A Study of Dalteparin Prophylaxis in High-Risk Ambulatory Cancer Patients

Inclusion Criteria: * A histologic diagnosis of malignancy; * At planned initiation of a new systemic chemotherapy regimen (including patients starting on first chemotherapy or patients previously treated but starting on a new regimen); * A risk score for VTE ≥3 \[assign score of 2 for very high risk sites of cancer (stomach, pancreas), score of 1 for high risk site (lung, lymphoma, gynecologic, bladder, testicular) and score of 0 for all other sites\], hemoglobin \<10 g/dL or planned use of erythropoiesis stimulating agents, platelet count ≥350,000/mm3, total leukocyte count \> 11,000/mm3 or body mass index ≥ 35 kg/m2\]. Any counts meeting criteria drawn within 2 weeks prior to enrollment are considered acceptable. * Age 18 years or older * Provide written, informed consent. Exclusion Criteria: * Active bleeding or at high risk of serious bleeding complication in the opinion of the investigator * Diagnosis of primary brain tumor multiple myeloma, leukemia, or myelodysplastic syndrome * Planned stem cell transplant * Life expectancy \< 6 months * Known allergy to heparin or LMWH * Patient or caregiver incapable of daily self-injection * Acute or chronic renal insufficiency with creatinine clearance \< 30 mL/min * History of heparin-induced thrombocytopenia * Allergy to contrast agents * Pregnancy * Need for anticoagulant therapy * Platelet count \< 75,000/mm3