[Incidence of cancer after primary deep venous thrombosis or pulmonary embolism]

We report a nationwide study based on a cohort of patients with a thromboembolic event (TE) defined as deep venous thrombosis and/or pulmonary embolism identified from the Danish National Registry of Patients from 1977 to 1993. Cancer occurrence in the cohort was determined by linkage to the Danish Cancer Registry. Expected number of cancer cases was estimated from age, sex and site-specific incidence rates. A total of 26,653 TE-cases were identified. We observed 1737 cases of cancer versus 1371 expected (SIR 1.3; 95% CI, 1.21 to 1.33). The risk was particularly high during the first months of follow-up, but declined rapidly hereafter to a constant level slightly above 1.0 one year after the TE. Forty percent of patients diagnosed with cancer within one year from the hospitalization for TE had distant metastases at the time of cancer diagnosis. The observed risk pattern provides evidence that most often a preclinical cancer gives rise to a subsequent TE. An aggressive search for hidden cancer in patients with TE is not warranted.