Clinical outcomes of isolated distal deep vein thrombosis versus proximal venous thromboembolism in cancer patients: The Cleveland Clinic experience

Background Previous studies suggest isolated distal deep vein thrombosis (IDDVT) has a self-limited clinical course. However, these studies excluded cancer patients, who remain a high-risk population. In addition, studies to evaluate the long-term clinical outcomes of IDDVT in cancer patients have been limited. Here, we report outcomes from our experience in treating cancer-associated IDDVT versus proximal venous thromboembolism (VTE). Methods We prospectively evaluated a cohort of patients referred to our cancer-associated thrombosis clinic from August 2014 through May 2018. We compared clinical characteristics, anticoagulation prescription, VTE recurrence, overall survival, major bleeding, and subsequent hospital admission between cancer patients with IDDVT and proximal VTE. A propensity score matching method was used to reduce bias from confounding variables. Results Of 1100 patients referred to the clinic, 124 IDDVT and 178 proximal VTE events were analyzed. After propensity score matching, 96 patients were included in each cohort. There was no difference in the rate of recurrent VTE between cancer patients with proximal VTE vs IDDVT, with or without matching (matched: hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.31-1.92; P = .58). There was no difference in overall survival between cancer patients with proximal VTE vs. IDDVT with or without matching (matched: HR, 1.18; 95% CI, 0.77-1.82; P = .45). Furthermore, subsequent hospital admissions and major bleeding events were similar between patients with proximal VTE events versus IDDVT. Conclusions Cancer patients with IDDVT have similar outcomes as their proximal counterparts, including rate of recurrence and overall survival. These findings suggest treatment of cancer-associated IDDVT should mirror treatment of proximal events.