Treatment of Blood Clots in Children With Cancer

Inclusion Criteria:

1. Have an active malignancy (defined as a diagnosis of cancer, other than basal cell or squamous cell carcinoma of the skin).
2. Have been objectively diagnosed with thrombosis involving a deep vein (documented using compression ultrasound with Doppler [CUD], computed tomography with/without venography [CT/CTV], magnetic resonance imaging with/without venography [MRI/MRV], conventional venography [CV]) or pulmonary artery (ventilation-perfusion scan [V/Q], spiral CT angiography [SCTA], or conventional pulmonary angiogram [CPA]) within the 96 hours of enrollment, and require anticoagulation therapy.
3. Are judged clinically to require anticoagulation therapy.
4. Are in the age range of ≥ 36 weeks gestation and < 19 years.
5. Have given signed informed consent (and assent, as appropriate) to participate prior to enrollment.

Exclusion Criteria:

1. Weight ≤ 3.0 kg or > 100 kg.
2. Platelet count ≤ 50,000/mm3 (despite appropriate medical measures to support platelet count).
3. Received oral anticoagulant therapy within 72 hours of enrollment.
4. History of administration of therapeutic doses of LMWH or unfractionated heparin for a treat period of > 96 hours (or > 8 doses of LMWH) for the qualifying VTE.
5. Received unfractionated heparin within 3 hours, or LMWH within 15 hours of the first dose of dalteparin.
6. Acute VTE intervention which includes thrombolytic therapy.
7. Major bleeding at the time of screening or enrollment or an unacceptably high risk of bleeding at the discretion of the investigator.
8. aPTT > 5 seconds above ULN, and that corrects to within normal limits upon 1:1 mixing with normal plasma.
9. PT > 2 seconds above ULN, and that corrects to within normal limits upon 1:1 mixing with normal plasma.
10. Calculated creatinine clearance (Schwartz method) < 60 mL/min in subjects > 1 month of age.
11. Uncontrolled hypertension characterized by a sustained systolic pressure or diastolic pressure > 99th percentile of age- and height-related norms.
12. History of heparin-induced thrombocytopenia (HIT).
13. Any condition in which the investigator feels the subject is unsafe or inappropriate for study participation.
14. Insufficient subcutaneous tissue to facilitate subcutaneous drug administration.
15. Presently or previously received (within 30 days of enrollment) study drug for which an IND/IDE is in effect, with the exception of erwinia asparaginase.
16. Pregnant or lactating female.
17. Refusal by sexually active post-menarche female subjects to adhere to an acceptable form of contraception.
18. Unable or unwilling to comply with scheduled follow-up visits.
19. Inability to obtain written informed consent from subject or parent or legally acceptable representative for the subject.