Cancer Morbidity and Computed Tomography: “After” and “Due to” Challenge

The article discusses the problem of carcinogenic risk assessment in the context of relationship with diagnostic radiation resulted from Computed Tomography (CT). The study aimed to evaluate the possible long-term carcinogenic effects after the exposure to a low dose of diagnostic radiation, appeared within a decade after the 1st CT scan. Information on patients examined using CT in the District Hospital of Kasli (KDH) has been derived from the CT archives since 2009 when the first CT examinations has been performed in the KDH. The data were linked to local Cancer registry, the Death registry, and the “CT Registry” database (CTDB) to obtain the information on vital status, the cause of death, cancer morbidity and CT examinations outside KDH, respectively. 275 CT examinations of 246 patients have been recorded to the data file (KDH cluster). To the end of the study, 46 cases of malignant tumours (MT) have been accumulated in the study group. The average observation time was 6.5 years (90% CI 6.2-6.8). The distribution of cancers among patients exposed to CT has been shown retrospectively through the date of birth of patient to December, 31, 2018. The cases of MT diagnosed prior to 1st CT examination have been excluded from the analyses. Cancer-related conditions stated before the date of 1stCT examination have been accounted. The cumulative cancer incidence after the exposure to CT, adjusted for predisposed conditions in the study group was 4.8%. The study results have been compared with the results of the LSS cohort study to assess the expected excess cancer morbidity. The data obtained in the study provide the information for a comprehensive epidemiological assessment of long-term effects related to diagnostic radiation exposure in the Ozyorsk Computed Tomography Cohort (OCTC study). Doi: 10.28991/SciMedJ-2021-0304-3 Full Text: PDF

Diagnostic Imaging Radiation in Severe Sickle Cell Disease: Cancer Risk Implications

Introduction: Patients with sickle cell disease (SCD) are repeatedly exposed to diagnostic radiation. Radiographs, computed tomography (CT) and nuclear medicine scans are often ordered for suspected complications caused by sickle cell disease that exposes patients with SCD to ionizing or another form of radiation. A few studies of low-dose cumulative radiation exposure (in people without SCD) suggest that 30 to 100 mSv over 30 decades is associated with higher excess risk of leukemia. New epidemiologic data of low quality suggests that individuals with sickle cell disease (SCD) accumulate "driver mutations" for acute myelogenous leukemia (AML) about 20-30 years earlier than the general population, and have higher risk of AML. In a gene therapy protocol with a few dozen patients, 2 cases of AML have occurred in sickle cell disease and none in thalassemia. It has been reported that children with SCD are frequently exposed to ionizing radiation in the form of plain radiographs, fluoroscopy, computed tomography (CT) scans, bone scans, and other tests. Exposure to ionizing radiation during childhood carries a risk of developing cancer that is directly related to the total radiation dose.Epidemiological data has demonstrated an increase both in diagnostic radiation and in actual or predicted resultant cancer diagnosis. Children are particularly vulnerable to radiation-induced cancer because they are still actively growing and thus are at greater risk of acquiring an oncogenic mutation in an actively dividing cell. Hypothesis: Frequent diagnostic imaging for children and adults with SCD can have significant cumulative radiation exposure that could add excess risk of AML. Methods: The study design was a retrospective chart review. The sample was selected to be enriched for the most severely-affected children and adults in the Sickle Cell Center at UI Health, which provides medical care for over 700 patients with SCD. The subgroup on chronic erythrocytapheresis blood transfusionswere selected as a sample of severe of SCD who are more likely to be exposed to repeated diagnostic radiation. Many have had stroke, which often leads to repeated head CT and cerebral angiograms. Others had pulmonary embolism or acute chest syndrome, which can lead to chest CT angiograms. Other SCD complications with high risk of morbidity or morbidity lead to similar likelihood that patients on chronic exchange transfusion therapy would have histories of multiple imaging studies. Medical records were reviewed for the type and number of all radiographic tests, especially CT scans, during the 10-year period 2011-2020. A second observer confirmed a subset of charts. Standard references were used to estimate radiation exposure in mSv for each type of test. The sum of mSv for each individual was a rough estimate of cumulative radiation in 10 years. The IRB approved the protocol. Results: Chart review on 39 patients (ages 16 - 60y) identified 1,030 radiographic tests with a mean of 26.4 tests/patient. Seven patients had > 50 tests, and one patient had > 100 tests over a 10-year period. Thirty-three patients had at least one CT scan. Eighteen patients had at least 3 CT scans. Twenty patients had cumulative radiation exposure > 30 mSv over a 10-year period, 4 patients had > 100 mSv, and one patient had > 200 mSv. Plain radiographs comprised 71% (736) of the studies and relatively low dose radiation exposure. Discussion: This retrospective study estimated that diagnostic radiography exposed 20 of 39 patients with severe SCD to the range of 30 to 200 mSv over 10 years, mostly from numerous CT scans. This range of cumulative radiation exposure has mixed evidence about possible heightened risk of AML and other cancers. The study is limited by the small sample at a single institution and a heavy bias toward patients with stroke and chest complications, but this severely-affected subgroup comprises many of those eligible for transplant and gene therapy in SCD. Cumulative exposure to diagnostic radiation might be one mechanism for the unexplained patterns of AML in SCD after gene therapy that led to a pause in SCD gene therapy studies for a few months in 2021. Further studies are needed. Disclosures Hsu: Global Blood Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aruvant: Consultancy, Membership on an entity's Board of Directors or advisory committees; Hoffman LaRoche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Forma Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cyclerion: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Imara: Research Funding; Eli Lilly: Research Funding; Baxalta / Shire / Takeda: Research Funding.

GCT-69. VOLUMETRIC CHANGE BEFORE CHEMORADIOTHERAPY AND INFLUENCE OF DIAGNOSTIC RADIATION EXPOSURE IN INTRACRANIAL GERMINOMAS

BACKGROUND Spontaneous regression in intracranial germ cell tumors has been reported in some literatures, but the mechanism has not been well known. We retrospectively measured the tumor volume before chemoradiotherapy and analyzed factors that influence reduction of tumor volume. PATIENTS AND METHODS Plural MRI scans were done before the first course of chemotherapy regimen in 27 patients with primary intracranial germinomas. Their age ranged from 8 to 31 years. 35 lesions from them were enrolled and included 13 pineal, 4 neurohypophyseal, 4 basal ganglia, 4 bifocal type, and 2 multiple lesions. All regions were verified as pure germinoma or HCG-producing germinoma by histopathological examination. Tumor volume of 35 lesions was analyzed by volumetric assessment based on MRI. Ratio of volumetric change between the first MRI and the scan immediately before chemotherapy was defined as shrinking rate (%). Period between disease onset and the first chemotherapy was 20 to 47 days. Diagnostic radiation dose was calculated in each case. RESULTS Initial tumor volume ranged from 0.962 to 72.356 cubic centimeters (mean: 8.27). Diagnostic radiation dose: 40.5 to 910.1 mGy. Shrinking rate ranged from -57.8 to 85.4% (mean: 30.8). In 10 regions, shrinking rate was within 30%. Shrinking rate was significant positively influenced by diagnostic radiation dose (p<0.05) and negatively influenced by initial volume (p<0.05). But, other factors such as age, sex, histopathological parameters did not influence tumor shrinkage. CONCLUSION This study shows that the volume of intracranial germ cell tumors is changing dynamically before chemoradiotherapy in many cases. Diagnostic exposure to low-dose radiation influences tumor shrinkage of intracranial germinomas.

Lower abdominal and pelvic radiation and testicular germ cell tumor risk

Background Testicular germ cell tumor (TGCT) incidence has increased in recent decades along with the use and dose of diagnostic radiation. Here we examine the association between reported exposure to diagnostic radiation and TGCT risk. Methods We conducted a case-control study of men with and without TGCT recruited from hospital- and population-based settings. Participants reported on exposures to 1) x-ray or CT below the waist and 2) lower GI series or barium enema, which consists of a series of x-rays of the colon. We also derived a combined measure of exposure. We used logistic regression to determine the risk of developing TGCT according to categories of exposures (0, 1–2, or ≥3 exposures) and age at first exposure, adjusting for age, year of birth, race, county, body mass index at diagnosis, family history of TGCT, and personal history of cryptorchidism. Results There were 315 men with TGCT and 931 men without TGCT in our study. Compared to no exposures, risk of TGCT was significantly elevated among those reporting at least three exposures to x-ray or CT (OR≥3 exposures, 1.78; 95% CI, 1.15–2.76; p = 0.010), lower GI series or barium enema (OR≥3 exposures, 4.58; 95% CI, 2.39–8.76; p<0.001), and the combined exposure variable (OR≥3 exposures, 1.59; 95% CI, 1.05–2.42; p = 0.029). The risk of TGCT was elevated for those exposed to diagnostic radiation at age 0–10 years, compared to those first exposed at age 18 years or later, although this association did not reach statistical significance (OR, 2.00; 95% CI, 0.91–4.42; p = 0.086). Conclusions Exposure to diagnostic radiation below the waist may increase TGCT risk. If these results are validated, efforts to reduce diagnostic radiation doses to the testes should be prioritized.

Evaluation of Effects of Diagnostic Exposure Using Data from Epidemiological Registry of Ozyorsk Population Exposed to Computed Tomography

Purpose: To assess the contribution of low doses of diagnostic radiation due to computed tomography to carcinogenic risk among population of Ozersk. Material and methods: The study describes the results of the analysis of data from the radiation-epidemiological register created in the laboratory of radiation epidemiology of the Southern Urals Biophysics Institute of Ozersk. The register contains information on 26,626 CT examinations of Ozersk residents of all age groups, including children under 1 year old, carried out in medical departments of the Chelyabinsk region during the period from 1993 to 2018. Results: Based on the analyzed medical and dosimetric information from the CT Register database, the chances of malignant neoplasms among patients exposed to diagnostic irradiation during computed tomography were assessed taking into account the presence of the main radiation and non-radiation factors (age, sex, occupational exposure, number of CT examinations, effective dose and DLP). Conclusion: In a cohort of Ozersk residents who were exposed to low doses of diagnostic radiation during computed tomography, a statistically significant effect of sex and age attained to malignant neoplasm was obtained. Also, a significant relationship was found between the effective dose from diagnostic CT and the likelihood of subsequent cancer development diagnosed no earlier than 2 years after the first CT examination. At the same time, the DLP did not statistically significantly increase the chances of developing a malignant neoplasm in the study cohort for both the population and the personnel of the Mayak PA.

X-Ray Hesitancy: Patients’ Radiophobic Concerns Over Medical X-rays

All too often the family physician, orthopedic surgeon, dentist or chiropractor is met with radiophobic concerns about X-ray imaging in the clinical setting. These concerns, however, are unwarranted fears based on common but ill-informed and perpetuated ideology versus current understanding of the effects of low-dose radiation exposures. Themes of X-ray hesitancy come in 3 forms: 1. All radiation exposures are harmful (i.e. carcinogenic); 2. Radiation exposures are cumulative; 3. Children are more susceptible to radiation. Herein we address these concerns and find that low-dose radiation activates the body’s adaptive responses and leads to reduced cancers. Low-dose radiation is not cumulative as long as enough time (e.g. 24 hrs) passes prior to a repeated exposure, and any damage is repaired, removed, or eliminated. Children have more active immune systems; the literature shows children are no more affected than adults by radiation exposures. Medical X-rays present a small, insignificant addition to background radiation exposure that is not likely to cause harm. Doctors and patients alike should be better informed of the lack of risks from diagnostic radiation and the decision to image should rely on the best evidence, unique needs of the patient, and the expertise of the physician—not radiophobia.