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Re: Screening with low dose CT Scan: Is there a radiation risk?

We read with great interest the article by MacRedmond et al (1) on Screening for lung cancer using low dose CT scan and the related editorial by Gleeson which provides a comprehensive summary on the benefits and potential pitfalls of such a screening.

However, we notice in both articles, another important issue of potential radiation risks associated with a low dose CT screening for lung cancer has not been addressed.

There have been reports previously which suggest radiation risks even with a low dose CT scan as part of a regular screening (2) and also of a possible synergestic interaction between smoking risk and radiation exposure (4)(5)(6).

David Brennar in his article (2) estimates that, if 50% of all current and former smokers in the U.S. population aged 50–75 years received annual CT screening, the estimated number of lung cancers associated with radiation from screening would be 1.8% (95% credibility interval: 0.5%, 5.5%) more than the otherwise expected number. Considering an upper limit of 5.5% increase in lung cancer risk attributable to annual CT-related radiation exposure, he feels mortality benefit of considerably more than 5% may be necessary to outweigh the potential radiation risks. This estimation was derived from cancer incidence data for atomic bomb survivors.

Several other reports (3)(4)(5)(7) exist which suggest link between radiation exposure and lung cancer.

Hence, potential radiation risks associated with multiple CT scans should be considered as one of the limiting factors for such a screening.

References:

(1). R MacRedmond et al. Screening for lung cancer using low dose CT scanning: results of 2 year follow up. Thorax 2006; 61: 54-56

(2). David J. Brenner, Radiation Risks Potentially Associated with Low-Dose CT Screening of Adult Smokers for Lung Cancer. Radiology 2004;231:440-445

(3). Gilbert ES, Stovall M, Gospodarowicz M, et al. Lung cancer after treatment for Hodgkin’s disease: focus on radiation effects. Radiat Res 2003; 159:161-173.

(4). Tokarskaya ZB, Scott BR, Zhuntova GV, et al. Interaction of radiation and smoking in lung cancer induction among workers at the Mayak nuclear enterprise. Health Phys 2002; 83:833-846

(5). Neugut AI, Murray T, Santos J, et al. Increased risk of lung cancer after breast cancer radiation therapy in cigarette smokers. Cancer 1994; 73:1615-1620.

(6). Pierce DA, Sharp GB, Mabuchi K. Joint effects of radiation and smoking on lung cancer risk among atomic bomb survivors. Radiat Res 2003; 159:511-520.