Background: In 2018, an estimated 510,000 new cases of non-Hodgkin lymphoma (NHL) were diagnosed globally (GLOBOCAN), the majority of which comprised DLBCL and FL. Treatment for DLCBL and FL has been rapidly evolving over recent years especially for patients treated in later line of therapy (LoT), we aimed to estimate the number of patients eligible for and treated by LoT. Methods: We combined data on all grades of DLBCL and FL from country-specific cancer registries in the US and EU (France, Germany, Italy, Spain and the United Kingdom) and physician survey results from the CancerMPact® (CMP) database. The most recent country-, age- and sex-specific incidence rates for DLBCL and FL were projected and multiplied by the respective projected country populations (US Census, United Nations) to estimate the annual number of incident cases with DLBCL and FL from 2020 through 2025. 10-year limited duration prevalence was calculated using a function of incidence and observed survival data (SEER, Eurocare-5). Proportions of patients who were treated (by systemic therapies or stem cell transplant) by LoT and the proportions of patients who progressed from the prior line, were derived from averages of the two most recent annual CMP physician surveys (2018, 2019) conducted among NHL specialists in the US and EU. For both DLBCL and FL, treatment eligible patients for first line included all newly diagnosed patients. The proportions of treatment in second and third lines were applied to treatment eligible patients, which included those patients who progressed from the prior line. Results: The total number of incident and prevalent cases of DLBCL and FL are expected to increase between 2020 and 2025. Increases in the estimated incidence over time are related to increases in the underlying patient populations in older age groups with higher incidence rates. Less than 60% of third line eligible patients initiated treatment for both NHL subtypes consistently in the US and EU (Figure 1). Conclusions: Future incidence and prevalence for both DLBCL and FL are likely to rise in the US and EU. Further research is warranted to understand the reasons behind the high proportion of treatment eligible patients who do not initiate treatment, especially in the third line plus setting.