Impact of anatomical location of lower limb venous thrombus on the risk of subsequent cancer.

After a proximal deep-vein thrombosis (P-DVT), the risk of diagnosis of a previously unsuspected cancer is high. Isolated distal DVT (iD-DVT; i.e. infra-popliteal DVT without pulmonary embolism [PE]) and isolated superficial-vein thrombosis (iSVT; i.e. without concomitant DVT and PE) are at least as frequent as P-DVT but their association with subsequent cancer is uncertain. We exploited data from the OPTIMEV prospective, observational, multicentre study to i) compare the risk of subsequent cancer three years after a first objectively confirmed iSVT, iD-DVT and iP-DVT in patients without a prior history of cancer or of venous thromboembolism, ii) assess predictors of subsequent cancer in cases of iD-DVT. The overall cumulative rates of cancer among the 304 patients with iSVT, 536 patients with iD-DVT, and 327 patients with iP-DVT were similar (3.4% 95% confidence interval [1.8-6.2], 3.9% [2.5-5.9] and 3.9% [2.3-6.8], respectively), regardless of whether the index venous thromboembolic event was unprovoked or associated with a major transient risk factor. Neither anatomical (muscular vs deep-calf DVT) nor ultrasound scan characteristics (number of thrombosed veins, clot diameter under compression) seemed strongly associated with the risk of cancer in cases of iD-DVT. In patients managed in routine practice, all the different clinical expressions of lower limb venous thromboembolism are associated with a similar risk of subsequent cancer. From a clinical practice point of view, this suggests that cancer screening, without discussing the necessity, or not, of such screening, should not differ between a deep-proximal, deep-distal or superficial location of thrombosis.