Introduction: The epidemiology of isolated distal deep venous thrombosis (iDDVT) among cancer patients is not well described, particularly the incidence of recurrent venous thromboembolism (rVTE) and effect on mortality by cancer type.
Methods: The cumulative incidence (CI) of iDDVT was determined for patients with 13 common cancers between 2005 and 2017 using the California Cancer Registry linked to the California Patient Discharge and Emergency Department Utilization datasets. The CI of rVTE was calculated and association of incident cancer-associated thrombosis (CT) location with rVTE was determined using Cox proportional hazards regression models. The association of incident CT location with overall and cancer-specific mortality was determined using Cox models, stratified by cancer site, and adjusted for individual characteristics.
Results: Among 942,109 cancer patients, CT occurred in 62,003 (6.6%): of these, 6,841 (11.0%) were iDDVT. Compared with more proximal sites of CT, iDDVT was associated with similar risk for rVTE. IDDVT was associated with increased mortality across all cancer types when compared with patients without CT (hazard ratio: 1.56-4.60). The effect of iDDVT on mortality was similar to that of proximal DVT (pDVT) for most cancers except lung, colorectal, bladder, uterine, brain, and myeloma, where iDDVT was associated with a lesser association with mortality.
Conclusion: iDDVT represented 11% of CT. The risk of rVTE after iDDVT was similar to other sites of CT and rVTE occurred in more proximal locations after an incident iDDVT. IDDVT was associated with increased mortality and this effect was similar to that of pulmonary embolism or pDVT for most cancer types.
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