Purpose: Cancer is associated with thrombosis, but the frequency of thromboembolism in hospitalized cancer patients receiving current chemotherapy regimens is not known. We investigated venous and arterial thromboembolism and associated outcomes in hospitalized cancer patients actively receiving therapy, as identified by neutropenia.

Methods: We conducted a retrospective cohort study using the discharge database of the University HealthSystem Consortium. This included 66,106 adult neutropenic cancer patients with 88,074 hospitalizations between 1995 and 2002 at 115 medical centers in the United States.

Results: Thromboembolism was reported in 5,272 patients (8%), with 5.4% patients developing venous thromboembolism and 1.5% developing arterial thromboembolism during the first hospitalization. Patients with lymphoma and leukemia accounted for one third of venous and nearly one half of arterial events. Clinical variables most frequently associated with thromboembolism were age > or = 65 years; primary site of cancer, including lung, GI, gynecologic, and brain; and comorbidities, including infection, pulmonary and renal disease, and obesity. In-hospital mortality was significantly greater in patients with venous (odds ratio [OR] = 2.01; 95% CI, 1.83 to 2.22) or arterial thromboembolism (OR = 5.04; 95% CI, 4.38 to 5.79). From 1995 to 2002, there was a 36% increase in venous events and a 124% increase in arterial events (P < .0001 for trend).

Conclusion: Thromboembolism is frequent in hospitalized neutropenic cancer patients, including in perceived low-risk subgroups such as patients with hematologic malignancies and nonmetastatic disease, and seems to be increasing. Thromboembolism is associated with increased in-hospital mortality. Increased efforts at thromboprophylaxis are warranted.