Submitted October 5, 2007
Accepted January 19, 2008
Development and validation of a predictive model for chemotherapy-associated thrombosis
Alok A. Khorana*, Nicole M. Kuderer, Eva Culakova, Gary H Lyman, and Charles W. Francis
Department of Medicine, James P. Wilmot Cancer Center, University of Rochester, Rochester, NY, United States
Duke University Medical Center and the Duke Comprehensive Cancer Center, Durham, NC, United States
* Corresponding author; email: alok_khorana{at}urmc.rochester.edu.
Risk of venous thromboembolism (VTE) is elevated in cancer, but individual risk factors cannot identify a sufficiently high-risk group of outpatients for thromboprophylaxis. We developed a simple model for predicting chemotherapy-associated VTE using baseline clinical and laboratory variables. The association of VTE with multiple variables was characterized in a derivation cohort of 2,701 cancer outpatients from a prospective observational study. A risk model was derived and validated in an independent cohort of 1,365 patients from the same study. Five predictive variables were identified in a stage-adjusted multivariate model: site of cancer (2 points for very high risk site, 1 point for high risk site), platelet count 
350,000/mm3, hemoglobin <10g/dL and/or use of erythropoiesis-stimulating agents, leukocyte count >11,000/mm3 and body mass index 35 kg/m2 (1 point each). Rates of VTE in the derivation and validation cohorts, respectively, were 0.8% and 0.3% in low-risk (score=0), 1.8% and 2% in intermediate-risk (score=1-2), and 7.1% and 6.7% in high-risk category (score3) over a median of 2.5 months (C-statistic= 0.7 for both cohorts). Thus, this model can identify cancer patients with a nearly 7% short-term risk of symptomatic VTE and may be used to select cancer outpatients for studies of thromboprophylaxis.
