Thrombus

Credit: Andre E.X. Brown

A large-scale analysis assessing the real-world risk of venous thromboembolism (VTE) among chemotherapy patients showed a greater occurrence of VTE than that identified in clinical trials.

The data also revealed a progressively increased risk during the year following treatment initiation.

The study, published in The Oncologist, showed that outpatients receiving chemotherapy were at high risk of both VTE and major bleeding complications.

The risks were particularly high for patients with pancreas, stomach, and lung cancer.

Gary H. Lyman, MD, of the Duke University School of Medicine in Durham, North Carolina, and his colleagues conducted this research, analyzing data from the United States IMPACT healthcare claims database.

Their sample included 27,479 patients with solid tumor malignancies who had undergone chemotherapy. The researchers retrospectively evaluated the patients’ VTE risk, as well as their risk of bleeding and the economic burden borne by the patient as a result of the disease.

The team used 3 definitions of VTE. Definition A included patients who had 1 or more VTE claim. Definition B included patients with 2 or more VTE claims 30 days or more apart, 1 inpatient claim, or 1 outpatient claim in which they received an anticoagulant within 90 days.

Definition C excluded from definition B any VTE events within 90 days of any major or invasive surgery. Codes relating to esophageal, renal, and uterine cancer were excluded.

VTE risk

The risk of VTE increased over time, with a greater percentage of patients developing the complication at 12 months after initiation of chemotherapy than at 3.5 months. This held true across the 3 definitions of VTE considered.

According to definition A, the overall VTE incidence was 7.3% (4.6%-11.6%) at 3.5 months and 13.5% (9.8%-21.3%) at a year.

Rates of VTE were similar according to definitions B and C. At 3.5 months, the rates were 3.4%-9.6% and 3.2%-8.7%, respectively. At 12 months, they were 7.1%-17.7% and 6.7%-16.6%, respectively.

According to definition A, VTE was most frequently observed in cancers of the pancreas (11.6%), lung (8.5%), and stomach (8.3%).

Major bleeding

Patients with VTE had a higher risk of major bleeding events in the year following chemotherapy initiation.

Individuals receiving outpatient chemotherapy who developed VTE according to definition A at 3.5 months had a higher risk for major bleeding complications within 3.5 months than patients who were not receiving outpatient chemotherapy—11.0% and 3.8%, respectively.

The incidence of major bleeding within 12 months after the index date was 19.8% in patients with VTE (according to definition A) and 9.6% in patients without VTE.

Healthcare costs

While the baseline healthcare costs of patients who would develop VTE were comparable to those of patients who would not, the costs soared for VTE patients over the year following chemotherapy initiation.

On average, in the first 12 months after the index date, patients with VTE had $110,719 worth of healthcare costs, compared with $76,804 for patients without VTE. This difference was primarily accounted for by VTE-related inpatient, outpatient, and emergency room expenses.

Claims data vs trial data

The researchers noted that the incidence of VTE reported in this study is inconsistent with data previously reported in randomized clinical trials, which may be due to the selection of lower-risk patients for participation in these studies.

“Importantly, this observational study suggests that the observed rates of symptomatic VTE in real-world practice are considerably greater than reported in patients eligible for randomized clinical trials,” Dr Lyman said.

“Clinical oncologists need to be aware of the increased risk of this serious complication of cancer and cancer treatment, and, when the risk is sufficiently great, and the balance of benefits and harms acceptable, oncologists should consider prophylactic anticoagulation.”

Dr Lyman and his colleagues hypothesized that there is a definable, high-risk cohort of patients who would benefit from thromboprophylaxis.

And the scope of this risk warrants consideration for the use of treatments such as low- and ultra-low-molecular-weight heparins, which recent studies have found to be safe and effective thromboprophylaxis for chemotherapy patients.

Chemo patients may have higher VTE risk than trials suggest