Background: The reported incidence of a subsequent diagnosis of malignancy in patients presenting with deep vein thrombosis (DVT) varies from 2-25%. Risk indicators and diagnostic procedures to be performed in these patients are controversial.
Methods: Four hundred consecutive patients with confirmed DVT included in a randomized clinical trial were followed prospectively for 6 months. The incidence of a subsequent diagnosis of malignancy was calculated and compared between patients with unexplained DVT and patients with secondary DVT. Potential risk indicators for subsequent malignant disease were evaluated.
Results: Of the 400 patients, 70 already had been diagnosed with malignancy; another four patients were lost to follow-up. Of the remaining 326 patients, 10 new malignancies were diagnosed among 137 patients with unexplained DVT (7.3%) and 3 new malignancies were diagnosed in 189 patients with secondary DVT (1.6%). The relative risk was 4.6 (95% confidence interval, 1.3-16; P=0.009). Age, gender, or location of the DVT had no significant effect on the incidence of diagnosis when adjusted for unexplained DVT. Ten of these 13 patients (77%) had abnormal clinical findings suggestive of malignancy at the time of presentation with DVT.
Conclusions: Unexplained DVT is a significant risk indicator of underlying malignancy. The majority of patients with undiagnosed malignancy have some clinical abnormality suggestive of underlying malignancy at the time of presentation with unexplained DVT. A simple clinical evaluation comprised of medical history, physical examination, routine laboratory tests, and chest X-ray can detect such patients. Extensive screening of all patients presenting with unexplained DVT does not appear to be justified.