Blood clot risk high in outpatient chemotherapy patients

The occurrence of venous thromboembolism (VTE) is greater than has been identified in clinical trials, according to a large-scale analysis that assessed the real-world risk. The risk was found to progressively increase during the year following treatment initiation. These findings led to the conclusion that blood-thinning treatments (thromboprophylaxis) should be considered for patients at high risk.

The study found that outpatients receiving chemotherapy are at high risk of developing VTE and of major bleeding complications. These risks are especially high for those with pancreatic, stomach, and lung cancers. The study was published in The Oncologist (2013; doi:10.1634/theoncologist.2013-0226).

The research team, led by Gary H. Lyman, MD, of Duke University School of Medicine and Duke Cancer Institute in Durham, North Carolina, hypothesized that a definable high-risk cohort of patients would benefit from thromboprophylactic treatment for VTE. They also hypothesized that the scope of this risk warrants consideration for the use of prophylaxes such as low- and ultra-low-molecular-weight heparins.

The study involved a random sample of approximately 27,500 patients with high-VTE-risk cancer types (ie, lung, pancreas, stomach, colon/rectum, bladder, or ovary) who had undergone chemotherapy. The researchers retrospectively evaluated the patients' VTE risk, their risk of bleeding, and the economic burden borne by the patient as a result of the disease.

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 months. VTE was most frequently observed in cancers of the pancreas, lung, and stomach, and the overall incidence of the complication was 13.5% at 1 year, with no indication of plateau or tapering at that time point. Patients with VTE showed a higher risk of major bleeding events in the year following chemotherapy initiation (19.8%) compared with 9.6% in patients without VTE. These rates are higher than has been reported with anticoagulant use in clinical trials, likely reflecting how clinical claims data can be more representative of actual practice than clinical trial data. 

Moreover, while the baseline health care costs of patients who would develop VTE were comparable with those of patients who would not, the costs of the VTE patients soared over the year following chemotherapy initiation. On average, patients with VTE had $110,719 in expenses compared with $76,804 for patients without VTE, a difference primarily accounted for by VTE-related inpatient, outpatient, and emergency room expenses.

 “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,” said Lyman. “[The] risk continues to increase over time during the year following initial treatment.”

Lyman stated, “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.”

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