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Point and Counterpoint |

Rebuttal From Dr McCunneyRebuttal From Dr McCunney FREE TO VIEW

Robert J. McCunney, MD, MPH
Author and Funding Information

From Brigham and Women’s Hospital.

CORRESPONDENCE TO: Robert J. McCunney, MD, MPH, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02215; e-mail: mccunney@mit.edu


FINANCIAL/NONFINANCIAL DISCLOSURES: The author has reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;147(4):877-878. doi:10.1378/chest.14-3021
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Dr Doss raises interesting points about low-dose radiation and cancer risks, including a role for hormesis in reducing risk of cancer.1 Although a uniform definition of low-dose radiation appears lacking, we agree that radiation concerns are insignificant in therapeutic and diagnostic uses. In contrast, lung cancer screening programs, performed on healthy people without symptoms, are intended to last at least 25 years and involve radiation exposure in screening and diagnostic follow-up of nodules.2 Annual low-dose CT scans will be accompanied by the inevitable follow-up of suspicious nodules, > 96% of which were benign in the National Lung Screening Trial (NLST).3

Dr Doss described a threshold of about 0.5 Gy for radiation-induced cancer based on his analysis of data from atomic bomb survivors; however, the authors of the study drew different conclusions: “The estimated lowest dose range with a significant ERR [estimated relative risk] for all solid cancers 0 to 0.2 Gy and a formal dose-response analysis indicated no threshold; i.e., zero dose was the best estimate of the threshold.”4 In our analysis of potential cumulative radiation exposure from lung cancer screening, many participants will exceed cumulative exposures > 0.2 Gy.5 Indeed, determination of a precise threshold is a challenging undertaking that depends on the study group and fundamental scientific assumptions, such as exposure-response relationships at low levels of exposure.

The manner in which radiation exposure occurs, whether acute or chronic, high or low dose, affects risk. Therapeutic radiation—administered at high doses to targeted areas of the body for limited amounts of time—differs from the intermittent exposure associated with diagnostic studies. Radiation exposure of atomic bomb survivors was acute, whereas exposure experienced by nuclear workers is chronic, low dose, and, in some ways, similar to lung screening participants. Studies of disparate groups, such as those who undergo therapeutic radiation (ie, high doses over short periods), may not apply to screening programs in which the exposure is low dose over long periods of time. The one comparison group to which chronic radiation exposure in a lung cancer screening program can be contrasted is nuclear industry workers.6 These studies, however, include very few workers with radiation exposures > 100 mSv, levels easily reached in lung cancer screening programs, per NLST criteria.3,5,6 As a result, it is not possible to directly contrast the relative exposure scenarios of nuclear industry workers with lung cancer screening participants.

Guidelines on lung cancer screening advise follow-up of nodules > 6 mm as opposed to the 4-mm value for follow-up used in the NLST.7 This recommendation will reduce the need for diagnostic studies involving ionizing radiation. Even if the risk of radiation-induced cancer from chronic low-level exposure is relatively insignificant (as low as 0.5%), small increases may have a significant aggregate impact, since upwards of 8 million Americans meet the guidelines for lung cancer screening.8 Until risks of long-term radiation exposure potentially associated with lung cancer screening programs are more well defined, it seems prudent to continue efforts to both refine the criteria for following up nodules7 and reduce imaging radiation exposures, without compromising health care.

References

Doss M. Counterpoint: should radiation dose from CT scans be a factor in patient care? No. Chest. 2015;147(4):874-877.
 
Humphrey LL, Deffebach M, Pappas M, et al. Screening for lung cancer with low-dose computed tomography: a systematic review to update the US Preventive Services Task Force recommendation. Ann Intern Med. 2013;159(6):411-420. [CrossRef] [PubMed]
 
Aberle DR, Adams AM, Berg CD, et al; National Lung Screening Trial Research Team. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med. 2011;365(5):395-409. [CrossRef] [PubMed]
 
Ozasa K, Shimizu Y, Suyama A, et al. Studies of the mortality of atomic bomb survivors, report 14, 1950-2003: an overview of cancer and noncancer diseases. Radiat Res. 2012;177(3):229-243. [CrossRef] [PubMed]
 
McCunney RJ, Li J. Radiation risks in lung cancer screening programs: a comparison with nuclear industry workers and atomic bomb survivors. Chest. 2014;145(3):618-624. [CrossRef] [PubMed]
 
Cardis M, Vrijheid M, Blettner M, et al. The 15-country collaborative study of cancer risk in the nuclear industry: estimates of radiation-related cancer risks. Radiat Res. 2007;167(4):396-416. [CrossRef] [PubMed]
 
 National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology: Lung Cancer Screening. Version 1.2012. Fort Washington, PA: National Comprehensive Cancer Network; 2011.
 
Bach PB, Mirkin JN, Oliver TK, et al. Benefits and harms of CT screening for lung cancer: a systematic review. JAMA. 2102;307(22):2418-2429. [CrossRef]
 

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References

Doss M. Counterpoint: should radiation dose from CT scans be a factor in patient care? No. Chest. 2015;147(4):874-877.
 
Humphrey LL, Deffebach M, Pappas M, et al. Screening for lung cancer with low-dose computed tomography: a systematic review to update the US Preventive Services Task Force recommendation. Ann Intern Med. 2013;159(6):411-420. [CrossRef] [PubMed]
 
Aberle DR, Adams AM, Berg CD, et al; National Lung Screening Trial Research Team. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med. 2011;365(5):395-409. [CrossRef] [PubMed]
 
Ozasa K, Shimizu Y, Suyama A, et al. Studies of the mortality of atomic bomb survivors, report 14, 1950-2003: an overview of cancer and noncancer diseases. Radiat Res. 2012;177(3):229-243. [CrossRef] [PubMed]
 
McCunney RJ, Li J. Radiation risks in lung cancer screening programs: a comparison with nuclear industry workers and atomic bomb survivors. Chest. 2014;145(3):618-624. [CrossRef] [PubMed]
 
Cardis M, Vrijheid M, Blettner M, et al. The 15-country collaborative study of cancer risk in the nuclear industry: estimates of radiation-related cancer risks. Radiat Res. 2007;167(4):396-416. [CrossRef] [PubMed]
 
 National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology: Lung Cancer Screening. Version 1.2012. Fort Washington, PA: National Comprehensive Cancer Network; 2011.
 
Bach PB, Mirkin JN, Oliver TK, et al. Benefits and harms of CT screening for lung cancer: a systematic review. JAMA. 2102;307(22):2418-2429. [CrossRef]
 
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