Researchers Define Long-Term Outcomes of Cancer-Associated Thrombosis

Patients diagnosed with cancer-associated thrombosis (CAT) remain at a high risk for recurrent venous thromboembolism (VTE), bleeding, and death – even while on therapeutic anticoagulation – according to a retrospective analysis presented at the 2018 ASCO Annual Meeting.

“[CAT] is a common complication of malignancies,” lead author Robert Schmidt, a medical student in the department of internal medicine at University of British Columbia in Vancouver, and colleagues wrote. “However, little is known about the clinical course of CAT beyond the initial treatment period of three to six months.”

To define longer-term characteristics of CAT, the researchers analyzed health records of 523 consecutive adults with active cancer who presented to the Vancouver General Hospital Thrombosis clinic with a first CAT between 2013 and 2015.

A total of 327 patients (median age = 63 years; range not reported) were alive six months after diagnosis of CAT and constituted the survivors’ cohort. The authors documented patient and cancer characteristics, as well as incidence of recurrent VTE, clinically relevant bleeding, and overall mortality.

Participants were followed for a median of 605 days (range = 1-730 days) post-diagnosis. Beyond six months, anticoagulation was continued in 68.8 percent of patients, for a median duration of 93 days (range not reported), and, more often than not, patients were receiving anticoagulation (54.3% of patient-days were on anticoagulation).

In the six to 24 months after the initial CAT diagnosis, 30 patients (9.2%) experienced a total of 34 recurrent VTEs, corresponding to 10.6 recurrent VTEs per 100 patient-years. Fourteen patients (4.3%) experienced 16 events of clinically relevant bleeding, corresponding to 5.0 episodes per 100 patient-years.

The authors observed that most of these events occurred while patients were receiving anticoagulation: 21 recurrent VTEs (61.8%) and 11 clinically relevant bleeding episodes (68.8%).

When looking at risk factors associated with recurrent VTE or clinically relevant bleeding, the researchers observed that female sex and cancer surgery were linked with a lower risk of recurrent VTE:

  • cancer surgery preceding initial VTE (hazard ratio [HR] = 0.12; 95% CI 0.01-0.85; p=0.034)
  • female sex (HR=0.39; 95% CI 0.18-0.85; p=0.018)

Diagnosis of a cancer type with a known high thrombotic risk (including brain, pancreatic, ovarian, upper gastrointestinal, and lung), presence of two or more comorbidities, and progressive cancer appeared to be associated with a higher risk for recurrent VTE, but these associations did not reach statistical significance.

A total of 141 patients (43.1%) died during follow-up. The most common cause of death, occurring at least six months after diagnosis, was cancer (n=112; 79.4%), followed by bleeding (n=6; 4.3%) and recurrent VTE (n=3; 2.1%); the remaining causes of death were identified as “other” (n=10; 7.1%) or “unknown” (n=10; 7.1%). All instances of fatal recurrent VTE and four of the six instances of fatal clinically relevant bleeding occurred while patients were receiving anticoagulation, the researchers reported, suggesting that “there is a high case fatality rate for both recurrent VTE (10%) and clinically relevant bleeding (42.9%).”

Treatment guidelines recommend anticoagulation for three to six months after diagnosis of CAT, the authors explained. “After six months, anticoagulation is re-evaluated, but optimal duration has not been studied. [The] information [from this review] is important for clinicians and patients to inform their decision regarding duration of anticoagulation,” they concluded.

The study is limited by its single-center, retrospective design.

The authors report no financial conflicts.

Reference

Schmidt RA, Alzaki A, Desilet N, et al. Patient characteristics and long-term outcomes beyond the first 6 months after a diagnosis of cancer-associated thrombosis. Abstract #10057. Presented at the 2018 ASCO Annual Meeting, June 4, 2018; Chicago, IL.

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