Background: Several small studies have indicated an association between deep venous thrombosis or pulmonary embolism and a subsequent diagnosis of cancer, but the subject is controversial.
Methods: We conducted a nationwide study of a cohort of patients with deep venous thrombosis or pulmonary embolism that was drawn from the Danish National Registry of Patients for the years 1977 through 1992. The occurrence of cancer in the cohort was determined by linkage to the Danish Cancer Registry. The expected number of cancer cases was estimated on the basis of national age-, sex-, and site-specific incidence rates.
Results: A total of 15,348 patients with deep venous thrombosis and 11,305 patients with pulmonary embolism were identified. We observed 1737 cases of cancer in the cohort with deep venous thrombosis, as compared with 1372 expected cases (standardized incidence ratio, 1.3; 95 percent confidence interval, 1.21 to 1.33). Among the patients with pulmonary embolism, the standardized incidence ratio was 1.3, with a 95 percent confidence interval of 1.22 to 1.41. The risk was substantially elevated only during the first six months of follow-up and declined rapidly thereafter to a constant level slightly above 1.0 one year after the thrombotic event. Forty percent of the patients given a diagnosis of cancer within one year after hospitalization for thromboembolism had distant metastases at the time of the diagnosis of cancer. There were strong associations with several cancers, most pronounced for those of the pancreas, ovary, liver (primary hepatic cancer), and brain.
Conclusions: An aggressive search for a hidden cancer in a patient with a primary deep venous thrombosis or pulmonary embolism is not warranted.