Thyroid cancer in childhood cancer survivors: a detailed evaluation of radiation dose response and its modifiers

Thyroid adenomas after solid cancer in childhood

PURPOSE

Very few childhood cancer survivor studies have been devoted to thyroid adenomas. We assessed the role of chemotherapy and the radiation dose to the thyroid in the risk of thyroid adenoma after childhood cancer.

METHODS AND MATERIALS

A cohort of 3254 2-year survivors of a solid childhood cancer treated in 5 French centers before 1986 was established. The dose received by the isthmus and the 2 lobes of the thyroid gland during each course of radiation therapy was estimated after reconstruction of the actual radiation therapy conditions in which each child was treated as well as the dose received at other anatomical sites of interest.

RESULTS

After a median follow-up of 25 years, 71 patients had developed a thyroid adenoma. The risk strongly increased with the radiation dose to the thyroid up to a few Gray, plateaued, and declined for high doses. Chemotherapy slightly increased the risk when administered alone but also lowered the slope of the dose-response curve for the radiation dose to the thyroid. Overall, for doses up to a few Gray, the excess relative risk of thyroid adenoma per Gray was 2.8 (90% CI: 1.2-6.9), but it was 5.5 (90% CI: 1.9-25.9) in patients who had not received chemotherapy or who had received only 1 drug, and 1.1 (90% CI: 0.4-3.4) in the children who had received more than 1 drug (P=.06, for the difference). The excess relative risk per Gray was also higher for younger children at the time of radiation therapy than for their older counterparts and was higher before attaining 40 years of age than subsequently.

CONCLUSIONS

The overall pattern of thyroid adenoma after radiation therapy for a childhood cancer appears to be similar to that observed for thyroid carcinoma.

Chemotherapy and thyroid cancer risk: a report from the childhood cancer survivor study

BACKGROUND

Although ionizing radiation is an established environmental risk factor for thyroid cancer, the effect of chemotherapy drugs on thyroid cancer risk remains unclear. We evaluated the chemotherapy-related risk of thyroid cancer in childhood cancer survivors and the possible joint effects of chemotherapy and radiotherapy.

METHODS

The study included 12,547 five-year survivors of childhood cancer diagnosed during 1970 through 1986. Chemotherapy and radiotherapy information was obtained from medical records, and radiation dose was estimated to the thyroid gland. Cumulative incidence and relative risks were calculated with life-table methods and Poisson regression. Chemotherapy-related risks were evaluated separately by categories of radiation dose.

RESULTS

Histologically confirmed thyroid cancer occurred in 119 patients. Thirty years after the first childhood cancer treatment, the cumulative incidence of thyroid cancer was 1.3% (95% CI, 1.0-1.6) for females and 0.6% (0.4-0.8) for males. Among patients with thyroid radiation doses of 20 Gy or less, treatment with alkylating agents was associated with a significant 2.4-fold increased risk of thyroid cancer (95% CI, 1.3-4.5; P = 0.002). Chemotherapy risks decreased as radiation dose increased, with a significant decrease for patients treated with alkylating agents (P(trend) = 0.03). No chemotherapy-related risk was evident for thyroid radiation doses more than 20 Gy.

CONCLUSIONS

Treatments with alkylating agents increased thyroid cancer risk, but only in the radiation dose range less than 20 Gy, in which cell sparing likely predominates over cell killing.

IMPACT

Our study adds to the evidence for chemotherapy agent-specific increased risks of thyroid cancer, which to date, were mainly thought to be related to prior radiotherapy.

Discriminating gene expression signature of radiation-induced thyroid tumors after either external exposure or internal contamination

Both external radiation exposure and internal radionuclide contamination are well known risk factors in the development of thyroid epithelial tumors. The identification of specific molecular markers deregulated in radiation-induced thyroid tumors is important for the etiological diagnosis since neither histological features nor genetic alterations can discriminate between sporadic and radiation-induced tumors. Identification of highly discriminating markers in radiation-induced tumors is challenging as it relies on the ability to identify marker deregulation which is associated with a cellular stress that occurred many years before in the thyroid cells. The existence of such a signature is still controversial, as it was not found in several studies while a highly discriminating signature was found in both post-radiotherapy and post-Chernobyl series in other studies. Overall, published studies searching for radiation-induced thyroid tumor specificities, using transcriptomic, proteomic and comparative genomic hybridization approaches, and bearing in mind the analytical constraints required to analyze such small series of tumors, suggest that such a molecular signature could be found. In comparison with sporadic tumors, we highlight molecular similarities and specificities in tumors occurring after high-dose external radiation exposure, such as radiotherapy, and in post-Chernobyl tumors that occurred after internal 131I contamination. We discuss the relevance of signature extrapolation from series of tumors developing after high and low doses in the identification of tumors induced at very low doses of radiation.

Modeling the risk of secondary malignancies after radiotherapy

In developed countries, more than half of all cancer patients receive radiotherapy at some stage in the management of their disease. However, a radiation-induced secondary malignancy can be the price of success if the primary cancer is cured or at least controlled. Therefore, there is increasing concern regarding radiation-related second cancer risks in long-term radiotherapy survivors and a corresponding need to be able to predict cancer risks at high radiation doses. Of particular interest are second cancer risk estimates for new radiation treatment modalities such as intensity modulated radiotherapy, intensity modulated arc-therapy, proton and heavy ion radiotherapy. The long term risks from such modern radiotherapy treatment techniques have not yet been determined and are unlikely to become apparent for many years, due to the long latency time for solid tumor induction. Most information on the dose-response of radiation-induced cancer is derived from data on the A-bomb survivors who were exposed to γ-rays and neutrons. Since, for radiation protection purposes, the dose span of main interest is between zero and one Gy, the analysis of the A-bomb survivors is usually focused on this range. With increasing cure rates, estimates of cancer risk for doses larger than one Gy are becoming more important for radiotherapy patients. Therefore in this review, emphasis was placed on doses relevant for radiotherapy with respect to radiation induced solid cancer. Simple radiation protection models should be used only with extreme care for risk estimates in radiotherapy, since they are developed exclusively for low dose. When applied to scatter radiation, such models can predict only a fraction of observed second malignancies. Better semi-empirical models include the effect of dose fractionation and represent the dose-response relationships more accurately. The involved uncertainties are still huge for most of the organs and tissues. A major reason for this is that the underlying processes of the induction of carcinoma and sarcoma are not well known. Most uncertainties are related to the time patterns of cancer induction, the population specific dependencies and to the organ specific cancer induction rates. For radiotherapy treatment plan optimization these factors are irrelevant, as a treatment plan comparison is performed for a patient of specific age, sex, etc. If a treatment plan is compared relative to another one only the shape of the dose-response curve (the so called risk-equivalent dose) is of importance and errors can be minimized.

Estimate of the uncertainties in the relative risk of secondary malignant neoplasms following proton therapy and intensity-modulated photon therapy

Theoretical calculations have shown that proton therapy can reduce the incidence of radiation-induced secondary malignant neoplasms (SMN) compared with photon therapy for patients with prostate cancer. However, the uncertainties associated with calculations of SMN risk had not been assessed. The objective of this study was to quantify the uncertainties in projected risks of secondary cancer following contemporary proton and photon radiotherapies for prostate cancer. We performed a rigorous propagation of errors and several sensitivity tests to estimate the uncertainty in the ratio of relative risk (RRR) due to the largest contributors to the uncertainty: the radiation weighting factor for neutrons, the dose-response model for radiation carcinogenesis and interpatient variations in absorbed dose. The interval of values for the radiation weighting factor for neutrons and the dose-response model were derived from the literature, while interpatient variations in absorbed dose were taken from actual patient data. The influence of each parameter on a baseline RRR value was quantified. Our analysis revealed that the calculated RRR was insensitive to the largest contributors to the uncertainty. Uncertainties in the radiation weighting factor for neutrons, the shape of the dose-risk model and interpatient variations in therapeutic and stray doses introduced a total uncertainty of 33% to the baseline RRR calculation.

Thyroid cancer risk 40+ years after irradiation for an enlarged thymus: an update of the Hempelmann cohort

Although ionizing radiation is a known carcinogen, the long-term risk from relatively higher-dose diagnostic procedures during childhood is less well known. We evaluated this risk indirectly by assessing thyroid cancer incidence in a cohort treated with "lower-dose" chest radiotherapy more than 55 years ago. Between 2004 and 2008, we re-surveyed a population-based cohort of subjects treated with radiation for an enlarged thymus during infancy between 1926 and 1957 and their unexposed siblings. Thyroid cancer occurred in 50 irradiated subjects (mean thyroid dose, 1.29 Gy) and in 13 nonirradiated siblings during 334,347 person-years of follow-up. After adjusting for attained age, Jewish religion, sex and history of goiter, the rate ratio for thyroid cancer was 5.6 (95% CI: 3.1-10.8). The adjusted excess relative risk per gray was 3.2 (95% CI: 1.5-6.6). The adjusted excess absolute risk per gray was 2.2 cases (95% CI: 1.4-3.2) per 10,000 person-years. Cumulative thyroid cancer incidence remains elevated in this cohort after a median 57.5 years of follow-up and is dose-dependent. Although the incidence appeared to decrease after 40 years, increased risk remains a lifelong concern in those exposed to lower doses of medical radiation during early childhood.

Risk of second primary thyroid cancer after radiotherapy for a childhood cancer in a large cohort study: an update from the childhood cancer survivor study

Previous studies have indicated that thyroid cancer risk after a first childhood malignancy is curvilinear with radiation dose, increasing at low to moderate doses and decreasing at high doses. Understanding factors that modify the radiation dose response over the entire therapeutic dose range is challenging and requires large numbers of subjects. We quantified the long-term risk of thyroid cancer associated with radiation treatment among 12,547 5-year survivors of a childhood cancer (leukemia, Hodgkin lymphoma and non-Hodgkin lymphoma, central nervous system cancer, soft tissue sarcoma, kidney cancer, bone cancer, neuroblastoma) diagnosed between 1970 and 1986 in the Childhood Cancer Survivor Study using the most current cohort follow-up to 2005. There were 119 subsequent pathologically confirmed thyroid cancer cases, and individual radiation doses to the thyroid gland were estimated for the entire cohort. This cohort study builds on the previous case-control study in this population (69 thyroid cancer cases with follow-up to 2000) by allowing the evaluation of both relative and absolute risks. Poisson regression analyses were used to calculate standardized incidence ratios (SIR), excess relative risks (ERR) and excess absolute risks (EAR) of thyroid cancer associated with radiation dose. Other factors such as sex, type of first cancer, attained age, age at exposure to radiation, time since exposure to radiation, and chemotherapy (yes/no) were assessed for their effect on the linear and exponential quadratic terms describing the dose-response relationship. Similar to the previous analysis, thyroid cancer risk increased linearly with radiation dose up to approximately 20 Gy, where the relative risk peaked at 14.6-fold (95% CI, 6.8-31.5). At thyroid radiation doses >20 Gy, a downturn in the dose-response relationship was observed. The ERR model that best fit the data was linear-exponential quadratic. We found that age at exposure modified the ERR linear dose term (higher radiation risk with younger age) (P < 0.001) and that sex (higher radiation risk among females) (P  =  0.008) and time since exposure (higher radiation risk with longer time) (P < 0.001) modified the EAR linear dose term. None of these factors modified the exponential quadratic (high dose) term. Sex, age at exposure and time since exposure were found to be significant modifiers of the radiation-related risk of thyroid cancer and as such are important factors to account for in clinical follow-up and thyroid cancer risk estimation among childhood cancer survivors.

Long-term effects of radiation exposure among adult survivors of childhood cancer: results from the childhood cancer survivor study

In the last four decades, advances in therapies for primary cancers have improved overall survival for childhood cancer. Currently, almost 80% of children will survive beyond 5 years from diagnosis of their primary malignancy. These improved outcomes have resulted in a growing population of childhood cancer survivors. Radiation therapy, while an essential component of primary treatment for many childhood malignancies, has been associated with risk of long-term adverse outcomes. The Childhood Cancer Survivor Study (CCSS), a retrospective cohort of over 14,000 survivors of childhood cancer diagnosed between 1970 and 1986, has been an important resource to quantify associations between radiation therapy and risk of long-term adverse health and quality of life outcomes. Radiation therapy has been associated with increased risk for late mortality, development of second neoplasms, obesity, and pulmonary, cardiac and thyroid dysfunction as well as an increased overall risk for chronic health conditions. Importantly, the CCSS has provided more precise estimates for a number of dose-response relationships, including those for radiation therapy and development of subsequent malignant neoplasms of the central nervous system, thyroid and breast. Ongoing study of childhood cancer survivors is needed to establish long-term risks and to evaluate the impact of newer techniques such as conformal radiation therapy or proton-beam therapy.

Subsequent neoplasms in 5-year survivors of childhood cancer: the Childhood Cancer Survivor Study

BACKGROUND

The occurrence of subsequent neoplasms has direct impact on the quantity and quality of life in cancer survivors. We have expanded our analysis of these events in the Childhood Cancer Survivor Study (CCSS) to better understand the occurrence of these events as the survivor population ages.

METHODS

The incidence of and risk for subsequent neoplasms occurring 5 years or more after the childhood cancer diagnosis were determined among 14,359 5-year survivors in the CCSS who were treated from 1970 through 1986 and who were at a median age of 30 years (range = 5-56 years) for this analysis. At 30 years after childhood cancer diagnosis, we calculated cumulative incidence at 30 years of subsequent neoplasms and calculated standardized incidence ratios (SIRs), excess absolute risks (EARs) for invasive second malignant neoplasms, and relative risks for subsequent neoplasms by use of multivariable Poisson regression.

RESULTS

Among 14,359 5-year survivors, 1402 subsequently developed 2703 neoplasms. Cumulative incidence at 30 years after the childhood cancer diagnosis was 20.5% (95% confidence interval [CI] = 19.1% to 21.8%) for all subsequent neoplasms, 7.9% (95% CI = 7.2% to 8.5%) for second malignant neoplasms (excluding nonmelanoma skin cancer), 9.1% (95% CI = 8.1% to 10.1%) for nonmelanoma skin cancer, and 3.1% (95% CI = 2.5% to 3.8%) for meningioma. Excess risk was evident for all primary diagnoses (EAR = 2.6 per 1000 person-years, 95% CI = 2.4 to 2.9 per 1000 person-years; SIR = 6.0, 95% CI = 5.5 to 6.4), with the highest being for Hodgkin lymphoma (SIR = 8.7, 95% CI = 7.7 to 9.8) and Ewing sarcoma (SIR = 8.5, 95% CI = 6.2 to 11.7). In the Poisson multivariable analysis, female sex, older age at diagnosis, earlier treatment era, diagnosis of Hodgkin lymphoma, and treatment with radiation therapy were associated with increased risk of subsequent neoplasm.

CONCLUSIONS

As childhood cancer survivors progress through adulthood, risk of subsequent neoplasms increases. Patients surviving Hodgkin lymphoma are at greatest risk. There is no evidence of risk reduction with increasing duration of follow-up.

Breast cancer risk 55+ years after irradiation for an enlarged thymus and its implications for early childhood medical irradiation today

BACKGROUND

Radiotherapy during childhood increases long-term cancer risk, but the risk from radiation as a result of relatively higher dose diagnostic procedures remains less well known. This study, which evaluates breast cancer incidence in a cohort treated with "lower dose" chest radiotherapy over 50 years ago, can assist with estimating lifetime breast cancer risk in young children exposed to radiation from procedures such as chest computed tomography (CT) or treatment with recent "lower dose" chest radiotherapy protocols.

METHODS

A population-based, longitudinal cohort of subjects exposed to thymic irradiation during infancy from 1926 to 1957 and of their unexposed siblings was re-established. Previously followed until 1987, we resurveyed cohort members from 2004 to 2008. Poisson regression models compared breast cancer incidence rates between women in the cohort by treatment and dose category groups.

RESULTS

Breast cancer occurred in 96 treated (mean breast dose, 0.71 Gy) and 57 untreated women during 159,459 person-years of follow-up. After adjusting for attained age and treatment/birth cohort, the rate ratio was 3.01 (2.18-4.21). The adjusted excess relative risk per Gy was 1.10 (95% confidence interval, 0.61-1.86). Traditional breast cancer risk factors did not contribute significantly to multivariate model fit.

CONCLUSION

Our results show that at radiation doses between those received by the breast from chest CT and cancer therapy during early childhood, breast cancer incidence rates remain elevated >50 years after exposure. This implies that increased breast cancer risk will remain a lifelong concern in females treated during childhood with currently reduced radiotherapy doses and for infants receiving multiple chest CTs.

Radiation carcinogenesis: lessons from Chernobyl

Radiation is a carcinogen, interacting with DNA to produce a range of mutations. Irradiated cells also show genomic instability, as do adjacent non-irradiated cells (the bystander effect); the importance to carcinogenesis remains to be established. Current knowledge of radiation effects is largely dependent on evidence from exposure to atomic bomb whole body radiation, leading to increases in a wide range of malignancies. In contrast, millions of people were exposed to radioactive isotopes in the fallout from the Chernobyl accident, within the first 20 years there was a large increase in thyroid carcinoma incidence and a possible radiation-related increase in breast cancer, but as yet there is no general increase in malignancies. The increase in thyroid carcinoma, attributable to the very large amounts of iodine 131 released, was first noticed in children with a strong relationship between young age at exposure and risk of developing papillary thyroid carcinoma (PTC). The extent of the increase, the reasons for the relationship to age at exposure, the reduction in attributable fraction with increasing latency and the role of environmental factors are discussed. The large number of radiation-induced PTCs has allowed new observations. The subtype and molecular findings change with latency; most early cases were solid PTCs with RET-PTC3 rearrangements, later cases were classical PTCs with RET-PTC1 rearrangements. Small numbers of many other RET rearrangements have occurred in 'Chernobyl' PTCs, and also rearrangement of BRAF. Five of the N-terminal genes found in papillary carcinoma rearrangements are also involved in rearrangements in hematological malignancies; three are putative tumor suppressor genes, and two are further genes fused to RET in PTCs. Radiation causes double-strand breaks; the rearrangements common in these radiation-induced tumors reflect their etiology. It is suggested that oncogenic rearrangements may commonly involve both a tumor-suppressor gene (or a DNA repair gene) as well as an oncogene. Involvement of two relevant genes would give a greater chance of progression and a shorter latency than a single-gene mutation. More information is needed on germline mutations conferring susceptibility to radiation-induced PTCs, particularly DNA repair genes. The radiation exposure to the fallout after Chernobyl was very different from the whole body radiation after the atomic bombs. The type and molecular pathology of the thyroid tumors is changing with increasing latency, long latency tumors in other organs could occur in the future. A comprehensive follow up must continue for the lifetime of those exposed.

Second malignant neoplasms in survivors of pediatric Hodgkin's lymphoma treated with low-dose radiation and chemotherapy

PURPOSE

Survivors of childhood Hodgkin's lymphoma (HL) are at risk for second malignant neoplasms (SMNs). It is theorized that this risk may be attenuated in patients treated with lower doses of radiation. We report the first long-term outcomes of a cohort of pediatric survivors of HL treated with chemotherapy and low-dose radiation.

PATIENTS AND METHODS

Pediatric patients with HL (n = 112) treated at Stanford from 1970 to 1990 on two combined modality treatment protocols were identified. Treatment included six cycles of chemotherapy with 15 to 25.5 Gy involved-field radiation with optional 10 Gy boosts to bulky sites. Follow-up through September 1, 2007, was obtained from retrospective chart review and patient questionnaires.

RESULTS

One hundred ten children completed HL therapy; median follow-up was 20.6 years. Eighteen patients developed one or more SMNs, including four leukemias, five thyroid carcinomas, six breast carcinomas, and four sarcomas. Cumulative incidence of first SMN was 17% (95% CI, 10.5 to 26.7) at 20 years after HL diagnosis. The standard incidence ratio for any SMN was 22.9 (95% CI, 14.2 to 35) with an absolute excess risk of 93.7 cases per 10,000 person-years. All four secondary leukemias were fatal. For those with second solid tumors, the mean (+/- SE) 5-year disease-free and overall survival were 76% +/- 12% and 85% +/- 10% with median follow-up 5 years from SMN diagnosis.

CONCLUSION

Despite treatment with low-dose radiation, children treated for HL remain at significant risk for SMN. Sarcomas, breast and thyroid carcinomas occurred with similar frequency and latency as found in studies of children with HL who received high-dose radiation.

Secondary malignancies across the age spectrum

Development of a second malignancy is one of the most serious late effects in survivors of both childhood and adult-onset cancers. Patterns of second malignancy risk across the age spectrum can differ in terms of the types of second malignancies observed, magnitude of the risks, the latency period, associated risk factors, and modifying influences. Potential explanations for the varying risk patterns by age include differences in susceptibility of individual tissue/organ to carcinogenesis based on stage of development and level of tissue maturity, microenvironment, attained age, and lifestyle factors. A thorough understanding of these differences is essential when considering treatment modifications in newly diagnosed cancer patients who are aimed at reducing the risk of second malignancy and other late effects without compromising cure. Moreover, an understanding of the variations in second cancer risk according to age at treatment is important in customizing patient follow-up.

Risk of thyroid dysfunction and subsequent thyroid cancer among survivors of acute lymphoblastic leukemia: a report from the Childhood Cancer Survivor Study

BACKGROUND

To determine the risk of thyroid dysfunction and subsequent thyroid cancer among childhood acute lymphoblastic leukemia (ALL) survivors.

PROCEDURE

Rates of self-reported thyroid dysfunction and thyroid cancer were determined among 3,579 ALL survivors participating in the Childhood Cancer Survivor Study, a cohort of 5-year survivors of pediatric cancers diagnosed from 1970 to 1986, and compared with 3,846 siblings and population rates, respectively.

RESULTS

The cumulative incidence of hypo- and hyperthyroidism among survivors 15 years following leukemia diagnosis was 1.6% (95% CI 1.1, 2.1) and 0.6% (95% CI 0.3, 1.1), respectively, both significantly increased compared with siblings. In multivariate analysis, survivors who received >or=20 Gy cranial radiotherapy plus any spinal radiotherapy had the highest risk of subsequent hypothyroidism (HR 8.3, 95% CI 3.3, 20.5) compared with those treated with chemotherapy alone. Craniospinal radiotherapy also was associated with an increased risk of subsequent hyperthyroidism (HR 6.1, 95% CI 1.1, 34.2) compared with chemotherapy alone, as well as an increased risk of subsequent thyroid cancers (SIR 30.3, 95% CI 14.5, 55.7) compared with population rates. In radiation dosimetry analysis, pituitary doses >or=20 Gy combined with thyroid doses >or=10 Gy were associated with hypothyroidism, whereas pituitary doses >or=20 Gy combined with thyroid doses >or=15 Gy were associated with hyperthyroidism.

CONCLUSIONS

The risk of thyroid dysfunction and thyroid cancer was increased among childhood ALL survivors treated with craniospinal radiotherapy. In these individuals, long-term surveillance is warranted as no obvious plateau in risk was seen, even after 25 years of follow-up.

A new view of radiation-induced cancer: integrating short- and long-term processes. Part II: second cancer risk estimation

As the number of cancer survivors grows, prediction of radiotherapy-induced second cancer risks becomes increasingly important. Because the latency period for solid tumors is long, the risks of recently introduced radiotherapy protocols are not yet directly measurable. In the accompanying article, we presented a new biologically based mathematical model, which, in principle, can estimate second cancer risks for any protocol. The novelty of the model is that it integrates, into a single formalism, mechanistic analyses of pre-malignant cell dynamics on two different time scales: short-term during radiotherapy and recovery; long-term during the entire life span. Here, we apply the model to nine solid cancer types (stomach, lung, colon, rectal, pancreatic, bladder, breast, central nervous system, and thyroid) using data on radiotherapy-induced second malignancies, on Japanese atomic bomb survivors, and on background US cancer incidence. Potentially, the model can be incorporated into radiotherapy treatment planning algorithms, adding second cancer risk as an optimization criterion.

Thyroid adenomas and carcinomas following radiotherapy for a hemangioma during infancy

BACKGROUND AND PURPOSE

A cohort study was performed to investigate the carcinogenic effect of treating skin hemangioma with ionizing radiation during early childhood. This paper presents the incidence of differentiated thyroid adenomas and carcinomas after radiotherapy in this cohort.

METHODS AND MATERIALS

Of a total of 8307 patients treated for a skin hemangioma between 1940 and 1973 at the Institut Gustave-Roussy, 4767 were included in an incidence study, among whom 3795 had received radiotherapy. Seventy-three percent were less than 1-year-old at the time of treatment. External radiotherapy, Radium 226, Strontium 90, Yttrium 90, and Phosphorus 32 were used. The radiation dose received by the thyroid during radiotherapy, estimated in 3497 of the 3795 patients using specific software, was 41 mGy on average. Thyroid tumor cases were obtained by sending out a questionnaire, and were verified in pathological reports. Estimates of thyroid cancer specific incidence rates in the French population were obtained from the French cancer registry network. External and internal analyses were performed.

RESULTS

During an average follow-up of 35 years, 11 patients developed a differentiated thyroid carcinoma and 44 a thyroid adenoma. The incidence of thyroid adenoma was found to be higher among taller and heavier individuals. The incidence of both thyroid carcinoma and adenoma was higher among non-smoker patients. A significant dose-response relationship was found between the radiation dose received by thyroid and the risk of thyroid cancer (Excess Relative Risk per GY, ERR/Gy: 14.7, 95%CI: 1.6-62.9) and of adenoma (ERR/Gy: 5.7, 95%CI: 0.7-19.4).

CONCLUSION

This study confirms that radiation treatment performed in the past for hemangioma during infancy increased the risk of thyroid carcinoma and adenoma. Patients treated with external radiotherapy or with Radium 226 applicators for hemangiomas have to be more specifically followed up because this is the subgroup in whom the highest doses were received by the thyroid gland (more than 90% of the radiation doses were higher than 100 mGy). They are therefore more at risk of developing thyroid cancer.

Exposure to ionizing radiation in adulthood and thyroid cancer incidence

BACKGROUND

Recent reviews of the radiation epidemiology literature have concluded that there is little evidence that exposure to ionizing radiation in adulthood causes thyroid cancer. This paper examines the association between radiation dose and thyroid cancer incidence among Japanese survivors who were adults at the time of the atomic bombings of Hiroshima and Nagasaki.

METHODS

Analyses were conducted using data on cancer incidence during the period 1958-1998 among 59,687 members of the Life Span Study of atomic bomb survivors who were 20 years or older at time of bombings of Hiroshima and Nagasaki. Poisson regression methods were used to derive estimates of associations between thyroid dose in gray (Gy) and thyroid cancer incidence by sex, age at exposure, and time-since-exposure.

RESULTS

The number of thyroid cancer cases among women (n = 241) was nearly 5-fold the number of cases among men (n = 55). Estimated thyroid dose was positively associated with thyroid cancer incidence among women A-bomb survivors (excess relative rate/Gy = 0.70; 90% confidence interval = 0.20-1.46). In contrast, a negative association was observed between thyroid dose and thyroid cancer among men (excess relative rate/Gy = -0.25; <0 to 90% confidence interval = 0.35). The association among women was positive for all time-since-exposure periods examined but tended to diminish in magnitude with time-since-exposure.

CONCLUSIONS

Exposure to ionizing radiation in adulthood was positively associated with thyroid cancer among women A-bomb survivors, although the risk seems to be lower than for those exposed to radiation in childhood.

The Childhood Cancer Survivor Study: a National Cancer Institute-supported resource for outcome and intervention research

Survival for childhood cancer has increased dramatically over the last 40 years with 5-year survival rates now approaching 80%. For many diagnostic groups, rapid increases in survival began in the 1970s with the broader introduction of multimodality approaches, often including combination chemotherapy with or without radiation therapy. With this increase in rates of survivorship has come the recognition that survivors are at risk for adverse health and quality-of-life outcomes, with risk being influenced by host-, disease-, and treatment-related factors. In 1994, the US National Cancer Institute funded the Childhood Cancer Survivor Study, a multi-institutional research initiative designed to establish a large and extensively characterized cohort of more than 14,000 5-year survivors of childhood and adolescent cancer diagnosed between 1970 and 1986. This ongoing study, which reflects the single most comprehensive body of information ever assembled on childhood and adolescent cancer survivors, provides a dynamic framework and resource to investigate current and future questions about childhood cancer survivors.

High-risk populations identified in Childhood Cancer Survivor Study investigations: implications for risk-based surveillance

Childhood cancer survivors often experience complications related to cancer and its treatment that may adversely affect quality of life and increase the risk of premature death. The purpose of this manuscript is to review how data derived from Childhood Cancer Survivor Study (CCSS) investigations have facilitated identification of childhood cancer survivor populations at high risk for specific organ toxicity and secondary carcinogenesis and how this has informed clinical screening practices. Articles previously published that used the resource of the CCSS to identify risk factors for specific organ toxicity and subsequent cancers were reviewed and results summarized. CCSS investigations have characterized specific groups to be at highest risk of morbidity related to endocrine and reproductive dysfunction, pulmonary toxicity, cerebrovascular injury, neurologic and neurosensory sequelae, and subsequent neoplasms. Factors influencing risk for specific outcomes related to the individual survivor (eg, sex, race/ethnicity, age at diagnosis, attained age), sociodemographic status (eg, education, household income, health insurance) and cancer history (eg, diagnosis, treatment, time from diagnosis) have been consistently identified. These CCSS investigations that clarify risk for treatment complications related to specific treatment modalities, cumulative dose exposures, and sociodemographic factors identify profiles of survivors at high risk for cancer-related morbidity who deserve heightened surveillance to optimize outcomes after treatment for childhood cancer.

Second neoplasms in survivors of childhood cancer: findings from the Childhood Cancer Survivor Study cohort

PURPOSE

To review the reports of subsequent neoplasms (SNs) in the Childhood Cancer Survivor Study (CCSS) cohort that were made through January 1, 2006, and published before July 31, 2008, and to discuss the host-, disease-, and therapy-related risk factors associated with SNs.

PATIENTS AND METHODS

SNs were ascertained by survivor self-reports and subsequently confirmed by pathology findings or medical record review. Cumulative incidence of SNs and standardized incidence ratios for second malignant neoplasms (SMNs) were calculated. The impact of host-, disease-, and therapy-related risk factors was evaluated by Poisson regression.

RESULTS

Among 14,358 cohort members, 730 reported 802 SMNs (excluding nonmelanoma skin cancers). This represents a 2.3-fold increase in the number of SMNs over that reported in the first comprehensive analysis of SMNs in the CCSS cohort, which was done 7 years ago. In addition, 66 cases of meningioma and 1,007 cases of nonmelanoma skin cancer were diagnosed. The 30-year cumulative incidence of SMNs was 9.3% and that of nonmelanoma skin cancer was 6.9%. Risk of SNs remains elevated for more than 20 years of follow-up for all primary childhood cancer diagnoses. In multivariate analyses, risks differ by SN subtype, but include radiotherapy, age at diagnosis, sex, family history of cancer, and primary childhood cancer diagnosis. Female survivors whose primary childhood cancer diagnosis was Hodgkin's lymphoma or sarcoma and who received radiotherapy are at particularly increased risk. Analyses of risk associated with radiotherapy demonstrated different dose-response curves for specific SNs.

CONCLUSION

Childhood cancer survivors are at a substantial and increasing risk for SNs, including nonmelanoma skin cancer and meningiomas. Health care professionals should understand the magnitude of these risks to provide individuals with appropriate counseling and follow-up.

Solid cancers after allogeneic hematopoietic cell transplantation

Transplant recipients have been reported to have an increased risk of solid cancers but most studies are small and have limited ability to evaluate the interaction of host, disease, and treatment-related factors. In the largest study to date to evaluate risk factors for solid cancers, we studied a multi-institutional cohort of 28 874 allogeneic transplant recipients with 189 solid malignancies. Overall, patients developed new solid cancers at twice the rate expected based on general population rates (observed-to-expected ratio 2.1; 95% confidence interval 1.8-2.5), with the risk increasing over time (P trend < .001); the risk reached 3-fold among patients followed for 15 years or more after transplantation. New findings showed that the risk of developing a non-squamous cell carcinoma (non-SCC) following conditioning radiation was highly dependent on age at exposure. Among patients irradiated at ages under 30 years, the relative risk of non-SCC was 9 times that of nonirradiated patients, while the comparable risk for older patients was 1.1 (P interaction < .01). Chronic graft-versus-host disease and male sex were the main determinants for risk of SCC. These data indicate that allogeneic transplant survivors, particularly those irradiated at young ages, face increased risks of solid cancers, supporting strategies to promote lifelong surveillance among these patients.

Thyroid disorders: evaluation and management of thyroid nodules

Although thyroid nodules are a common clinical entity, few (5% to 10%) are malignant and require surgical treatment. Most nodules are discovered incidentally in patients undergoing surveillance for medical reasons unrelated to thyroid disorders. Therefore, a systematic approach to their evaluation is important to avoid unnecessary surgery. High-resolution ultrasonography and fine-needle aspiration have resulted in substantial improvements in diagnostic accuracy, cost reductions, and higher malignancy yield at the time of surgery. In this article, the authors present practical guidelines and a suggested management strategy for the effective diagnosis and management of incidentally discovered thyroid nodules.

A review of dosimetry studies on external-beam radiation treatment with respect to second cancer induction

It has been long known that patients treated with ionizing radiation carry a risk of developing a second cancer in their lifetimes. Factors contributing to the recently renewed concern about the second cancer include improved cancer survival rate, younger patient population as well as emerging treatment modalities such as intensity-modulated radiation treatment (IMRT) and proton therapy that can potentially elevate secondary exposures to healthy tissues distant from the target volume. In the past 30 years, external-beam treatment technologies have evolved significantly, and a large amount of data exist but appear to be difficult to comprehend and compare. This review article aims to provide readers with an understanding of the principles and methods related to scattered doses in radiation therapy by summarizing a large collection of dosimetry and clinical studies. Basic concepts and terminology are introduced at the beginning. That is followed by a comprehensive review of dosimetry studies for external-beam treatment modalities including classical radiation therapy, 3D-conformal x-ray therapy, intensity-modulated x-ray therapy (IMRT and tomotherapy) and proton therapy. Selected clinical data on second cancer induction among radiotherapy patients are also covered. Problems in past studies and controversial issues are discussed. The needs for future studies are presented at the end.

Size, number, and distribution of thyroid nodules and the risk of malignancy in radiation-exposed patients who underwent surgery

CONTEXT

The chance that a thyroid nodule is malignant is higher when there is a history of childhood radiation exposure.

OBJECTIVE

The objective of the study was to determine how the size of a thyroid nodule, the number of nodules, and the distribution of nodules influence the risk of cancer in irradiated patients.

PATIENTS

From a cohort of 4296 radiation-exposed people, we studied the 1059 that underwent thyroid surgery. DESIGN AND OUTCOMES: We studied the association between the size, number, distribution, and rank order of thyroid nodules and the chance of malignancy.

RESULTS

There were 612 malignant nodules in 358 patients and 2037 benign ones in 930 patients. There was no change in the risk that a nodule was malignant with increasing size (odds ratio 0.91/cm, P = 0.11) among the 1709 nodules that were 0.5 cm or greater. A solitary nodule had a similar likelihood of being malignant as a nodule that was one of several (18.8 vs. 17.3%), whereas patients with multiple nodules were more likely to have thyroid cancer than those with solitary nodules [30.7 vs. 18.7%; risk ratio 1.64 (1.27-2.13)]. Aspirating only the largest nodule would have missed 111 of the cancers (42%), whereas aspirating the two largest nodules would have missed 45 of the cases (17%), although none would have been 10 mm or greater.

CONCLUSIONS

In radiation-exposed patients, the following conclusions were made: 1) the likelihood that a nodule is malignant is independent of nodule number and size; 2) the likelihood of cancer is increased if more than one nodule is present; 3) evaluating the two largest nodules by fine-needle aspiration would have resulted in a significant number of cases being missed but none with large cancers; and 4) more than half of the patients with thyroid cancer had multifocal tumors.

Long-term endocrine sequelae of childhood cancer

PURPOSE OF REVIEW

To update knowledge related to the long-term endocrine sequelae of childhood cancer.

RECENT FINDINGS

Endocrine deficiencies are common after cranial irradiation, chemotherapy and specific tumors. These deficiencies include growth hormone, thyrotropin, adrenocorticotropin and gonadotropin deficiencies, primary hypothyroidism, gonadal failure and obesity. Recent studies highlight the impact of radiation on the development of endocrine sequelae. Risks for obesity after childhood tumors include hypothalamic injury, with inactivity and daytime sleepiness. About 6% of adult female survivors of childhood cancer develop persistent ovarian failure. Risks for ovarian damage include ovarian irradiation and alkylating agents. Appropriate fertility-preservation options should be offered. Offspring of women who had uterine irradiation as children are more likely to be born preterm or have low birth weight. Secondary neoplasia or relapse should be considered when treating endocrine deficiencies in cancer survivors. Risk of secondary neoplasia is increased following radiation exposure and certain malignancies. Treatment with growth hormone does not increase cancer recurrence, but survivors may have a 2-fold risk of developing a secondary solid tumor, most commonly a meningioma.

SUMMARY

Standardized, multidisciplinary long-term surveillance is important in childhood cancer survivors to identify and treat endocrine and other late effects of cancer and its therapy.