New Study on Incidental Pulmonary Embolism and Cancer

Roxanne Nelson

December 11, 2014

SAN FRANCISCO ― Cancer patients who have an incidental pulmonary embolism (IPE) discovered during imaging studies should receive long-term anticoagulation, according to a new meta-analysis.

That is because, among these patients, the risk for symptomatic recurrent venous thromboembolism (VTE) was more than double among those who did not receive anticoagulant treatment compared with those who did.

The risk for recurrent VTE was 6.2% for patients treated with low-molecular-weight heparin (LMWH) and 6.4% for those treated with a vitamin K antagonist, including warfarin. By contrast, the risk for recurrent VTE was 12% for untreated patients.

"Our study confirms the high risk of recurrent VTE in patients with cancer-associated incidental pulmonary embolism, but it also provides outcomes if patients are left untreated," said lead author Tom van der Hulle, MD, of Leiden University Medical Center in the Netherlands, at a press briefing held during the American Society of Hematology (ASH) 56th Annual Meeting.

Dr Tom van der Hulle

Importantly, the researchers also found that the risk for major bleeding was significantly higher in patients taking vitamin K antagonists compared those taking LMWH: 13% vs 3.9% (HR, 3.2).

IPE is defined as a pulmonary embolism diagnosed on a CT scan performed for reasons other than a clinical suspicion. IPE is estimated to occur in 3.1% of all cancer patients, explained Dr van der Hulle. However, knowledge about the treatment and prognosis of cancer-associated IPE is quite limited and is based mostly on small observational studies.

Dr van der Hulle and colleagues conducted a pooled meta-analysis of 926 patients with cancer who had an incidental PE, using individual patient data from 11 observational studies and ongoing registries.

The primary objective was to compare risk for VTE reoccurrence, major bleeding, and death among cancer patients with IPE who had received anticoagulant treatment with those who had not.

Most patients were treated with LMWH (79%); 11% received vitamin K antagonists (predominantly warfarin, 11%); and 6% did not receive any anticoagualant, generally because of contraindications.

The overall pooled 6-month mortality was 37%. It was higher in untreated patients (47%) than in patients treated with LMWH (37%) and vitamin K antagonists (28%).

Dr van der Hulle noted that all-cause mortality at 6 months was significantly higher for patients with a central thrombus (either central or lobar) compared with those with a more peripheral IPE (either segmental or subsegmental): 42% vs 30% (HR, 1.8).

Isolated subsegmental pulmonary embolism occurred in 7.8% of patients, and central pulmonary embolism was reported in 5.5% of the cohort (HR = 1.1).

There should be similar management for isolated subsegmental incidental PE, explained Dr van der Hulle. He pointed out that the association between more centrally located thrombi and mortality following IPE is a new finding that parallels outcomes for patients with symptomatic PE.

He reiterated that these findings support the use of current guidelines to treat incidental pulmonary embolism. "Ideally, our findings should be confirmed in a randomized clinical trial," said Dr van der Hulle, but he acknowledged that that might not be feasible.

"Given our current and previous results, we believe that it would be ethically challenging and perhaps unfeasible to design a trial allocating patients with cancer-associated IPE to placebo," he added.

The study was internally supported. Dr van der Hulle reports no relevant financial relationships.

American Society of Hematology (ASH) 56th Annual Meeting: Abstract 325. Presented December 7, 2014.

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