Currently, the effect of the diagnosis-to-treatment interval (DTI) on survival in patients with mantle cell lymphoma (MCL) has not been extensively examined. Researchers aimed to determine the feasibility of active surveillance compared with delayed treatment among patients with MCL and to examine the potential effect of DTI on survival of those in need of treatment. The study team used the National Cancer Database to identify adult patients diagnosed with MCL from 2004-2017. They categorized patients into an early treatment (treatment initiated within 3 months; ET) group, delayed treatment (treatment started after 3 months; DT) group, and surveillance (a watch-and-wait approach with treatment; SUR) group. Clinical characteristics at baseline were compared between the three groups. Among 27,867 patients newly diagnosed with MCL, 995 patients (4%) were in the SUR group, 21,425 patients (77%) were in the ET group, and 1,052 patients (4%) were in the DT group. Median follow-up was 38.2 months for the full cohort. Results showed a significant difference in overall survival (OS) across groups, with a median OS of 107 months (95% CI, 92.7-122.7) in the SUR group, 84.9 months (95% CI, 74.2-95.7) in the DT group, and 68.9 months (95% CI, 66.8-70.9) in the ET group (P=0.001). Among patients in the DT group, a shorter DTI was associated with a trend for inferior OS (median OS, 82 months; 95% CI, 73.2-90.8) for those with a DTI of 3-12 months and not reached for those with a DTI of more than 12 months (P=0.095). In the ET group, a shorter DTI was tied to shorter OS (median OS, 53 months; 95% CI, 50.2-55.8) for patients with a DTI of 15 days or less, 71.7 months (95% CI, 67.1-76.3) for those with a DTI of 16-30 days, and 87.1 months (95% CI, 82.8-91.4) for patients with a DTI of 31-90 days (P<0.001). The results confirm the feasibility of delayed therapy in certain patients with MCL, according to the researchers.