PURPOSE Although follicular lymphoma is characterized by long natural history and frequent relapses, data on the number of patients receiving subsequent therapy lines are scarce. To perform reliable health economical calculations for various treatment options, data regarding the lifetime number of therapy courses are needed. The purpose of this study was to use real-world data to create a model that could estimate the treatment burden over a 20-year period. MATERIALS AND METHODS We performed a 20-year simulation on the basis of retrospectively obtained multicenter data of 743 patients with follicular lymphoma. The simulation was carried out in two steps: First, a competing risk model on the basis of Weibull distribution was used to simulate the state transitions from diagnosis onward and from first-line therapy onward. Then, the data were completed by imputing on the basis of the existing data. Completion of data was repeated for 1,000 times to estimate reliability. RESULTS In 20 years, 97% (2.5-97.5 percentile range: 96%-98%), 66% (61%-70%), 34% (30%-41%), and 15% (9%-18%) of the patients received first-line, second-line, third-line, and fourth-line therapies, respectively. The median number of therapy lines received by each patient was two. CONCLUSION Despite long remissions, approximately two thirds of the patients receive at least two lines and one-third at least three lines of therapy during their lifetime.