Dalteparin for Primary Venous Thromboembolism (VTE) Prophylaxis in Pancreatic Cancer Patients

Inclusion Criteria: 1. Patients with the diagnosis of advanced stage (unresectable or metastatic) adenocarinoma of the pancreas. Patients with borderline resectable will also be eligible if they are starting chemotherapy and/or chemo/radiation therapy (RT) prior to attempting resection. 2. Patients must be planning to initiate systemic chemotherapy within 2 weeks. Chemotherapy that is being given concurrently with radiation is allowed. 3. Age \>/= 18 years old 4. Adequate renal function defined as a calculated creatinine clearance of \> 50 mL/min (as reported by the MDACC laboratory using MDRD method or using Cockroft and Gault formula). 5. Eastern Cooperative Oncology Group (ECOG) Performance Status 0-2. 6. Negative urine or serum pregnancy test in women with childbearing potential, within one week prior to initiation of treatment. 7. Patients must sign an Informed Consent. 8. Patient must agree to transfusion of blood products, when indicated. 9. Ability to administer subcutaneous injections of the study drug by the patient and/or care giver. Exclusion Criteria: 1. Patients with evidence of venous thrombosis on the initial lower extremity screening ultrasound or incidental VTE of other sites (e.g. PE, Abdominal/pelvic vein thrombosis, etc.). 2. Patients already taking prophylactic or full dose anticoagulation (eg. heparin, low-molecular weight heparin, fondaparinux, or coumadin). 3. Patients with currently active bleeding. 4. The presence of a condition with a high risk for bleeding, including but not limited to active peptic ulcer, recent neurosurgery, or cirrhosis with esophageal varices. 5. Patients with known brain metastases. 6. Patients with a known bleeding diathesis. 7. Patients with a platelet count \< 50,000. 8. Patients with known hypersensitivity to dalteparin. 9. Patients who regularly use medications known to increase the risk of bleeding such as \>/= 325 mg of aspirin daily, or daily clopidogrel, or daily non-steroidal antiinflammatory medications (eg., ibuprofen, naproxen).