Insights into the survival impact of delayed immunochemotherapy in newly diagnosed diffuse large B-cell lymphoma: results from a nationwide registry study

Abstract Background The prognostic impact of the diagnosis-to-treatment interval (DTI) in diffuse large B-cell lymphoma (DLBCL) remains controversial. We investigated the association between DTI and three-year all-cause mortality in a nationwide cohort. Methods We conducted a retrospective population-based cohort study using harmonised German cancer registry data (2020–2023), with vital status follow-up until December 2024. Patients with a first primary DLBCL diagnosis were included. Kaplan–Meier analyses and Cox regression assessed DTI in relation to survival, unadjusted and adjusted for patient, tumor, and structural characteristics. Missing International Prognostic Index (IPI) data formed a separate category, with complete-case and imputation sensitivity analyses. Results Of 16,443 patients, 10,872 initiated systemic therapy within 56 days (eight weeks) and entered the primary analysis. Median age was 71 years, 44.2% were female, and median follow-up was 1.5 years. Three-year overall survival ranged from ~ 63% to 75% across the five treatment-week groups. Compared with week 1, later initiation was associated with progressively lower hazard of death (week 3: HR 0.72, 95% CI 0.64–0.81; week 4: HR 0.63, 0.55–0.72; weeks 5–8: HR 0.62, 0.54–0.70). Lower-risk IPI predicted better survival (low risk: HR 0.24, 0.17–0.34 vs high risk). Later initiation was predicted by low-risk IPI (+ 7.89 days), older age (+ 0.62 days/SD), and surviving the first year (+ 3.26 days). Conclusion Early treatment in DLBCL is primarily driven by adverse disease characteristics. A residual association between longer DTI and improved survival persisted after IPI adjustment, suggesting DTI may be an independent prognostic factor in less aggressive disease.