Lifetime Attributable Risk Of Cancer Research Articles

Pediatrics organ dose and lifetime attributable cancer risk estimates in routine computed tomography

ObjectivesEvaluating organ doses received by pediatric patients and estimating lifetime attributable risk (LAR) in Riyadh, Saudi Arabia from chest and abdominal pelvic Computed Tomography (CT) scans. MethodsA total of 155 patients under the age of 15 were divided into four age groups: under 1, 1–5, 5–10, and 10–15. The organ dose was determined using the National Cancer Institute dosimetry system for (NCICT) software, and the LAR if cancer incident was measured according to the BEIR VII report. The 1st, 2nd, and 3rd quartiles were calculated for organs received primary X-ray beams. ResultsThe highest and lowest median doses were for the kidney in the 10-15-year-old group 4.84 mGy (Cl95%, 0.15–9.54) and the prostate in the >1-year-old group 0.02 mGy (Cl95%, −0.01 – 0.05), respectively. Furthermore, there was a correlation between age and breast doses in chest scans, as median doses increased from 0.08 mGy to 3.70 mGy. Breast cancer in females had a highest LAR from chest CT and colon cancer in abdomen-pelvic CT. The group 1–5 years old had the highest risk of breast cancer, followed by chest CT (LAR = 25.94). However, colon cancer (LAR = 10.39), followed by an abdomen-pelvic CT, had the highest risk in the same group in both genders. Colon and breast cancers had the highest LAR among males and females in all groups. ConclusionThe study found that older patients received higher median organ doses for the same examination than younger patients. Females have greater organ doses in the thorax compared to males, resulting in a higher mean LAR. While CT scans are useful tools for diagnosis, it's essential to consider the patient's dose, particularly in pediatric cases.

Low-dose radiation therapy for COVID-19 pneumonia: Comparison of dosimetry and life-time attributable risk of cancer with conventional AP-PA fields and bone marrow sparing VMAT.

Low-dose radiation therapy (LDRT) to lungs did show encouraging results in COVID-19 patients in some clinical trials. However, there has been some concern regarding the long-term risk of radiation-induced cancer (RIC). Compared to the conventional AP-PA field technique, volumetric modulated arc therapy (VMAT) can potentially reduce the dose to the marrow and other organs at risk (OARs) and thus minimize the risk of cancer. We designed a dosimetry study to study if VMAT can reduce the exposure to the marrow and other OAR doses and curtail the estimated life-time attributable risk (LAR) of cancer. We retrieved the computed tomography scan data of 10 patients (aged 40-60 years, median 48 years) who have been already treated for any malignancy in the region of the thorax. A dose of 1.0 Gy in single fraction was prescribed to both lungs. All the organs were delineated as per the established guidelines. The dosimetry achieved by the two plans was compared to find the difference. Mean OAR doses were used to estimate the LAR for both plans and compared. Planning target volume coverage parameters like conformity index and homogeneity index were significantly better with VMAT (P value < 0.05 for all). The mean dose to most OARs was significantly lower with VMAT (P value < 0.05 for all). The mean dose to the marrow was significantly lower with VMAT (59.05 vs 81.9 cGy with P value < 0.05). The overall LAR was significantly lower with VMAT as compared to the conventional plan (0.357% vs 0.398%, P value < 0.05). Compared to the conventional technique, VMAT provides better OAR dosimetry for lung irradiation (a prescription dose of 1.0 Gy or more) in COVID-19 pneumonia. VMAT significantly reduces the risk of RIC. We therefore suggest if lung LDRT is used for COVID-19 patients, VMAT is the preferred technique for a prescription dose of ≥1.0 Gy.

Life Time Attributable Cancer Risk Estimated Using Scanner Reported Dose Length Product during Chest Computed Tomography Imaging in Young Children

Life Time Attributable Cancer Risk Estimated Using Scanner Reported Dose Length Product during Chest Computed Tomography Imaging in Young Children

An evaluation of CT radiation doses within the Yorkshire Lung Screening Trial.

To evaluate radiation doses for all low-dose CT scans performed during the first year of a lung screening trial. For all lung screening scans that were performed using a CT protocol that delivered image quality meeting the RSNA QIBA criteria, radiation dose metrics, participant height, weight, gender, and age were recorded. Values of volume CT dose index (CTDIvol) and dose length product (DLP) were evaluated as a function of weight in order to assess the performance of the scan protocol across the participant cohort. Calculated effective doses were used to establish the additional lifetime attributable cancer risks arising from trial scans. Median values of CTDIvol, DLP, and effective dose (IQR) from the 3521 scans were 1.1mGy (0.70), 42.4mGycm (24.9), and 1.15mSv (0.67), whilst for 60-80kg participants the values were 1.0mGy (0.30), 35.8mGycm (11.4), and 0.97mSv (0.31). A statistically significant correlation between CTDIvol and weight was identified for males (r = 0.9123, P < .001) and females (r = 0.9052, P < .001), however, the effect of gender on CTDIvol was not statistically significant (P = .2328) despite notable differences existing at the extremes of the weight range. The additional lifetime attributable cancer risks from a single scan were in the range 0.001%-0.006%. Low radiation doses can be achieved across a typical lung screening cohort using scan protocols that have been shown to deliver high levels of image quality. The observed dose levels may be considered as typical values for lung screening scans on similar types of scanners for an equivalent participant cohort. Presentation of typical radiation dose levels for CT lung screening examinations in a large UK trial. Effective radiation doses can be of the order of 1mSv for standard sized participants. Lifetime attributable cancer risks resulting from a single low-dose CT scan did not exceed 0.006%.

LARCalc, a tool to estimate sex- and age-specific lifetime attributable risk in populations after nuclear power plant fallout

A tool called LARCalc, for calculating the radiological consequences of accidental large scale nuclear power plant releases based on estimates of 137Cs ground deposition, is presented. LARCalc is based on a previously developed models that has been further developed and packaged into an easy-to-use decision support tool for training of decision makers. The software visualises the radiological impact of accidental nuclear power plant releases and the effects of various protective measures. It is thus intended as a rapid alternative for planning protective measures in emergency preparedness management. The tool predicts projected cumulative effective dose, projected lifetime attributable cancer risk, and residual dose for some default accidental release scenarios. Furthermore, it can predict the residual dose and avertable cumulative lifetime attributable risk (LAR) resulting from various protective measures such as evacuation and decontamination. It can also be used to predict the avertable collective dose and the increase in cancer incidence within the specified population. This study presents the theoretical models and updates to the previous models, and examples of different nuclear fallout scenarios and subsequent protective actions to illustrate the potential use of LARCalc.

Cumulative exposure and lifetime cancer risk from diagnostic radiation in patients undergoing orthognathic surgery: a cross-sectional analysis

Radiation doses in dentomaxillofacial imaging are typically very low. However, diagnostic and follow-up protocols in orthognathic surgery result in a patient-specific risk in effective dose. Estimating the cancer risks from these exposures remains abstract for many maxillofacial surgeons. In this study, 40 orthognathic patients were randomly sampled and their cumulative effective dose (ED) calculated. The lifetime attributable risk of cancer (LAR) was calculated based on the standard radiological protocol for orthognathic surgery follow-up using methods described in the BEIR VII report and RadRAT. The mean cumulative ED of the 40 sampled patients at the end of their 2-year follow-up period was 1.91 ± 0.58 mSv. The LAR at the end of follow-up was 17.65 (90% confidence interval 6.46–32.90) per 100,000 person-years for male orthognathic patients and 13.93 (90% confidence interval 6.27–25.24) per 100,000 person-years for female orthognathic patients. This represents 0.70% and 0.68%, respectively, of the baseline cancer risk for oral, thyroid, and brain cancer combined. Although theoretical, these results provide a framework for interpreting radiation doses and cancer risks in patients undergoing orthognathic surgery. Considering the increased radiation sensitivity in children and adolescents, indication-oriented and patient-specific imaging protocols should be advised.

Radiation Exposure and Lifetime Attributable Risk of Cancer Incidence and Mortality from Low- and Standard-Dose CT Chest: Implications for COVID-19 Pneumonia Subjects.

Since the novel coronavirus disease 2019 (COVID-19) outbreak, there has been an unprecedented increase in the acquisition of chest computed tomography (CT) scans. Nearly 616 million people have been infected by COVID-19 worldwide to date, of whom many were subjected to CT scanning. CT exposes the patients to hazardous ionizing radiation, which can damage the genetic material in the cells, leading to stochastic health effects in the form of heritable genetic mutations and increased cancer risk. These probabilistic, long-term carcinogenic effects of radiation can be seen over a lifetime and may sometimes take several decades to manifest. This review briefly describes what is known about the health effects of radiation, the lowest dose for which there exists compelling evidence about increased radiation-induced cancer risk and the evidence regarding this risk at typical CT doses. The lifetime attributable risk (LAR) of cancer from low- and standard-dose chest CT scans performed in COVID-19 subjects is also discussed along with the projected number of future cancers that could be related to chest CT scans performed during the COVID-19 pandemic. The LAR of cancer Incidence from chest CT has also been compared with those from other radiation sources, daily life risks and lifetime baseline risk.

How well Nigerian radiographers adhere to pediatrics-specific protocols during computed tomography procedures

&#x0D; &#x0D; &#x0D; INTRODUCTION: Enormously high-dose procedures such as computed tomography requires pediatrics-specific protocols due to high tissue radio-sensitivity and higher lifetime attributable cancer risks. It’s not known if radiographers in Nigeria consider this fact at all times.This work aimed to survey head computed tomography dose in Nigeria for evidence of pediatric- specific practice.&#x0D; METHODS: The census of CT scanners was undertaken prospectively across the country from June 2019 to September 2021, while the dose survey was undertaken retrospectively in 14 facilities distributed evenly across the geopolitical zones between February to September 2021. Data on computed tomography installations were supplied by radiographers spread across the country. A dose survey involving 490 and 700 pediatrics and adult patients emanated from fourteen of those facilities. Doses were extracted from on-screen volumetric CT dose index (CTDIvol) and dose- length product (DLP) in non-contrast investigations.&#x0D; RESULTS: There were 209 CT scanners installed in Nigeria as of September 2021, with a triennial growth rate of 12.4% (n = 26). Monthly patient throughput for all CT requests was ≤ 41,412 with pediatric cases accounting for 10.4 % (n = 4,311). Mean head dose for pediatrics and adults with CTDIvol (41/58 mGy) and DLP (922/1198 mGy-cm) appeared different prima facie. However, a paired - sample t-test gave statistically significant difference in the CTDIvol (p = 0.001), but not with DLP (p = 0.055).&#x0D; CONCLUSION: The installation of CT scanners is on the increase in Nigeria. Pediatric and adult CT dose had minimal differences. Given the higher lifetime attributable cancer risks for pediatrics, this should be worrisome. This calls for pediatric- specific protocol design and enforcement by relevant regulatory agencies, as well as meticulous optimization of protection from radiation by radiation practitioners.&#x0D; &#x0D; &#x0D;

Patient radiation dose and lifetime attributable risk of cancer due to ionizing radiation in cardiovascular interventional radiological procedures

The aim of this study is to calculate the patient radiation dose and Lifetime Attributable Risk (LAR) in Cardiovascular Interventional Radiological (CVIR) procedures. The patient population included 327 patients who underwent Coronary Angiography (CA) and Percutaneous Coronary Interventions (PCI). Exposure data were reported for every examination such as Kerma-Area Product (KAP), fluoroscopy time and number of exposures. Organ dose and effective dose were assessed by PCXMC software. LAR values were determined according to BEIR VII report. The mean effective dose per examination in CA is 12.6 mSv for males and 10.25 mSv for females. In PCI, the mean effective dose is 18.06 mSv for males and 22.73 mSv for females. Organs with highest dose are thymus, heart, breast, and lung. The mean of LAR value in CA is 62 and 60 for males and females, respectively. In PCI, the mean of LAR value is 89 and 132 for males and females, respectively. Also, the KAP to effective dose conversion factors (CFKAP-ED) were calculated. CFKAP-ED for CA is 0.249 in males and 0.228 in females, and for PCI is 0.2446 and 0.2316 for males and females, respectively. This study will help better understand the concept of ionizing radiation dose in the CVIR procedures and how the individual patient’s effective dose and LAR can evaluate the cancer risk.

Radiation safety for cardiovascular computed tomography imaging in paediatric cardiology: a joint expert consensus document of the EACVI, ESCR, AEPC, and ESPR.

Children with congenital and acquired heart disease may be exposed to relatively high lifetime cumulative doses of ionizing radiation from necessary medical invasive and non-invasive imaging procedures. Although these imaging procedures are all essential to the care of these complex paediatric population and have contributed to meaningfully improved outcomes in these patients, exposure to ionizing radiation is associated with potential risks, including an increased lifetime attributable risk of cancer. The goal of this manuscript is to provide a comprehensive review of radiation dose management and cardiac computed tomography performance in the paediatric population with congenital and acquired heart disease, to encourage informed imaging to achieve indication-appropriate study quality at the lowest achievable dose.

Estimated Effective Lifetime Risks of Radiation-Induced Thyroid Cancer in Computed Tomography (CT) Brain Examination

Thyroid is one of the most radiosensitive organs in the human body. Although the scanning range of brain computed tomography (CT) does not include lower neck region, there is possibility for thyroid to be irradiated due to scattered radiation because of its location near to the external beam collimation. The objective of this study was to evaluate effective lifetime risk of radiation-induced thyroid cancer in young adults following brain CT examination. A total of 306 patient data within the age range between 18 and 39 years old were retrospectively analysed. Absorbed dose of the thyroid organ was obtained through the input of data using WAZA- ARI v2. Effective lifetime risk was calculated by multiplying equivalent dose of the thyroid organ with the lifetime attributable cancer risk adapted from Biological Effects in Ionising Radiation (BEIR) Report V11. The effective lifetime risks were recorded as 0.45 ± 0.70 per 100 000 and 0.93 ± 1.52 per 100 000 for single and multiple exposures, respectively. In terms of gender, woman data (0.99 ± 0.76; 1.95 ± 2.15) were found higher as compared to man data (0.13 ± 0.39; 0.35 ± 0.45) for both single and multiple exposure. The percentage difference of effective lifetime risks between single and multiple exposures was up to 107%. The effective lifetime risk noted in this study may be low, however, the long-term risk of cancer development should be considered. This study serves as preliminary reference when revising clinical protocol especially in those involving repeated exposures in young adult patients. Future study should include other radiosensitive organs exploring the effective lifetime risk of radiation induced cancer following CT procedure.

Lifetime attributable cancer risk related to prevalent CT scan procedures in pediatric medical imaging centers

Purpose Evaluation of the organ dose in pediatric patients up to 15 years old and Estimation of lifetime attributable risk (LAR) of cancer incidence in pediatric computed tomography procedures. Materials and methods Data from 532 patients below 15 years old was collected and they were categorized into four age groups of <1, 1–5, 5–10, and 10–15 years old. NCICT software was used to calculate the organ dose, and LAR of cancer incidence has been estimated according to the BEIR VII report. Results The highest median dose in all age groups was related to eye lens (head scan), thyroid (chest scan), and colon (abdomen-pelvic scan). The highest average LAR of cancer incidence was observed for breast cancer and colon cancer following a chest CT scan of the youngest group (<1-year-olds) [68.23 per 100,000] and abdomen-pelvic scans of the oldest group (10- to 15-year-olds) [57.30 per 100,000]. Conclusion This study shows that the average LAR is higher in females and it decreases with age in both genders. Although CT scan has an indispensable application in diagnosis, the patient dose should be taken into account before any examination specifically in pediatric patients.

Estimation of x-ray radiation related cancers in US dental offices: Is it worth the risk?

The objective of this study was to estimate the possible number of cancer cases produced during 2019 in US dental offices from radiography, estimate the possible reduction in those rates resulting from use of intraoral rectangular collimation and selection criteria, and determine the frequency and quality of website radiation risk information and informed consent forms. An analysis of dental radiation examinations in 2014 to 2015 US national survey data, Nationwide Evaluation of X-ray Trends, and National Council on Radiation Protection and Measurements surveys was performed, in addition to an analysis of 2008 to 2020 Journal of Clinical Orthodontics national orthodontic surveys for radiographic examination frequencies. Lifetime attributable cancer risk estimates from US and European studies were used to generate the total dental and orthodontic office cancer totals. In total, 150 offices were examined online for the quality and frequency of risk information in websites and consent forms. The 2019 estimate for all office cancers is 967. Collimation and selection criteria could reduce this to 237 cancer cases. Most cancers arise from intraoral and cone beam computed tomography examinations, with 135 orthodontic cancers over 21 months (average treatment time). Collimation and selection criteria could reduce this to 68. Only 1% of offices use collimators or informed consent for radiography. The website and consent information were of poor quality. Dentists are not following selection criteria or using collimators according to guidelines. Up to 75% of cancer cases could be avoided.

COPD Imaging on a 3rd Generation Dual-Source CT: Acquisition of Paired Inspiratory-Expiratory Chest Scans at an Overall Reduced Radiation Risk.

As stated by the Fleischner Society, an additional computed tomography (CT) scan in expiration is beneficial in patients with chronic obstructive pulmonary disease (COPD). It was thus the aim of this study to evaluate the radiation risk of a state-of-the-art paired inspiratory-expiratory chest scan compared to inspiration-only examinations. Radiation doses to 28 organs were determined for 824 COPD patients undergoing routine chest examinations at three different CT systems–a conventional multi-slice CT (MSCT), a 2nd generation (2nd-DSCT), and 3rd generation dual-source CT (3rd-DSCT). Patients examined at the 3rd-DSCT received a paired inspiratory-expiratory scan. Organ doses, effective doses, and lifetime attributable cancer risks (LAR) were calculated. All organ and effective doses were significantly lower for the paired inspiratory-expiratory protocol (effective doses: 4.3 ± 1.5 mSv (MSCT), 3.0 ± 1.2 mSv (2nd-DSCT), and 2.0 ± 0.8 mSv (3rd-DSCT)). Accordingly, LAR was lowest for the paired protocol with an estimate of 0.025 % and 0.013% for female and male patients (50 years) respectively. Image quality was not compromised. Paired inspiratory-expiratory scans can be acquired on 3rd-DSCT systems at substantially lower dose and risk levels when compared to inspiration-only scans at conventional CT systems, offering promising prospects for improved COPD diagnosis.

Dosimetric impact of natural terrestrial radioactivity on residents of lower Himalayas, India.

A comprehensive radio-ecological evaluation of soil samples of Solan and Shimla districts of Himachal Pradesh has been carried out for risk and dose assessment. Twenty-six randomly selected environmental soil samples were analysed for natural radionuclide concentrations (226Ra, 232Th and 40K) using NaI(Tl) scintillator detector. The average concentration of 226Ra, 232Th and 40K was observed as 37, 59 and 430Bqkg-1, respectively, which exceeded the worldwide average of 33, 45 and 412Bqkg-1 reported by UNSCEAR (Sources and effects of ionizing radiation. Report to the general assembly with scientific annexes, New York, 2008). Radium equivalent activity (Raeq), hazard indices (Hex, Hin) and radioactivity level indices (Iϒr, Iα, AUI) and Clark value were checked against their threshold limits, and their mean values were safely below the recommended criteria. This confirms the soil applicability for construction purposes. Indoor and outdoor dose rates (Ḋ), age-dependent annual effective doses (AED), organ-specific doses and lifetime attributable cancer risk (both cancer incidence and cancer mortality) were also computed. Strong positive correlation was established between radon/thoron exhalation rate and their parent radionuclides. Multivariate statistical technique was employed to explore spatial distribution of radionuclides and homogeneity between various radiological parameters.

Low dose radiation therapy for COVID-19: Effective dose and estimation of cancer risk

Background and purposeThe objective of this work is to evaluate the risk of carcinogenesis of low dose ionizing radiation therapy (LDRT), for treatment of immune-related pneumonia following COVID-19 infection, through the estimation of effective dose and the lifetime attributable risk of cancer (LAR). Material and methodsLDRT treatment was planned in male and female computational phantoms. Equivalent doses in organs were estimated using both treatment planning system calculations and a peripheral dose model (based on ionization chamber measurements). Skin dose was estimated using radiochromic films. Later, effective dose and LAR were calculated following radiation protection procedures. ResultsEquivalent doses to organs per unit of prescription dose range from 10 mSv/cGy to 0.0051 mSv/cGy. Effective doses range from 204 mSv to 426 mSv, for prescription doses ranging from 50 cGy to 100 cGy. Total LAR for a prescription dose of 50 cGy ranges from 1.7 to 0.29% for male and from 4.9 to 0.54% for female, for ages ranging from 20 to 80 years old. ConclusionsThe organs that mainly contribute to risk are lung and breast. Risk for out-of-field organs is low, less than 0.06 cases per 10000. Female LAR is on average 2.2 times that of a male of the same age. Effective doses are of the same order of magnitude as the higher-dose interventional radiology techniques. For a 60 year-old male, LAR is 8 times that from a cardiac CT, when prescription dose is 50 cGy.

Cardiac catheterization real-time dynamic radiation dose measurement to estimate lifetime attributable risk of cancer.

Cardiac catheterization procedure is the gold standard to diagnose and treat cardiovascular disease. However, radiation safety and cancer risk remain major concerns. This study aimed to real-time dynamic radiation dose measurement to estimate lifetime attributable risk (LAR) of cancer incidence and mortality in operators. Coronary angiography (CA) with percutaneous coronary intervention (PCI), CA, and others (radiofrequency ablation, pacemaker and defibrillator implantation) procedures with different beam directions, were undertaken on x-ray angiography system. A real-time electronic personal dosimeter (EPD) system was used to measure the radiation dose of staff during all procedures. We followed the Biological Effects of Ionizing Radiation (BEIR) VII report to estimate the LAR of all cancer incidence and mortality. Primary operators received radiation dose in CA with PCI, CA, and others procedures were 59.33 ± 95.03 μSv, 39.81 ± 103.85 μSv, and 21.92 ± 37.04 μSv, respectively. As to the assistant operators were 30.03 ± 55.67 μSv, 14.67 ± 14.88 μSv, and 4 μSv, respectively. LAR of all cancer incidences for staffs aged from 18 to 65 are varied from 0.40% for males to 1.50% for females. LAR of all cancer mortality for staffs aged from 18 to 65 are varied from 0.22% for males to 0.83% for females. Our study provided an easy, real-time and dynamic radiation dose measurement to estimate LAR of cancer for staff during the cardiac catheterization procedures. The LAR for all cancer incidence is about twice that for cancer mortality. Although the radiation doses of staff are lower during each procedure, the increased years of service leads to greater radiation risk to the staff.

Risk Of Cancer And Radiation Dose Received By Patients From Common Diagnostic Radiological Examinations

Background: Although radiological diagnostic studies (RDS) are an important and acceptable part of medical practice, it is not without hazards. It is associated with increased risk of cancer. Unfortunately the typical and safe dose of each radiological examination is not known. Most of our knowledge of cancer risk comes from studies of survivors of those exposed to whole body radiation from atomic bomb in Hiroshima &amp; Nagasaki, jobs associated with radiation exposure, Chernobyl survivors &amp; patients treated with radiation therapy for cancer and other diseases.&#x0D; Objectives To estimate radiation dose received by patients from diagnostic radiological examinations and lifetime attributable risk of cancer (LTARC).&#x0D; Type of the study: A prospective study.&#x0D; Methods A prospective study was conducted in Al-Kindi Teaching Hospital (KTH) during the period from 1st June to 31st august 2016. The study was performed on 910 adult patients. There were 595 males (65.38%) and 315 females (34.62%); mean age was 41.5 years (range 20-63).Different RDS were considered including chest-x ray (CXR), skull x-ray(SXR), x-ray of limbs and pelvis (LPXR) for orthopedic causes , computed tomography scan (CTS) and mammography (MG) .&#x0D; Results CXR was performed for 260 (28.57%) patients which delivers 0.12 mSv. SXR was done for 160 (17.58%) patients which delivers 0.3 mSv. LPXR was performed for 220 (24.175%) which delivers 0.3-0.6 mSv. MG exposes 150 (16.48%) to 3 mSv. While CTS ,which delivers 6.2-16 mSv according to anatomic area being scanned, was done for 120(13.19%) patients.&#x0D; Conclusion There is great abuse for using RDS from both patients and doctors, without realizing their danger and association with cancer development. It was proved that RDS expos patients to different kinds of tissues injury including cancer.

How have advances in CT dosimetry software impacted estimates of CT radiation dose and cancer incidence? A comparison of CT dosimetry software: Implications for past and future research.

ObjectiveOrgan radiation dose from a CT scan, calculated by CT dosimetry software, can be combined with cancer risk data to estimate cancer incidence resulting from CT exposure. We aim to determine to what extent the use of improved anatomical representation of the adult human body “phantom” in CT dosimetry software impacts estimates of radiation dose and cancer incidence, to inform comparison of past and future research.MethodsWe collected 20 adult cases for each of three CT protocols (abdomen/pelvis, chest and head) from each of five public hospitals (random sample) (January-April inclusive 2010) and three private clinics (self-report). Organ equivalent and effective dose were calculated using both ImPACT (mathematical phantom) and NCICT (voxelised phantom) software. Bland-Altman plots demonstrate agreement and Passing-Bablok regression reports systematic, proportional or random differences between results. We modelled the estimated lifetime attributable risk of cancer from a single exposure for each protocol, using age-sex specific risk-coefficients from the Biologic Effects of Ionizing Radiation VII report.ResultsFor the majority of organs used in epidemiological studies of cancer incidence, the NCICT software (voxelised) provided higher dose estimates. Across the lifespan NCICT resulted in cancer estimates 2.9%-6.6% and 14.8%-16.3% higher in males and females (abdomen/pelvis) and 7.6%-19.7% and 12.9%-26.5% higher in males and females respectively (chest protocol). For the head protocol overall cancer estimates were lower for NCICT, but with greatest disparity, >30% at times.ConclusionWhen the results of previous studies estimating CT dose and cancer incidence are compared to more recent, or future, studies the dosimetry software must be considered. Any change in radiation dose or cancer risk may be attributable to the software and phantom used, rather than—or in addition to—changes in scanning practice. Studies using dosimetry software to estimate radiation dose should describe software comprehensively to facilitate comparison with past and future research.

Intensive Imaging Surveillance of Survivors of Breast Cancer May Increase Risk of Radiation-induced Malignancy

BackgroundCurrent clinical guidelines recommend mammography as the only imaging method for surveillance in asymptomatic survivors of early breast cancer (EBC). However, non-recommended tests are commonly used. We estimated the imaging radiation-induced malignancies (IRIM) risks in survivors of EBC undergoing different imaging surveillance models. Materials and MethodsWe built 5 theoretical models of imaging surveillance, from annual mammography only (model 1) to increasingly imaging-intensive approaches, including computed tomography (CT) scan, positron emission tomography-CT, bone scan, and multigated acquisition scan (models 2 through 5). Using the National Cancer Institute’s Radiation Risk Assessment Tool, we compared the excess lifetime attributable cancer risk (LAR) for hypothetical survivors of EBC starting surveillance at the ages of 30, 60, or 75 years and ending at 81 years. ResultsFor all age groups analyzed, there is a statistically significant increase in LAR when comparing model 1 with more intensive models. As an example, in a patient beginning surveillance at the age of 60 years, there is a 28.5-fold increase in the IRIM risk when comparing mammography only versus a schedule with mammography plus CT scan of chest-abdomen and bone scan. We found no differences when comparing models 2 through 5. LAR is higher when surveillance starts at a younger age, although the age effect was only statistically significant in model 1. ConclusionNon-recommended imaging during EBC surveillance can be associated with a significant increase in LAR. In addition to the lack of survival benefit, additional tests may have significant IRIM risks and should be avoided.