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Essentials Isolated distal deep vein thrombosis (IDDVT) is frequently associated with cancer. No study has specifically evaluated the long-term clinical course of cancer-associated IDDVT. Patients with cancer-associated IDDVT are at very high risk of symptomatic recurrence and death. We observed low rates of major bleeding during anticoagulation. SummaryBackground Although isolated distal deep vein thrombosis (IDDVT) is frequently associated with cancer, no study has specifically evaluated the long-term clinical course of IDDVT in this setting. Aim To provide data on the rate of recurrent venous thromboembolism (VTE), major bleeding events and death in IDDVT patients with active cancer. Patients and Methods Consecutive patients with active cancer and an objective IDDVT diagnosis (January 2011 to September 2014) were included from our files. We collected information on baseline characteristics, IDDVT location and extension, VTE risk factors, and type and duration of anticoagulant treatment. Results A total of 308 patients (mean age 66.2 [standard deviation (SD), 13.2 years]; 57.1% female) with symptomatic IDDVT and a solid (n = 261) or hematologic (n = 47) cancer were included at 13 centers. Cancer was metastatic in 148 (48.1%) patients. All but three (99.0%) patients received anticoagulant therapy, which consisted of low-molecular-weight heparin in 288 (93.5%) patients. Vitamin K antagonists were used for the long-term treatment in 46 (14.9%) patients, whereas all others continued the initial parenteral agent for a mean treatment duration of 4.2 months (SD, 4.6 months). During a total follow-up of 355.8 patient-years (mean, 13.9 months), there were 47 recurrent objectively diagnosed VTEs for an incidence rate of 13.2 events per 100 patient-years. During anticoagulant treatment, the annual incidence of major bleeding was 2.0 per 100 patient-years. Conclusions Cancer patients with IDDVT have a high risk of VTE recurrence. Additional studies are warranted to investigate the optimal intensity and duration of anticoagulant treatment for these patients.

Introduction Isolated distal deep vein thrombosis (IDDVT) accounts for one-fourth to one-half of all deep vein thrombosis (DVT) of the leg. Patients with IDDVT are frequently treated for a shorter period of time compared to patients with proximal DVT and/or pulmonary embolism (PE) due to a perceived lower risk of recurrence. About 10-20% of patients with venous thromboembolic events (VTEs) have concomitant cancer. Guidelines recommend long-term anticoagulant treatment in this group of patients due to their high risk of VTE recurrence. Unfortunately, information on the clinical history of IDDVT patients is limited and, to date, no study has evaluated the long-term risk of VTE recurrence in IDDVT patients with cancer. Aim To provide information on the clinical history of IDDVT patients with active cancer. Materials and Methods A multicenter, cohort study including active-cancer patients with an objective diagnosis of IDDVT (between January 2011 and September 2014) was conducted. Information on baseline characteristics, thrombosis location and extension, concomitant risk factors, type and duration of treatment was collected. All patients were followed for a minimum of 12 months and up to 24 months. During follow-up, VTE recurrence, major bleeding episodes and death were registered. Potential risk factors for VTE recurrence were evaluated. Results 308 patients (mean age 66.2 ± 13.2 years, female 57.1%) in 13 centers were included, Table 1; 261 patients had solid cancer and 47 patients hematologic cancer. At the time of IDDVT diagnosis, the disease was metastatic in 148 patients (48.1%); 99.0% of patients received anticoagulant treatment: 288 patients (93.5%) were initially treated with low molecular weight heparin, 15 with fondaparinux (5.2%) and 1 with unfractionated heparin; vitamin K antagonists were used in 46 patients (14.9%) only. Total follow-up was 389 patient-years, mean follow-up 15.2 months. Mean duration of treatment was 4.2 months. During the study period there were 47 episodes of VTE recurrence (36 proximal DVT or PE) for a incidence rate of 13.2 events per 100 patient-years; 7 patients had major bleeding (2.3%) and 137 died (44.5%). At multivariate analysis, previous VTE was associated with an increased risk of recurrence (OR 2.10; 95% 1.06, 4.14), whereas patients with gastrointestinal cancer had a lower risk of recurrence (OR 0.26; 95% CI 0.08, 0.86). Table 1 . Baseline characteristics of the population Number of patients 308 Age (years), mean ± SD 66.2 ± 13.2 Women 176 (57.1%) Men 132 (42.9%) Body-mass index > 30 Kg/m 2 25 (8.1%) Concomitant risk factors for VTE Recent surgery or trauma 79 (25.6%) In-patients/immobilization 45 (14.6%) Prolonged bed rest 47 (15.3%) Local or systemic infections 19 (6.2%) Qualifying distal venous thrombosis Axial calf veins 135 (43.8%) Muscolar calf veins 149 (48.4%) Medial gastrocnemius veins 113 (36.7%) Lateral gastrocnemius veins 45 (14.6%) Soleal veins 73 (23.7%) Bilateral venous thrombosis 22 (7.1%) More than one vein involved 127 (41.2%) Previous history of VTE 45 (14.6%) Family history of VTE 16 (5.2%) Primary cancer site Breast 54 (17.5%) Gastrointestinal 51 (16.6%) Pancreas 18 (5.8%) Hepatic 9 (2.9%) Lung 44 (14.3%) Hematologic 47 (15.3%) Prostate 17 (5.5%) Brain 15 (4.9%) Other 53 (17.2%) Metastases 148 (48.1%) Cancer therapy Systemic chemotherapy 174 (56.5%) Radiotherapy 20 (6.5%) Hormonal therapy 36 (11.7%) Anticoagulant therapy 305 (99%) Low-molecular-weight heparin 288 (93.5%) Fondaparinux 16 (5.2%) Unfractionated heparin 1 (0.3%) Heparin-Vitamin K antagonists 46 (14.9%) VTE = venous thromboembolism. Conclusions Cancer patients with IDDVT have a high risk of VTE recurrence. Other studies are warranted to address the adequate management of these patients.