Incidental versus symptomatic venous thrombosis in cancer: a prospective observational study of 340 consecutive patients.

BACKGROUND The clinical significance of incidental venous thrombosis (IVT) is uncertain. The objective of this study was to compare the clinical characteristics and the outcome of cancer patients with IVT with those of patients with symptomatic venous thrombosis (SVT). PATIENTS AND METHODS Prospective observational study enrolling consecutive cancer patients newly diagnosed with venous thromboembolism (May 2006-April 2009). Diagnosis of IVT was based on vascular filling defects in scheduled computed tomography scans in the absence of clinical symptoms. Anticoagulant therapy was routinely prescribed regardless of SVT or IVT. RESULTS IVT was diagnosed in 94 out of 340 (28%) patients. Patients with IVT were older (63.7 ± 10.5 versus 60.8 ± 10.5 years, P = 0.035), more frequently had metastatic cancer (82% versus 65%, P = 0.01) and were less likely to be receiving chemotherapy at the time of the thrombotic event (53% versus 67%, P = 0.018). Mean follow-up was 477 days. A lower risk of venous rethromboses was observed in patients with IVT (log-rank P = 0.043), with no differences in major bleeding and overall survival compared with SVT patients. CONCLUSIONS A high proportion of venous thrombotic events in cancer patients are diagnosed incidentally during scheduled imaging. Prospective controlled trials evaluating the optimal therapy in this setting are required.