Risk of recurrent venous thromboembolism according to malignancy characteristics in patients with cancer-associated thrombosis: a systematic review of observational and intervention studies.

Patients with cancer-associated venous thromboembolism (VTE) should be treated with low molecular weight heparin. The ideal duration of anticoagulation in this population is unknown. It is important to evaluate whether there is variation in susceptibility for recurrent VTE according to malignancy characteristics. In this systematic review we sought to evaluate cancer characteristics that may influence the risk for VTE recurrence and the success of anticoagulation in patients with cancer-associated VTE. A systematic literature search strategy identified potential studies on MEDLINE, Embase, the Cochrane Register of Controlled Trials, MEDLINE In-Process and other nonindexed citations using the Ovid interface. There was no restriction to study design or language. No randomized controlled trials fulfilled our inclusion criteria. We included four retrospective and six prospective studies. VTE recurrence rate according to tumour stage suggested an increased risk for patients with metastatic malignancy compared with patients with localized disease (relative risk 1.36; 95% confidence interval 1.06-1.74, P = 0.01). We were unable to pool data to evaluate VTE recurrence according to tumour site and histology. The isolated evaluation of the included studies suggested that younger patients with adenocarcinoma, lung or gastrointestinal malignancy have the highest risk. There is paucity of data regarding detailed malignancy characteristics in patients with cancer-associated VTE. It appears that metastatic malignancy, or adenocarcinoma, or lung malignancy confers a higher risk of VTE recurrence than patients with localized malignancy, nonadenocarcinoma or breast cancer.