National Epidemiology of Venous Thromboembolism in Patients with Malignancy in United States from 1993 to 2012

Background: Venous thromboembolism (VTE) is an important cause of morbidity and mortality in cancer patients. National burden of inpatient VTE in patients with cancer is not known.

Methods: We used the National Inpatient Sample (NIS), one of the largest publicly-available inpatient dataset in United States (U.S.), which represents a 20% stratified random sample of discharges from all hospitals, excluding rehabilitation and long-term acute care hospitals. The NIS is drawn from all States participating in Healthcare Cost and Utilization Project, representing more than 95 percent of the U.S. population. Discharge weights are used to generate national estimates. Patients with cancer were identified using ICD9 codes published by NIS. VTE was defined by ICD9 codes 451 - 453 and 415.1. Annual rates of inpatient VTE were calculated from 1993 to 2012 by cancer type. Multivariate odds of inpatient VTE was determined by logistic regression controlling for confounders (Age, sex, Charlson co-morbidity index, metastatic disease, chemotherapy, blood transfusion, major therapeutic operating room procedure, primary hypercoaguable state, disseminated intravascular coagulation, heparin induced thrombocytopenia, anti-phospholipid antibody syndrome, obesity and calendar year). Incidence of VTE in population was calculated by using prevalence published by CDC as our denominator from 2001 to 2011.

Results: 69.1 million hospitalized patients (weighted number) with cancer were identified, and 2.6 million had VTE (3.8%). Rates of inpatient VTE increased for all cancers from 1993 and 2012 (Table 1). The cancers with sharpest rise in inpatient VTE rate were liver and bile duct (LBD), pancreas and esophagus (Slope: 0.33, 0.31 and 0.22 percent per year). The cancers with highest odds of inpatient VTE were pancreas, brain and LBD (OR: 2.49, 2.41, and 2.23). The cancers with highest incidence of VTE in population were pancreas, LBD and esophagus (182, 116, and 67 per 1000 person-year). The cancers with lowest odds of inpatient VTE were thyroid, head and neck and prostate (OR: 0.5, 0.67, and 0.87). The cancers with lowest incidence of VTE in population were thyroid, melanoma and testis (2, 2.5, and 4.8 per 1000 person-year).

Conclusions: Our study provides national estimates of VTE, which are increasing across all cancer types. Certain cancers have higher incidence and odds of VTE as compared to others. Identification of these trends provides valuable information for the use of prophylaxis in cancers with high risk of VTE.