BackgroundThe ONCO DVT study revealed superiority of 12-month relative to 3-month edoxaban treatment for the thrombotic risk in cancer-associated isolated distal deep vein thrombosis (DVT). However, it is unknown whether the superiority could be common in different modified Ottawa score subgroups. MethodsIn this post-hoc subgroup analysis of the ONCO DVT study, we stratified 601 patients into the low (≤-1, N=126), intermediate (0, N=323), and high (≥1, N=152) modified Ottawa score subgroups, and compared clinical outcomes between the 12-month and 3-month edoxaban treatment groups. ResultsThe cumulative incidence of symptomatic recurrent venous thromboembolism (VTE) or VTE-related death was not different between the 12-month and 3-month edoxaban treatment groups in the low score subgroup (0.0% vs. 2.2%), whereas it was lower in the 12-month than in the 3-month edoxaban treatment group in the intermediate (0.8% vs. 7.6%) and high (3.1% vs. 15.6%) score subgroups. There were no significant differences in the cumulative incidences of the major bleeding between the 12-month and 3-month edoxaban treatment groups in the low (10.1% vs. 7.6%), intermediate (8.8% vs. 5.0%), and high (13.9% vs. 12.6%) score subgroups. ConclusionsA 12-month compared to 3-month edoxaban treatment showed a lower risk of thrombotic events in patients with cancer-associated isolated distal DVT in the intermediate and high modified Ottawa score subgroups, but not in the low score subgroup, suggesting a limited benefit of extended anticoagulation therapy beyond 3 months in patients with low modified Ottawa score.