Radiation Exposure for CT Lung Cancer Screening

Radiation exposure and cancer risk from low dose CT lung cancer screening is acceptable in light of the substantial mortality reduction associated with screening, according to a study published in BMJ.

Researchers from Italy performed a non-randomized study to estimate the cumulative radiation exposure and lifetime attributable risk of cancer incidence associated with lung cancer screening using annual low dose CT. The 10-year study took place from 2004 to 2015.

A total of 5,203 participants (3,439 men, 1,764 women) participated in the study, undergoing 42,228 low dose CT and 635 PET CT scans. All participants were high risk asymptomatic smokers aged 50 and older, current or former smokers (20 pack years or more), and had no history of cancer in the previous five years.

The results showed:

• Median cumulative effective dose at the 10th year of screening was 9.3 mSv for men and 13.0 mSv for women.

• According to 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 numbers of lung cancer and major cancer cases induced by 10 years of screening in our cohort were 1.5 and 2.4, respectively, which corresponded to an additional risk of induced major cancers of 0.05% (2.4/5203).

• 259 lung cancers were diagnosed in 10 years of screening; one radiation induced major cancer would be expected for every 108 (259/2.4) lung cancers detected through screening.

The researchers concluded that radiation exposure and cancer risk from low dose CT screening for lung cancer, even if non-negligible, can be considered acceptable in light of the substantial mortality reduction associated with screening.