To assess the shape of the dose response for various circulatory disease endpoints, and modifiers by age and time since exposure.
Methods and Materials
Analysis of the US peptic ulcer data testing for heterogeneity of radiogenic risk by circulatory disease endpoint (ischemic heart, cerebrovascular, other circulatory disease).
There are significant excess risks for all circulatory disease, with an excess relative risk Gy−1 of 0.082 (95% CI 0.031, 0.140), and ischemic heart disease, with an excess relative risk Gy−1 of 0.102 (95% CI 0.039, 0.174) (both p<0.01), and indications of excess risk for stroke. There are no statistically significant (p>0.2) differences between risks by endpoint, and few indications of curvature in the dose response. There are significant modifications of relative risk by time since exposure, the magnitude of which does not vary between endpoints (p>0.2). Risk modifications are similar if analysis is restricted to those receiving radiation, although relative risks are slightly larger and the risk of stroke fails to be significant. The slopes of the dose response are generally consistent with those observed in the Japanese atomic bomb survivors and in occupationally and medically exposed groups.
There are excess risks for a variety of circulatory diseases in this dataset, with significant modification of risk by time since exposure. The consistency of the dose-response slopes with those observed in radiotherapeutically-treated groups at much higher dose, as well as in lower-dose exposed cohorts such as the Japanese atomic bomb survivors and nuclear workers implies that there may be little sparing effects of fractionation of dose or low dose-rate exposure.
circulatory disease; ischemic heart disease; stroke; peptic ulcer; benign disease
Autosomal dominant conditions are known to be associated with advanced paternal age, and it has been suggested that retinoblastoma (Rb) also exhibits a paternal age effect due to the paternal origin of most new germline RB1 mutations. To further our understanding of the association of parental age and risk of de novo germline Rb mutations, we evaluated the effect of parental age in a cohort of Rb survivors in the United States. A cohort of 262 retinoblastoma patients was retrospectively identified at one institution, and telephone interviews were conducted with parents of 160 survivors (65.3%). We built two sets of hierarchical stepwise logistic regression models to detect an increased odds of a de novo germline mutation related to older parental age compared to sporadic and familial Rb. The modeling strategy evaluated effects of continuous increasing maternal and paternal age and five-year age increases adjusted for the age of the other parent. Mean maternal ages for patients with de novo germline mutations and sporadic Rb were similar (28.3 and 28.5 respectively) as were mean paternal ages (31.9 and 31.2 respectively), and all were significantly higher than the weighted general U.S. population means. In contrast, maternal and paternal ages for familial Rb did not differ significantly from the weighted U.S. general population means. Although we noted no significant differences between mean maternal and paternal ages between each of the three Rb classification groups, we found increased odds of having a de novo germline mutation for each five-year increase in paternal age, but these findings were not statistically significant (de novo versus sporadic ORs: 30-34 = 1.65 [0.69-4], ≥35 = 1.34 [0.54-3.3]; de novo versus familial ORs: 30-34 = 2.82 [0.95 – 8.4], ≥35 = 1.61 [0.57-4.6]). Our study suggests a weak paternal age effect for Rb resulting from de novo germline mutations consistent with the paternal origin of most of these mutations.
The purpose of this study is to quantify cancer mortality in relationship to organ-specific radiation dose among women irradiated for benign gynecologic disorders. Included in this study are 12,955 women treated for benign gynecologic disorders at hospitals in the Northeastern U.S. between 1925 and 1965; 9,770 women treated by radiation and 3,186 women treated by other methods. The average age at treatment was 45.9 years (range, 13–88 years), and the average follow-up period was 30.1 years (maximum, 69.9 years). Radiation doses to organs and active bone marrow were reconstructed by medical physicists using original radiotherapy records. The highest doses were received by the uterine cervix (median, 120 Gy) and uterine corpus (median, 34 Gy), followed by the bladder, rectum and colon (median, 1.7–7.2 Gy), with other abdominal organs receiving median doses ≤1 Gy and organs in the chest and head receiving doses <0.1 Gy. Standardized mortality rate ratios relative to the general U.S. population were calculated. Radiation-related risks were estimated in internal analyses using Poisson regression models. Mortality was significantly elevated among irradiated women for cancers of the uterine corpus, ovary, bladder, rectum, colon and brain, as well as for leukemia (exclusive of chronic lymphocytic leukemia) but not for cancer of the cervix, Hodgkin or non-Hodgkin lymphoma, multiple myeloma, or chronic lymphocytic leukemia. Evidence of a dose-response was seen for cancers of the ovary [excess relative risk (ERR) 0.31/Gy, P < 0.001], bladder (ERR = 0.21/Gy, P = 0.02) and rectum (ERR = 0.23/Gy, P = 0.05) and suggested for colon (ERR = 0.09/Gy, P = 0.10), but not for cancers of the uterine corpus or brain nor for non-chronic lymphocytic leukemia. Relative risks of mortality due to cancers of the stomach, pancreas, liver and kidney were close to 1.0, with no evidence of dose-response over the range of 0–1.5 Gy. Breast cancer was not significantly associated with dose to the breast or ovary. Mortality due to cancers of heavily irradiated organs remained elevated up to 40 years after irradiation. Significantly elevated radiation-related risk was seen for cancers of organs proximal to the radiation source or fields (bladder, rectum and ovary), as well as for non-chronic lymphocytic leukemia. Our results corroborate those from previous studies that suggest that cells of the uterine cervix and lymphopoietic system are relatively resistant to the carcinogenic effects of radiation. Studies of women irradiated for benign gynecologic disorders, together with studies of women treated with higher doses of radiation for uterine cancers, provide quantitative information on cancer risks associated with a broad range of pelvic radiation exposures.
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.
The 600% increase in medical radiation exposure to the US population since 1980 has provided immense benefit, but potential future cancer risks to patients. Most of the increase is from diagnostic radiologic procedures. The objectives of this review are to summarize epidemiologic data on cancer risks associated with diagnostic procedures, describe how exposures from recent diagnostic procedures relate to radiation levels linked with cancer occurrence, and propose a framework of strategies to reduce radiation from diagnostic imaging in patients. We briefly review radiation dose definitions, mechanisms of radiation carcinogenesis, key epidemiologic studies of medical and other radiation sources and cancer risks, and dose trends from diagnostic procedures. We describe cancer risks from experimental studies, future projected risks from current imaging procedures, and the potential for higher risks in genetically susceptible populations. To reduce future projected cancers from diagnostic procedures, we advocate widespread use of evidence-based appropriateness criteria for decisions about imaging procedures, oversight of equipment to deliver reliably the minimum radiation required to attain clinical objectives, development of electronic lifetime records of imaging procedures for patients and their physicians, and commitment by medical training programs, professional societies, and radiation protection organizations to educate all stakeholders in reducing radiation from diagnostic procedures.
Radiotherapy decreases cancer mortality, but is associated with an increased incidence of second primary cancers, including osteosarcomas, especially after exposure in childhood. It remains uncertain whether radiation is related to other histologic types of bone sarcomas such as chondrosarcomas that are more common in adulthood.
Using data from 1973–2008 SEER registries, we evaluated long-term risk of bone cancer in 1,284,537 adult 5-year cancer survivors. We used standardized incidence ratios (SIRs) to compare second bone sarcoma rates to the general population for each histologic type. We also used multivariate Poisson regression to estimate the relative risk (RR) associated with radiotherapy for the most common subtypes, osteosarcoma and chondrosarcoma.
By the end of 2008, 159 second bone sarcomas were reported. Compared with the general population, the risk of developing any bone sarcoma was increased by 25% in patients with no history of radiotherapy (Observed(O)=89, SIR=1.25(1.00–1.54)) and by 257% in patients with a history of radiotherapy (O=70, SIR=3.57(2.78–4.50)). For each histologic subtype SIRs were higher among patients who had previously received radiotherapy than among those who had not. The RR for radiotherapy for osteosarcoma(n=63) was 5.08(3.05–8.59) and for chondrosarcoma(n=69) was 1.54(0.88–2.59), and these risks were even greater for second sarcomas that arose in the radiotherapy field used to treat the first cancer (osteosarcoma RR=10.35(4.96–23.66), chondrosarcoma RR=8.21(2.09–39.89)).
Our findings provide the first evidence of a likely association between radiation exposure and chondrosarcoma.
These results further our understanding of radiotherapy-related cancer risks and will potentially direct practices in long-term surveillance of cancer survivors.
Second cancers; bone sarcomas; radiation
To evaluate the risk of second cancer (SC) in long-term survivors of retinoblastoma (Rb) according to classification of germline mutation, based on family history of Rb and laterality.
Patients and Methods
We assembled a cohort of 1,852 1-year survivors of Rb (bilateral, n = 1,036; unilateral, n = 816). SCs were ascertained by medical records and self-reports and confirmed by pathology reports. Classification of RB1 germline mutation, inherited or de novo, was inferred by laterality of Rb and positive family history of Rb. Standardized incidence ratios and cumulative incidence for all SCs combined and for soft tissue sarcomas, bone cancers, and melanoma were calculated. The influence of host- and therapy-related risk factors for SC was assessed by Poisson regression for bilateral survivors.
We observed a relative risk (RR) of 1.37 (95% CI, 1.00 to 1.86) for SCs in bilateral survivors associated with a family history of Rb, adjusted for treatment, age, and length of follow-up. The risk for melanoma was significantly elevated for survivors with a family history of Rb (RR, 3.08; 95% CI, 1.23 to 7.16), but risks for bone or soft tissue sarcomas were not elevated. The cumulative incidence of SCs 50 years after diagnosis of bilateral Rb, with adjustment for competing risk of death, was significantly higher for survivors with a family history (47%; 95% CI, 35% to 59%) than survivors without a family history (38%; 95% CI, 32% to 44%; P = .004).
Rb survivors with bilateral disease and an inherited germline mutation are at slightly higher risk of an SC compared with those with a de novo germline mutation, in particular melanoma, perhaps because of shared genetic alterations.
Retinoblastoma (RB) is an important ocular malignancy of childhood. It has been commonly accepted for some time that knockout of the two alleles of the RB1 gene is the principal molecular target associated with the occurrence of RB. In this paper, we examine the validity of the two-hit theory for retinoblastoma by comparing the fit of a stochastic model with two or more mutational stages. Unlike many such models, our model assumes a fully stochastic stem cell compartment, which is crucial to its behavior. Models are fitted to a population-based dataset comprising 1,553 cases of retinoblastoma for the period 1962–2000 in Great Britain (England, Scotland, Wales). The population incidence of retinoblastoma is best described by a fully stochastic model with two stages, although models with a deterministic stem cell compartment yield equivalent fit; models with three or more stages fit much less well. The results strongly suggest that knockout of the two alleles of the RB1 gene is necessary and may be largely sufficient for the development of retinoblastoma, in support of Knudson’s two-hit hypothesis.
Retinoblastoma; carcinogenesis modeling; two-hit theory; stochastic MVK model; RB1 gene
In the US, second non-ocular malignancies are the primary cause of death in retinoblastoma survivors with the germline RB1 mutation. Soft tissue sarcomas are one of the most likely malignancies to pose a risk to these patients, with leiomyosarcoma (LMS) being the most common subtype. As our cohort is followed for a longer period, we discover new second malignancy risks for these patients.
We estimated the risk for uterine leiomyosarcoma (ULMS) in a cohort of 1854 patients with retinoblastoma who were diagnosed at two US institutions from 1914 through 1996. The standardized incidence ratio and excess absolute risk were calculated by comparison with population data from the Connecticut Tumor Registry or from National Cancer Institute Surveillance, Epidemiology, and End Results (SEER) database. The cumulative risk at 50 years of age was also calculated.
Seven of 525 female hereditary retinoblastoma patients developed ULMS. Five of these patients were used in the risk analysis, resulting in an excess risk of 3.87 per 10,000 women. Among hereditary patients who developed ULMS the excess risk increases dramatically with age: to 20/10,000 for female hereditary retinoblastoma patients aged between 30–39 years, and to 27/10,000 for patients aged 40+ years.
There is a substantial excess risk of ULMS in female hereditary retinoblastoma patients. As more patients survive into their thirties, this number is likely to increase. These findings raise the question of early childbearing, screening and prophylactic measures in hereditary retinoblastoma patients: all issues that would benefit from confirmation from other retinoblastoma cohorts, to allow for better guided counsel of these patients.
Retinoblastoma; Uterine Leiomyosarcoma; Secondary Cancers
Children diagnosed with the hereditary form of retinoblastoma (Rb), a rare eye cancer caused by a germline mutation in the RB1 tumor suppressor gene, have excellent survival, but face an increased risk of bone and soft tissue sarcomas. This predisposition to sarcomas has been attributed to genetic susceptibility due to inactivation of the RB1 gene as well as past radiotherapy for Rb. The majority of bone and soft tissue sarcomas among hereditary Rb survivors occur in the head, within the radiation field, but they also occur outside the radiation field. Sarcomas account for almost half of the second primary cancers in hereditary Rb survivors, but they are very rare following non-hereditary Rb. Sarcomas among hereditary Rb survivors arise at ages similar to the pattern of occurrence in the general population. There has been a trend over the past two decades to replace radiotherapy with chemotherapy and other focal therapies (laser or cryosurgery), and most recently, chemosurgery in order to reduce the incidence of sarcomas and other second cancers in Rb survivors. Given the excellent survival of most Rb patients treated in the past, it is important for survivors, their families and health care providers to be aware of the heightened risk for sarcomas in hereditary patients.
Retinoblastoma; Soft tissue sarcoma; Bone sarcoma; Radiotherapy; Epidemiology; RB1 gene; Hereditary
We report the pathology and outcome of secondary skull base tumors in patients previously treated with external beam radiation for retinoblastoma (Rb). Rb patients are at increased risk of second head and neck primary malignancies due to early radiation exposure during treatment and loss of RB1 protein in genetic carriers. An institutional database was reviewed for patients with retinoblastoma who had previously received radiation therapy and subsequently developed skull base tumors. Seventeen patients met the selection criteria. The median age of Rb diagnosis was 12 months. Thirteen cases underwent enucleation in addition to radiation therapy as part of initial Rb treatment. A median of 19 years elapsed between the diagnosis of Rb and diagnosis of skull base malignancy. The most common tumors were osteogenic sarcoma (39%) and leiomyosarcoma (22%). Eleven (71%) patients received postoperative chemotherapy, and 7 (41%) received postoperative radiotherapy. Three (24%) patients underwent salvage surgery for recurrent disease. Five-year survival was 68%, and 10-year survival was 51% by Kaplan-Meier analysis. Secondary malignancy in Rb patients is a well-defined event. The use of surgery with appropriate adjuvant therapy was associated with a 51% 10-year survival in this study population.
Skull base neoplasms; retinoblastoma; neoplasms; second primary; radiotherapy
Biodosimetry measurements can potentially be an important and integral part of the dosimetric methods used in long-term studies of health risk following radiation exposure. Such studies rely on accurate estimation of doses to the whole body or to specific organs of individuals in order to derive reliable estimates of cancer risk. However, dose estimates based on analytical dose reconstruction (i.e., models) or personnel monitoring measurements, e.g., film-badges, can have substantial uncertainty. Biodosimetry can potentially reduce uncertainty in health risk studies by corroboration of model-based dose estimates or by using them to assess bias in dose models. While biodosimetry has begun to play a more significant role in long-term health risk studies, its use is still generally limited in that context due to one or more factors including, inadequate limits of detection, large inter-individual variability of the signal measured, high per-sample cost, and invasiveness. Presently, the most suitable biodosimetry methods for epidemiologic studies are chromosome aberration frequencies from fluorescence in situ hybridization (FISH) of peripheral blood lymphocytes and electron paramagnetic resonance (EPR) measurements made on tooth enamel. Both types of measurements, however, are usually invasive and require difficult to obtain biological samples. Moreover, doses derived from these methods are not always directly relevant to the tissues of interest. To increase the value of biodosimetry to epidemiologic studies, a number of issues need to be considered including limits of detection, effects of inhomogenous exposure of the body, how to extrapolate from the tissue sampled to the tissues of interest, and how to adjust dosimetry models applied to large populations based on sparse biodosimetry measurements. The requirements of health risk studies suggest a set of characteristics that, if satisfied by new biodosimetry methods, would increase the overall usefulness of biodosimetry to determining radiation health risks.
Background and Objectives
For over 100 years, radiotherapy has been widely used to treat retinoblastoma. One of the most common adverse effects of orbital radiotherapy is cataract formation. The objective of this study was to investigate the risk of cataract extraction among adult retinoblastoma survivors.
Methods and Design
A retrospective cohort study was performed on survivors who were diagnosed with retinoblastoma from 1914 to 1984 and responded to a telephone interview in 2000. The interview elicited information about medical outcomes including cataract extraction, demographic and several lifestyle factors. Doses to the lens of each eye for individuals were estimated from available radiotherapy (external beam therapy or brachytherapy) records. The cumulative time interval to cataract extraction between dose groups was compared using the log-rank test, and Cox regression was used to estimate hazard ratios of cataract extraction in multivariate analyses.
753 subjects (828 eyes) were available for analysis for an average of 32 years of follow-up per eye. During this period, 51 cataract extractions were reported. One extraction was reported in an eye with no radiotherapy compared to 36 extractions in 306 eyes with one course of radiotherapy, and 14 among 38 eyes with two or three courses of treatment. The average time interval to cataract extraction in irradiated eyes was 51 years (95% CI: 48–54) following one treatment and 32 years (95% CI: 27–37) for 2 or 3 treatments. Eyes exposed to a therapeutic radiation dose of 5 Gray (Gy) or more (mean exposure of 8.1 Gy) had a six-fold increased risk (95% CI: 1.3–27.2) for cataract extraction compared to eyes exposed to 2.5 Gy or less.
Nearly all cataracts that were extracted within 30 years after diagnosis of retinoblastoma could be associated with radiotherapy and more than 75% of the eyes treated with two or more radiotherapy treatments had a cataract extracted. The results emphasize the importance of ophthalmologic examination throughout adulthood of retinoblastoma survivors who have undergone radiotherapy. In contrast, the annual risk of cataract extraction in non treated eyes is comparable with the risk of the general population.
Subsequent malignant neoplasms are a major cause of premature death in survivors of hereditary retinoblastoma. Radiotherapy further increases the risk of death. Mortality information is limited among long-term survivors who were irradiated for hereditary retinoblastoma.
We examined cause-specific mortality among 1854 retinoblastoma survivors who were diagnosed from January 1, 1914, through December 31, 1996, at two US institutions. Standardized mortality ratios (SMRs) were calculated by use of US mortality data to estimate expected numbers of deaths. The relative rates (RRs) of mortality due to subsequent malignant neoplasms associated with multiple risk factors were evaluated with Poisson regression models. Cumulative mortality from subsequent malignant neoplasms was calculated by treating other causes of death as competing risks.
A total of 151 deaths due to subsequent malignant neoplasms occurred among 1092 hereditary retinoblastoma survivors (SMR = 35, 95% confidence interval [CI] = 30 to 41) compared with 12 deaths among 762 nonhereditary retinoblastoma survivors (SMR = 2.5, 95% CI = 1.3 to 4.4). In this extended follow-up of retinoblastoma survivors, we found no evidence of excess mortality from non-neoplastic causes compared with the general population. However, excess mortality from subsequent malignant neoplasms (particularly sarcomas, melanomas, and cancers of the brain and other parts of the nervous system) among hereditary retinoblastoma survivors extended beyond 40 years after retinoblastoma diagnosis. The additional 13 years of follow-up since our last mortality study revealed a previously unreported increased risk of death due to cancers of the corpus uteri (primarily sarcomas) and confirmed the previously reported elevated risk of death from lung cancer among hereditary retinoblastoma survivors. Among hereditary and nonhereditary retinoblastoma survivors, the relative rates of mortality from subsequent malignant neoplasm were higher in those who had been treated with radiotherapy than in those who had not. Cumulative mortality from subsequent malignant neoplasms at 50 years after retinoblastoma diagnosis was 25.5% (95% CI = 20.8% to 30.2%) for hereditary retinoblastoma survivors and 1.0% (95% CI = 0.2% to 1.8%) for nonhereditary retinoblastoma survivors.
The temporal patterns of site-specific excess risks of subsequent malignant neoplasms in retinoblastoma survivors should inform screening programs designed for the early detection and treatment of subsequent malignant neoplasms.
Although cervical squamous cell carcinoma (SCC) and adenocarcinoma (AC) are both caused by human papillomavirus (HPV) infection, they differ in cofactors such as cigarette smoking. We assessed whether these cofactor differences translate into differences in second cancer risk.
Patients and Methods
We assessed second cancer risk among 85,109 cervical SCC and 10,280 AC survivors reported to population-based cancer registries in Denmark, Finland, Norway, Sweden, and the United States. Risks compared to the general population were assessed using standardized incidence ratios (SIR).
Overall cancer risk was significantly increased among both cervical SCC survivors (n = 10,559 second cancers; SIR, 1.31; 95% CI, 1.29 to 1.34) and AC survivors (n = 920 second cancers; SIR, 1.29; 95% CI, 1.22 to 1.38). Risks of HPV-related and radiation-related cancers were increased to a similar extent among cervical SCC and AC survivors. Although significantly increased in both groups when compared with the general population, risk of smoking-related cancers was significantly higher among cervical SCC than AC survivors (P = .015; SIR for cervical SCC = 2.07 v AC = 1.78). This difference was limited to lung cancer (SIR for cervical SCC = 2.69 v AC = 2.18; P = .026). The increased lung cancer risk among cervical AC survivors was observed for both lung SCC and lung AC. SIRs for second cancers of the colon, soft tissue, melanoma, and non-Hodgkin's lymphoma were significantly higher among cervical AC than SCC survivors.
The second cancer profiles among cervical SCC and AC survivors mirror the similarities and differences in cofactors for these two histologies. Because smoking is not a cofactor for cervical AC, the increased lung cancer risk suggests a role for additional factors.
Major advances in pediatric cancer treatment have resulted in substantial improvements in survival. However, concern has emerged about the late effects of cancer therapy, especially radiation-related second cancers. Studies of childhood cancer patients with inherited cancer syndromes can provide insights into the interaction between radiation and genetic susceptibility to multiple cancers. Children with retinoblastoma (Rb), neurofibromatosis type 1 (NF1), Li-Fraumeni syndrome (LFS), and nevoid basal cell carcinoma syndrome (NBCCS) are at substantial risk of developing radiation-related second and third cancers. A radiation dose-response for bone and soft tissue sarcomas has been observed for hereditary Rb patients, with many of these cancers occurring in the radiation field. Studies of NF1 patients irradiated for optic pathway gliomas have reported increased risks for developing another cancer associated with radiotherapy. High relative risks for second and third cancers were observed for a cohort of 200 LFS family members, especially children, possibly related to radiotherapy. Children with NBCCS are very sensitive to radiation and develop multiple basal cell cancers in irradiated areas. Clinicians following these patients should be aware of their increased genetic susceptibility to multiple primary malignancies enhanced by sensitivity to ionizing radiation.
second cancers; radiotherapy; retinoblastoma; neurofibromatosis type 1; Li-Fraumeni syndrome; Nevoid Basal Cell Carcinoma Syndrome
Chromosome translocations in peripheral blood lymphocytes of normal, healthy humans increase with age, but the effects of gender, race, and cigarette smoking on background translocation yields have not been examined systematically. Further, the shape of the relationship between age and translocation frequency (TF) has not been definitively determined. We collected existing data from sixteen laboratories in North America, Europe, and Asia on TFs measured in peripheral blood lymphocytes by fluorescence in situ hybridization whole chromosome painting among 1933 individuals. In Poisson regression models, age, ranging from newborns (cord blood) to 85 years, was strongly associated with TF and this relationship showed significant upward curvature at older ages vs. a linear relationship (p <0.001). Ever smokers had significantly higher TFs than non-smokers (rate ratio (RR) = 1.19, 95% confidence interval (CI), 1.09–1.30) and smoking modified the effect of age on TFs with a steeper age-related increase among ever smokers compared to non-smokers (p<0.001). TFs did not differ by gender. Interpreting an independent effect of race was difficult owing to laboratory variation. Our study is three times larger than any pooled effort to date, confirming a suspected curvilinear relationship of TF with age. The significant effect of cigarette smoking has not been observed with previous pooled studies of TF in humans. Our data provide stable estimates of background TF by age, gender, race, and smoking status and suggest an acceleration of chromosome damage above age 60 and among those with a history of smoking cigarettes.
chromosome translocations; background frequency; controls; fluorescence in situ hybridization
The growing use of interventional and fluoroscopic imaging in children represents a tremendous benefit for the diagnosis and treatment of benign conditions. Along with the increasing use and complexity of these procedures comes concern about the cancer risk associated with ionizing radiation exposure to children. Children are considerably more sensitive to the carcinogenic effects of ionizing radiation than adults, and children have a longer life expectancy in which to express risk. Numerous epidemiologic cohort studies of childhood exposure to radiation for treatment of benign diseases have demonstrated radiation-related risks of cancer of the thyroid, breast, brain and skin, as well as leukemia. Many fewer studies have evaluated cancer risk following diagnostic radiation exposure in children. Although radiation dose for a single procedure might be low, pediatric patients often receive repeated examinations over time to evaluate their conditions, which could result in relatively high cumulative doses. Several cohort studies of girls and young women subjected to multiple diagnostic radiation exposures have been informative about increased mortality from breast cancer with increasing radiation dose, and case-control studies of childhood leukemia and postnatal diagnostic radiation exposure have suggested increased risks with an increasing number of examinations. Only two long-term follow-up studies of cancer following cardiac catheterization in childhood have been conducted, and neither reported an overall increased risk of cancer. Most cancers can be induced by radiation, and a linear dose-response has been noted for most solid cancers. Risks of radiation-related cancer are greatest for those exposed early in life, and these risks appear to persist throughout life.
Radiation risks; Carcinogenesis; Diagnostic radiation; Therapeutic radiation