Rate and Time Course of Thromboembolism Events in Cancer Patients
Authors: Hull Russell D , Merali Tazmin , Mills Allan , Liang Jane , Komari Nelly 
Published: October 2019

Abstract
Abstract 4773

Background:
Venous thromboembolism (VTE) prophylaxis has been recommended in clinical guidelines as an appropriate strategy for hospitalized cancer patients based on evidence of reduced VTE events and reduced mortality. However, current guidelines do not specify the appropriate length of VTE prophylaxis in this population. Real world data is needed to understand the prevalence of symptomatic and confirmed VTE for this patient population to help clinicians determine strategies regarding the appropriate duration of treatment.

Objective:
To document the incidence of symptomatic late VTE events in hospitalized patients who have active cancer.

Methods:
Charts from 1134 consecutive medical patients age > 60 years who were hospitalized in the Calgary region and discharged between January and February 2008 were abstracted using standardized case record forms. All hospitals in the region use a common unique patient identifier number, thus enabling the tracking of subsequent patient visits to the emergency room, inpatient admissions or outpatient visits occurring anywhere in the region's acute care system. Any identified patient was followed for a subsequent visit related to VTE.
Active cancer patients were defined as those who have a cancer diagnosis at hospital admission and have a planned cancer surgery or receiving cancer treatment or were receiving palliative treatment or whose cancer treatment was not specified. Records were excluded if the patient was admitted for VTE or to rule out VTE, receiving chronic anticoagulation, experiencing acute coronary syndromes, had a hospital stay ≤ 3 days, had a remote cancer history, was a surgical or orthopedic patient, or pregnant. Data was collected on the timing of VTE related events for up to 100 days post discharge.

Results:
A total of 358 patients met criteria over the review period. Seventy-three percent (261/358) of all active cancer patients received mechanical or pharmacological prophylaxis in hospital. Twenty-three percent of these patients were identified as requiring medical care for symptoms associated with VTE. Confirmation of VTE by diagnostic testing occurred in 4.8% (95% CI, 2.6% to 7%) while the other 18% (95% CI, 14.0% to 22%) had diagnostic tests that were negative or inconclusive.
The mean length of time to confirmed first VTE event was 38.2 days post admission.

Conclusion:
This study demonstrates that in a real life setting 23% of active cancer patients would develop symptoms of VTE requiring a health professional's attention with 4.8% having VTE confirmed by diagnostic testing. These events occurred despite thromboprophylaxis in hospital and suggest that the risk of symptomatic VTE could be higher in real life compared to that reported in randomized clinical trials where patients are screened for asymptomatic VTE. These findings show that the prevalence of VTE warrants consideration of extended thromboprophylaxis in active cancer patients, as the benefits of extended prophylactic therapy may outweigh the risks in this population.

Disclosures:
Hull: sanofi-aventis: Consultancy; LEO Pharma: Consultancy; Pfizer: Consultancy; Portola: Consultancy; Merck: Consultancy; Bayer: Consultancy; Johnson & Johnson: Consultancy. Merali:sanofi-aventis: Consultancy; Amgen: Consultancy; Pfizer: Consultancy; BMS: Consultancy; Abbott: Consultancy; Boehringer Ingelheim: Consultancy; Genzyme: Consultancy; LEO Pharma: Consultancy; Nycomed: Consultancy; Otsuka: Consultancy. Mills:Pfizer: Consultancy; sanofi-aventis: Research Funding. Komari:sanofi-aventis: Employment.