Lung cancer screening with low-dose CT: Simulating the effect of starting screening at a younger age in women

Background: The US has recently lowered the entry age for lung cancer screening with low-dose computed tomography (LDCT) from 55 to 50 years. The effect of the younger age for starting screening on the rates of screen-detected and radiation-induced lung cancers in women remains unclear. Methods: A modeling study was conducted. A static cohort of 100,000 heavy female smokers was simulated to undergo annual lung cancer screening with LDCT. The number of screen-detected lung cancers (benefit) and radiation-induced lung cancers (harm) per 1000 screenees were calculated for scenarios with two starting ages (55-50 years) and fixed stopping age (75 years). The benefit-harm ratio and incremental benefit-harm ratio (IBHR) were calculated for each scenario. Results: For annual screening from 55 to 75 years, the number of screen-detected and radiation-induced lung cancers was 112.4 and 2.2, respectively. For annual screening from 50 to 75 years, those numbers were 117.0 and 3.4, respectively. The benefit-harm ratio decreased from 51 to 35 and the IBHR decreased from 6.3 to 4.0 when lowering the screening starting age from 55 to 50 years. Conclusions: The risk of radiation induced lung cancers increased by 50% when lowering the screening starting age by 5 years in women. However, the benefits of LDCT lung cancer screening still outweigh the assumed radiation harm.