番茄社区

AUSTIN, Texas -- Inferior vena cava (IVC) filters had mixed results against cancer-related venous thromboembolism (VTE) in studies presented here.

In a population-based analysis of more than 90,000 cancer patients with deep vein thrombosis (DVT), patients who got IVC filters had better pulmonary embolism (PE)-free survival at 24 months (94.0% vs 89.7%, P<0.001), according to Samyuktha Balabhadra, MD, of the University of Texas MD Anderson Cancer Center in Houston.

A separate single-center study of only IVC recipients suggested no difference in the inpatient impact of these filters between cancer patients and those with other reasons for hospitalization.

Both studies, reported at the annual meeting of the (SIR), faced criticism, though.

They were flawed "as it is unclear how many patients were investigated for development of pulmonary embolism both at the time of initial DVT diagnosis and after IVC filter placement," commented David Brown, MD, of Washington University School of Medicine in St. Louis, who was not involved in either study.

In addition, clinical outcomes data that would actually "help inform us who would be better off with an IVC filter, if any," were missing in both studies, said Rita Redberg, MD, of the University of California, San Francisco.

The studies come 9 years after the safety of IVC filters was first called into question. Late last year, the CASSINI trial of oral anticoagulant rivaroxaban (Xarelto) failed for its primary endpoint of reduction in VTE for cancer patients in the outpatient setting.

"I appreciate that evidence is sorely needed to inform the use of IVC filters, as currently there are no randomized studies showing outcomes benefits while there are definite harms from IVC [filters]," Redberg told 番茄社区. "Unfortunately, these two abstracts will not help in closing that evidence gap."

IVC Filter Impact in Cancer

While Balabhadra's study showed a modestly better outcome with filter use, "the degree of PE-free survival may be impacted by cancer histotype," Balabhadra said.

In some cancers like breast cancer, survival was to a small degree better with IVC filters. But in pancreatic cancer, the survival curve separated as early as 100 days.

Her study utilized the Healthcare Cost and Utilization Project state inpatient database to collect information on IVC filters placed for prevention of pulmonary embolism in patients with lower-extremity DVT treated at acute-care hospitals in California (2005-2011) and Florida (2005-2014).

Propensity-score matching was done to compare those with and without IVC filter placement. Before matching, groups were largely well-balanced, with 51% women and a median age of 70. But the IVC filter group had a higher rate of intracranial hemorrhage, GI bleeds, metastatic disease, and coagulopathy.

An audience member suggested that pancreatic cancer is so painful that some may find it better to die of a pulmonary embolism. The audience laughed.

Balabhadra acknowledged that her group's reliance on the database meant not knowing if the data were coded accurately and lacking granularity in details such as filter type, PE size, and lab values.

Cancer's Impact on IVC Filter Effect

Separately, another group of researchers found that outcomes were generally the same for IVC filter recipients regardless of cancer -- with the exception of lower readmission-free survival.

Patients with and without cancer at their single center had statistically indistinguishable rates of:

• VTE within 30 days of admission
• Pulmonary embolism within 30 days of admission
• VTE within 30 days of discharge
• Mortality during index admission
• 30-day post-discharge acute VTE-free survival

"IVC filter placement among cancer in-patients has no significant VTE-related morbidity or mortality," according to Muhammad Umair, MBBS, of Northwestern University's Feinberg School of Medicine in Chicago, during the same SIR session.

His study included 1,995 inpatients who got IVC filters in 1997-2015 at his center. Among them, 18.7% had cancer.

Umair's group did find shorter readmission-free survival for cancer patients (median 27 vs 57 days, P=0.003), he reported. And when they did occur, more than half of cancer patients' readmissions and VTEs occurred within 30 days.

The researcher noted that his study lacked information about longer-term outcomes. Moreover, his group did not account for out-of-hospital mortality in its analyses, he said.