ATLANTA – An expert panel convened by the American Society of Hematology will recommend against routine venous thromboembolism (VTE) prophylaxis with low-molecular-weight heparin, except in patients deemed high risk, the panel chair told attendees at the group’s annual meeting.
The recommendations will be posted for public comment in early 2018 and are expected to be finalized and published later in the year.
The panel found strong evidence to recommend against prophylaxis in cancer patients at low risk of VTE, said Gary H. Lyman, MD, of the Fred Hutchinson Cancer Research Center and the University of Washington, both in Seattle.
For cancer patients at high risk of VTE, the panel will make a conditional recommendation – based on weaker evidence – in favor of low-molecular-weight thromboprophylaxis (LMWH) “with a caveat that patients should have no major bleeding risk or other contraindication to anticoagulation,” Dr. Lyman said.
The panel also found weaker evidence to support a conditional recommendation against routine prophylaxis in patients at intermediate risk of VTE, based on results from a systematic review.
These recommendations, which were described during a special education session at the annual meeting of the American Society of Hematology, are just one piece of a larger effort by ASH to develop evidence-based guidelines on VTE management. More than 100 thrombosis experts have reviewed evidence and drafted more than 200 recommendations on diagnosis, prevention, and treatment of VTE, according to ASH.
The cancer-specific recommendations described by Dr. Lyman are based in part on a meta-analysis of 17 randomized controlled trials of cancer patients receiving LMWH thromboprophylaxis that were published between 2008 and 2017. Across cancer types and settings, LMWH prophylaxis in these trials was associated with a reduced risk of VTE and an increased risk of bleeding, Dr. Lyman said.
For all cancer types, relative risk (RR) of VTE was 0.55 (95% confidence interval, 0.46-0.65), with an absolute risk reduction of just 2.7% “because of the low baseline risk of VTE in this setting,” Dr. Lyman said.
However, the baseline risk increased for certain cancer types, including lung cancer, which had a similar relative risk of 0.53 (95% CI, 0.41-0.69) but an absolute risk reduction of 4.3%, according to data Dr. Lyman presented. Likewise, pancreatic cancer was associated with a relative risk of 0.43 (95% CI, 0.25-0.73) but an absolute risk reduction of 10.1%.
Major bleeding across all trials was significantly increased (RR 1.40; 95% CI, 1.01-1.92), but the presented data show that, in absolute terms, the increase was just 0.7% overall and similarly, 0.7% and 0.9% for lung and pancreatic cancer, respectively.
However, VTE risk depends on more than the site of the cancer, Dr. Lyman noted. In their deliberations, the panel considered the validated Khorana Risk Score, which incorporates factors such as body mass index, platelet count, leukocyte count, and hemoglobin level.
Specific analysis of high-risk patients suggested a pronounced risk reduction associated with LMWH prophylaxis, according to Dr. Lyman, who noted that a patient-level analysis including nearly 8,000 patients from 13 randomized, controlled trials showed a relative risk of 0.58, with VTE events seen in 4.0% patients in the LMWH group versus 7.0% of controls.
The forthcoming ASH guidelines also will address other aspects of cancer-associated VTE, according to Dr. Lyman, including initial treatment, secondary prophylaxis, perioperative prophylaxis, and prophylaxis or treatment in patients with a central venous catheter.
“The risk of venous thromboembolism in patients with cancer is well recognized, and that risk is especially notable in patients receiving cancer treatment,” Dr. Lyman said.
Dr. Lyman reported having no relevant financial disclosures.