BackgroundWe studied trends in lung cancer treatment cost over time by phase of care, treatment strategy, age, stage at diagnosis, and histology.MethodsUsing the Surveillance, Epidemiology, and End Results (SEER)‐Medicare database for years 1998‐2013, we allocated total and patient‐liability costs into the following phases of care for 145 988 lung cancer patients: prediagnosis, staging, surgery, initial, continuing, and terminal. Patients served as self‐controls to determine cancer‐attributable costs based on individual precancer diagnosis healthcare costs. We fit linear regression models to determine cost by age and calendar year for each stage at diagnosis, histology, and treatment strategy and presented all costs in 2017 US dollars.ResultsMonthly healthcare costs prior to lung cancer diagnosis were $861 for a 70 years old in 2017 and rose by an average of $17 per year (P < 0.001). Surgery in 2017 cost $30 096, decreasing by $257 per year (P = 0.007). Chemotherapy and radiation costs remained stable or increased for most stage and histology groups, ranging from $4242 to $8287 per month during the initial six months of care. Costs during the final six months of life decreased for those who died of lung cancer or other causes.ConclusionsCost‐effectiveness analyses of lung cancer control interventions in the United States have been using outdated and incomplete treatment cost estimates. Our cost estimates enable updated cost‐effectiveness analyses to determine the benefit of lung cancer control from a health economics point of view.