Neige Journy

Hyperthyroidism, Hypothyroidism, and Cause-Specific Mortality in a Large Cohort of Women

BACKGROUND The prevalence of hyperthyroidism and hypothyroidism is 0.5-4% in iodine-replete communities, but it is 5-10 times higher in women than in men. Those conditions are associated with a broad range of metabolic disorders and cardiovascular diseases. Biological evidence of a role of thyroid hormones in carcinogenesis also exists. However, the association between thyroid dysfunction and cardiovascular disease or cancer mortality risk remains controversial. In a large cohort of women, the associations of hyperthyroidism and hypothyroidism with cause-specific mortality were evaluated after nearly 30 years of follow-up. METHODS The prospective study included 75,076 women aged 20-89 years who were certified as radiologic technologists in the United States in 1926-1982, completed baseline questionnaires in 1983-1998 from which medical history was ascertained, and reported no malignant disease or benign thyroid disease except thyroid dysfunction. A passive follow-up of this cohort was performed through the Social Security Administration database and the National Death Index-Plus. Cause-specific mortality risks were compared according to self-reported thyroid status, with proportional hazards models adjusted for baseline year and age, race/ethnicity, body mass index, family history of breast cancer, and life-style and reproductive factors. RESULTS During a median follow-up of 28 years, 2609 cancer, 1789 cardiovascular or cerebrovascular, and 2442 other non-cancer deaths were recorded. Women with hyperthyroidism had an elevated risk of breast cancer mortality after 60 years of age (hazard ratio [HR] = 2.04 [confidence interval (CI) 1.16-3.60], 13 cases in hyperthyroid women) compared to women without thyroid disease. Hypothyroid women had increased mortality risks for diabetes mellitus (HR = 1.58 [CI 1.03-2.41], 27 cases in hypothyroid women), cardiovascular disease (HR = 1.20 [CI 1.01-1.42], 179 cases), and cerebrovascular disease (HR = 1.45 [CI 1.01-2.08], 35 cases, when restricting the follow-up to ≥10 years after baseline). Other causes of death were not associated with hyperthyroidism or hypothyroidism, though there was a suggestion of an elevated risk of ovarian cancer mortality in hyperthyroid women based on very few cases. CONCLUSION The excess mortality risks observed in a large, prospective 30-year follow-up of patients with thyroid dysfunction require confirmation, and, if replicated, further investigation will be needed because of the clinical implications.

Projected cancer risks potentially related to past, current, and future practices in paediatric CT in the United Kingdom, 1990–2020

Background:To project risks of developing cancer and the number of cases potentially induced by past, current, and future computed tomography (CT) scans performed in the United Kingdom in individuals aged <20 years.Methods:Organ doses were estimated from surveys of individual scan parameters and CT protocols used in the United Kingdom. Frequencies of scans were estimated from the NHS Diagnostic Imaging Dataset. Excess lifetime risks (ELRs) of radiation-related cancer were calculated as cumulative lifetime risks, accounting for survival probabilities, using the RadRAT risk assessment tool.Results:In 2000–2008, ELRs ranged from 0.3 to 1 per 1000 head scans and 1 to 5 per 1000 non-head scans. ELRs per scan were reduced by 50–70% in 2000–2008 compared with 1990–1995, subsequent to dose reduction over time. The 130 750 scans performed in 2015 in the United Kingdom were projected to induce 64 (90% uncertainty interval (UI): 38–113) future cancers. Current practices would lead to about 300 (90% UI: 230–680) future cancers induced by scans performed in 2016–2020.Conclusions:Absolute excess risks from single exposures would be low compared with background risks, but even small increases in annual CT rates over the next years would substantially increase the number of potential subsequent cancers.

SynthèseExposition à la scanographie dans l’enfance et risque de cancer à long terme. Une synthèse des études épidémiologiques récentesExposure to CT scans in childhood and long-term cancer risk: A review of epidemiological studies

Amongst medical exams requiring ionizing radiation, computed tomography (CT) scans are used more frequently, including in children. These CT examinations are associated with absorbed doses that are much higher than those associated with conventional radiology. In comparison to adults, children have a greater sensitivity to radiation and a longer life span with more years at cancer risks. Five epidemiological studies on cancer risks after CT scan exposure during childhood were published between 2012 and 2015. The results of these studies are consistent and show an increase of cancer risks in children who have been exposed to several CT scans. However, methodological limits due to indication bias, retrospective assessment of radiation exposure from CT scans and lack of statistical power are to be taken into consideration. International projects such as EPI-CT (Epidemiological study to quantify risks for pediatric computerized tomography and to optimize dose), with a focus on dosimetric reconstruction and minimization of bias will provide more precise results. In the meantime, available results reinforce the necessity of justification and optimization of doses.

Cataract Risk in a Cohort of U.S. Radiologic Technologists Performing Nuclear Medicine Procedures

Purpose To estimate the risk of cataract in a cohort of nuclear medicine (NM) radiologic technologists on the basis of their work histories and radiation protection practices. Materials and Methods In the years 2003-2005 and 2012-2013, 42 545 radiologic technologists from a U.S. prospective study completed questionnaires in which they provided information regarding their work histories and cataract histories. Cox proportional hazards models, stratified according to birth-year cohort (born before 1940 or born in 1940 or later) and adjusted for age, sex, and race, were used to estimate hazard ratios (HRs) for the risk of cataract in radiologic technologists according to NM work history practices according to decade. Results During the follow-up period (mean follow-up, 7½ years), 7137 incident cataracts were reported. A significantly increased risk of cataract (HR, 1.08; 95% confidence interval [CI]: 1.03, 1.14) was observed among workers who performed an NM procedure at least once-as opposed to never. Risks of cataract were increased in the group who had performed a diagnostic (HR, 1.07; 95% CI: 1.01, 1.12) or therapeutic (HR, 1.10; 95% CI: 1.04, 1.17) NM procedure. Risks were higher for those who had first performed diagnostic NM procedures in the 1980s to early 2000s (HR, 1.30; 95% CI: 1.08, 1.58) and those who had performed therapeutic NM procedures in the 1970s (HR, 1.11; 95% CI: 1.01, 1.23) and in the 1980s to early 2000s (HR, 1.14; 95% CI: 1.02, 1.29). With the exception of a significantly increased risk associated with performing therapeutic NM procedures without shielding the radiation source in the 1980s (HR, 1.32; 95% CI: 1.04, 1.67), analyses revealed no association between cataract risk and specific radiation protection technique used. Conclusion An increased risk of cataract was observed among U.S. radiologic technologists who had performed an NM procedure at least once. This association should be examined in future studies incorporating estimated lens doses.

No association between radiation dose from pediatric CT scans and risk of subsequent Hodgkin lymphoma.

Background: We examined the relationship between estimated radiation dose from CT scans and subsequent Hodgkin lymphoma in the UK pediatric CT scans cohort. Methods: A retrospective, record linkage cohort included patients ages 0 to 21 years who underwent CT scans between 1980 and 2002 and were followed up for cancer or death until 2008. Poisson regression analysis was used to evaluate the relationship between estimated radiation dose (lagged by 2 years) and incident Hodgkin lymphoma diagnosed at least 2 years after the first CT scan. Results: There were 65 incident cases of Hodgkin lymphoma in the cohort of 178,601 patients. Neither estimated red bone marrow dose nor mean lymphocyte dose from CT scans was clearly associated with an increased risk of Hodgkin lymphoma (RR for 20+ mGy vs. <5 mGy = 0.92 (0.38–2.22) Ptrend > 0.5 and 1.44 (0.60–3.48) Ptrend > 0.5), respectively. Conclusions: Radiation exposure from pediatric CT scans 2 or more years before diagnosis was not associated with Hodgkin lymphoma in this large UK cohort. Impact: These findings are consistent with the majority of previous studies, which do not support a link between ionizing radiation and Hodgkin lymphoma. The results contrast our previous positive findings in this cohort for brain tumors and leukemia, both of which are known to be strongly linked to radiation exposure during childhood. Cancer Epidemiol Biomarkers Prev; 26(5); 804–6. ©2017 AACR.

Cumulative Radiation Exposures from CT Screening and Surveillance Strategies for von Hippel-Lindau–associated Solid Pancreatic Tumors

Purpose To assess the potential ionizing radiation exposure from CT scans for both screening and surveillance of patients with von Hippel-Lindau (VHL) syndrome. Materials and Methods For this retrospective study, abdomen-pelvic (AP) and chest-abdomen-pelvic (CAP) CT scans were performed with either a three-phase (n = 1242) or a dual-energy virtual noncontrast protocol (VNC; n = 149) in 747 patients with VHL syndrome in the National Institutes of Health Clinical Center between 2009 and 2015 (mean age, 47.6 years ± 14.6 [standard deviation]; age range, 12-83 years; 320 women [42.8%]). CT scanning parameters for patients with pancreatic neuroendocrine tumors (PNETs; 124 patients and 381 scans) were compared between a tumor diameter-based surveillance protocol and a VHL genotype and tumor diameter-based algorithm (a tailored algorithm) developed by three VHL clinicians. Organ and lifetime radiation doses were estimated by two radiologists and five radiation scientists. Cumulative radiation doses were compared between the PNET surveillance algorithms by analyses of variance, and a two-tailed P value less than .05 indicated statistical significance. Results Median cumulative colon doses for annual CAP and AP CT scans from age 15 to 40 years ranged from 0.34 Gy (5th-95th percentiles, 0.18-0.75; dual-energy VNC CT) to 0.89 Gy (5th-95th percentiles, 0.42-1.0; three-phase CT). For the current PNET surveillance protocol, the cumulative effective radiation dose from age 40 to 65 years was 682 mSv (tumors < 1.2 cm) and 2125 mSv (tumors > 3 cm). The tailored algorithm could halve these doses for patients with initial tumor diameter less than 1.2 cm (P < .001). Conclusion CT screening of patients with von Hippel-Lindau syndrome can lead to substantial radiation exposures, even with dual-energy virtual noncontrast CT. A genome and tumor diameter-based algorithm for pancreatic neuroendocrine tumor surveillance may potentially reduce lifetime radiation exposure.