Sex-specific lung cancer risk among radiation workers in the million-person study and patients TB-Fluoroscopy

Abstract

Background

The study of Japanese atomic bomb survivors, exposed briefly to radiation, finds the risk of radiation-induced lung cancer to be nearly three times greater for women than for men. Because protection standards for astronauts are based on individual lifetime risk projections, this sex-specific difference limits the time women can spend in space. Populations exposed to chronic or fractionated radiation were evaluated to learn whether similar differences exist when exposures occur gradually over years.

Methods and materials

Five occupational cohorts within the Million Person Study of Low-Dose Health Effects (MPS) and a Canadian Fluoroscopy Cohort Study (CFCS) of tuberculosis patients who underwent frequent chest fluoroscopic examinations are evaluated. Included are male and female workers at the Mound nuclear facility, nuclear power plants (NPP), and industrial radiographers (IR). Workers at the Mallinckrodt Chemical Works and military participants at aboveground nuclear weapons tests provide information on the risk among males. Cox proportional hazards and Poisson regression models were used to estimate sex-specific radiation risks for lung cancer and to compare any differences.

Results

Overall, 15,065 lung cancers occurred among the 443,684 subjects studied: 50,111 women and 395,573 men. The mean cumulative dose to the lung was 166.3 mGy (range 6 to 1,055 mGy) with the highest among the TB-fluoroscopy patients (mean 1,055 mGy). Mean lung dose for women in the worker cohorts was generally 4 times lower than for men. Of the 12 estimates of radiation-related risk, only one, for male IRs, showed a significant elevation (ERR 0.09; 95% CI 0.02–0.16, at 100 mGy). In contrast, the dose response for male NPP workers was negative (ERR −0.05; 95% CI −0.10, 0.01, at 100 mGy). Combined, these two cohorts provided little evidence for a radiation effect among males (ERR 0.01; 95% CI −0.04, 0.06, at 100 mGy). There was no significant dose-response among females within any cohort. There was no difference in the sex-specific estimates of lung cancer risk.

Conclusions

There was little evidence that chronic or fractionated exposures increased the risk of lung cancer. There were no differences in the risks of lung cancer between men and women. However, the sex-specific analyses are limited because of small numbers of women and relatively low doses. A more definitive study is ongoing of medical radiation workers which include 85,000 women and 85,000 men (overall mean dose 82 mGy, max 1,140 mGy). Additional understanding will come from the ongoing follow-up of the CFCS.

Keywords:

• Epidemiology
• lung cancer
• radiation dose
• risk coefficients
• occupation
• tuberculosis

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

The Million Person Study of Low-Dose Health effects is supported in part by a grant from the U.S. Nuclear Regulatory Commission (NRC-HQ‐60‐14‐G‐0011), grants from the Centers for Disease Control and Prevention (5UE1EH000989, 5NUE1EH001315), grants from the National Aeronautics and Space Administration (NNX15AU88G, 80NSSC17M0016), grants from the U.S. Department of Energy (Grant No. DE-SC0008944 awarded to the National Council on Radiation Protection and Measurements, which included interagency support from the U.S. Nuclear Regulatory Commission, the U.S. Environmental Protection Agency, and the National Aeronautics and Space Administration; and more recent Grants No. DE-AU0000042 and DE-AU0000046, a grant from the National Cancer Institute (Grant No. U01 CA137026) and a Discovery Grant from the Vanderbilt-Ingram Cancer Center (Center no. 404-357-9682). Contract support was also received by Oak Ridge National Laboratory from the Office of Radiation and Indoor Air, U.S. Environmental Protection Agency, under Interagency Agreement DOE No. 1824 S581‐A1, under contract No. DE-AC05‐00OR22725 with UT-Battelle; and contract support was received by Oak Ridge Associated Universities from the U.S. Department of Energy under contract No. DE-SC0014664. Dr. Zablotska was supported by National Cancer Institute and National Institutes of Health (Grant No. R01CA197422).

Notes on contributors

John D. Boice

John Boice is President of the National Council on Radiation Protection and Measurements and Professor of Medicine at Vanderbilt University. He is an international authority on radiation effects and served on the Main Commission of the International Commission on Radiological Protection and on the United Nations Scientific Committee on the Effects of Atomic Radiation. He directs the Million Person Study of Low-Dose Health Effects.

Elizabeth D. Ellis

Elizabeth (Betsy) Dupree Ellis currently works in the Health, Energy and the Environment Program, Oak Ridge Associated Universities. Dr. Ellis does research in Public Health, Occupational Health, and Epidemiology. A major project is contributing to the 'Million Person Study'. She is also active in human subject protection in research.

Ashley P. Golden

Ashley Golden is a biostatistician and project manager at Oak Ridge Associated Universities where she directs and supports multi-disciplinary projects in the areas of occupational epidemiology, radiation exposure and dosimetry, medical surveillance, survey analyses, and environmental assessments. She has been a collaborator on the Million Person Study of Low-Dose Health Effects for nearly six years.

Lydia B. Zablotska

Lydia Zablotska is a Professor in the Department of Epidemiology and Biostatistics in the School of Medicine at the University of California, San Francisco (UCSF), where she serves as the Leader of the Occupational and Environmental Epidemiology Area of Concentration. She is the Principal Investigator of the NCI-funded study to update dosimetry and conduct lifespan mortality and incidence follow-up of the Canadian Fluoroscopy Cohort Study.

Michael T. Mumma

Michael Mumma is the Director of Information Technology at the International Epidemiology Institute and the International Epidemiology Field Station for Vanderbilt University Medical Center. He has over 20 years of experience in data analysis and conducting epidemiologic investigations.

Sarah S. Cohen

Sarah Cohen is a Principal Epidemiologist at EpidStat Institute where she directs observational research studies in the areas of pharmacoepidemiology, nutritional epidemiology, and occupational epidemiology as well as leads large data management projects and statistical analyses. She is also an Adjunct Assistant Research Professor of Medicine in the Department of Medicine at Vanderbilt University School of Medicine. She has been a collaborator on the Million Person Study of Low-Dose Health Effects for nearly twenty years, providing analytic support as well as co-authoring numerous publications.