Identification and Treatment of Clinically Silent Catheter-Related Deep Vein Thrombosis in Children With Cancer

This is a two-part study with an initial diagnosis component followed by a treatment
component. The number of subjects to be consented for the diagnosis component is 350, and 50
for the treatment portion (25 on the observation arm, and 25 for enoxaparin treatment).

Study Procedures:

Patients diagnosed with cancer at the Center for Cancer and Blood Disorders will have a
catheter inserted for cancer related treatment. After insertion, eligible patients who
provide consent will be enrolled in the diagnosis component of the study. The principal
investigator and research team will monitor for catheter complications (occlusion and
bacteremia/fungemia). After two complications, participants will be screened for occult
central venous catheter (CVC)-related DVT by contrast venography, ultrasonography, or
magnetic resonance venography. If DVT is not diagnosed, participant will go off the study. If
DVT is diagnosed, participant will be asked to consent to enroll in the treatment study.
After enrollment, participant is randomized between the two arms of observation and
enoxaparin treatment. After 6 weeks, patients will have another image; this represents the
end of treatment period. After the follow-up imaging, patients will be monitored for 10 weeks
to obtain primary outcomes. Once a primary outcome (progression to symptomatic DVT or
pulmonary embolism (PE), blood stream infection or catheter removal) is achieved the
participants can be treated with anticoagulation again if necessary, but primary oncologist
will determine treatment.

Analysis:

The hypothesis is that the enoxaparin treatment group will have a median adverse catheter
event free survival time of 12 weeks versus 4 weeks for the control group with a hazard
ration of 0.4. A total sample size of 50 (25 in each arm) will detect such a difference with
90% power at an α=0.05. If there is a drop out rate of 10% in each arm, a difference can
still be detected with 80% power.

Approximately 200 to 250 patients are diagnosed with cancer each year at Children's Medical
Center Dallas, and based on prior institutional experience, two-thirds will have catheters
inserted to facilitate chemotherapy. However, one-quarter of these patients have brain tumors
and are not eligible due to the potential increased risk of intracranial hemorrhage with
anticoagulation. There will be 100 patients each year who are at risk for CVC-related DVT.
Based on previous studies, up to 50% of patients should develop occult DVT; however, only 35%
of patients will likely be screened with radiographic imaging. Approximately 17 patients a
year enrolled in the diagnosis study may be diagnosed with DVT and eligible for
randomization. Therefore, total enrollment will be completed in approximately 3 years with an
additional 4 months necessary to complete the follow-up period.

Inclusion Criteria:

1. Diagnosis of cancer

2. Age ≤ 18 years

3. First tunneled central venous catheter (implanted port or external) inserted in the
upper venous system (subclavian, brachiocephalic, or jugular vein) within the previous
2 weeks

4. Catheter expected to be in place for duration of chemotherapy (≥ 3 months)

5. History of no more than one catheter complication (occlusion or infection)

Exclusion Criteria:

1. Prior history of DVT

2. Currently receiving an anticoagulant or anti-platelet agents on a daily basis

3. Diagnosis of high grade malignant brain tumor or metastasis to the brain

4. Clinical signs/symptoms of DVT

5. Clinical signs/symptoms of Pulmonary embolism

6. Renal failure

7. Recent major hemorrhage