Routine Diagnostic X-ray Examinations and Increased Frequency of Chromosome Translocations among U.S. Radiologic Technologists

Abstract

The U.S. population has nearly one radiographic examination per person per year, and concern about cancer risks associated with medical radiation has increased. Radiologic technologists were surveyed to determine whether their personal cumulative exposure to diagnostic X-rays was associated with increased frequencies of chromosome translocations, an established radiation biomarker and possible intermediary suggesting increased cancer risk. Within a large cohort of U.S. radiologic technologists, 150 provided a blood sample for whole chromosome painting and were interviewed about past X-ray examinations. The number and types of examinations reported were converted to a red bone marrow (RBM) dose score with units that approximated 1 mGy. The relationship between dose score and chromosome translocation frequency was assessed using Poisson regression. The estimated mean cumulative RBM radiation dose score was 49 (range, 0-303). After adjustment for age, translocation frequencies significantly increased with increasing RBM dose score with an estimate of 0.004 translocations per 100 cell equivalents per score unit (95% confidence interval, 0.002-0.007; P < 0.001). Removing extreme values or adjustment for gender, cigarette smoking, occupational radiation dose, allowing practice X-rays while training, work with radioisotopes, and radiotherapy for benign conditions did not affect the estimate. Cumulative radiation exposure from routine X-ray examinations was associated independently with increased chromosome damage, suggesting the possibility of elevated long-term health risks, including cancer. The slope estimate was consistent with expectation based on cytogenetic experience and atomic bomb survivor data. [Cancer Res 2008;68(21):8825-31]

Checking the Foundation: Recent Radiobiology and the Linear No-Threshold Theory

“…The initial decline may be due at least in part to the co-occurrence of reciprocal translocations with unstable forms of chromosome damage (Tucker 2008). Recent studies of radiologic technologists have observed increased frequencies of chromosome aberrations in this cohort occupationally exposed to radiation (Bhatti et al 2007(Bhatti et al , 2008Sigurdson et al 2008a). These studies suggest that chromosome aberrations, particularly reciprocal translocations, hold promise as a biomarker of both exposure and cancer risk, but numerous concerns about potential confounding due to factors such as age, cigarette smoking, and phenotypic differences remain (Sigurdson et al 2008b;Tucker 2008).…”

Association of Chromosome Translocation Rate with Low Dose Occupational Radiation Exposures in U.S. Radiologic Technologists

“…(Further details on the technologists selected for blood sampling are shown in Appendix B.) We analyzed reciprocal chromosome translocations in two groups of radiologic technologists who provided blood samples in years 1994–1995 [Chromosome Translocation Study I (CTS-I), n = 90] and 2003 [Chromosome Translocation Study II (CTS-II), n = 152], as described previously (22–25) with the current estimated occupational radiation doses (11) (Appendix A). [Note: the CTS-I (22) that previously assessed only 79 subjects, now includes 11 additional subjects for whom we did not previously have sufficient data to estimate doses.]…”

“…Studies of FISH translocation data in the Japanese A-bomb survivors (15) accounted for dosimetric uncertainties using regression-calibration methods (20). In general, this has not been attempted in populations with occupational radiation exposure (13, 22–25), where complex patterns of shared errors (i.e., the component of dose error that is shared by a group of individuals in a study) and unshared errors (i.e., the component of dose error that is independent of the dose errors in other individuals) would be expected; or in populations where measurements of chemical or environmental exposures may not have been uniformly collected on individuals in the distant past. A distinction is often made between classical measurement error and Berkson error (20, 26).…”

“…Although we previously examined chromosome translocations in relationship to occupational dose (22–25) based on our earlier 2006 dose reconstruction (10), the current assessment of stable and unstable chromosomal translocations in relationship to our substantially revised occupational dose reconstruction has three additional features. First, to address issues of possible low-dose risk and dose thresholds, we have assessed the lowest estimated dose at which an excess translocation rate is detectable.…”

Prompt cytomolecular identification of chromosome aberration in irradiated blood cells

“…No relation was found between the age and gender, and frequency of CAs on the chromosomes, but some studies have indicated that the rate of CAs can be increased at the higher age (3,10). Moreover, the duration of exposure to radiation did not have any effect on the CAs.…”