ORLANDO – Among patients with cancer-associated thrombosis, women and those with lung cancer or a history of at least one venous thromboembolic event are at significantly increased risk for recurrent emboli and may require prophylaxis with low-molecular-weight heparin or more aggressive anticoagulation, investigators have reported.
In contrast, patients with stage I malignancies or breast cancer are at relatively low risk for venous thromboembolism (VTE) recurrence and may need only a vitamin K antagonist such as warfarin to prevent a second event, Dr. Martha L. Louzada said at a press briefing in advance of a Dec. 6 presentation at the annual meeting of the American Society of Hematology.
The investigators used the data from a retrospective chart study to develop a risk score for determining the clinical probability of VTE recurrence. Each independent risk predictor variable received a point score relative to the magnitude of risk it imposes. Patients with a score from –3 to 0 are deemed to be at low risk (4.5% chance of recurrence), whereas those with scores from 1 to 3 are considered to be at high risk (19.7% chance of recurrence). They were able to reproduce the rule by applying it to data from two randomized controlled trials that compared a low-molecular-weight heparin with a vitamin K antagonist.
"Our future goal is to prospectively validate this clinical prediction rule to assess further reproducibility and generalizability," Dr. Louzada of the University of Western Ontario in London said at the briefing.
To determine whether VTE prophylaxis strategies should be tailored to meet individual patient characteristics or cancer types, the investigators took a retrospective look at the charts of 543 patients with cancer and VTE who were followed at the thrombosis unit of the Ottawa Hospital from 2002 through 2004 and from 2007 through 2008. The investigators restricted their analysis to those patients who had recurrent VTE within 6 months of beginning anticoagulation therapy. They conducted a univariate analysis to gauge the strength of the association between each potential risk factor and VTE recurrence, and evaluated all likely risk-predictor candidates in a logistic regression model.
In all, 55 patients (10.1%) had a recurrent VTE, but the rates of recurrence were similar between the groups, suggesting that treatment type did not have an effect (recurrence rate 9.5% for vitamin K antagonists, 10.5% for low-molecular-weight heparin).
In the multivariate analysis, the authors identified as significant predictors of increased risk, lung cancer (odds ratio, 2.55); a history of prior VTE (OR, 2.42); and female gender (OR, 1.82). Predictors for decreased risk were stage I malignancies (OR, 0.75) and breast cancer (OR, 0.46).
"The patient even with breast cancer can have a high risk, because the majority of patients are females and being female is a high-risk predictor, whereas breast cancer is a low risk, so it’s going to depend on the stage of malignancy of the patient and also whether the patient has a previous history of venous thrombosis," she said.
The study was internally funded. Dr. Louzada said she had no relevant financial disclosures.