SAN FRANCISCO – Unless there is a clear contraindication to anticoagulation therapy, cancer patients who have an incidental pulmonary embolism discovered during imaging studies should receive chronic anticoagulation, preferably with a low-molecular-weight heparin, based on study results presented at the annual meeting of the American Society of Hematology.
Without anticoagulation therapy, the risk for a recurent venous thromboembolic event was fourfold higher among 926 cancer patients who had a pulmonary embolism discovered during CT imaging for reasons other than suspicion of pulmonary embolism (PE), according to Dr. Tom van der Hulle of Leiden (the Netherlands) University Medical Center.
Among cancer patients who did receive an anticoagulant, low-molecular-weight heparin (LMWH) was significantly better than warfarin at preventing recurrent venous thromboembolism (VTE) or PE. Compared with warfarin, LMWH also was associated with a significantly lower risk for bleeding.
“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,” Dr. van der Hulle said at a briefing prior to his presentation of the data.
Risk for primary and recurrent VTE is particularly high for patients with pancreatic cancer, lung cancer, metastatic adenocarcinoma of gastroinestinal or gynecologic origin, and brain tumors, noted Dr. Agnes Lee of the University of British Columbia in Vancouver. Dr. Lee also presented data at the briefing but was not involved with the study.
“Once the patients are started on treatment for their clotting episode, for a DVT or PE, a minimum of 3-6 months of anticoagulation is recommended. After that, we look at patients to see whether they have ongoing reasons to develop recurrent thrombosis. So this would be patients who have active cancer – they’re still receiving chemotherapy, they have obvious evidence of cancer or metastatic disease, or they’re sick for other reasons. These are patients who would then continue on anticoagulant therapy,” she added.
Dr. van der Hulle and his colleagues conducted a pooled meta-analysis of 926 patients with cancer who had an incidental PE discovered during a CT scan. The researchers compared results for patients treated with LMWH (79%), a vitamin K antagonist (predominantly warfarin, 11%), and for those who did not receive prophylaxis with an anticoagualant because of contraindications.
They looked at recurrent VTE, major bleeding episodes, and death at 6 months and conducted subgroup analyses based on patient management and thrombus location.
Patients with metastatic disease comprised 74% of those treated with LMWH, 62% of those treated with a vitamin K antagonist, and 73% of untreated patients.
The overall pooled 6-month risk of symptomatic recurrent VTE was 5.8%. The risk of major bleeding was 4.7%, and the risk of death was 37%.
Risk of recurrent VTE was 6.2% for patients treated with LMWH and 6.4% for those treated with a vitamin K antagonist. Recurrent VTE risk was 12% for untreated patients.
Major bleeding was seen in 3.9% of LMWH-treated patients and in 13% of vitamin K antagonist–treated patients (hazard ratio 3.9; 95% confidence interval, 1.6-10).The 6-month mortality rates were 37% for patients treated with LMWH, 28% for those treated with warfarin or a related drug, and 47% for untreated patients.
When the authors looked at the location of the thrombus – isolated subsegmental incidental PE vs. central PE – they found that the risk of recurrent isolated embolism was 7.8% and for central embolism was 5.5%.
Dr. van der Hulle said that the findings of this observational study should preferably be confirmed in a randomized trial, but acknowledged that, given the risk of no treatment, a placebo-controlled trial might be considered unethical.
The study was internally supported. Dr. van der Hulle and Dr. Lee reported no relevant conflicts of interest.