Development and Validation of a Novel Conditional Event-Free Survival Tool in Diffuse Large B-Cell Lymphoma

One quarter of patients with diffuse large B-cell lymphoma (DLBCL) who achieve a complete response following front-line therapy will eventually experience disease relapse. Existing prognostic models use baseline factors to predict outcomes from the start of initial therapy and are not intended for use following completion of treatment. We developed a conditional event-free survival (cEFS) tool that predicts a patient's risk of lymphoma recurrence after completing front-line therapy taking into consideration baseline risk characteristics plus the time the patient has been in remission. Model development used pooled and harmonized data from two observational cohorts and four randomized trials of patients with newly diagnosed DLBCL treated with immunochemotherapy and either achieving a complete response or not experiencing an event within 12 weeks of end of therapy. Cox proportional-hazards regression modeling with backwards stepwise selection was utilized for model development. External validation was performed using a large independent data registry. In total, data from 2757 patients were used for model development. The risk of experiencing an event at a time point after having survived a period of time could be computed parsimoniously using four basic predictors: age, ECOG performance status grade, Ann Arbor stage, and lactate dehydrogenase level. C-index in the model development cohort was 0.65 (95% CI, 0.63-0.68), compared to 0.64 (95% CI, 0.62-0.66) in the external validation cohort. We believe that this dynamic risk prediction tool will not only aid clinicians in providing data-driven recommendations for surveillance, but also assist patients themselves with key decisions, such as family planning.