People with cancer have a seven-fold increase in risk for deep vein thrombosis and pulmonary embolism compared with healthy peers, according to an article in the February 9th issue of the Journal of the American Medical Association.

Studies that identify patients at highest risk of thrombosis are scarce, according to background information in the article. It is unclear what risks are for various types and stages of cancer.

Jeanet W. Blom, MD, and her Dutch colleagues conducted a study to identify individuals with cancer with an increased thrombotic risk, evaluated different tumor sites, the presence of distant metastases, and carrier status of gene mutations.

The study (Multiple Environmental and Genetic Assessment [MEGA]) included 3,220 patients, aged 18 to 70 years, with a first thromboembolic event (deep venous thrombosis of the leg or pulmonary embolism) between March 1, 1999 and May 31, 2002, at 6 anticoagulation clinics in the Netherlands.

There were 2,131 control participants (partners of the patients). Both groups reported via a questionnaire on acquired risk factors for venous thrombosis. Three months after discontinuation of anticoagulant therapy, all patients and controls were interviewed, a blood sample was taken, and DNA was isolated to ascertain gene mutations, factor V Leiden and prothrombin 20210A, both linked to thrombosis.

The researchers found that the overall risk of venous thrombosis was increased seven-fold in patients with a malignancy compared with persons without malignancy. Patients with hematological malignancies had a 28-fold increased risk of venous thrombosis, followed by those with lung cancer and gastrointestinal cancer. The risk of venous thrombosis was highest in the first few months after diagnosis of malignancy (53 times greater risk).

Patients with cancer with distant metastases had a higher risk than patients without distant metastases (20 times greater risk). Carriers of the factor V Leiden mutation who also had cancer had a 12-fold increased risk compared with individuals without cancer and factor V Leiden. Similar results were indirectly calculated for the prothrombin 20210A mutation in patients with cancer.