Evaluation of the Duration of Therapy for Thrombosis in Children
Prospective Multi-Center Evaluation of the Duration of Therapy for Thrombosis in Children
The Kids-DOTT trial is a randomized controlled clinical trial whose primary objective is to
evaluate non-inferiority of shortened-duration (6 weeks) versus conventional-duration (3
months) anticoagulation in children with first-episode acute venous thrombosis. The first
stage of the trial has consisted of a pilot/feasibility component, which then continues as
the definitively-powered trial.
Children (birth to 21 years of age, inclusive) with first-episode venous thrombosis in
association with a reversible clinical trigger (key exclusions: history of cancer; severe
thrombophilia state disclosed) are enrolled and prescribed anticoagulation according to the
clinical standard of care and American College of Physicians (Chest journal) 2012
recommendations. At the 6 week (post-diagnosis) follow-up visit, repeat radiologic imaging
is performed to determine residual thrombus burden and its degree of occlusion. In addition,
those subjects with antiphospholipid antibodies (APA) disclosed at enrollment will undergo
repeat APA testing.
Patients with residual occlusive thrombosis or persistent APA are excluded from
randomization, and followed on parallel cohort arms (observational), with conventional
anticoagulation durations. All other patients are randomized to a total anticoagulant
duration of 6 weeks versus 3 months. Children are followed for primary efficacy endpoints of
symptomatic recurrent venous thromboembolism (VTE) and primary safety endpoints of
clinically-relevant bleeding (major plus clinically-relevant non-major, as per International
Society of Thrombosis and Haemostasis Scientific and Standardization Committee [Journal of
Thrombosis & Haemostasis] 2012 definitions/recommendations).
Children are followed through 2 years (with primary endpoint at 1 year). Those with deep
venous thromboses affecting venous return from the limbs also undergo standardized
post-thrombotic syndrome (PTS) outcome assessment using the Manco-Johnson pediatric PTS
The non-inferiority analysis uses a bivariate endpoint approach, modeling the inherent
clinical trade-off between the risks of recurrent VTE and bleeding. The trial will enroll
750 children across 40 participating centers, and allows for a 25% rate of exclusion from
the per-protocol population due to randomization non-eligibility (i.e. parallel cohort),
withdrawal/loss to follow-up, and protocol non-adherence.
A sub-study, completed in late 2013, used investigational dalteparin in lieu of formulary
low molecular weight heparin (typically enoxaparin) in those children who were clinically
prescribed a low molecular weight heparin for sub-acute anticoagulation. The goal of this
sub-study was to report dose-finding and outcomes data in children treated with dalteparin
for VTE. Outcomes in these patients were qualitatively compared with those of patients who
received enoxaparin, warfarin, or other anticoagulants for sub-acute anticoagulation. This
portion of the study was an industry-sponsored investigator-initiated sub-study with an
investigator-held IND. Since the closure of the sub-study, the overall Kids-DOTT study is no
longer conducted under an Investigational New Drug (IND) application.
Principal aims and hypotheses:
Specific Aim #1: To evaluate the efficacy and safety of shortened-duration (6 weeks total)
versus conventional-duration (3 months total) anticoagulation for first-episode, provoked,
acute venous thrombosis among children in whom thrombus resolution/non-occlusion (i.e.
established blood flow) is evident after the initial 6 weeks of anticoagulant therapy
Hypothesis: Among children with first-episode, provoked, acute venous thrombosis in whom
thrombosis is resolved or non-occlusive at six weeks follow-up, a shortened duration of
anticoagulation (total six weeks; i.e. no further therapy) is non-inferior in efficacy to
the conventional duration (total three months) of anticoagulation with respect to the risk
of symptomatic recurrent VTE at 1 year, and is superior in safety with respect to the risk
of clinically-relevant bleeding.(The hypothesis will also be tested in secondary analysis at
2 years, using the same efficacy and safety outcomes as for the 1 year primary analysis.)
Specific Aim #2: To determine whether outcomes of first-episode, provoked, acute venous
thrombosis (specifically, with respect to recurrent VTE and PTS) among children treated with
conventional-duration (3 months total) anticoagulation differ between those with and without
thrombus resolution/non-occlusion at 6 weeks.
Hypothesis: Among children with first-episode, provoked, acute venous thrombosis treated
with conventional-duration (3 months total) anticoagulation, the cumulative incidences of
recurrent VTE and PTS are significantly lower among those in whom thrombus
resolution/non-occlusion was, versus was not, evident after the initial 6 weeks of
Specific Aim #3: To evaluate whether the effect of treatment duration on the risks of
symptomatic recurrent VTE and clinically-relevant bleeding in children with first-episode,
provoked, acute venous thrombosis differs between subgroups defined by type of sub-acute
anticoagulant therapy in real-world clinical use (all prescribed clinically, with the
exception of investigational dalteparin, which was prescribed under an investigator-held IND
through December 2013).
Hypothesis: Among children with first-episode, provoked, acute venous thrombosis, the effect
of treatment duration on the risks of symptomatic recurrent VTE and clinically-relevant
bleeding does not differ among subgroups treated sub-acutely with enoxaparin, dalteparin,
fondaparinux, warfarin, oral direct factor Xa inhibitors, or oral direct thrombin inhibitors
Specific Aim #4: To establish a clinical trial-derived plasma and nucleic acids
biorepository for future proteomic, genomic, and metabolomic investigations of predictors
and modulators of VTE outcomes in children.
Exploratory Aim: To investigate whether duration of anticoagulation (over the range of 3
months to indefinite duration, as determined clinically in routine care) on influences the
risks of symptomatic recurrent VTE and clinically-relevant bleeding among children with
first-episode, provoked, acute venous thrombosis in whom persistent antiphospholipid
antibody positivity is evident at 6 and 12 weeks post-diagnosis.
Exploratory Hypothesis: Among children with first-episode, provoked, acute venous thrombosis
in whom persistent antiphospholipid antibody positivity is evident at 6 and 12 weeks
post-diagnosis, duration of anticoagulant therapy is not a predictor of symptomatic
recurrent VTE but is directly related to the risk of clinically-relevant bleeding..
1. Children (birth to <21 years of age) with radiologically-confirmed acute venous
thrombosis in the past 30 days
2. In the opinion of the investigator, the venous thrombosis was a provoked (i.e.,
non-spontaneous) event (e.g.: hospitalization; Central venous catheterization;
infection; dehydration; surgery; trauma; immobility; use of estrogen-containing oral
contraceptive pills; flare of autoimmune/rheumatologic condition).
1. prior episode of VTE;
2. presence or history of cancer;
3. systemic lupus erythematosus
4. known pulmonary embolism (PE), except when limited to peripheral cavitary lesions
representing septic emboli; (N.B. imaging for PE should only have been based upon
clinical signs/symptoms, and is not a study procedure or requirement)
5. Use of, or intent to use, thrombolytic therapy
6. Patients with congenital cardiac disease involving a single or hypoplastic ventricle
or otherwise requiring an intracardiac shunt
7. Moderate/severe anticoagulant deficiency as defined by any one of the following:
1. protein C <20 IU/dL if patient is ≥3 months of age, or protein C below lower
limit of detection if patient is <3 months of age;
2. antithrombin <30 IU/dL if patient is ≥3 months of age, or antithrombin below
lower limit of detection if patient is <3 months of age;
3. protein S (free antigen or activity) <20 IU/dL.