Current US screening guidelines recommend low dose computed tomography (LDCT) scans for high-risk individuals of lung cancer, however, only 13% of the eligible population adhere to the recommendation. Using circulating tumor DNA (ctDNA) as a blood-based cancer biomarker for screening may increase the adherence to screening programs while simultaneously decreasing radiation exposure and invasive follow-up procedures due to false-positives of LDCT. To estimate the health benefits of annual lung cancer screening with ctDNA, we built and applied a multi scale model of the natural history of lung cancer that includes clinical stage progression and ctDNA shedding, and models ctDNA detection. Our multi-scale model integrates data on lung cancer including clinical data from the Surveillance, Epidemiology, and End Results (SEER) database and molecular data on tumor growth, ctDNA shedding and ctDNA detection. The ctDNA detection function is based on a sequencing panel enriched for recurrent point mutations associated with lung cancer and leverages The Cancer Genome Atlas (TCGA) data. Using the model, we generated individual patient trajectories in term of the natural history of lung cancer and aggregated the results at the population level to compare overall health outcomes in the presence vs absence of an annual ctDNA screening. These outcomes include the tumor size and stage at detection, 5-year survival, age-specific incidence-based mortality rate, and cure fraction, which is identified by patients who would have died from lung cancer but instead died from other causes due to screen detection. Our work shows that annual ctDNA screening detected 35% of lung cancer patients while asymptomatic with 99% specificity. Among screen-detected patients, 36% were curable due to early detection but would have been uncurable without screening. Compared to not screening, annual ctDNA screening reduced the median tumor size at detection (from 3.2 cm to 2.2 cm), increased the proportion of early-stage cases (from 36% to 56%), increased 5-year survival (from 20% to 33%), and reduced the average age-specific mortality rate by 21%. In conclusion, an annual ctDNA screening program, even with low sensitivity but high specificity, is expected to provide measurable health benefits and warrants further consideration