The goal of this clinical research study is to learn if dalteparin can lower the risk of VTE occurring in the legs and lungs. This will be tested in patients with pancreatic cancer who are going to receive chemotherapy. Some patients will receive dalteparin and some will receive no study drug.

The safety of dalteparin will also be studied.

Study Drug:

Dalteparin is designed to thin the blood and block blood from clotting. This may lower the risk of VTE.

Study Groups:

If you are found to be eligible to take part in this study, you will be randomly assigned (as in the flip of a coin) into 1 of 2 groups. There is an equal chance of being assigned to either group.

Group 1 will receive dalteparin.

Group 2 will not receive a study drug.

During this study, all study participants will be routinely checked for VTE by ultrasounds and CT scans.

You may also receive standard therapies for preventing VTE. This may include blood-thinning drugs while you are in the hospital, getting up and moving around at least 5 times per day, and/or wearing special stockings or boot-like devices designed to put pressure on the feet.

Genetic Research Testing:

Before starting your therapy (at baseline), blood (about 1 teaspoon) will be drawn and stored for genetic testing. Researchers want to use DNA (the genetic material in cells) to look for markers that may be related to having a high risk for developing blood clots. The samples will be processed and stored at MD Anderson. Once this study ends, the DNA will be tested further in Dr. Futreal's laboratory and/or may be shipped outside to Illumina Sequencing Services (San Diego, CA) for genetic research. The samples will be deidentified before shipping.

Before your samples are sent to the outside laboratory for banking, your name and any personal identifying information will be coded to protect your privacy. The outside researchers will not have access to the codes that link the samples to your identity.

Study Drug Administration:

If you are in Group 1, you will receive dalteparin by injection under your skin, once a day for 16 weeks. You and/or your caregiver will be taught how to perform injections.

Study Visits:

At every study visit, the following tests and procedures will be performed:

• You will have a physical exam, including measurement of your vital signs (blood pressure, heart rate, temperature and breathing rate).
• Your medical history will be recorded.

About every 2 weeks after chemotherapy starts until Week 16, blood (about 2 teaspoons) will be drawn for routine tests. This test may be repeated more often if the doctor decides it is needed.

Before each new cycle of chemotherapy during Weeks 1-16, blood (about 2 teaspoons) will be drawn for routine tests to check the function of your liver and kidneys.

At Weeks 8 and 16 (+/- 7 days), the following procedures will be performed:

• You will have an ultrasound of your legs to check for blood clots.
• If the doctor decides it is needed, you will have CT scans to check the status of the cancer. Researchers will also check your chest CT scans to look for blood clots in the lungs.

Length of Study Participation:

You may remain on study for up to 16 weeks. You will be taken off study early if blood clots occur or you experience intolerable side effects.

Follow-Up Phone Calls:

This study has a 3-year follow-up period. In Year 1, you will receive a follow-up phone call from the study staff in the first month and then at Months 3, 6, 9, and 12. In Years 2 and 3, you will be called every 6 months.

The study staff will ask about your overall health. In the first phone call, you will also be asked about any side effects that may have occurred.

This is an investigational study. Dalteparin is commercially available and FDA approved for use in preventing VTE that may occur for other reasons. Those reasons include abdominal surgery; surgery for a hip fracture, hip replacement, or knee replacement; and illnesses causing patients to be unable to move around.

Dalteparin is also commercially available and FDA approved to treat VTE in cancer patients. However, it is investigational to use dalteparin to prevent VTE in cancer patients receiving chemotherapy.

Up to 87 patients will take part in this study. All will be enrolled at MD Anderson.

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).

Follow-up/observation for all adverse events will be through Day 28 following the last dose of study drug or until resolution of any toxicity related to the study drug at the end of treatment.