worldwide. Nevertheless, the 5-year survival of childhood cancer patients has been raised impressively to more than 80% during the past decades, primarily attributed to improved diagnostic technologies and multiagent cytotoxic regimens. This strong benefit of more efficient tumor control and prolonged survival is compromised by an increased risk of adverse and fatal late sequelae. Long-term survivors of pediatric tumors are at the utmost risk for non-carcinogenic late effects such as cardiomyopathies, neurotoxicity, or pneumopathies, as well as the development of secondary primary malignancies as the most detrimental consequence of genotoxic chemo- and radiotherapy. Promising approaches to reducing the risk of adverse late effects in childhood cancer survivors include high precision irradiation techniques like proton radiotherapy or non-genotoxic targeted therapies and immune-based treatments. However, to date, these therapies are rarely used to treat pediatric cancer patients and survival rates, as well as incidences of late effects, have changed little over the past two decades in this population. Here we provide an overview of the epidemiology and etiology of childhood cancers, current developments for their treatment, and therapy-related adverse late health consequences with a special focus on second primary malignancies.

Prevalence of thyroid malignancy and hormonal dysfunction following radiation exposure in childhood

INTRODUCTION

Childhood radiation exposure is a known risk factor for thyroid malignancy and dysfunction. However, local data are limited and there is no consensus on the modality and frequency of screening in this high-risk group.

METHODS

Retrospective analysis study evaluating patients with childhood radiation exposure in 2006-2016 and minimum of 1-year follow-up.

RESULTS

Of the 132 childhood cancer survivors in the study, thyroid malignancy was detected in 2 cases (1.5%) and thyroid nodules in 13 (9.8%). The earliest thyroid malignancy was detected 5 years post-radiotherapy via ultrasound. Of the 84 patients who had screening thyroid function test, 26 (31.0%) were detected with abnormal test results post-radiation, majority being subclinical hypothyroidism.

CONCLUSION

Regular screening via clinical examination for thyroid nodules should be performed at least annually. Where feasible and if resources permit, consideration should be given to using ultrasound for thyroid nodule(s) and malignancy screening at 5 years post-radiation therapy. Screening for thyroid dysfunction can be considered from 6-12 months post-radiotherapy.

Clinical and molecular characterization of thyroid cancer when seen as a second malignant neoplasm

BACKGROUND

Second malignant neoplasms (SMN) are among the most serious long-term adverse health conditions in cancer survivors. The aim of this study was to characterize clinical findings of patients who developed thyroid cancers as SMN, and to examine genomic alterations in thyroid cancer tissue.

METHODS

Retrospective analysis of medical records from patients seen for management of thyroid cancer over 10-year period was performed. Clinical and pathologic data were retrieved from their medical charts. Tumor DNA and RNA were extracted from formalin-fixed, paraffin-embedded tissue and subjected to next-generation sequencing (NGS) using Ion Torrent Oncomine Focus Assay. Microfluidic digital polymerase chain reactions (PCRs) were performed using QIAcuity Digital PCR System to identify BRAF ^V600E mutations and RET/PTC fusions.

RESULTS

Sixteen of 620 patients operated for thyroid cancer had history of previously diagnosed malignancy. Eight patients were male and eight patients were female, with a median age at diagnosis of 58.5 years (range, 4-78). Four patients had history of pediatric malignancy (PedCa), and 12 patients had a history of prior malignancy as an adult (AdCa). The latency periods for development of SMN in PedCa and AdCa patients were 10.8 (±5.2) years and 9.5 (±5.2) years, respectively. Histopathology revealed papillary thyroid cancers in 15 cases, and follicular thyroid cancer in 1 case. All tumors were classified as T1 or T2, and there were no patients presenting with metastases at the time of surgery. Genomic alterations were detected in 13/16 (81.2%) tumors including eight gene mutations (BRAF ^V600E (N = 4), RAS (N = 2), PI3CA (N = 2) and five gene fusions (RET/PTC1 (N = 4) and STRN/ALK (N = 1). In patients with PedCa and AdCa, mutations were detected in 1/4 (25%) and 7/12 (58.3%), respectively, p = 0.56; and fusions were detected in 3/4 (75%) and 2/12 (16.6%), respectively, p = 0.06. In patients with and without history of therapeutic irradiation, mutations were detected with the same frequencies (5/10 (50%), and 3/6 (50%), respectively, p = 1.0). Gene fusions were detected in patients with and without history of irradiation in 5/10 (55.5%) and 0/6 (0%), respectively, p = 0.09.

CONCLUSIONS

Monitoring of cancer survivors for thyroid disorders allowed diagnosis of second thyroid cancers at early stages. Second thyroid cancers harbor genomic alterations that are typical for sporadic as well as for radio-induced thyroid cancers.

The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Thyroid Disease in Adults

OBJECTIVE

To develop evidence-based recommendations for safe, effective, and appropriate thyroidectomy.

BACKGROUND

Surgical management of thyroid disease has evolved considerably over several decades leading to variability in rendered care. Over 100,000 thyroid operations are performed annually in the US.

METHODS

The medical literature from 1/1/1985 to 11/9/2018 was reviewed by a panel of 19 experts in thyroid disorders representing multiple disciplines. The authors used the best available evidence to construct surgical management recommendations. Levels of evidence were determined using the American College of Physicians grading system, and management recommendations were discussed to consensus. Members of the American Association of Endocrine Surgeons reviewed and commented on preliminary drafts of the content.

RESULTS

These clinical guidelines analyze the indications for thyroidectomy as well as its definitions, technique, morbidity, and outcomes. Specific topics include Pathogenesis and Epidemiology, Initial Evaluation, Imaging, Fine Needle Aspiration Biopsy Diagnosis, Molecular Testing, Indications, Extent and Outcomes of Surgery, Preoperative Care, Initial Thyroidectomy, Perioperative Tissue Diagnosis, Nodal Dissection, Concurrent Parathyroidectomy, Hyperthyroid Conditions, Goiter, Adjuncts and Approaches to Thyroidectomy, Laryngology, Familial Thyroid Cancer, Postoperative Care and Complications, Cancer Management, and Reoperation.

CONCLUSIONS

Evidence-based guidelines were created to assist clinicians in the optimal surgical management of thyroid disease.

Risk of second primary papillary thyroid cancer among adult cancer survivors in the United States, 2000-2015

BACKGROUND

While radiotherapy is a major risk factor for thyroid cancer after childhood cancer, factors contributing to increased thyroid cancer risk after adulthood cancer remain unclear.

METHODS

We evaluated second primary papillary thyroid cancer (PTC) risk among 3,175,216 ≥ 1-year adult survivors of non-thyroid malignancies from US population-based cancer registries (2000-2015), using standardized incidence ratios (SIRs). Because heightened surveillance may increase detection of indolent thyroid tumors and earlier detection of advanced tumors, we examined SIRs by PTC stage and time since first cancer (latency).

RESULTS

SIRs for second primary PTC (N = 4333) were statistically-significantly 1.2-3.5-fold elevated overall and after 23/27 first cancer types evaluated, with generally similar risks for localized and regional/distant PTC. SIRs for regional/distant PTC (N = 1501) were highest after pancreatic (SIR = 3.7; 95% confidence interval [CI] = 1.9-6.5) and soft tissue (SIR = 4.2; 95%CI = 2.8-6.2) cancers, followed by melanoma, chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), diffuse large B-cell lymphoma, and larynx, kidney, and brain/central nervous system (SIRs = 2.0-2.9) cancers. SIRs typically decreased with increasing latency but remained statistically-significantly elevated for regional/distant-PTC ≥5 years after diagnosis of cancers of the rectum, pancreas, lung/bronchus, soft tissue, female breast, uterine corpus, prostate, and kidney, and after melanoma, Hodgkin lymphoma, CLL/SLL, and follicular lymphoma. Neither total nor regional/distant PTC were clearly associated with initial course of radiotherapy or chemotherapy.

CONCLUSIONS

PTC risk was elevated after a range of first primary adult cancers but was not clearly related to treatment. Although surveillance may contribute to elevated short-term risks of PTC, longer-term elevations in regional/distant PTC may be attributable to shared risk factors.

Thyroid Sequelae of Pediatric Cancer Therapy

The hypothalamic-pituitary-thyroid axis is a common site of unintended, acquired disease either during or after the treatment of cancer. Children treated with external radiation therapy are at the highest risk for developing a thyroid-related late effect, but thyroid dysfunction and second primary thyroid neoplasms can also occur after treatment with radiopharmaceutical agents such as 131I-metaiodobenzylguanidine. Increasingly recognized is the development of early thyroid dysfunction as an off-target consequence of the more novel cancer therapeutics such as the tyrosine kinase inhibitors and immune checkpoint inhibitors. Thyroid sequelae resulting from irradiation may manifest only after years to decades of follow-up, and their resultant clinical symptoms may be indolent and non-specific. Therefore, lifelong monitoring of the childhood cancer survivor at risk for thyroid disease is paramount. In this comprehensive review, the myriad thyroid adverse effects resulting from pediatric cancer treatment are discussed and an overview of screening and treatment of these thyroid sequelae provided.

Phytoestrogens and Thyroid Cancer Risk: A Population-Based Case-Control Study in Connecticut

BACKGROUND

Very few previous studies have examined the relationship between thyroid cancer risk and intake of phytoestrogens (PE); furthermore, these studies have reached inconsistent results.

METHODS

We analyzed data from a population-based case-control study in Connecticut from 2010 to 2011, including 387 histologically confirmed thyroid cancer cases and 433 population-based controls, with compound data available concerning specific PEs. Multivariate unconditional logistic regression models were used to estimate the associations between specific PEs and the risk of thyroid cancer, adjusting for potential confounders.

RESULTS

An elevated risk of thyroid cancer was associated with moderate to high levels of coumestrol intake [OR = 2.48, 95% confidence interval (CI), 1.39-4.43 for 40-80 μg/day; OR = 2.41, 95% CI, 1.32-4.40 for 80-130 μg/day; and OR = 2.38, 95% CI, 1.26-4.50 for >200 μg/day compared with <40 μg/day], and the main elevation in risk appeared among microcarcinomas (≤1 cm). A decreased risk of papillary macrocarcinomas (>1 cm; OR = 0.26, 95% CI, 0.08-0.85 for 1,860-3,110 μg/day compared with <760 μg/day) was associated with moderate genistein intake among women.

CONCLUSIONS

Our study suggests that high coumestrol intake increases the risk of thyroid cancer, especially microcarcinomas, whereas moderate amounts of genistein intake appear to be protective for females with thyroid macrocarcinomas.

IMPACT

The study highlights the importance of distinguishing between microcarcinomas and macrocarcinomas in future research on the etiology of thyroid cancer.

Sulfasalazine suppresses thyroid cancer cell proliferation and metastasis through T-cell originated protein kinase

Thyroid cancer patients with radioactive iodine-refractory or rapidly progressing presentation require effective treatment. T-cell originated protein kinase (TOPK) is highly expressed in a number of different tumor types, where it promotes proliferation and metastasis. However, the expression of TOPK in thyroid cancer is poorly documented. Therefore, immunohistochemistry was used to detect the expression of TOPK in thyroid cancer tissues, and its clinical significance in this disease was investigated. Sulfasalazine, a targeted inhibitor of TOPK that directly binds the protein with a dissociation constant (Kd) of 228 µM, was also investigated using microscale thermophoresis. Sulfasalazine inhibited TOPK activity, as determined by an in vitro pull-down assay. Furthermore, sulfasalazine inhibited the proliferation and metastasis of thyroid cancer cells. The results indicated that TOPK may be a potential therapeutic target and diagnostic biomarker for thyroid cancer and may be used as an index to evaluate malignant thyroid nodules. Therefore, sulfasalazine is a potential novel compound for the targeted treatment of thyroid cancer.

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.

Review of risk factors of secondary cancers among cancer survivors

Improvements in cancer survival have made the long-term risks from treatments more important, in particular among the children, adolescents and young adults who are more at risk particularly due to a longer life expectancy and a higher sensitivity to treatments. Subsequent malignancies in cancer survivors now constitute 15 to 20% of all cancer diagnoses in the cancer registries. Lots of studies are published to determine risk factors, with some controversial findings. Just data from large cohorts with detailed information on individual treatments and verification of what is called "secondary cancers" can add some knowledge, because their main difficulty is that the number of events for most second cancer sites are low, which impact the statistical results. In this review of the literature, we distinguish second and secondary cancers and discuss the factors contributing to this increased risk of secondary cancers. The article concludes with a summary of current surveillance and screening recommendations.

Thyroid nodules and long-term follow-up among childhood cancer survivors who underwent hematopoietic stem cell transplantation

Thyroid nodules have been observed in childhood cancer survivors (CCS) treated with chemotherapy and radiotherapy. We report four patients with thyroid nodules identified during the long-term follow-up of children who underwent hematopoietic stem cell transplantation (HSCT). The thyroid nodules were diagnosed as adenomatous goiter in all four patients. The interval between the primary cancer diagnosis and the occurrence of the thyroid nodules was more than 10 yr. Furthermore, all four patients underwent HSCT in conditioning with total body irradiation (TBI) before the age of 10 yr. Two of four patients commenced treatment with levothyroxine due to elevated TSH levels. Only two patients showed elevated thyroglobulin levels (> 70 µg/L). In conclusion, we suggest that CCS who have undergone HSCT in conditioning with TBI more than 10 yr previously should be followed up carefully for thyroid nodules using ultrasound.

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.

Late Effects in Pediatric High-risk Neuroblastoma Survivors After Intensive Induction Chemotherapy Followed by Myeloablative Consolidation Chemotherapy and Triple Autologous Stem Cell Transplants

Multimodal treatment in high-risk neuroblastoma has modestly improved survival; limited data exist on the late effects from these regimens. We report the sequelae of treatment incorporating 3 consecutive cycles of high-dose therapy and autologous stem cell transplants (ASCTs) without the use of total body irradiation (TBI). We reviewed the medical records of 61 patients treated on or following the Chicago Pilot 2 protocol between 1991 and 2008. Of the 25 patients who are alive (41%), 19 had near complete data to report. Specific treatment modalities and therapy-related side effects were collected. Fourteen of these 19 patients (74%) received 3 cycles of high-dose therapy with ASCT; follow-up occurred over a median of 13.9 years (range, 5.8 to 18.8 y). The majority of late effects were endocrine-related, including growth failure, hypothyroidism, and hypogonadism. Patients also developed secondary neoplasms and skeletal deformities. The most frequent sequela was hearing loss, seen in 17/19 patients. We found a high prevalence of various late effects in survivors of high-risk neuroblastoma using a non-TBI-based regimen including 3 cycles of high-dose therapy with ASCTs. As current treatment regimens recommend tandem ASCT without TBI, it is imperative that we understand and monitor for the sequelae from these modalities.

Low dose of Bisphenol A enhance the susceptibility of thyroid carcinoma stimulated by DHPN and iodine excess in F344 rats

Thyroid carcinoma (TC) is the most common endocrine neoplasm. The risk of TC as a second primary malignancy (SPM) of breast cancer is significantly increased. Bisphenol A (BPA) is a widely contacted xenoestrogen and increases susceptibility to breast cancer through binding to estrogen receptor alpha (ERα). However, the effect of BPA on thyroid carcinogenesis has not been fully demonstrated. This present study aimed to characterize the effects of BPA on the development of TC using a Fischer 344 (F344) rat model. In this study, we established a TC model using female F344 rats pretreated with N-Bis (2-hydroxypropyl) nitrosamine (DHPN) at a single dose of 2800 mg/kg (the DA group) or without DHPN (the DN group), followed by stimulation with BPA at the level of 250 μg/kg (BPA250) or 1000 μg/kg (BPA1000) and a basic diet containing potassium iodine (KI, 1000 μg/L) for 64 weeks. We demonstrated that the incidence of TC in the BPA250 + KI of DA groups reached the highest at 50%, the incidence of thyroid hyperplasia lesions (including both tumors and focal hyperplasia lesions) in the BPA1000 + KI of DA groups reached 100% (P < 0.05). ERα protein and immunochemistry expression was upregulated in the BPA-exposed groups and the immunochemistry scores were positively correlated with PCNA. Thus, the present results indicate that BPA could enhance the susceptibility to TC stimulated by DHPN and iodine excess. ERα is probably involved in the proliferation effect of BPA. BPA or KI alone could not increase TC incidence.

Quantification of Thyroid Cancer and Multinodular Goiter Risk in the DICER1 Syndrome: A Family-Based Cohort Study

CONTEXT

The risk of thyroid cancer and multinodular goiter (MNG) in DICER1 syndrome, a rare tumor-predisposition disorder, is unknown.

OBJECTIVE

To quantify the risk of thyroid cancer and MNG in individuals with DICER1 syndrome.

DESIGN

Family-based cohort study.

SETTING

National Institutes of Health (NIH) Clinical Center (CC).

PARTICIPANTS

The National Cancer Institute DICER1 syndrome cohort included 145 individuals with a DICER1 germline mutation and 135 family controls from 48 families.

INTERVENTIONS

Each individual completed a detailed medical history questionnaire. A subset underwent a 3-day evaluation at the NIH CC.

MAIN OUTCOME MEASURES

The cumulative incidence of MNG (or thyroidectomy) was quantified using the complement of the Kaplan-Meier product limit estimator. We compared the observed number of thyroid cancers in the NCI DICER1 cohort with matched data from the Surveillance, Epidemiology, and End Results (SEER) Program. We performed germline and somatic (thyroid cancer, MNG) DICER1 sequencing.

RESULTS

By the age of 40 years, the cumulative incidence of MNG or thyroidectomy was 75% in women and 17% in men with DICER1 syndrome compared with 8% of control women (P < 0.001) and 0% of control men (P = 0.0096). During 3937 person-years of observation, individuals with DICER1 syndrome had a 16-fold increased risk of thyroid cancer (95% confidence interval, 4.3 to 41; P < 0.05) compared with the SEER rates. Of 19 MNG nodules and 3 thyroid cancers, 16 (84%) and 3 (100%), respectively, harbored germline and somatic pathogenic DICER1 mutations.

CONCLUSIONS

We propose a model of thyroid carcinogenesis in DICER1 syndrome. Early-onset, familial, or male MNG should prompt consideration of the presence of DICER1 syndrome.

DIAGNOSIS OF ENDOCRINE DISEASE: Endocrine late-effects of childhood cancer and its treatments

Endocrine complications are frequently observed in childhood cancer survivors (CCS). One of two CCS will experience at least one endocrine complication during the course of his/her lifespan, most commonly as a late-effect of cancer treatments, especially radiotherapy and alkylating agent chemotherapy. Endocrine late-effects include impairments of the hypothalamus/pituitary, thyroid and gonads, as well as decreased bone mineral density and metabolic derangements leading to obesity and/or diabetes mellitus. A systematic approach where CCS are screened for endocrine late-effects based on their cancer history and treatment exposures may improve health outcomes by allowing the early diagnosis and treatment of these complications.

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.

Risk factors for subsequent endocrine-related cancer in childhood cancer survivors

Long-term adverse health conditions, including secondary malignant neoplasms, are common in childhood cancer survivors. Although mortality attributable to secondary malignancies declined over the past decades, the risk for developing a solid secondary malignant neoplasm did not. Endocrine-related malignancies are among the most common secondary malignant neoplasms observed in childhood cancer survivors. In this systematic review, we describe risk factors for secondary malignant neoplasms of the breast and thyroid, since these are the most common secondary endocrine-related malignancies in childhood cancer survivors. Radiotherapy is the most important risk factor for secondary breast and thyroid cancer in childhood cancer survivors. Breast cancer risk is especially increased in survivors of Hodgkin lymphoma who received moderate- to high-dosed mantle field irradiation. Recent studies also demonstrated an increased risk after lower-dose irradiation in other radiation fields for other childhood cancer subtypes. Premature ovarian insufficiency may protect against radiation-induced breast cancer. Although evidence is weak, estrogen-progestin replacement therapy does not seem to be associated with an increased breast cancer risk in premature ovarian-insufficient childhood cancer survivors. Radiotherapy involving the thyroid gland increases the risk for secondary differentiated thyroid carcinoma, as well as benign thyroid nodules. Currently available studies on secondary malignant neoplasms in childhood cancer survivors are limited by short follow-up durations and assessed before treatment regimens. In addition, studies on risk-modifying effects of environmental and lifestyle factors are lacking. Risk-modifying effects of premature ovarian insufficiency and estrogen-progestin replacement therapy on radiation-induced breast cancer require further study.