The primary hypothesis of this study is that occult catheter-related DVT in children with
cancer is common and directly contributes to development of serious catheter complications,
specifically bacteremia/fungemia and/or recurrent occlusion of the catheter tip.
Accordingly, anticoagulant treatment of clinically silent (occult) DVT will reduce rates of
catheter-related infection and occlusion, delays in therapy and need for catheter
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).
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
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/ 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.
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.
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)
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