Radiation exposure and cancer risk from CT screening: a risk-benefit analysis

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After 10 years of low-dose CT screening in patients, 1.5 lung cancers and 2.4 major cancers per 10,000 people screened were induced by radiation.
After 10 years of low-dose CT screening in patients, 1.5 lung cancers and 2.4 major cancers per 10,000 people screened were induced by radiation.

The lifetime attributable risk of lung cancer and major cancers from low-dose computed tomography (CT) screening ranges from 5.5 to 1.4, and 8.1 to 2.6, respectively, per 10,000 participants, researchers reported in the BMJ.

However, radiation exposure and low-dose CT screening for lung cancer can be acceptable in light of the substantial mortality reduction associated with screening, the authors concluded.

Cristiano Rampinelli, MD, from the Department of Medical Imaging and Radiation Sciences at the European Institute of Oncology in Milan, Italy, and colleagues identified 5,203 high-risk asymptomatic smokers (3,439 men) aged 50 years or older with a smoking history of greater than 20 packs per year. Participants had no history of cancer in the previous 5 years. All data reported in the study were retrospectively assembled and analyzed from a 10-year, nonrandomized, observational, lung cancer screening trial (COSMOS study). The researchers evaluated the cumulated radiation exposure and lifetime risk of cancer incidence associated with low-dose CT.

The main outcome was cumulative radiation exposure from low-dose CT and positron emission tomography (PET) CT scans. For each age, sex, and organ, the researchers determined the lifetime attributed risk of cancer incidence from a 100-mSv organ equivalent dose calculated from the Biological Effects of Ionizing Radiation VII (BEIR VII).

During the 10 years of the COSMOS lung cancer screening trial, 5,203 high-risk participants underwent 42,228 low dose CT examinations, including 39,981 annual CT scans, 1,965 first recall CT scans, and 282 second recall CT scans for lung cancer screening. A total of 635 PET CT scans were performed in 522 participants with suspicious findings. A total of 259 lung cancers were diagnosed after 10 years of CT screening. The mean cumulative effective dose at the 10th year of screening was 9.2 mSv for men and 13.0 mSv for women.

In accordance with participants' age and sex, the lifetime attributable risk of lung cancer and major cancers after 10 years of CT screening ranged from 5.5 to 1.4 per 10,000 people screened, and from 8.1 to 2.6 per 10,000 people screened, respectively. In women aged 50 to 54, the lifetime attributable risk of lung cancer and major cancers was about fourfold and threefold higher than for men aged 65 and older, respectively.

The rates of lung cancer and major cancer cases were 1.5 and 2.4 per 10,000 people screened, respectively, which corresponded with an additional risk of induced major cancers by 0.05%. A total of 259 lung cancers were diagnosed in 10 years of screening; one radiation-induced major cancer would be expected for every 108 lung cancers detected through the screening.

Reference

  1. Rampinelli C, De Marco P, Origgi D, et al. Exposure to low dose computed tomography for lung cancer screening and risk of cancer: secondary analysis of trial data and risk-benefit analysis. BMJ. 8 Feb 2017. doi: 10.1136/bmj.j347.
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