OBJECTIVES: Patients with cancer are at increased risk of venous thromboembolism (VTE) and the risk is further elevated after a primary VTE.  To reduce the risk of recurrent VTE, prolonged prophylaxis with VKA is available.  However in a large randomized trial (CLOT; Lee et al, 2003), extended duration dalteparin reduced the relative risk of recurrent VTE by 52% compared to VKA (P=0.002). A recent subgroup analysis of patients with moderate to severe renal impairment at randomization also revealed lower absolute VTE rates with dalteparin (3% vs. 17%; p = 0.011). To measure the current economic value of secondary prophylaxis with dalteparin in patients with cancer and renal impairment, a patient level cost utility analysis was conducted. METHODS: Resource use data captured during the CLOT trial were linked to current Canadian unit cost estimates ($Can2015).  Univariate and multivariate regression analyses were conducted to compare the total direct cost of therapy between patient groups.  Health state utilities were then measured using the Time Trade-Off technique in 24 randomly selected members of the general Canadian public. RESULTS: When the costs were quantified for the entire CLOT trial population (n=676), patients in the dalteparin group had higher mean overall costs than the VKA group ($Can 5,771 vs. $Can 2,569; p < 0.001). However, the utility assessment revealed that 21 of 24 respondents (88%) selected dalteparin over VKA, with an associated gain of 0.14 (95%CI: 0.10 to 0.18) QALYs.  This translated to a cost per QALY gained of $Can 23,100 (95%CI: $19,200 to $25,800). The analysis in patients with moderate to severe renal impairment suggested even better economic value with the cost per QALY gained being less than $Can14,000. CONCLUSIONS: Extended duration dalteparin is an economically sound alternative to VKA for the prevention of recurrent VTE in patients with cancer, and especially in those with renal impairment.