Radiation Risks Potentially Associated with Low-Dose CT Screening of Adult Smokers for Lung Cancer

TLDR

The study estimates the radiation‑related lung cancer risks of annual low‑dose CT screening in adult smokers and former smokers, establishing a baseline risk that benefits must exceed. Using low‑dose CT dose estimates, excess relative risks derived from atomic bomb survivor data were applied to U.S. populations by age, sex, and smoking status to calculate per‑examination and cumulative annual screening lung cancer risks. For a 50‑year‑old female smoker screened annually until age 75, the added radiation risk is 0.85% on top of a 17% baseline, other organ risks are much lower, and if half of U.S.

Abstract

PURPOSE: To estimate the radiation-related lung cancer risks associated with annual low-dose computed tomographic (CT) lung screening in adult smokers and former smokers, and to establish a baseline risk that the potential benefits of such screening should exceed. MATERIALS AND METHODS: The estimated lung radiation dose from low-dose CT lung examinations corresponds to a dose range for which there is direct evidence of increased cancer risk in atomic bomb survivors. Estimated dose-, sex-, and smoking status–dependent excess relative risks of lung cancer were derived from cancer incidence data for atomic bomb survivors and used to calculate the excess lung cancer risks associated with a single CT lung examination at a given age in a U.S. population. From these, the overall radiation risks associated with annual CT lung screening were estimated. RESULTS: A 50-year-old female smoker who undergoes annual CT lung screening until age 75 would incur an estimated radiation-related lung cancer risk of 0.85%, in addition to her otherwise expected lung cancer risk of approximately 17%. The radiation-associated cancer risk to other organs would be far lower. 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 approximately 36,000, a 1.8% (95% credibility interval: 0.5%, 5.5%) increase over the otherwise expected number. CONCLUSION: Given the estimated upper limit of a 5.5% increase in lung cancer risk attributable to annual CT-related radiation exposure, a mortality benefit of considerably more than 5% may be necessary to outweigh the potential radiation risks. © RSNA, 2004