Diffuse large B-cell lymphoma (DLBCL) is an aggressive though potentially curable lymphoid malignancy requiring timely treatment initiation. We investigated the impact of individual socioeconomic status and home area-level (ecological) factors on the diagnosis-to-treatment interval (DTI) in DLBCL patients, focusing on extreme delays in a French real-world cohort (REALYSA). We analyzed patients with newly diagnosed DLBCL in the multicentric prospective cohort. DTI was defined as a duration in days between diagnosis confirmation and first-line therapy. Short and long DTIs (10th percentiles) were compared to intermediate DTI using multinomial models to identify factors associated with extreme DTIs. Socio-demographic data (including sex, education, employment, marital status, social support (SSQ6-score)…) and ecological characteristics (French deprivation index, local accessibility to general practitioners) were considered. Among 889 newly diagnosed DLBCL patients (median age 66 years, 49 % with aaIPI ≥1, 35 % with B-symptoms, 33 % with bulky disease), median DTI was 25 days (interquartile range: 15-39 days). The 10th- and 90th-percentile for extreme DTIs were  50 days respectively. In multivariable analysis, factors associated with short DTI included aaIPI (OR=3.03, CI95 %[1.44-6.41]), bulky disease (OR=3.06, CI95 %[1.68-5.58]), and B symptoms (OR=2.35, CI95 %[1.30-4.25]) - indicating expedited treatment for aggressive presentations. Conversely, factors associated with long DTI included older age (OR>80 y = 3.31, CI95 %[1.39-7.89]), being a blue-collar worker or farmer (OR=2.36, CI95 %[1.18-4.73]), or changing type of treatment facility between biopsy and initial treatment. In this large real-world cohort of newly diagnosed DLBCL patients, age, occupational status, and patients' pathway were linked to very long delays to treatment. Interventions to streamline DTIs, especially for older and/or blue-collar or farmer patients, and for those changing facility of treatment, are warranted to improve quality of care.Read less <