Original Article © JNCCN—Journal of the National Comprehensive Cancer Network | Volume 12 Number 11 | November 2014 1557 Abstract Venous thromboembolism (VTE) is a frequent clinical complication of cancer and its treatment. Although much of the epidemiologic data regarding this complication have been based on symptom- atic events, the use of multidetector row CT scanner technology has led to increased identifcation of VTE on scans ordered pri- marily for staging or restaging of malignancy. These incidentally discovered VTEs are variously referred to in the literature as inci- dental, asymptomatic, unexpected, or unsuspected VTE. A recent guidance paper by the Hemostasis and Malignancy Subcommittee of the International Society on Thrombosis and Haemostasis pro- vided recommendations regarding this terminology (now termed incidental) and reporting of incidental VTE for clinical trials. A growing number of retrospective and case-controlled reports have described the prevalence, prognostic implications, and treatment options for these incidentally discovered VTE events, and have re- ported similar clinical outcomes for patients with incidental and symptomatic VTE. Because most reported patients with incidental VTE have been treated in a manner similar to those with symp- tomatic events, the present recommendations, except in rare cir- cumstances, support the use of standard anticoagulation in the management of incidental deep vein thrombosis and pulmonary embolism. (J Natl Compr Canc Netw 2014;12:1557–1560) The development of VTE in patients with cancer is strongly infuenced by tumor type, stage, and treatment modality. 4 Thrombotic events contribute signifcantly to morbidity and mortality among patients with cancer, and VTE is the fourth leading cause of death among ambulatory patients. 7 Available guidelines all recom- mend use of low-molecular-weight heparins (LMWHs) as opposed to warfarin among patients with VTE. 8–11 However, anticoagulation for primary prophylaxis of VTE among patients with cancer is only recommended for those who are hospitalized, those who have multiple myeloma and are receiving lenalidomide and dexa- methasone, and most patients postoperatively. 8–11 Most available treatment guidelines using published clinical trial data do not recommend prophylactic anticoagula- tion for ambulatory patients receiving chemotherapy; however, one set of international guidelines suggests that primary pharmacologic prophylaxis “may be con- sidered” for patients with a low bleeding risk who are receiving chemotherapy for locally advanced or meta- static pancreatic (strong recommendation) or lung can- cer (weak recommendation). 10 Current knowledge of the incidence, demographics, and outcome of cancer-related VTE is generally based on reported symptomatic events. However, the unsus- pected fnding of PE, DVT, or intra-abdominal throm- bosis in the splanchnic or visceral veins is not uncom- mon on routine staging CT scans of chest, abdomen, and pelvis. 12 Studies addressing the clinical signifcance of these fndings have been retrospective and are reviewed herein. Unfortunately, clinical trials involving patients undergoing cancer treatments have not consistently distinguished between incidental and symptomatic or suspected VTE, and therefore limited prospective data are available on patients with incidental VTE. Thus no high-grade recommendations can be made regarding their treatment. This problem was addressed in a set of From Jane Ann Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California-Keck School of Medicine, Los Angeles, California. Submitted December 22, 2013; accepted for publication July 8, 2014. The authors have disclosed that they have no fnancial interests, arrangements, affliations, or commercial interests with the manufacturers of any products discussed in this article or their competitors. Correspondence: Casey L. O’Connell, MD, Norris Comprehensive Cancer Center, 1441 Eastlake Avenue, Los Angeles, CA 90089. E-mail: coconnel@usc.edu Approach to the Management of Incidental Venous Thromboembolic Events in Patients With Cancer Casey L. O’Connell, MD, and Howard A. Liebman, MD Venous thromboembolic (VTE), inclusive of deep vein thrombosis (DVT) and pulmonary embolism (PE), is a common complication of cancer and its treatment. Pa- tients with cancer have a 4- to 7-fold increased risk of VTE and a 5- to 7-fold increased risk of bleeding on an- ticoagulation compared with patients without cancer. 1–6